[drm-misc-next,v7,4/7] drm/gpuvm: add an abstraction for a VM / BO combination

  Add an abstraction layer between the drm_gpuva mappings of a particular
drm_gem_object and this GEM object itself. The abstraction represents a
combination of a drm_gem_object and drm_gpuvm. The drm_gem_object holds
a list of drm_gpuvm_bo structures (the structure representing this
abstraction), while each drm_gpuvm_bo contains list of mappings of this
GEM object.

This has multiple advantages:

1) We can use the drm_gpuvm_bo structure to attach it to various lists
   of the drm_gpuvm. This is useful for tracking external and evicted
   objects per VM, which is introduced in subsequent patches.

2) Finding mappings of a certain drm_gem_object mapped in a certain
   drm_gpuvm becomes much cheaper.

3) Drivers can derive and extend the structure to easily represent
   driver specific states of a BO for a certain GPUVM.

The idea of this abstraction was taken from amdgpu, hence the credit for
this idea goes to the developers of amdgpu.

Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Danilo Krummrich <dakr@redhat.com>
---
 drivers/gpu/drm/drm_gpuvm.c            | 335 +++++++++++++++++++++----
 drivers/gpu/drm/nouveau/nouveau_uvmm.c |  64 +++--
 include/drm/drm_gem.h                  |  32 +--
 include/drm/drm_gpuvm.h                | 188 +++++++++++++-
 4 files changed, 533 insertions(+), 86 deletions(-)
  

On Mon, 2023-10-23 at 22:16 +0200, Danilo Krummrich wrote:
> Add an abstraction layer between the drm_gpuva mappings of a
> particular
> drm_gem_object and this GEM object itself. The abstraction represents
> a
> combination of a drm_gem_object and drm_gpuvm. The drm_gem_object
> holds
> a list of drm_gpuvm_bo structures (the structure representing this
> abstraction), while each drm_gpuvm_bo contains list of mappings of
> this
> GEM object.
> 
> This has multiple advantages:
> 
> 1) We can use the drm_gpuvm_bo structure to attach it to various
> lists
>    of the drm_gpuvm. This is useful for tracking external and evicted
>    objects per VM, which is introduced in subsequent patches.
> 
> 2) Finding mappings of a certain drm_gem_object mapped in a certain
>    drm_gpuvm becomes much cheaper.
> 
> 3) Drivers can derive and extend the structure to easily represent
>    driver specific states of a BO for a certain GPUVM.
> 
> The idea of this abstraction was taken from amdgpu, hence the credit
> for
> this idea goes to the developers of amdgpu.
> 
> Cc: Christian König <christian.koenig@amd.com>
> Signed-off-by: Danilo Krummrich <dakr@redhat.com>
> ---
>  drivers/gpu/drm/drm_gpuvm.c            | 335 +++++++++++++++++++++--
> --
>  drivers/gpu/drm/nouveau/nouveau_uvmm.c |  64 +++--
>  include/drm/drm_gem.h                  |  32 +--
>  include/drm/drm_gpuvm.h                | 188 +++++++++++++-
>  4 files changed, 533 insertions(+), 86 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_gpuvm.c
> b/drivers/gpu/drm/drm_gpuvm.c
> index c03332883432..7f4f5919f84c 100644
> --- a/drivers/gpu/drm/drm_gpuvm.c
> +++ b/drivers/gpu/drm/drm_gpuvm.c
> @@ -70,6 +70,18 @@
>   * &drm_gem_object, such as the &drm_gem_object containing the root
> page table,
>   * but it can also be a 'dummy' object, which can be allocated with
>   * drm_gpuvm_resv_object_alloc().
> + *
> + * In order to connect a struct drm_gpuva its backing
> &drm_gem_object each
> + * &drm_gem_object maintains a list of &drm_gpuvm_bo structures, and
> each
> + * &drm_gpuvm_bo contains a list of &drm_gpuva structures.
> + *
> + * A &drm_gpuvm_bo is an abstraction that represents a combination
> of a
> + * &drm_gpuvm and a &drm_gem_object. Every such combination should
> be unique.
> + * This is ensured by the API through drm_gpuvm_bo_obtain() and
> + * drm_gpuvm_bo_obtain_prealloc() which first look into the
> corresponding
> + * &drm_gem_object list of &drm_gpuvm_bos for an existing instance
> of this
> + * particular combination. If not existent a new instance is created
> and linked
> + * to the &drm_gem_object.
>   */
>  
>  /**
> @@ -395,21 +407,28 @@
>  /**
>   * DOC: Locking
>   *
> - * Generally, the GPU VA manager does not take care of locking
> itself, it is
> - * the drivers responsibility to take care about locking. Drivers
> might want to
> - * protect the following operations: inserting, removing and
> iterating
> - * &drm_gpuva objects as well as generating all kinds of operations,
> such as
> - * split / merge or prefetch.
> - *
> - * The GPU VA manager also does not take care of the locking of the
> backing
> - * &drm_gem_object buffers GPU VA lists by itself; drivers are
> responsible to
> - * enforce mutual exclusion using either the GEMs dma_resv lock or
> alternatively
> - * a driver specific external lock. For the latter see also
> - * drm_gem_gpuva_set_lock().
> - *
> - * However, the GPU VA manager contains lockdep checks to ensure
> callers of its
> - * API hold the corresponding lock whenever the &drm_gem_objects GPU
> VA list is
> - * accessed by functions such as drm_gpuva_link() or
> drm_gpuva_unlink().
> + * In terms of managing &drm_gpuva entries DRM GPUVM does not take
> care of
> + * locking itself, it is the drivers responsibility to take care
> about locking.
> + * Drivers might want to protect the following operations:
> inserting, removing
> + * and iterating &drm_gpuva objects as well as generating all kinds
> of
> + * operations, such as split / merge or prefetch.
> + *
> + * DRM GPUVM also does not take care of the locking of the backing
> + * &drm_gem_object buffers GPU VA lists and &drm_gpuvm_bo
> abstractions by
> + * itself; drivers are responsible to enforce mutual exclusion using
> either the
> + * GEMs dma_resv lock or alternatively a driver specific external
> lock. For the
> + * latter see also drm_gem_gpuva_set_lock().
> + *
> + * However, DRM GPUVM contains lockdep checks to ensure callers of
> its API hold
> + * the corresponding lock whenever the &drm_gem_objects GPU VA list
> is accessed
> + * by functions such as drm_gpuva_link() or drm_gpuva_unlink(), but
> also
> + * drm_gpuvm_bo_obtain() and drm_gpuvm_bo_put().
> + *
> + * The latter is required since on creation and destruction of a
> &drm_gpuvm_bo
> + * the &drm_gpuvm_bo is attached / removed from the &drm_gem_objects
> gpuva list.
> + * Subsequent calls to drm_gpuvm_bo_obtain() for the same &drm_gpuvm
> and
> + * &drm_gem_object must be able to observe previous creations and
> destructions
> + * of &drm_gpuvm_bos in order to keep instances unique.
>   */
>  
>  /**
> @@ -439,6 +458,7 @@
>   *     {
>   *             struct drm_gpuva_ops *ops;
>   *             struct drm_gpuva_op *op
> + *             struct drm_gpuvm_bo *vm_bo;
>   *
>   *             driver_lock_va_space();
>   *             ops = drm_gpuvm_sm_map_ops_create(gpuvm, addr, range,
> @@ -446,6 +466,10 @@
>   *             if (IS_ERR(ops))
>   *                     return PTR_ERR(ops);
>   *
> + *             vm_bo = drm_gpuvm_bo_obtain(gpuvm, obj);
> + *             if (IS_ERR(vm_bo))
> + *                     return PTR_ERR(vm_bo);
> + *
>   *             drm_gpuva_for_each_op(op, ops) {
>   *                     struct drm_gpuva *va;
>   *
> @@ -458,7 +482,7 @@
>   *
>   *                             driver_vm_map();
>   *                             drm_gpuva_map(gpuvm, va, &op->map);
> - *                             drm_gpuva_link(va);
> + *                             drm_gpuva_link(va, vm_bo);
>   *
>   *                             break;
>   *                     case DRM_GPUVA_OP_REMAP: {
> @@ -485,11 +509,11 @@
>   *                             driver_vm_remap();
>   *                             drm_gpuva_remap(prev, next, &op-
> >remap);
>   *
> - *                             drm_gpuva_unlink(va);
>   *                             if (prev)
> - *                                     drm_gpuva_link(prev);
> + *                                     drm_gpuva_link(prev, va-
> >vm_bo);
>   *                             if (next)
> - *                                     drm_gpuva_link(next);
> + *                                     drm_gpuva_link(next, va-
> >vm_bo);
> + *                             drm_gpuva_unlink(va);
>   *
>   *                             break;
>   *                     }
> @@ -505,6 +529,7 @@
>   *                             break;
>   *                     }
>   *             }
> + *             drm_gpuvm_bo_put(vm_bo);
>   *             driver_unlock_va_space();
>   *
>   *             return 0;
> @@ -514,6 +539,7 @@
>   *
>   *     struct driver_context {
>   *             struct drm_gpuvm *gpuvm;
> + *             struct drm_gpuvm_bo *vm_bo;
>   *             struct drm_gpuva *new_va;
>   *             struct drm_gpuva *prev_va;
>   *             struct drm_gpuva *next_va;
> @@ -534,6 +560,7 @@
>   *                               struct drm_gem_object *obj, u64
> offset)
>   *     {
>   *             struct driver_context ctx;
> + *             struct drm_gpuvm_bo *vm_bo;
>   *             struct drm_gpuva_ops *ops;
>   *             struct drm_gpuva_op *op;
>   *             int ret = 0;
> @@ -543,16 +570,23 @@
>   *             ctx.new_va = kzalloc(sizeof(*ctx.new_va),
> GFP_KERNEL);
>   *             ctx.prev_va = kzalloc(sizeof(*ctx.prev_va),
> GFP_KERNEL);
>   *             ctx.next_va = kzalloc(sizeof(*ctx.next_va),
> GFP_KERNEL);
> - *             if (!ctx.new_va || !ctx.prev_va || !ctx.next_va) {
> + *             ctx.vm_bo = drm_gpuvm_bo_create(gpuvm, obj);
> + *             if (!ctx.new_va || !ctx.prev_va || !ctx.next_va ||
> !vm_bo) {
>   *                     ret = -ENOMEM;
>   *                     goto out;
>   *             }
>   *
> + *             // Typically protected with a driver specific GEM
> gpuva lock
> + *             // used in the fence signaling path for
> drm_gpuva_link() and
> + *             // drm_gpuva_unlink(), hence pre-allocate.
> + *             ctx.vm_bo = drm_gpuvm_bo_obtain_prealloc(ctx.vm_bo);
> + *
>   *             driver_lock_va_space();
>   *             ret = drm_gpuvm_sm_map(gpuvm, &ctx, addr, range, obj,
> offset);
>   *             driver_unlock_va_space();
>   *
>   *     out:
> + *             drm_gpuvm_bo_put(ctx.vm_bo);
>   *             kfree(ctx.new_va);
>   *             kfree(ctx.prev_va);
>   *             kfree(ctx.next_va);
> @@ -565,7 +599,7 @@
>   *
>   *             drm_gpuva_map(ctx->vm, ctx->new_va, &op->map);
>   *
> - *             drm_gpuva_link(ctx->new_va);
> + *             drm_gpuva_link(ctx->new_va, ctx->vm_bo);
>   *
>   *             // prevent the new GPUVA from being freed in
>   *             // driver_mapping_create()
> @@ -577,22 +611,23 @@
>   *     int driver_gpuva_remap(struct drm_gpuva_op *op, void *__ctx)
>   *     {
>   *             struct driver_context *ctx = __ctx;
> + *             struct drm_gpuva *va = op->remap.unmap->va;
>   *
>   *             drm_gpuva_remap(ctx->prev_va, ctx->next_va, &op-
> >remap);
>   *
> - *             drm_gpuva_unlink(op->remap.unmap->va);
> - *             kfree(op->remap.unmap->va);
> - *
>   *             if (op->remap.prev) {
> - *                     drm_gpuva_link(ctx->prev_va);
> + *                     drm_gpuva_link(ctx->prev_va, va->vm_bo);
>   *                     ctx->prev_va = NULL;
>   *             }
>   *
>   *             if (op->remap.next) {
> - *                     drm_gpuva_link(ctx->next_va);
> + *                     drm_gpuva_link(ctx->next_va, va->vm_bo);
>   *                     ctx->next_va = NULL;
>   *             }
>   *
> + *             drm_gpuva_unlink(va);
> + *             kfree(va);
> + *
>   *             return 0;
>   *     }
>   *
> @@ -774,6 +809,194 @@ drm_gpuvm_destroy(struct drm_gpuvm *gpuvm)
>  }
>  EXPORT_SYMBOL_GPL(drm_gpuvm_destroy);
>  
> +/**
> + * drm_gpuvm_bo_create() - create a new instance of struct
> drm_gpuvm_bo
> + * @gpuvm: The &drm_gpuvm the @obj is mapped in.
> + * @obj: The &drm_gem_object being mapped in the @gpuvm.
> + *
> + * If provided by the driver, this function uses the &drm_gpuvm_ops
> + * vm_bo_alloc() callback to allocate.
> + *
> + * Returns: a pointer to the &drm_gpuvm_bo on success, NULL on

Still needs s/Returns:/Return:/g

> failure
> + */
> +struct drm_gpuvm_bo *
> +drm_gpuvm_bo_create(struct drm_gpuvm *gpuvm,
> +                   struct drm_gem_object *obj)
> +{
> +       const struct drm_gpuvm_ops *ops = gpuvm->ops;
> +       struct drm_gpuvm_bo *vm_bo;
> +
> +       if (ops && ops->vm_bo_alloc)
> +               vm_bo = ops->vm_bo_alloc();
> +       else
> +               vm_bo = kzalloc(sizeof(*vm_bo), GFP_KERNEL);
> +
> +       if (unlikely(!vm_bo))
> +               return NULL;
> +
> +       vm_bo->vm = gpuvm;
> +       vm_bo->obj = obj;
> +       drm_gem_object_get(obj);
> +
> +       kref_init(&vm_bo->kref);
> +       INIT_LIST_HEAD(&vm_bo->list.gpuva);
> +       INIT_LIST_HEAD(&vm_bo->list.entry.gem);
> +
> +       return vm_bo;
> +}
> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_create);
> +
> +static void
> +drm_gpuvm_bo_destroy(struct kref *kref)
> +{
> +       struct drm_gpuvm_bo *vm_bo = container_of(kref, struct
> drm_gpuvm_bo,
> +                                                 kref);
> +       struct drm_gpuvm *gpuvm = vm_bo->vm;
> +       const struct drm_gpuvm_ops *ops = gpuvm->ops;
> +       struct drm_gem_object *obj = vm_bo->obj;
> +       bool lock = !drm_gpuvm_resv_protected(gpuvm);
> +
> +       if (!lock)
> +               drm_gpuvm_resv_assert_held(gpuvm);
> +
> +       drm_gem_gpuva_assert_lock_held(obj);
> +       list_del(&vm_bo->list.entry.gem);
> +
> +       if (ops && ops->vm_bo_free)
> +               ops->vm_bo_free(vm_bo);
> +       else
> +               kfree(vm_bo);
> +
> +       drm_gem_object_put(obj);
> +}
> +
> +/**
> + * drm_gpuvm_bo_put() - drop a struct drm_gpuvm_bo reference
> + * @vm_bo: the &drm_gpuvm_bo to release the reference of
> + *
> + * This releases a reference to @vm_bo.
> + *
> + * If the reference count drops to zero, the &gpuvm_bo is destroyed,
> which
> + * includes removing it from the GEMs gpuva list. Hence, if a call
> to this
> + * function can potentially let the reference count to zero the
> caller must
> + * hold the dma-resv or driver specific GEM gpuva lock.
> + */
> +void
> +drm_gpuvm_bo_put(struct drm_gpuvm_bo *vm_bo)
> +{
> +       if (vm_bo)
> +               kref_put(&vm_bo->kref, drm_gpuvm_bo_destroy);
> +}
> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_put);
> +
> +static struct drm_gpuvm_bo *
> +__drm_gpuvm_bo_find(struct drm_gpuvm *gpuvm,
> +                   struct drm_gem_object *obj)
> +{
> +       struct drm_gpuvm_bo *vm_bo;
> +
> +       drm_gem_gpuva_assert_lock_held(obj);
> +       drm_gem_for_each_gpuvm_bo(vm_bo, obj)
> +               if (vm_bo->vm == gpuvm)
> +                       return vm_bo;
> +
> +       return NULL;
> +}
> +
> +/**
> + * drm_gpuvm_bo_find() - find the &drm_gpuvm_bo for the given
> + * &drm_gpuvm and &drm_gem_object
> + * @gpuvm: The &drm_gpuvm the @obj is mapped in.
> + * @obj: The &drm_gem_object being mapped in the @gpuvm.
> + *
> + * Find the &drm_gpuvm_bo representing the combination of the given
> + * &drm_gpuvm and &drm_gem_object. If found, increases the reference
> + * count of the &drm_gpuvm_bo accordingly.
> + *
> + * Returns: a pointer to the &drm_gpuvm_bo on success, NULL on
> failure
> + */
> +struct drm_gpuvm_bo *
> +drm_gpuvm_bo_find(struct drm_gpuvm *gpuvm,
> +                 struct drm_gem_object *obj)
> +{
> +       struct drm_gpuvm_bo *vm_bo = __drm_gpuvm_bo_find(gpuvm, obj);
> +
> +       return vm_bo ? drm_gpuvm_bo_get(vm_bo) : NULL;
> +}
> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_find);
> +
> +/**
> + * drm_gpuvm_bo_obtain() - obtains and instance of the &drm_gpuvm_bo
> for the
> + * given &drm_gpuvm and &drm_gem_object
> + * @gpuvm: The &drm_gpuvm the @obj is mapped in.
> + * @obj: The &drm_gem_object being mapped in the @gpuvm.
> + *
> + * Find the &drm_gpuvm_bo representing the combination of the given
> + * &drm_gpuvm and &drm_gem_object. If found, increases the reference
> + * count of the &drm_gpuvm_bo accordingly. If not found, allocates a
> new
> + * &drm_gpuvm_bo.
> + *
> + * A new &drm_gpuvm_bo is added to the GEMs gpuva list.
> + *
> + * Returns: a pointer to the &drm_gpuvm_bo on success, an ERR_PTR on
> failure
> + */
> +struct drm_gpuvm_bo *
> +drm_gpuvm_bo_obtain(struct drm_gpuvm *gpuvm,
> +                   struct drm_gem_object *obj)
> +{
> +       struct drm_gpuvm_bo *vm_bo;
> +
> +       vm_bo = drm_gpuvm_bo_find(gpuvm, obj);
> +       if (vm_bo)
> +               return vm_bo;
> +
> +       vm_bo = drm_gpuvm_bo_create(gpuvm, obj);
> +       if (!vm_bo)
> +               return ERR_PTR(-ENOMEM);
> +
> +       drm_gem_gpuva_assert_lock_held(obj);
> +       list_add_tail(&vm_bo->list.entry.gem, &obj->gpuva.list);
> +
> +       return vm_bo;
> +}
> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_obtain);
> +
> +/**
> + * drm_gpuvm_bo_obtain_prealloc() - obtains and instance of the
> &drm_gpuvm_bo
> + * for the given &drm_gpuvm and &drm_gem_object
> + * @__vm_bo: A pre-allocated struct drm_gpuvm_bo.
> + *
> + * Find the &drm_gpuvm_bo representing the combination of the given
> + * &drm_gpuvm and &drm_gem_object. If found, increases the reference
> + * count of the found &drm_gpuvm_bo accordingly, while the @__vm_bo
> reference
> + * count is decreased. If not found @__vm_bo is returned without
> further
> + * increase of the reference count.
> + *
> + * A new &drm_gpuvm_bo is added to the GEMs gpuva list.
> + *
> + * Returns: a pointer to the found &drm_gpuvm_bo or @__vm_bo if no
> existing
> + * &drm_gpuvm_bo was found
> + */
> +struct drm_gpuvm_bo *
> +drm_gpuvm_bo_obtain_prealloc(struct drm_gpuvm_bo *__vm_bo)
> +{
> +       struct drm_gpuvm *gpuvm = __vm_bo->vm;
> +       struct drm_gem_object *obj = __vm_bo->obj;
> +       struct drm_gpuvm_bo *vm_bo;
> +
> +       vm_bo = drm_gpuvm_bo_find(gpuvm, obj);
> +       if (vm_bo) {
> +               drm_gpuvm_bo_put(__vm_bo);
> +               return vm_bo;
> +       }
> +
> +       drm_gem_gpuva_assert_lock_held(obj);
> +       list_add_tail(&__vm_bo->list.entry.gem, &obj->gpuva.list);
> +
> +       return __vm_bo;
> +}
> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_obtain_prealloc);
> +
>  static int
>  __drm_gpuva_insert(struct drm_gpuvm *gpuvm,
>                    struct drm_gpuva *va)
> @@ -864,24 +1087,33 @@ EXPORT_SYMBOL_GPL(drm_gpuva_remove);
>  /**
>   * drm_gpuva_link() - link a &drm_gpuva
>   * @va: the &drm_gpuva to link
> + * @vm_bo: the &drm_gpuvm_bo to add the &drm_gpuva to
>   *
> - * This adds the given &va to the GPU VA list of the &drm_gem_object
> it is
> - * associated with.
> + * This adds the given &va to the GPU VA list of the &drm_gpuvm_bo
> and the
> + * &drm_gpuvm_bo to the &drm_gem_object it is associated with.
> + *
> + * For every &drm_gpuva entry added to the &drm_gpuvm_bo an
> additional
> + * reference of the latter is taken.
>   *
>   * This function expects the caller to protect the GEM's GPUVA list
> against
> - * concurrent access using the GEMs dma_resv lock.
> + * concurrent access using either the GEMs dma_resv lock or a driver
> specific
> + * lock set through drm_gem_gpuva_set_lock().
>   */
>  void
> -drm_gpuva_link(struct drm_gpuva *va)
> +drm_gpuva_link(struct drm_gpuva *va, struct drm_gpuvm_bo *vm_bo)
>  {
>         struct drm_gem_object *obj = va->gem.obj;
> +       struct drm_gpuvm *gpuvm = va->vm;
>  
>         if (unlikely(!obj))
>                 return;
>  
> -       drm_gem_gpuva_assert_lock_held(obj);
> +       drm_WARN_ON(gpuvm->drm, obj != vm_bo->obj);
>  
> -       list_add_tail(&va->gem.entry, &obj->gpuva.list);
> +       va->vm_bo = drm_gpuvm_bo_get(vm_bo);
> +
> +       drm_gem_gpuva_assert_lock_held(obj);
> +       list_add_tail(&va->gem.entry, &vm_bo->list.gpuva);
>  }
>  EXPORT_SYMBOL_GPL(drm_gpuva_link);
>  
> @@ -892,20 +1124,31 @@ EXPORT_SYMBOL_GPL(drm_gpuva_link);
>   * This removes the given &va from the GPU VA list of the
> &drm_gem_object it is
>   * associated with.
>   *
> + * This removes the given &va from the GPU VA list of the
> &drm_gpuvm_bo and
> + * the &drm_gpuvm_bo from the &drm_gem_object it is associated with
> in case
> + * this call unlinks the last &drm_gpuva from the &drm_gpuvm_bo.
> + *
> + * For every &drm_gpuva entry removed from the &drm_gpuvm_bo a
> reference of
> + * the latter is dropped.
> + *
>   * This function expects the caller to protect the GEM's GPUVA list
> against
> - * concurrent access using the GEMs dma_resv lock.
> + * concurrent access using either the GEMs dma_resv lock or a driver
> specific
> + * lock set through drm_gem_gpuva_set_lock().
>   */
>  void
>  drm_gpuva_unlink(struct drm_gpuva *va)
>  {
>         struct drm_gem_object *obj = va->gem.obj;
> +       struct drm_gpuvm_bo *vm_bo = va->vm_bo;
>  
>         if (unlikely(!obj))
>                 return;
>  
>         drm_gem_gpuva_assert_lock_held(obj);
> -
>         list_del_init(&va->gem.entry);
> +
> +       va->vm_bo = NULL;
> +       drm_gpuvm_bo_put(vm_bo);
>  }
>  EXPORT_SYMBOL_GPL(drm_gpuva_unlink);
>  
> @@ -1050,10 +1293,10 @@ drm_gpuva_remap(struct drm_gpuva *prev,
>                 struct drm_gpuva *next,
>                 struct drm_gpuva_op_remap *op)
>  {
> -       struct drm_gpuva *curr = op->unmap->va;
> -       struct drm_gpuvm *gpuvm = curr->vm;
> +       struct drm_gpuva *va = op->unmap->va;
> +       struct drm_gpuvm *gpuvm = va->vm;
>  
> -       drm_gpuva_remove(curr);
> +       drm_gpuva_remove(va);
>  
>         if (op->prev) {
>                 drm_gpuva_init_from_op(prev, op->prev);
> @@ -1695,9 +1938,8 @@ drm_gpuvm_prefetch_ops_create(struct drm_gpuvm
> *gpuvm,
>  EXPORT_SYMBOL_GPL(drm_gpuvm_prefetch_ops_create);
>  
>  /**
> - * drm_gpuvm_gem_unmap_ops_create() - creates the &drm_gpuva_ops to
> unmap a GEM
> - * @gpuvm: the &drm_gpuvm representing the GPU VA space
> - * @obj: the &drm_gem_object to unmap
> + * drm_gpuvm_bo_unmap_ops_create() - creates the &drm_gpuva_ops to
> unmap a GEM
> + * @vm_bo: the &drm_gpuvm_bo abstraction
>   *
>   * This function creates a list of operations to perform unmapping
> for every
>   * GPUVA attached to a GEM.
> @@ -1714,15 +1956,14 @@
> EXPORT_SYMBOL_GPL(drm_gpuvm_prefetch_ops_create);
>   * Returns: a pointer to the &drm_gpuva_ops on success, an ERR_PTR
> on failure
>   */
>  struct drm_gpuva_ops *
> -drm_gpuvm_gem_unmap_ops_create(struct drm_gpuvm *gpuvm,
> -                              struct drm_gem_object *obj)
> +drm_gpuvm_bo_unmap_ops_create(struct drm_gpuvm_bo *vm_bo)
>  {
>         struct drm_gpuva_ops *ops;
>         struct drm_gpuva_op *op;
>         struct drm_gpuva *va;
>         int ret;
>  
> -       drm_gem_gpuva_assert_lock_held(obj);
> +       drm_gem_gpuva_assert_lock_held(vm_bo->obj);
>  
>         ops = kzalloc(sizeof(*ops), GFP_KERNEL);
>         if (!ops)
> @@ -1730,8 +1971,8 @@ drm_gpuvm_gem_unmap_ops_create(struct drm_gpuvm
> *gpuvm,
>  
>         INIT_LIST_HEAD(&ops->list);
>  
> -       drm_gem_for_each_gpuva(va, obj) {
> -               op = gpuva_op_alloc(gpuvm);
> +       drm_gpuvm_bo_for_each_va(va, vm_bo) {
> +               op = gpuva_op_alloc(vm_bo->vm);
>                 if (!op) {
>                         ret = -ENOMEM;
>                         goto err_free_ops;
> @@ -1745,10 +1986,10 @@ drm_gpuvm_gem_unmap_ops_create(struct
> drm_gpuvm *gpuvm,
>         return ops;
>  
>  err_free_ops:
> -       drm_gpuva_ops_free(gpuvm, ops);
> +       drm_gpuva_ops_free(vm_bo->vm, ops);
>         return ERR_PTR(ret);
>  }
> -EXPORT_SYMBOL_GPL(drm_gpuvm_gem_unmap_ops_create);
> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_unmap_ops_create);
>  
>  /**
>   * drm_gpuva_ops_free() - free the given &drm_gpuva_ops
> diff --git a/drivers/gpu/drm/nouveau/nouveau_uvmm.c
> b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
> index ed439bf4032f..1e95b0a1b047 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_uvmm.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
> @@ -62,6 +62,8 @@ struct bind_job_op {
>         enum vm_bind_op op;
>         u32 flags;
>  
> +       struct drm_gpuvm_bo *vm_bo;
> +
>         struct {
>                 u64 addr;
>                 u64 range;
> @@ -1113,22 +1115,28 @@ bind_validate_region(struct nouveau_job *job)
>  }
>  
>  static void
> -bind_link_gpuvas(struct drm_gpuva_ops *ops, struct
> nouveau_uvma_prealloc *new)
> +bind_link_gpuvas(struct bind_job_op *bop)
>  {
> +       struct nouveau_uvma_prealloc *new = &bop->new;
> +       struct drm_gpuvm_bo *vm_bo = bop->vm_bo;
> +       struct drm_gpuva_ops *ops = bop->ops;
>         struct drm_gpuva_op *op;
>  
>         drm_gpuva_for_each_op(op, ops) {
>                 switch (op->op) {
>                 case DRM_GPUVA_OP_MAP:
> -                       drm_gpuva_link(&new->map->va);
> +                       drm_gpuva_link(&new->map->va, vm_bo);
>                         break;
> -               case DRM_GPUVA_OP_REMAP:
> +               case DRM_GPUVA_OP_REMAP: {
> +                       struct drm_gpuva *va = op->remap.unmap->va;
> +
>                         if (op->remap.prev)
> -                               drm_gpuva_link(&new->prev->va);
> +                               drm_gpuva_link(&new->prev->va, va-
> >vm_bo);
>                         if (op->remap.next)
> -                               drm_gpuva_link(&new->next->va);
> -                       drm_gpuva_unlink(op->remap.unmap->va);
> +                               drm_gpuva_link(&new->next->va, va-
> >vm_bo);
> +                       drm_gpuva_unlink(va);
>                         break;
> +               }
>                 case DRM_GPUVA_OP_UNMAP:
>                         drm_gpuva_unlink(op->unmap.va);
>                         break;
> @@ -1150,10 +1158,18 @@ nouveau_uvmm_bind_job_submit(struct
> nouveau_job *job)
>  
>         list_for_each_op(op, &bind_job->ops) {
>                 if (op->op == OP_MAP) {
> -                       op->gem.obj = drm_gem_object_lookup(job-
> >file_priv,
> -                                                           op-
> >gem.handle);
> -                       if (!op->gem.obj)
> +                       struct drm_gem_object *obj;
> +
> +                       obj = drm_gem_object_lookup(job->file_priv,
> +                                                   op->gem.handle);
> +                       if (!(op->gem.obj = obj))
>                                 return -ENOENT;
> +
> +                       dma_resv_lock(obj->resv, NULL);
> +                       op->vm_bo = drm_gpuvm_bo_obtain(&uvmm->base,
> obj);
> +                       dma_resv_unlock(obj->resv);
> +                       if (IS_ERR(op->vm_bo))
> +                               return PTR_ERR(op->vm_bo);
>                 }
>  
>                 ret = bind_validate_op(job, op);
> @@ -1364,7 +1380,7 @@ nouveau_uvmm_bind_job_submit(struct nouveau_job
> *job)
>                 case OP_UNMAP_SPARSE:
>                 case OP_MAP:
>                 case OP_UNMAP:
> -                       bind_link_gpuvas(op->ops, &op->new);
> +                       bind_link_gpuvas(op);
>                         break;
>                 default:
>                         break;
> @@ -1511,6 +1527,12 @@ nouveau_uvmm_bind_job_free_work_fn(struct
> work_struct *work)
>                 if (!IS_ERR_OR_NULL(op->ops))
>                         drm_gpuva_ops_free(&uvmm->base, op->ops);
>  
> +               if (!IS_ERR_OR_NULL(op->vm_bo)) {
> +                       dma_resv_lock(obj->resv, NULL);
> +                       drm_gpuvm_bo_put(op->vm_bo);
> +                       dma_resv_unlock(obj->resv);
> +               }
> +
>                 if (obj)
>                         drm_gem_object_put(obj);
>         }
> @@ -1776,15 +1798,18 @@ void
>  nouveau_uvmm_bo_map_all(struct nouveau_bo *nvbo, struct nouveau_mem
> *mem)
>  {
>         struct drm_gem_object *obj = &nvbo->bo.base;
> +       struct drm_gpuvm_bo *vm_bo;
>         struct drm_gpuva *va;
>  
>         dma_resv_assert_held(obj->resv);
>  
> -       drm_gem_for_each_gpuva(va, obj) {
> -               struct nouveau_uvma *uvma = uvma_from_va(va);
> +       drm_gem_for_each_gpuvm_bo(vm_bo, obj) {
> +               drm_gpuvm_bo_for_each_va(va, vm_bo) {
> +                       struct nouveau_uvma *uvma = uvma_from_va(va);
>  
> -               nouveau_uvma_map(uvma, mem);
> -               drm_gpuva_invalidate(va, false);
> +                       nouveau_uvma_map(uvma, mem);
> +                       drm_gpuva_invalidate(va, false);
> +               }
>         }
>  }
>  
> @@ -1792,15 +1817,18 @@ void
>  nouveau_uvmm_bo_unmap_all(struct nouveau_bo *nvbo)
>  {
>         struct drm_gem_object *obj = &nvbo->bo.base;
> +       struct drm_gpuvm_bo *vm_bo;
>         struct drm_gpuva *va;
>  
>         dma_resv_assert_held(obj->resv);
>  
> -       drm_gem_for_each_gpuva(va, obj) {
> -               struct nouveau_uvma *uvma = uvma_from_va(va);
> +       drm_gem_for_each_gpuvm_bo(vm_bo, obj) {
> +               drm_gpuvm_bo_for_each_va(va, vm_bo) {
> +                       struct nouveau_uvma *uvma = uvma_from_va(va);
>  
> -               nouveau_uvma_unmap(uvma);
> -               drm_gpuva_invalidate(va, true);
> +                       nouveau_uvma_unmap(uvma);
> +                       drm_gpuva_invalidate(va, true);
> +               }
>         }
>  }
>  
> diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
> index 16364487fde9..369505447acd 100644
> --- a/include/drm/drm_gem.h
> +++ b/include/drm/drm_gem.h
> @@ -580,7 +580,7 @@ int drm_gem_evict(struct drm_gem_object *obj);
>   * drm_gem_gpuva_init() - initialize the gpuva list of a GEM object
>   * @obj: the &drm_gem_object
>   *
> - * This initializes the &drm_gem_object's &drm_gpuva list.
> + * This initializes the &drm_gem_object's &drm_gpuvm_bo list.
>   *
>   * Calling this function is only necessary for drivers intending to
> support the
>   * &drm_driver_feature DRIVER_GEM_GPUVA.
> @@ -593,28 +593,28 @@ static inline void drm_gem_gpuva_init(struct
> drm_gem_object *obj)
>  }
>  
>  /**
> - * drm_gem_for_each_gpuva() - iternator to walk over a list of
> gpuvas
> - * @entry__: &drm_gpuva structure to assign to in each iteration
> step
> - * @obj__: the &drm_gem_object the &drm_gpuvas to walk are
> associated with
> + * drm_gem_for_each_gpuvm_bo() - iterator to walk over a list of
> &drm_gpuvm_bo
> + * @entry__: &drm_gpuvm_bo structure to assign to in each iteration
> step
> + * @obj__: the &drm_gem_object the &drm_gpuvm_bo to walk are
> associated with
>   *
> - * This iterator walks over all &drm_gpuva structures associated
> with the
> - * &drm_gpuva_manager.
> + * This iterator walks over all &drm_gpuvm_bo structures associated
> with the
> + * &drm_gem_object.
>   */
> -#define drm_gem_for_each_gpuva(entry__, obj__) \
> -       list_for_each_entry(entry__, &(obj__)->gpuva.list, gem.entry)
> +#define drm_gem_for_each_gpuvm_bo(entry__, obj__) \
> +       list_for_each_entry(entry__, &(obj__)->gpuva.list,
> list.entry.gem)
>  
>  /**
> - * drm_gem_for_each_gpuva_safe() - iternator to safely walk over a
> list of
> - * gpuvas
> - * @entry__: &drm_gpuva structure to assign to in each iteration
> step
> - * @next__: &next &drm_gpuva to store the next step
> - * @obj__: the &drm_gem_object the &drm_gpuvas to walk are
> associated with
> + * drm_gem_for_each_gpuvm_bo_safe() - iterator to safely walk over a
> list of
> + * &drm_gpuvm_bo
> + * @entry__: &drm_gpuvm_bostructure to assign to in each iteration
> step
> + * @next__: &next &drm_gpuvm_bo to store the next step
> + * @obj__: the &drm_gem_object the &drm_gpuvm_bo to walk are
> associated with
>   *
> - * This iterator walks over all &drm_gpuva structures associated
> with the
> + * This iterator walks over all &drm_gpuvm_bo structures associated
> with the
>   * &drm_gem_object. It is implemented with
> list_for_each_entry_safe(), hence
>   * it is save against removal of elements.
>   */
> -#define drm_gem_for_each_gpuva_safe(entry__, next__, obj__) \
> -       list_for_each_entry_safe(entry__, next__, &(obj__)-
> >gpuva.list, gem.entry)
> +#define drm_gem_for_each_gpuvm_bo_safe(entry__, next__, obj__) \
> +       list_for_each_entry_safe(entry__, next__, &(obj__)-
> >gpuva.list, list.entry.gem)
>  
>  #endif /* __DRM_GEM_H__ */
> diff --git a/include/drm/drm_gpuvm.h b/include/drm/drm_gpuvm.h
> index 47cbacb244b9..466fdd76c71a 100644
> --- a/include/drm/drm_gpuvm.h
> +++ b/include/drm/drm_gpuvm.h
> @@ -25,6 +25,7 @@
>   * OTHER DEALINGS IN THE SOFTWARE.
>   */
>  
> +#include <linux/dma-resv.h>
>  #include <linux/list.h>
>  #include <linux/rbtree.h>
>  #include <linux/types.h>
> @@ -33,6 +34,7 @@
>  #include <drm/drm_gem.h>
>  
>  struct drm_gpuvm;
> +struct drm_gpuvm_bo;
>  struct drm_gpuvm_ops;
>  
>  /**
> @@ -73,6 +75,12 @@ struct drm_gpuva {
>          */
>         struct drm_gpuvm *vm;
>  
> +       /**
> +        * @vm_bo: the &drm_gpuvm_bo abstraction for the mapped
> +        * &drm_gem_object
> +        */
> +       struct drm_gpuvm_bo *vm_bo;
> +
>         /**
>          * @flags: the &drm_gpuva_flags for this mapping
>          */
> @@ -108,7 +116,7 @@ struct drm_gpuva {
>                 struct drm_gem_object *obj;
>  
>                 /**
> -                * @entry: the &list_head to attach this object to a
> &drm_gem_object
> +                * @entry: the &list_head to attach this object to a
> &drm_gpuvm_bo
>                  */
>                 struct list_head entry;
>         } gem;
> @@ -141,7 +149,7 @@ struct drm_gpuva {
>  int drm_gpuva_insert(struct drm_gpuvm *gpuvm, struct drm_gpuva *va);
>  void drm_gpuva_remove(struct drm_gpuva *va);
>  
> -void drm_gpuva_link(struct drm_gpuva *va);
> +void drm_gpuva_link(struct drm_gpuva *va, struct drm_gpuvm_bo
> *vm_bo);
>  void drm_gpuva_unlink(struct drm_gpuva *va);
>  
>  struct drm_gpuva *drm_gpuva_find(struct drm_gpuvm *gpuvm,
> @@ -188,10 +196,16 @@ static inline bool drm_gpuva_invalidated(struct
> drm_gpuva *va)
>   * enum drm_gpuvm_flags - flags for struct drm_gpuvm
>   */
>  enum drm_gpuvm_flags {
> +       /**
> +        * @DRM_GPUVM_RESV_PROTECTED: GPUVM is protected externally
> by the
> +        * GPUVM's &dma_resv lock
> +        */
> +       DRM_GPUVM_RESV_PROTECTED = BIT(0),
> +
>         /**
>          * @DRM_GPUVM_USERBITS: user defined bits
>          */
> -       DRM_GPUVM_USERBITS = BIT(0),
> +       DRM_GPUVM_USERBITS = BIT(1),
>  };
>  
>  /**
> @@ -280,6 +294,19 @@ bool drm_gpuvm_interval_empty(struct drm_gpuvm
> *gpuvm, u64 addr, u64 range);
>  struct drm_gem_object *
>  drm_gpuvm_resv_object_alloc(struct drm_device *drm);
>  
> +/**
> + * drm_gpuvm_resv_protected() - indicates whether
> &DRM_GPUVM_RESV_PROTECTED is
> + * set
> + * @gpuvm: the &drm_gpuvm
> + *
> + * Returns: true if &DRM_GPUVM_RESV_PROTECTED is set, false
> otherwise.
> + */
> +static inline bool
> +drm_gpuvm_resv_protected(struct drm_gpuvm *gpuvm)
> +{
> +       return gpuvm->flags & DRM_GPUVM_RESV_PROTECTED;
> +}
> +
>  /**
>   * drm_gpuvm_resv() - returns the &drm_gpuvm's &dma_resv
>   * @gpuvm__: the &drm_gpuvm
> @@ -298,6 +325,12 @@ drm_gpuvm_resv_object_alloc(struct drm_device
> *drm);
>   */
>  #define drm_gpuvm_resv_obj(gpuvm__) ((gpuvm__)->r_obj)
>  
> +#define drm_gpuvm_resv_held(gpuvm__) \
> +       dma_resv_held(drm_gpuvm_resv(gpuvm__))
> +
> +#define drm_gpuvm_resv_assert_held(gpuvm__) \
> +       dma_resv_assert_held(drm_gpuvm_resv(gpuvm__))
> +
>  #define drm_gpuvm_resv_held(gpuvm__) \
>         dma_resv_held(drm_gpuvm_resv(gpuvm__))
>  
> @@ -382,6 +415,128 @@ __drm_gpuva_next(struct drm_gpuva *va)
>  #define drm_gpuvm_for_each_va_safe(va__, next__, gpuvm__) \
>         list_for_each_entry_safe(va__, next__, &(gpuvm__)->rb.list,
> rb.entry)
>  
> +/**
> + * struct drm_gpuvm_bo - structure representing a &drm_gpuvm and
> + * &drm_gem_object combination
> + *
> + * This structure is an abstraction representing a &drm_gpuvm and
> + * &drm_gem_object combination. It serves as an indirection to
> accelerate
> + * iterating all &drm_gpuvas within a &drm_gpuvm backed by the same
> + * &drm_gem_object.
> + *
> + * Furthermore it is used cache evicted GEM objects for a certain
> GPU-VM to
> + * accelerate validation.
> + *
> + * Typically, drivers want to create an instance of a struct
> drm_gpuvm_bo once
> + * a GEM object is mapped first in a GPU-VM and release the instance
> once the
> + * last mapping of the GEM object in this GPU-VM is unmapped.
> + */
> +struct drm_gpuvm_bo {
> +       /**
> +        * @vm: The &drm_gpuvm the @obj is mapped in. This pointer is
> not
> +        * reference counted.
> +        *
> +        * A struct drm_gpuvm_bo is not allowed to out-live its
> &drm_gpuvm
> +        * context. Implicitly, this is ensured by the fact that the
> driver is
> +        * responsible to ensure the VM doesn't contain mappings once
> it's
> +        * freed, since a struct drm_gpuvm_bo should be freed once
> the last
> +        * mapping being backed by the corresponding buffer object is
> unmapped.
> +        */


I don't think the above is completely true. Let's assume in the
!RESV_PROTECTED case that a reference is grabbed on the drm_gpuvm_bo
during an iteration over a list. Then user-space closes the vm and all
vmas are unlinked, but this reference remains but the vm pointer
becomes stale. In the RESV_PROTECTED case this is ensured not to happen
if by the vm->resv being grabbed during unlink, but in the
!RESV_PROTECTED case, the above wording isn't sufficient. The caller
needs to ensure the vm stays alive using some sort of similar rule or
use kref_get_unless_zero() on the vm under the spinlock if
dereferenced.

> +       struct drm_gpuvm *vm;
> +
> +       /**
> +        * @obj: The &drm_gem_object being mapped in @vm. This is a
> reference
> +        * counted pointer.
> +        */
> +       struct drm_gem_object *obj;
> +
> +       /**
> +        * @kref: The reference count for this &drm_gpuvm_bo.
> +        */
> +       struct kref kref;
> +
> +       /**
> +        * @list: Structure containing all &list_heads.
> +        */
> +       struct {
> +               /**
> +                * @gpuva: The list of linked &drm_gpuvas.
> +                */
> +               struct list_head gpuva;

Still missing doc on how the @gpuva stays alive during iteration over
the list?



8<-------------------------------------------------------------

Thanks,
Thomas
  

On Mon, 2023-10-23 at 22:16 +0200, Danilo Krummrich wrote:
> Add an abstraction layer between the drm_gpuva mappings of a
> particular
> drm_gem_object and this GEM object itself. The abstraction represents
> a
> combination of a drm_gem_object and drm_gpuvm. The drm_gem_object
> holds
> a list of drm_gpuvm_bo structures (the structure representing this
> abstraction), while each drm_gpuvm_bo contains list of mappings of
> this
> GEM object.
> 
> This has multiple advantages:
> 
> 1) We can use the drm_gpuvm_bo structure to attach it to various
> lists
>    of the drm_gpuvm. This is useful for tracking external and evicted
>    objects per VM, which is introduced in subsequent patches.
> 
> 2) Finding mappings of a certain drm_gem_object mapped in a certain
>    drm_gpuvm becomes much cheaper.
> 
> 3) Drivers can derive and extend the structure to easily represent
>    driver specific states of a BO for a certain GPUVM.
> 
> The idea of this abstraction was taken from amdgpu, hence the credit
> for
> this idea goes to the developers of amdgpu.
> 
> Cc: Christian König <christian.koenig@amd.com>
> Signed-off-by: Danilo Krummrich <dakr@redhat.com>
> ---
>  drivers/gpu/drm/drm_gpuvm.c            | 335 +++++++++++++++++++++--
> --
>  drivers/gpu/drm/nouveau/nouveau_uvmm.c |  64 +++--
>  include/drm/drm_gem.h                  |  32 +--
>  include/drm/drm_gpuvm.h                | 188 +++++++++++++-
>  4 files changed, 533 insertions(+), 86 deletions(-)

That checkpatch.pl error still remains as well.

Thanks,
Thomas
  

On Tue, 31 Oct 2023, Thomas Hellström <thomas.hellstrom@linux.intel.com> wrote:
> On Mon, 2023-10-23 at 22:16 +0200, Danilo Krummrich wrote:
>> + * Returns: a pointer to the &drm_gpuvm_bo on success, NULL on
>
> Still needs s/Returns:/Return:/g

FWIW, both work to accommodate the variance across the kernel, although
I think only the latter is documented and recommended. It's also the
most popular:

  10577 Return
   3596 Returns
   1104 RETURN
    568 return
    367 returns
    352 RETURNS
      1 RETURNs

BR,
Jani.
  

On 10/31/23 12:45, Jani Nikula wrote:
> On Tue, 31 Oct 2023, Thomas Hellström <thomas.hellstrom@linux.intel.com> wrote:
>> On Mon, 2023-10-23 at 22:16 +0200, Danilo Krummrich wrote:
>>> + * Returns: a pointer to the &drm_gpuvm_bo on success, NULL on
>>
>> Still needs s/Returns:/Return:/g
> 
> FWIW, both work to accommodate the variance across the kernel, although
> I think only the latter is documented and recommended. It's also the
> most popular:
> 
>    10577 Return
>     3596 Returns

I'd like to keep "Returns", since that's what GPUVM uses already everywhere else.

>     1104 RETURN
>      568 return
>      367 returns
>      352 RETURNS
>        1 RETURNs
> 
> BR,
> Jani.
> 
>
  

On 10/31/23 12:25, Thomas Hellström wrote:
> On Mon, 2023-10-23 at 22:16 +0200, Danilo Krummrich wrote:
>> Add an abstraction layer between the drm_gpuva mappings of a
>> particular
>> drm_gem_object and this GEM object itself. The abstraction represents
>> a
>> combination of a drm_gem_object and drm_gpuvm. The drm_gem_object
>> holds
>> a list of drm_gpuvm_bo structures (the structure representing this
>> abstraction), while each drm_gpuvm_bo contains list of mappings of
>> this
>> GEM object.
>>
>> This has multiple advantages:
>>
>> 1) We can use the drm_gpuvm_bo structure to attach it to various
>> lists
>>     of the drm_gpuvm. This is useful for tracking external and evicted
>>     objects per VM, which is introduced in subsequent patches.
>>
>> 2) Finding mappings of a certain drm_gem_object mapped in a certain
>>     drm_gpuvm becomes much cheaper.
>>
>> 3) Drivers can derive and extend the structure to easily represent
>>     driver specific states of a BO for a certain GPUVM.
>>
>> The idea of this abstraction was taken from amdgpu, hence the credit
>> for
>> this idea goes to the developers of amdgpu.
>>
>> Cc: Christian König <christian.koenig@amd.com>
>> Signed-off-by: Danilo Krummrich <dakr@redhat.com>
>> ---
>>   drivers/gpu/drm/drm_gpuvm.c            | 335 +++++++++++++++++++++--
>> --
>>   drivers/gpu/drm/nouveau/nouveau_uvmm.c |  64 +++--
>>   include/drm/drm_gem.h                  |  32 +--
>>   include/drm/drm_gpuvm.h                | 188 +++++++++++++-
>>   4 files changed, 533 insertions(+), 86 deletions(-)
> 
> That checkpatch.pl error still remains as well.

I guess you refer to:

ERROR: do not use assignment in if condition
#633: FILE: drivers/gpu/drm/nouveau/nouveau_uvmm.c:1165:
+                       if (!(op->gem.obj = obj))

This was an intentional decision, since in this specific case it seems to
be more readable than the alternatives.

However, if we consider this to be a hard rule, which we never ever break,
I'm fine changing it too.

> 
> Thanks,
> Thomas
>
  

On Tue, 2023-10-31 at 17:39 +0100, Danilo Krummrich wrote:
> On 10/31/23 12:25, Thomas Hellström wrote:
> > On Mon, 2023-10-23 at 22:16 +0200, Danilo Krummrich wrote:
> > > Add an abstraction layer between the drm_gpuva mappings of a
> > > particular
> > > drm_gem_object and this GEM object itself. The abstraction
> > > represents
> > > a
> > > combination of a drm_gem_object and drm_gpuvm. The drm_gem_object
> > > holds
> > > a list of drm_gpuvm_bo structures (the structure representing
> > > this
> > > abstraction), while each drm_gpuvm_bo contains list of mappings
> > > of
> > > this
> > > GEM object.
> > > 
> > > This has multiple advantages:
> > > 
> > > 1) We can use the drm_gpuvm_bo structure to attach it to various
> > > lists
> > >     of the drm_gpuvm. This is useful for tracking external and
> > > evicted
> > >     objects per VM, which is introduced in subsequent patches.
> > > 
> > > 2) Finding mappings of a certain drm_gem_object mapped in a
> > > certain
> > >     drm_gpuvm becomes much cheaper.
> > > 
> > > 3) Drivers can derive and extend the structure to easily
> > > represent
> > >     driver specific states of a BO for a certain GPUVM.
> > > 
> > > The idea of this abstraction was taken from amdgpu, hence the
> > > credit
> > > for
> > > this idea goes to the developers of amdgpu.
> > > 
> > > Cc: Christian König <christian.koenig@amd.com>
> > > Signed-off-by: Danilo Krummrich <dakr@redhat.com>
> > > ---
> > >   drivers/gpu/drm/drm_gpuvm.c            | 335
> > > +++++++++++++++++++++--
> > > --
> > >   drivers/gpu/drm/nouveau/nouveau_uvmm.c |  64 +++--
> > >   include/drm/drm_gem.h                  |  32 +--
> > >   include/drm/drm_gpuvm.h                | 188 +++++++++++++-
> > >   4 files changed, 533 insertions(+), 86 deletions(-)
> > 
> > That checkpatch.pl error still remains as well.
> 
> I guess you refer to:
> 
> ERROR: do not use assignment in if condition
> #633: FILE: drivers/gpu/drm/nouveau/nouveau_uvmm.c:1165:
> +                       if (!(op->gem.obj = obj))
> 
> This was an intentional decision, since in this specific case it
> seems to
> be more readable than the alternatives.
> 
> However, if we consider this to be a hard rule, which we never ever
> break,
> I'm fine changing it too.

With the errors, sooner or later they are going to start generate
patches to "fix" them. In this particular case also Xe CI is
complaining and abort building when I submit the Xe adaptation, so it'd
be good to be checkpatch.pl conformant IMHO.

Thanks,
Thomas




> 
> > 
> > Thanks,
> > Thomas
> > 
>
  

On Tue, 2023-10-31 at 17:30 +0100, Danilo Krummrich wrote:
> On 10/31/23 12:45, Jani Nikula wrote:
> > On Tue, 31 Oct 2023, Thomas Hellström
> > <thomas.hellstrom@linux.intel.com> wrote:
> > > On Mon, 2023-10-23 at 22:16 +0200, Danilo Krummrich wrote:
> > > > + * Returns: a pointer to the &drm_gpuvm_bo on success, NULL on
> > > 
> > > Still needs s/Returns:/Return:/g
> > 
> > FWIW, both work to accommodate the variance across the kernel,
> > although
> > I think only the latter is documented and recommended. It's also
> > the
> > most popular:
> > 
> >    10577 Return
> >     3596 Returns
> 
> I'd like to keep "Returns", since that's what GPUVM uses already
> everywhere else.

Ok. It looks like the Returns: are converted to Return in the rendered
output so I guess that's why it's the form that is documented.

I pointed this out since in the last review you replied you were going
to change it, and also when the code starts seeing updates from other,
it might become inconsistent if those patches follow the documented
way.

But I'm OK either way.

/Thomas


> 
> >     1104 RETURN
> >      568 return
> >      367 returns
> >      352 RETURNS
> >        1 RETURNs
> > 
> > BR,
> > Jani.
> > 
> > 
>
  

On 10/31/23 11:32, Thomas Hellström wrote:
> On Mon, 2023-10-23 at 22:16 +0200, Danilo Krummrich wrote:
>> Add an abstraction layer between the drm_gpuva mappings of a
>> particular
>> drm_gem_object and this GEM object itself. The abstraction represents
>> a
>> combination of a drm_gem_object and drm_gpuvm. The drm_gem_object
>> holds
>> a list of drm_gpuvm_bo structures (the structure representing this
>> abstraction), while each drm_gpuvm_bo contains list of mappings of
>> this
>> GEM object.
>>
>> This has multiple advantages:
>>
>> 1) We can use the drm_gpuvm_bo structure to attach it to various
>> lists
>>     of the drm_gpuvm. This is useful for tracking external and evicted
>>     objects per VM, which is introduced in subsequent patches.
>>
>> 2) Finding mappings of a certain drm_gem_object mapped in a certain
>>     drm_gpuvm becomes much cheaper.
>>
>> 3) Drivers can derive and extend the structure to easily represent
>>     driver specific states of a BO for a certain GPUVM.
>>
>> The idea of this abstraction was taken from amdgpu, hence the credit
>> for
>> this idea goes to the developers of amdgpu.
>>
>> Cc: Christian König <christian.koenig@amd.com>
>> Signed-off-by: Danilo Krummrich <dakr@redhat.com>
>> ---
>>   drivers/gpu/drm/drm_gpuvm.c            | 335 +++++++++++++++++++++--
>> --
>>   drivers/gpu/drm/nouveau/nouveau_uvmm.c |  64 +++--
>>   include/drm/drm_gem.h                  |  32 +--
>>   include/drm/drm_gpuvm.h                | 188 +++++++++++++-
>>   4 files changed, 533 insertions(+), 86 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_gpuvm.c
>> b/drivers/gpu/drm/drm_gpuvm.c
>> index c03332883432..7f4f5919f84c 100644
>> --- a/drivers/gpu/drm/drm_gpuvm.c
>> +++ b/drivers/gpu/drm/drm_gpuvm.c
>> @@ -70,6 +70,18 @@
>>    * &drm_gem_object, such as the &drm_gem_object containing the root
>> page table,
>>    * but it can also be a 'dummy' object, which can be allocated with
>>    * drm_gpuvm_resv_object_alloc().
>> + *
>> + * In order to connect a struct drm_gpuva its backing
>> &drm_gem_object each
>> + * &drm_gem_object maintains a list of &drm_gpuvm_bo structures, and
>> each
>> + * &drm_gpuvm_bo contains a list of &drm_gpuva structures.
>> + *
>> + * A &drm_gpuvm_bo is an abstraction that represents a combination
>> of a
>> + * &drm_gpuvm and a &drm_gem_object. Every such combination should
>> be unique.
>> + * This is ensured by the API through drm_gpuvm_bo_obtain() and
>> + * drm_gpuvm_bo_obtain_prealloc() which first look into the
>> corresponding
>> + * &drm_gem_object list of &drm_gpuvm_bos for an existing instance
>> of this
>> + * particular combination. If not existent a new instance is created
>> and linked
>> + * to the &drm_gem_object.
>>    */
>>   
>>   /**
>> @@ -395,21 +407,28 @@
>>   /**
>>    * DOC: Locking
>>    *
>> - * Generally, the GPU VA manager does not take care of locking
>> itself, it is
>> - * the drivers responsibility to take care about locking. Drivers
>> might want to
>> - * protect the following operations: inserting, removing and
>> iterating
>> - * &drm_gpuva objects as well as generating all kinds of operations,
>> such as
>> - * split / merge or prefetch.
>> - *
>> - * The GPU VA manager also does not take care of the locking of the
>> backing
>> - * &drm_gem_object buffers GPU VA lists by itself; drivers are
>> responsible to
>> - * enforce mutual exclusion using either the GEMs dma_resv lock or
>> alternatively
>> - * a driver specific external lock. For the latter see also
>> - * drm_gem_gpuva_set_lock().
>> - *
>> - * However, the GPU VA manager contains lockdep checks to ensure
>> callers of its
>> - * API hold the corresponding lock whenever the &drm_gem_objects GPU
>> VA list is
>> - * accessed by functions such as drm_gpuva_link() or
>> drm_gpuva_unlink().
>> + * In terms of managing &drm_gpuva entries DRM GPUVM does not take
>> care of
>> + * locking itself, it is the drivers responsibility to take care
>> about locking.
>> + * Drivers might want to protect the following operations:
>> inserting, removing
>> + * and iterating &drm_gpuva objects as well as generating all kinds
>> of
>> + * operations, such as split / merge or prefetch.
>> + *
>> + * DRM GPUVM also does not take care of the locking of the backing
>> + * &drm_gem_object buffers GPU VA lists and &drm_gpuvm_bo
>> abstractions by
>> + * itself; drivers are responsible to enforce mutual exclusion using
>> either the
>> + * GEMs dma_resv lock or alternatively a driver specific external
>> lock. For the
>> + * latter see also drm_gem_gpuva_set_lock().
>> + *
>> + * However, DRM GPUVM contains lockdep checks to ensure callers of
>> its API hold
>> + * the corresponding lock whenever the &drm_gem_objects GPU VA list
>> is accessed
>> + * by functions such as drm_gpuva_link() or drm_gpuva_unlink(), but
>> also
>> + * drm_gpuvm_bo_obtain() and drm_gpuvm_bo_put().
>> + *
>> + * The latter is required since on creation and destruction of a
>> &drm_gpuvm_bo
>> + * the &drm_gpuvm_bo is attached / removed from the &drm_gem_objects
>> gpuva list.
>> + * Subsequent calls to drm_gpuvm_bo_obtain() for the same &drm_gpuvm
>> and
>> + * &drm_gem_object must be able to observe previous creations and
>> destructions
>> + * of &drm_gpuvm_bos in order to keep instances unique.
>>    */
>>   
>>   /**
>> @@ -439,6 +458,7 @@
>>    *     {
>>    *             struct drm_gpuva_ops *ops;
>>    *             struct drm_gpuva_op *op
>> + *             struct drm_gpuvm_bo *vm_bo;
>>    *
>>    *             driver_lock_va_space();
>>    *             ops = drm_gpuvm_sm_map_ops_create(gpuvm, addr, range,
>> @@ -446,6 +466,10 @@
>>    *             if (IS_ERR(ops))
>>    *                     return PTR_ERR(ops);
>>    *
>> + *             vm_bo = drm_gpuvm_bo_obtain(gpuvm, obj);
>> + *             if (IS_ERR(vm_bo))
>> + *                     return PTR_ERR(vm_bo);
>> + *
>>    *             drm_gpuva_for_each_op(op, ops) {
>>    *                     struct drm_gpuva *va;
>>    *
>> @@ -458,7 +482,7 @@
>>    *
>>    *                             driver_vm_map();
>>    *                             drm_gpuva_map(gpuvm, va, &op->map);
>> - *                             drm_gpuva_link(va);
>> + *                             drm_gpuva_link(va, vm_bo);
>>    *
>>    *                             break;
>>    *                     case DRM_GPUVA_OP_REMAP: {
>> @@ -485,11 +509,11 @@
>>    *                             driver_vm_remap();
>>    *                             drm_gpuva_remap(prev, next, &op-
>>> remap);
>>    *
>> - *                             drm_gpuva_unlink(va);
>>    *                             if (prev)
>> - *                                     drm_gpuva_link(prev);
>> + *                                     drm_gpuva_link(prev, va-
>>> vm_bo);
>>    *                             if (next)
>> - *                                     drm_gpuva_link(next);
>> + *                                     drm_gpuva_link(next, va-
>>> vm_bo);
>> + *                             drm_gpuva_unlink(va);
>>    *
>>    *                             break;
>>    *                     }
>> @@ -505,6 +529,7 @@
>>    *                             break;
>>    *                     }
>>    *             }
>> + *             drm_gpuvm_bo_put(vm_bo);
>>    *             driver_unlock_va_space();
>>    *
>>    *             return 0;
>> @@ -514,6 +539,7 @@
>>    *
>>    *     struct driver_context {
>>    *             struct drm_gpuvm *gpuvm;
>> + *             struct drm_gpuvm_bo *vm_bo;
>>    *             struct drm_gpuva *new_va;
>>    *             struct drm_gpuva *prev_va;
>>    *             struct drm_gpuva *next_va;
>> @@ -534,6 +560,7 @@
>>    *                               struct drm_gem_object *obj, u64
>> offset)
>>    *     {
>>    *             struct driver_context ctx;
>> + *             struct drm_gpuvm_bo *vm_bo;
>>    *             struct drm_gpuva_ops *ops;
>>    *             struct drm_gpuva_op *op;
>>    *             int ret = 0;
>> @@ -543,16 +570,23 @@
>>    *             ctx.new_va = kzalloc(sizeof(*ctx.new_va),
>> GFP_KERNEL);
>>    *             ctx.prev_va = kzalloc(sizeof(*ctx.prev_va),
>> GFP_KERNEL);
>>    *             ctx.next_va = kzalloc(sizeof(*ctx.next_va),
>> GFP_KERNEL);
>> - *             if (!ctx.new_va || !ctx.prev_va || !ctx.next_va) {
>> + *             ctx.vm_bo = drm_gpuvm_bo_create(gpuvm, obj);
>> + *             if (!ctx.new_va || !ctx.prev_va || !ctx.next_va ||
>> !vm_bo) {
>>    *                     ret = -ENOMEM;
>>    *                     goto out;
>>    *             }
>>    *
>> + *             // Typically protected with a driver specific GEM
>> gpuva lock
>> + *             // used in the fence signaling path for
>> drm_gpuva_link() and
>> + *             // drm_gpuva_unlink(), hence pre-allocate.
>> + *             ctx.vm_bo = drm_gpuvm_bo_obtain_prealloc(ctx.vm_bo);
>> + *
>>    *             driver_lock_va_space();
>>    *             ret = drm_gpuvm_sm_map(gpuvm, &ctx, addr, range, obj,
>> offset);
>>    *             driver_unlock_va_space();
>>    *
>>    *     out:
>> + *             drm_gpuvm_bo_put(ctx.vm_bo);
>>    *             kfree(ctx.new_va);
>>    *             kfree(ctx.prev_va);
>>    *             kfree(ctx.next_va);
>> @@ -565,7 +599,7 @@
>>    *
>>    *             drm_gpuva_map(ctx->vm, ctx->new_va, &op->map);
>>    *
>> - *             drm_gpuva_link(ctx->new_va);
>> + *             drm_gpuva_link(ctx->new_va, ctx->vm_bo);
>>    *
>>    *             // prevent the new GPUVA from being freed in
>>    *             // driver_mapping_create()
>> @@ -577,22 +611,23 @@
>>    *     int driver_gpuva_remap(struct drm_gpuva_op *op, void *__ctx)
>>    *     {
>>    *             struct driver_context *ctx = __ctx;
>> + *             struct drm_gpuva *va = op->remap.unmap->va;
>>    *
>>    *             drm_gpuva_remap(ctx->prev_va, ctx->next_va, &op-
>>> remap);
>>    *
>> - *             drm_gpuva_unlink(op->remap.unmap->va);
>> - *             kfree(op->remap.unmap->va);
>> - *
>>    *             if (op->remap.prev) {
>> - *                     drm_gpuva_link(ctx->prev_va);
>> + *                     drm_gpuva_link(ctx->prev_va, va->vm_bo);
>>    *                     ctx->prev_va = NULL;
>>    *             }
>>    *
>>    *             if (op->remap.next) {
>> - *                     drm_gpuva_link(ctx->next_va);
>> + *                     drm_gpuva_link(ctx->next_va, va->vm_bo);
>>    *                     ctx->next_va = NULL;
>>    *             }
>>    *
>> + *             drm_gpuva_unlink(va);
>> + *             kfree(va);
>> + *
>>    *             return 0;
>>    *     }
>>    *
>> @@ -774,6 +809,194 @@ drm_gpuvm_destroy(struct drm_gpuvm *gpuvm)
>>   }
>>   EXPORT_SYMBOL_GPL(drm_gpuvm_destroy);
>>   
>> +/**
>> + * drm_gpuvm_bo_create() - create a new instance of struct
>> drm_gpuvm_bo
>> + * @gpuvm: The &drm_gpuvm the @obj is mapped in.
>> + * @obj: The &drm_gem_object being mapped in the @gpuvm.
>> + *
>> + * If provided by the driver, this function uses the &drm_gpuvm_ops
>> + * vm_bo_alloc() callback to allocate.
>> + *
>> + * Returns: a pointer to the &drm_gpuvm_bo on success, NULL on
> 
> Still needs s/Returns:/Return:/g
> 
>> failure
>> + */
>> +struct drm_gpuvm_bo *
>> +drm_gpuvm_bo_create(struct drm_gpuvm *gpuvm,
>> +                   struct drm_gem_object *obj)
>> +{
>> +       const struct drm_gpuvm_ops *ops = gpuvm->ops;
>> +       struct drm_gpuvm_bo *vm_bo;
>> +
>> +       if (ops && ops->vm_bo_alloc)
>> +               vm_bo = ops->vm_bo_alloc();
>> +       else
>> +               vm_bo = kzalloc(sizeof(*vm_bo), GFP_KERNEL);
>> +
>> +       if (unlikely(!vm_bo))
>> +               return NULL;
>> +
>> +       vm_bo->vm = gpuvm;
>> +       vm_bo->obj = obj;
>> +       drm_gem_object_get(obj);
>> +
>> +       kref_init(&vm_bo->kref);
>> +       INIT_LIST_HEAD(&vm_bo->list.gpuva);
>> +       INIT_LIST_HEAD(&vm_bo->list.entry.gem);
>> +
>> +       return vm_bo;
>> +}
>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_create);
>> +
>> +static void
>> +drm_gpuvm_bo_destroy(struct kref *kref)
>> +{
>> +       struct drm_gpuvm_bo *vm_bo = container_of(kref, struct
>> drm_gpuvm_bo,
>> +                                                 kref);
>> +       struct drm_gpuvm *gpuvm = vm_bo->vm;
>> +       const struct drm_gpuvm_ops *ops = gpuvm->ops;
>> +       struct drm_gem_object *obj = vm_bo->obj;
>> +       bool lock = !drm_gpuvm_resv_protected(gpuvm);
>> +
>> +       if (!lock)
>> +               drm_gpuvm_resv_assert_held(gpuvm);
>> +
>> +       drm_gem_gpuva_assert_lock_held(obj);
>> +       list_del(&vm_bo->list.entry.gem);
>> +
>> +       if (ops && ops->vm_bo_free)
>> +               ops->vm_bo_free(vm_bo);
>> +       else
>> +               kfree(vm_bo);
>> +
>> +       drm_gem_object_put(obj);
>> +}
>> +
>> +/**
>> + * drm_gpuvm_bo_put() - drop a struct drm_gpuvm_bo reference
>> + * @vm_bo: the &drm_gpuvm_bo to release the reference of
>> + *
>> + * This releases a reference to @vm_bo.
>> + *
>> + * If the reference count drops to zero, the &gpuvm_bo is destroyed,
>> which
>> + * includes removing it from the GEMs gpuva list. Hence, if a call
>> to this
>> + * function can potentially let the reference count to zero the
>> caller must
>> + * hold the dma-resv or driver specific GEM gpuva lock.
>> + */
>> +void
>> +drm_gpuvm_bo_put(struct drm_gpuvm_bo *vm_bo)
>> +{
>> +       if (vm_bo)
>> +               kref_put(&vm_bo->kref, drm_gpuvm_bo_destroy);
>> +}
>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_put);
>> +
>> +static struct drm_gpuvm_bo *
>> +__drm_gpuvm_bo_find(struct drm_gpuvm *gpuvm,
>> +                   struct drm_gem_object *obj)
>> +{
>> +       struct drm_gpuvm_bo *vm_bo;
>> +
>> +       drm_gem_gpuva_assert_lock_held(obj);
>> +       drm_gem_for_each_gpuvm_bo(vm_bo, obj)
>> +               if (vm_bo->vm == gpuvm)
>> +                       return vm_bo;
>> +
>> +       return NULL;
>> +}
>> +
>> +/**
>> + * drm_gpuvm_bo_find() - find the &drm_gpuvm_bo for the given
>> + * &drm_gpuvm and &drm_gem_object
>> + * @gpuvm: The &drm_gpuvm the @obj is mapped in.
>> + * @obj: The &drm_gem_object being mapped in the @gpuvm.
>> + *
>> + * Find the &drm_gpuvm_bo representing the combination of the given
>> + * &drm_gpuvm and &drm_gem_object. If found, increases the reference
>> + * count of the &drm_gpuvm_bo accordingly.
>> + *
>> + * Returns: a pointer to the &drm_gpuvm_bo on success, NULL on
>> failure
>> + */
>> +struct drm_gpuvm_bo *
>> +drm_gpuvm_bo_find(struct drm_gpuvm *gpuvm,
>> +                 struct drm_gem_object *obj)
>> +{
>> +       struct drm_gpuvm_bo *vm_bo = __drm_gpuvm_bo_find(gpuvm, obj);
>> +
>> +       return vm_bo ? drm_gpuvm_bo_get(vm_bo) : NULL;
>> +}
>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_find);
>> +
>> +/**
>> + * drm_gpuvm_bo_obtain() - obtains and instance of the &drm_gpuvm_bo
>> for the
>> + * given &drm_gpuvm and &drm_gem_object
>> + * @gpuvm: The &drm_gpuvm the @obj is mapped in.
>> + * @obj: The &drm_gem_object being mapped in the @gpuvm.
>> + *
>> + * Find the &drm_gpuvm_bo representing the combination of the given
>> + * &drm_gpuvm and &drm_gem_object. If found, increases the reference
>> + * count of the &drm_gpuvm_bo accordingly. If not found, allocates a
>> new
>> + * &drm_gpuvm_bo.
>> + *
>> + * A new &drm_gpuvm_bo is added to the GEMs gpuva list.
>> + *
>> + * Returns: a pointer to the &drm_gpuvm_bo on success, an ERR_PTR on
>> failure
>> + */
>> +struct drm_gpuvm_bo *
>> +drm_gpuvm_bo_obtain(struct drm_gpuvm *gpuvm,
>> +                   struct drm_gem_object *obj)
>> +{
>> +       struct drm_gpuvm_bo *vm_bo;
>> +
>> +       vm_bo = drm_gpuvm_bo_find(gpuvm, obj);
>> +       if (vm_bo)
>> +               return vm_bo;
>> +
>> +       vm_bo = drm_gpuvm_bo_create(gpuvm, obj);
>> +       if (!vm_bo)
>> +               return ERR_PTR(-ENOMEM);
>> +
>> +       drm_gem_gpuva_assert_lock_held(obj);
>> +       list_add_tail(&vm_bo->list.entry.gem, &obj->gpuva.list);
>> +
>> +       return vm_bo;
>> +}
>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_obtain);
>> +
>> +/**
>> + * drm_gpuvm_bo_obtain_prealloc() - obtains and instance of the
>> &drm_gpuvm_bo
>> + * for the given &drm_gpuvm and &drm_gem_object
>> + * @__vm_bo: A pre-allocated struct drm_gpuvm_bo.
>> + *
>> + * Find the &drm_gpuvm_bo representing the combination of the given
>> + * &drm_gpuvm and &drm_gem_object. If found, increases the reference
>> + * count of the found &drm_gpuvm_bo accordingly, while the @__vm_bo
>> reference
>> + * count is decreased. If not found @__vm_bo is returned without
>> further
>> + * increase of the reference count.
>> + *
>> + * A new &drm_gpuvm_bo is added to the GEMs gpuva list.
>> + *
>> + * Returns: a pointer to the found &drm_gpuvm_bo or @__vm_bo if no
>> existing
>> + * &drm_gpuvm_bo was found
>> + */
>> +struct drm_gpuvm_bo *
>> +drm_gpuvm_bo_obtain_prealloc(struct drm_gpuvm_bo *__vm_bo)
>> +{
>> +       struct drm_gpuvm *gpuvm = __vm_bo->vm;
>> +       struct drm_gem_object *obj = __vm_bo->obj;
>> +       struct drm_gpuvm_bo *vm_bo;
>> +
>> +       vm_bo = drm_gpuvm_bo_find(gpuvm, obj);
>> +       if (vm_bo) {
>> +               drm_gpuvm_bo_put(__vm_bo);
>> +               return vm_bo;
>> +       }
>> +
>> +       drm_gem_gpuva_assert_lock_held(obj);
>> +       list_add_tail(&__vm_bo->list.entry.gem, &obj->gpuva.list);
>> +
>> +       return __vm_bo;
>> +}
>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_obtain_prealloc);
>> +
>>   static int
>>   __drm_gpuva_insert(struct drm_gpuvm *gpuvm,
>>                     struct drm_gpuva *va)
>> @@ -864,24 +1087,33 @@ EXPORT_SYMBOL_GPL(drm_gpuva_remove);
>>   /**
>>    * drm_gpuva_link() - link a &drm_gpuva
>>    * @va: the &drm_gpuva to link
>> + * @vm_bo: the &drm_gpuvm_bo to add the &drm_gpuva to
>>    *
>> - * This adds the given &va to the GPU VA list of the &drm_gem_object
>> it is
>> - * associated with.
>> + * This adds the given &va to the GPU VA list of the &drm_gpuvm_bo
>> and the
>> + * &drm_gpuvm_bo to the &drm_gem_object it is associated with.
>> + *
>> + * For every &drm_gpuva entry added to the &drm_gpuvm_bo an
>> additional
>> + * reference of the latter is taken.
>>    *
>>    * This function expects the caller to protect the GEM's GPUVA list
>> against
>> - * concurrent access using the GEMs dma_resv lock.
>> + * concurrent access using either the GEMs dma_resv lock or a driver
>> specific
>> + * lock set through drm_gem_gpuva_set_lock().
>>    */
>>   void
>> -drm_gpuva_link(struct drm_gpuva *va)
>> +drm_gpuva_link(struct drm_gpuva *va, struct drm_gpuvm_bo *vm_bo)
>>   {
>>          struct drm_gem_object *obj = va->gem.obj;
>> +       struct drm_gpuvm *gpuvm = va->vm;
>>   
>>          if (unlikely(!obj))
>>                  return;
>>   
>> -       drm_gem_gpuva_assert_lock_held(obj);
>> +       drm_WARN_ON(gpuvm->drm, obj != vm_bo->obj);
>>   
>> -       list_add_tail(&va->gem.entry, &obj->gpuva.list);
>> +       va->vm_bo = drm_gpuvm_bo_get(vm_bo);
>> +
>> +       drm_gem_gpuva_assert_lock_held(obj);
>> +       list_add_tail(&va->gem.entry, &vm_bo->list.gpuva);
>>   }
>>   EXPORT_SYMBOL_GPL(drm_gpuva_link);
>>   
>> @@ -892,20 +1124,31 @@ EXPORT_SYMBOL_GPL(drm_gpuva_link);
>>    * This removes the given &va from the GPU VA list of the
>> &drm_gem_object it is
>>    * associated with.
>>    *
>> + * This removes the given &va from the GPU VA list of the
>> &drm_gpuvm_bo and
>> + * the &drm_gpuvm_bo from the &drm_gem_object it is associated with
>> in case
>> + * this call unlinks the last &drm_gpuva from the &drm_gpuvm_bo.
>> + *
>> + * For every &drm_gpuva entry removed from the &drm_gpuvm_bo a
>> reference of
>> + * the latter is dropped.
>> + *
>>    * This function expects the caller to protect the GEM's GPUVA list
>> against
>> - * concurrent access using the GEMs dma_resv lock.
>> + * concurrent access using either the GEMs dma_resv lock or a driver
>> specific
>> + * lock set through drm_gem_gpuva_set_lock().
>>    */
>>   void
>>   drm_gpuva_unlink(struct drm_gpuva *va)
>>   {
>>          struct drm_gem_object *obj = va->gem.obj;
>> +       struct drm_gpuvm_bo *vm_bo = va->vm_bo;
>>   
>>          if (unlikely(!obj))
>>                  return;
>>   
>>          drm_gem_gpuva_assert_lock_held(obj);
>> -
>>          list_del_init(&va->gem.entry);
>> +
>> +       va->vm_bo = NULL;
>> +       drm_gpuvm_bo_put(vm_bo);
>>   }
>>   EXPORT_SYMBOL_GPL(drm_gpuva_unlink);
>>   
>> @@ -1050,10 +1293,10 @@ drm_gpuva_remap(struct drm_gpuva *prev,
>>                  struct drm_gpuva *next,
>>                  struct drm_gpuva_op_remap *op)
>>   {
>> -       struct drm_gpuva *curr = op->unmap->va;
>> -       struct drm_gpuvm *gpuvm = curr->vm;
>> +       struct drm_gpuva *va = op->unmap->va;
>> +       struct drm_gpuvm *gpuvm = va->vm;
>>   
>> -       drm_gpuva_remove(curr);
>> +       drm_gpuva_remove(va);
>>   
>>          if (op->prev) {
>>                  drm_gpuva_init_from_op(prev, op->prev);
>> @@ -1695,9 +1938,8 @@ drm_gpuvm_prefetch_ops_create(struct drm_gpuvm
>> *gpuvm,
>>   EXPORT_SYMBOL_GPL(drm_gpuvm_prefetch_ops_create);
>>   
>>   /**
>> - * drm_gpuvm_gem_unmap_ops_create() - creates the &drm_gpuva_ops to
>> unmap a GEM
>> - * @gpuvm: the &drm_gpuvm representing the GPU VA space
>> - * @obj: the &drm_gem_object to unmap
>> + * drm_gpuvm_bo_unmap_ops_create() - creates the &drm_gpuva_ops to
>> unmap a GEM
>> + * @vm_bo: the &drm_gpuvm_bo abstraction
>>    *
>>    * This function creates a list of operations to perform unmapping
>> for every
>>    * GPUVA attached to a GEM.
>> @@ -1714,15 +1956,14 @@
>> EXPORT_SYMBOL_GPL(drm_gpuvm_prefetch_ops_create);
>>    * Returns: a pointer to the &drm_gpuva_ops on success, an ERR_PTR
>> on failure
>>    */
>>   struct drm_gpuva_ops *
>> -drm_gpuvm_gem_unmap_ops_create(struct drm_gpuvm *gpuvm,
>> -                              struct drm_gem_object *obj)
>> +drm_gpuvm_bo_unmap_ops_create(struct drm_gpuvm_bo *vm_bo)
>>   {
>>          struct drm_gpuva_ops *ops;
>>          struct drm_gpuva_op *op;
>>          struct drm_gpuva *va;
>>          int ret;
>>   
>> -       drm_gem_gpuva_assert_lock_held(obj);
>> +       drm_gem_gpuva_assert_lock_held(vm_bo->obj);
>>   
>>          ops = kzalloc(sizeof(*ops), GFP_KERNEL);
>>          if (!ops)
>> @@ -1730,8 +1971,8 @@ drm_gpuvm_gem_unmap_ops_create(struct drm_gpuvm
>> *gpuvm,
>>   
>>          INIT_LIST_HEAD(&ops->list);
>>   
>> -       drm_gem_for_each_gpuva(va, obj) {
>> -               op = gpuva_op_alloc(gpuvm);
>> +       drm_gpuvm_bo_for_each_va(va, vm_bo) {
>> +               op = gpuva_op_alloc(vm_bo->vm);
>>                  if (!op) {
>>                          ret = -ENOMEM;
>>                          goto err_free_ops;
>> @@ -1745,10 +1986,10 @@ drm_gpuvm_gem_unmap_ops_create(struct
>> drm_gpuvm *gpuvm,
>>          return ops;
>>   
>>   err_free_ops:
>> -       drm_gpuva_ops_free(gpuvm, ops);
>> +       drm_gpuva_ops_free(vm_bo->vm, ops);
>>          return ERR_PTR(ret);
>>   }
>> -EXPORT_SYMBOL_GPL(drm_gpuvm_gem_unmap_ops_create);
>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_unmap_ops_create);
>>   
>>   /**
>>    * drm_gpuva_ops_free() - free the given &drm_gpuva_ops
>> diff --git a/drivers/gpu/drm/nouveau/nouveau_uvmm.c
>> b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
>> index ed439bf4032f..1e95b0a1b047 100644
>> --- a/drivers/gpu/drm/nouveau/nouveau_uvmm.c
>> +++ b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
>> @@ -62,6 +62,8 @@ struct bind_job_op {
>>          enum vm_bind_op op;
>>          u32 flags;
>>   
>> +       struct drm_gpuvm_bo *vm_bo;
>> +
>>          struct {
>>                  u64 addr;
>>                  u64 range;
>> @@ -1113,22 +1115,28 @@ bind_validate_region(struct nouveau_job *job)
>>   }
>>   
>>   static void
>> -bind_link_gpuvas(struct drm_gpuva_ops *ops, struct
>> nouveau_uvma_prealloc *new)
>> +bind_link_gpuvas(struct bind_job_op *bop)
>>   {
>> +       struct nouveau_uvma_prealloc *new = &bop->new;
>> +       struct drm_gpuvm_bo *vm_bo = bop->vm_bo;
>> +       struct drm_gpuva_ops *ops = bop->ops;
>>          struct drm_gpuva_op *op;
>>   
>>          drm_gpuva_for_each_op(op, ops) {
>>                  switch (op->op) {
>>                  case DRM_GPUVA_OP_MAP:
>> -                       drm_gpuva_link(&new->map->va);
>> +                       drm_gpuva_link(&new->map->va, vm_bo);
>>                          break;
>> -               case DRM_GPUVA_OP_REMAP:
>> +               case DRM_GPUVA_OP_REMAP: {
>> +                       struct drm_gpuva *va = op->remap.unmap->va;
>> +
>>                          if (op->remap.prev)
>> -                               drm_gpuva_link(&new->prev->va);
>> +                               drm_gpuva_link(&new->prev->va, va-
>>> vm_bo);
>>                          if (op->remap.next)
>> -                               drm_gpuva_link(&new->next->va);
>> -                       drm_gpuva_unlink(op->remap.unmap->va);
>> +                               drm_gpuva_link(&new->next->va, va-
>>> vm_bo);
>> +                       drm_gpuva_unlink(va);
>>                          break;
>> +               }
>>                  case DRM_GPUVA_OP_UNMAP:
>>                          drm_gpuva_unlink(op->unmap.va);
>>                          break;
>> @@ -1150,10 +1158,18 @@ nouveau_uvmm_bind_job_submit(struct
>> nouveau_job *job)
>>   
>>          list_for_each_op(op, &bind_job->ops) {
>>                  if (op->op == OP_MAP) {
>> -                       op->gem.obj = drm_gem_object_lookup(job-
>>> file_priv,
>> -                                                           op-
>>> gem.handle);
>> -                       if (!op->gem.obj)
>> +                       struct drm_gem_object *obj;
>> +
>> +                       obj = drm_gem_object_lookup(job->file_priv,
>> +                                                   op->gem.handle);
>> +                       if (!(op->gem.obj = obj))
>>                                  return -ENOENT;
>> +
>> +                       dma_resv_lock(obj->resv, NULL);
>> +                       op->vm_bo = drm_gpuvm_bo_obtain(&uvmm->base,
>> obj);
>> +                       dma_resv_unlock(obj->resv);
>> +                       if (IS_ERR(op->vm_bo))
>> +                               return PTR_ERR(op->vm_bo);
>>                  }
>>   
>>                  ret = bind_validate_op(job, op);
>> @@ -1364,7 +1380,7 @@ nouveau_uvmm_bind_job_submit(struct nouveau_job
>> *job)
>>                  case OP_UNMAP_SPARSE:
>>                  case OP_MAP:
>>                  case OP_UNMAP:
>> -                       bind_link_gpuvas(op->ops, &op->new);
>> +                       bind_link_gpuvas(op);
>>                          break;
>>                  default:
>>                          break;
>> @@ -1511,6 +1527,12 @@ nouveau_uvmm_bind_job_free_work_fn(struct
>> work_struct *work)
>>                  if (!IS_ERR_OR_NULL(op->ops))
>>                          drm_gpuva_ops_free(&uvmm->base, op->ops);
>>   
>> +               if (!IS_ERR_OR_NULL(op->vm_bo)) {
>> +                       dma_resv_lock(obj->resv, NULL);
>> +                       drm_gpuvm_bo_put(op->vm_bo);
>> +                       dma_resv_unlock(obj->resv);
>> +               }
>> +
>>                  if (obj)
>>                          drm_gem_object_put(obj);
>>          }
>> @@ -1776,15 +1798,18 @@ void
>>   nouveau_uvmm_bo_map_all(struct nouveau_bo *nvbo, struct nouveau_mem
>> *mem)
>>   {
>>          struct drm_gem_object *obj = &nvbo->bo.base;
>> +       struct drm_gpuvm_bo *vm_bo;
>>          struct drm_gpuva *va;
>>   
>>          dma_resv_assert_held(obj->resv);
>>   
>> -       drm_gem_for_each_gpuva(va, obj) {
>> -               struct nouveau_uvma *uvma = uvma_from_va(va);
>> +       drm_gem_for_each_gpuvm_bo(vm_bo, obj) {
>> +               drm_gpuvm_bo_for_each_va(va, vm_bo) {
>> +                       struct nouveau_uvma *uvma = uvma_from_va(va);
>>   
>> -               nouveau_uvma_map(uvma, mem);
>> -               drm_gpuva_invalidate(va, false);
>> +                       nouveau_uvma_map(uvma, mem);
>> +                       drm_gpuva_invalidate(va, false);
>> +               }
>>          }
>>   }
>>   
>> @@ -1792,15 +1817,18 @@ void
>>   nouveau_uvmm_bo_unmap_all(struct nouveau_bo *nvbo)
>>   {
>>          struct drm_gem_object *obj = &nvbo->bo.base;
>> +       struct drm_gpuvm_bo *vm_bo;
>>          struct drm_gpuva *va;
>>   
>>          dma_resv_assert_held(obj->resv);
>>   
>> -       drm_gem_for_each_gpuva(va, obj) {
>> -               struct nouveau_uvma *uvma = uvma_from_va(va);
>> +       drm_gem_for_each_gpuvm_bo(vm_bo, obj) {
>> +               drm_gpuvm_bo_for_each_va(va, vm_bo) {
>> +                       struct nouveau_uvma *uvma = uvma_from_va(va);
>>   
>> -         ��     nouveau_uvma_unmap(uvma);
>> -               drm_gpuva_invalidate(va, true);
>> +                       nouveau_uvma_unmap(uvma);
>> +                       drm_gpuva_invalidate(va, true);
>> +               }
>>          }
>>   }
>>   
>> diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
>> index 16364487fde9..369505447acd 100644
>> --- a/include/drm/drm_gem.h
>> +++ b/include/drm/drm_gem.h
>> @@ -580,7 +580,7 @@ int drm_gem_evict(struct drm_gem_object *obj);
>>    * drm_gem_gpuva_init() - initialize the gpuva list of a GEM object
>>    * @obj: the &drm_gem_object
>>    *
>> - * This initializes the &drm_gem_object's &drm_gpuva list.
>> + * This initializes the &drm_gem_object's &drm_gpuvm_bo list.
>>    *
>>    * Calling this function is only necessary for drivers intending to
>> support the
>>    * &drm_driver_feature DRIVER_GEM_GPUVA.
>> @@ -593,28 +593,28 @@ static inline void drm_gem_gpuva_init(struct
>> drm_gem_object *obj)
>>   }
>>   
>>   /**
>> - * drm_gem_for_each_gpuva() - iternator to walk over a list of
>> gpuvas
>> - * @entry__: &drm_gpuva structure to assign to in each iteration
>> step
>> - * @obj__: the &drm_gem_object the &drm_gpuvas to walk are
>> associated with
>> + * drm_gem_for_each_gpuvm_bo() - iterator to walk over a list of
>> &drm_gpuvm_bo
>> + * @entry__: &drm_gpuvm_bo structure to assign to in each iteration
>> step
>> + * @obj__: the &drm_gem_object the &drm_gpuvm_bo to walk are
>> associated with
>>    *
>> - * This iterator walks over all &drm_gpuva structures associated
>> with the
>> - * &drm_gpuva_manager.
>> + * This iterator walks over all &drm_gpuvm_bo structures associated
>> with the
>> + * &drm_gem_object.
>>    */
>> -#define drm_gem_for_each_gpuva(entry__, obj__) \
>> -       list_for_each_entry(entry__, &(obj__)->gpuva.list, gem.entry)
>> +#define drm_gem_for_each_gpuvm_bo(entry__, obj__) \
>> +       list_for_each_entry(entry__, &(obj__)->gpuva.list,
>> list.entry.gem)
>>   
>>   /**
>> - * drm_gem_for_each_gpuva_safe() - iternator to safely walk over a
>> list of
>> - * gpuvas
>> - * @entry__: &drm_gpuva structure to assign to in each iteration
>> step
>> - * @next__: &next &drm_gpuva to store the next step
>> - * @obj__: the &drm_gem_object the &drm_gpuvas to walk are
>> associated with
>> + * drm_gem_for_each_gpuvm_bo_safe() - iterator to safely walk over a
>> list of
>> + * &drm_gpuvm_bo
>> + * @entry__: &drm_gpuvm_bostructure to assign to in each iteration
>> step
>> + * @next__: &next &drm_gpuvm_bo to store the next step
>> + * @obj__: the &drm_gem_object the &drm_gpuvm_bo to walk are
>> associated with
>>    *
>> - * This iterator walks over all &drm_gpuva structures associated
>> with the
>> + * This iterator walks over all &drm_gpuvm_bo structures associated
>> with the
>>    * &drm_gem_object. It is implemented with
>> list_for_each_entry_safe(), hence
>>    * it is save against removal of elements.
>>    */
>> -#define drm_gem_for_each_gpuva_safe(entry__, next__, obj__) \
>> -       list_for_each_entry_safe(entry__, next__, &(obj__)-
>>> gpuva.list, gem.entry)
>> +#define drm_gem_for_each_gpuvm_bo_safe(entry__, next__, obj__) \
>> +       list_for_each_entry_safe(entry__, next__, &(obj__)-
>>> gpuva.list, list.entry.gem)
>>   
>>   #endif /* __DRM_GEM_H__ */
>> diff --git a/include/drm/drm_gpuvm.h b/include/drm/drm_gpuvm.h
>> index 47cbacb244b9..466fdd76c71a 100644
>> --- a/include/drm/drm_gpuvm.h
>> +++ b/include/drm/drm_gpuvm.h
>> @@ -25,6 +25,7 @@
>>    * OTHER DEALINGS IN THE SOFTWARE.
>>    */
>>   
>> +#include <linux/dma-resv.h>
>>   #include <linux/list.h>
>>   #include <linux/rbtree.h>
>>   #include <linux/types.h>
>> @@ -33,6 +34,7 @@
>>   #include <drm/drm_gem.h>
>>   
>>   struct drm_gpuvm;
>> +struct drm_gpuvm_bo;
>>   struct drm_gpuvm_ops;
>>   
>>   /**
>> @@ -73,6 +75,12 @@ struct drm_gpuva {
>>           */
>>          struct drm_gpuvm *vm;
>>   
>> +       /**
>> +        * @vm_bo: the &drm_gpuvm_bo abstraction for the mapped
>> +        * &drm_gem_object
>> +        */
>> +       struct drm_gpuvm_bo *vm_bo;
>> +
>>          /**
>>           * @flags: the &drm_gpuva_flags for this mapping
>>           */
>> @@ -108,7 +116,7 @@ struct drm_gpuva {
>>                  struct drm_gem_object *obj;
>>   
>>                  /**
>> -                * @entry: the &list_head to attach this object to a
>> &drm_gem_object
>> +                * @entry: the &list_head to attach this object to a
>> &drm_gpuvm_bo
>>                   */
>>                  struct list_head entry;
>>          } gem;
>> @@ -141,7 +149,7 @@ struct drm_gpuva {
>>   int drm_gpuva_insert(struct drm_gpuvm *gpuvm, struct drm_gpuva *va);
>>   void drm_gpuva_remove(struct drm_gpuva *va);
>>   
>> -void drm_gpuva_link(struct drm_gpuva *va);
>> +void drm_gpuva_link(struct drm_gpuva *va, struct drm_gpuvm_bo
>> *vm_bo);
>>   void drm_gpuva_unlink(struct drm_gpuva *va);
>>   
>>   struct drm_gpuva *drm_gpuva_find(struct drm_gpuvm *gpuvm,
>> @@ -188,10 +196,16 @@ static inline bool drm_gpuva_invalidated(struct
>> drm_gpuva *va)
>>    * enum drm_gpuvm_flags - flags for struct drm_gpuvm
>>    */
>>   enum drm_gpuvm_flags {
>> +       /**
>> +        * @DRM_GPUVM_RESV_PROTECTED: GPUVM is protected externally
>> by the
>> +        * GPUVM's &dma_resv lock
>> +        */
>> +       DRM_GPUVM_RESV_PROTECTED = BIT(0),
>> +
>>          /**
>>           * @DRM_GPUVM_USERBITS: user defined bits
>>           */
>> -       DRM_GPUVM_USERBITS = BIT(0),
>> +       DRM_GPUVM_USERBITS = BIT(1),
>>   };
>>   
>>   /**
>> @@ -280,6 +294,19 @@ bool drm_gpuvm_interval_empty(struct drm_gpuvm
>> *gpuvm, u64 addr, u64 range);
>>   struct drm_gem_object *
>>   drm_gpuvm_resv_object_alloc(struct drm_device *drm);
>>   
>> +/**
>> + * drm_gpuvm_resv_protected() - indicates whether
>> &DRM_GPUVM_RESV_PROTECTED is
>> + * set
>> + * @gpuvm: the &drm_gpuvm
>> + *
>> + * Returns: true if &DRM_GPUVM_RESV_PROTECTED is set, false
>> otherwise.
>> + */
>> +static inline bool
>> +drm_gpuvm_resv_protected(struct drm_gpuvm *gpuvm)
>> +{
>> +       return gpuvm->flags & DRM_GPUVM_RESV_PROTECTED;
>> +}
>> +
>>   /**
>>    * drm_gpuvm_resv() - returns the &drm_gpuvm's &dma_resv
>>    * @gpuvm__: the &drm_gpuvm
>> @@ -298,6 +325,12 @@ drm_gpuvm_resv_object_alloc(struct drm_device
>> *drm);
>>    */
>>   #define drm_gpuvm_resv_obj(gpuvm__) ((gpuvm__)->r_obj)
>>   
>> +#define drm_gpuvm_resv_held(gpuvm__) \
>> +       dma_resv_held(drm_gpuvm_resv(gpuvm__))
>> +
>> +#define drm_gpuvm_resv_assert_held(gpuvm__) \
>> +       dma_resv_assert_held(drm_gpuvm_resv(gpuvm__))
>> +
>>   #define drm_gpuvm_resv_held(gpuvm__) \
>>          dma_resv_held(drm_gpuvm_resv(gpuvm__))
>>   
>> @@ -382,6 +415,128 @@ __drm_gpuva_next(struct drm_gpuva *va)
>>   #define drm_gpuvm_for_each_va_safe(va__, next__, gpuvm__) \
>>          list_for_each_entry_safe(va__, next__, &(gpuvm__)->rb.list,
>> rb.entry)
>>   
>> +/**
>> + * struct drm_gpuvm_bo - structure representing a &drm_gpuvm and
>> + * &drm_gem_object combination
>> + *
>> + * This structure is an abstraction representing a &drm_gpuvm and
>> + * &drm_gem_object combination. It serves as an indirection to
>> accelerate
>> + * iterating all &drm_gpuvas within a &drm_gpuvm backed by the same
>> + * &drm_gem_object.
>> + *
>> + * Furthermore it is used cache evicted GEM objects for a certain
>> GPU-VM to
>> + * accelerate validation.
>> + *
>> + * Typically, drivers want to create an instance of a struct
>> drm_gpuvm_bo once
>> + * a GEM object is mapped first in a GPU-VM and release the instance
>> once the
>> + * last mapping of the GEM object in this GPU-VM is unmapped.
>> + */
>> +struct drm_gpuvm_bo {
>> +       /**
>> +        * @vm: The &drm_gpuvm the @obj is mapped in. This pointer is
>> not
>> +        * reference counted.
>> +        *
>> +        * A struct drm_gpuvm_bo is not allowed to out-live its
>> &drm_gpuvm
>> +        * context. Implicitly, this is ensured by the fact that the
>> driver is
>> +        * responsible to ensure the VM doesn't contain mappings once
>> it's
>> +        * freed, since a struct drm_gpuvm_bo should be freed once
>> the last
>> +        * mapping being backed by the corresponding buffer object is
>> unmapped.
>> +        */
> 
> 
> I don't think the above is completely true. Let's assume in the
> !RESV_PROTECTED case that a reference is grabbed on the drm_gpuvm_bo
> during an iteration over a list. Then user-space closes the vm and all
> vmas are unlinked, but this reference remains but the vm pointer
> becomes stale. In the RESV_PROTECTED case this is ensured not to happen
> if by the vm->resv being grabbed during unlink, but in the
> !RESV_PROTECTED case, the above wording isn't sufficient. The caller
> needs to ensure the vm stays alive using some sort of similar rule or
> use kref_get_unless_zero() on the vm under the spinlock if
> dereferenced.

The list is part of the GPUVM. Hence, the caller *must* either already hold
a reference to the GPUVM or otherwise ensure it's not freed while iterating
this list. All the drm_gpuvm_bo structures within this list can't have a
pointer to another VM than this one by definition.

Anyway, I recognize that this isn't very obvious. Hence, I think we should
probably reference count GPUVMs as well. I'd think of the same way we do it
with drm_gem_objects. However, I'd prefer to introduce this with a subsequent
patch.

> 
>> +       struct drm_gpuvm *vm;
>> +
>> +       /**
>> +        * @obj: The &drm_gem_object being mapped in @vm. This is a
>> reference
>> +        * counted pointer.
>> +        */
>> +       struct drm_gem_object *obj;
>> +
>> +       /**
>> +        * @kref: The reference count for this &drm_gpuvm_bo.
>> +        */
>> +       struct kref kref;
>> +
>> +       /**
>> +        * @list: Structure containing all &list_heads.
>> +        */
>> +       struct {
>> +               /**
>> +                * @gpuva: The list of linked &drm_gpuvas.
>> +                */
>> +               struct list_head gpuva;
> 
> Still missing doc on how the @gpuva stays alive during iteration over
> the list?

Thanks for pointing this out again, I missed that one.

- Danilo

> 
> 
> 
> 8<-------------------------------------------------------------
> 
> Thanks,
> Thomas
>
  

On 10/31/23 17:50, Thomas Hellström wrote:
> On Tue, 2023-10-31 at 17:30 +0100, Danilo Krummrich wrote:
>> On 10/31/23 12:45, Jani Nikula wrote:
>>> On Tue, 31 Oct 2023, Thomas Hellström
>>> <thomas.hellstrom@linux.intel.com> wrote:
>>>> On Mon, 2023-10-23 at 22:16 +0200, Danilo Krummrich wrote:
>>>>> + * Returns: a pointer to the &drm_gpuvm_bo on success, NULL on
>>>>
>>>> Still needs s/Returns:/Return:/g
>>>
>>> FWIW, both work to accommodate the variance across the kernel,
>>> although
>>> I think only the latter is documented and recommended. It's also
>>> the
>>> most popular:
>>>
>>>     10577 Return
>>>      3596 Returns
>>
>> I'd like to keep "Returns", since that's what GPUVM uses already
>> everywhere else.
> 
> Ok. It looks like the Returns: are converted to Return in the rendered
> output so I guess that's why it's the form that is documented.
> 
> I pointed this out since in the last review you replied you were going
> to change it, and also when the code starts seeing updates from other,
> it might become inconsistent if those patches follow the documented
> way.

Sorry for that. I think I wrote this answer when I was at XDC and hence was
a little bit distracted.

> 
> But I'm OK either way.

Ok, then let's just keep it as it is.

> 
> /Thomas
> 
> 
>>
>>>      1104 RETURN
>>>       568 return
>>>       367 returns
>>>       352 RETURNS
>>>         1 RETURNs
>>>
>>> BR,
>>> Jani.
>>>
>>>
>>
>
  

On 10/31/23 17:45, Thomas Hellström wrote:
> On Tue, 2023-10-31 at 17:39 +0100, Danilo Krummrich wrote:
>> On 10/31/23 12:25, Thomas Hellström wrote:
>>> On Mon, 2023-10-23 at 22:16 +0200, Danilo Krummrich wrote:
>>>> Add an abstraction layer between the drm_gpuva mappings of a
>>>> particular
>>>> drm_gem_object and this GEM object itself. The abstraction
>>>> represents
>>>> a
>>>> combination of a drm_gem_object and drm_gpuvm. The drm_gem_object
>>>> holds
>>>> a list of drm_gpuvm_bo structures (the structure representing
>>>> this
>>>> abstraction), while each drm_gpuvm_bo contains list of mappings
>>>> of
>>>> this
>>>> GEM object.
>>>>
>>>> This has multiple advantages:
>>>>
>>>> 1) We can use the drm_gpuvm_bo structure to attach it to various
>>>> lists
>>>>      of the drm_gpuvm. This is useful for tracking external and
>>>> evicted
>>>>      objects per VM, which is introduced in subsequent patches.
>>>>
>>>> 2) Finding mappings of a certain drm_gem_object mapped in a
>>>> certain
>>>>      drm_gpuvm becomes much cheaper.
>>>>
>>>> 3) Drivers can derive and extend the structure to easily
>>>> represent
>>>>      driver specific states of a BO for a certain GPUVM.
>>>>
>>>> The idea of this abstraction was taken from amdgpu, hence the
>>>> credit
>>>> for
>>>> this idea goes to the developers of amdgpu.
>>>>
>>>> Cc: Christian König <christian.koenig@amd.com>
>>>> Signed-off-by: Danilo Krummrich <dakr@redhat.com>
>>>> ---
>>>>    drivers/gpu/drm/drm_gpuvm.c            | 335
>>>> +++++++++++++++++++++--
>>>> --
>>>>    drivers/gpu/drm/nouveau/nouveau_uvmm.c |  64 +++--
>>>>    include/drm/drm_gem.h                  |  32 +--
>>>>    include/drm/drm_gpuvm.h                | 188 +++++++++++++-
>>>>    4 files changed, 533 insertions(+), 86 deletions(-)
>>>
>>> That checkpatch.pl error still remains as well.
>>
>> I guess you refer to:
>>
>> ERROR: do not use assignment in if condition
>> #633: FILE: drivers/gpu/drm/nouveau/nouveau_uvmm.c:1165:
>> +                       if (!(op->gem.obj = obj))
>>
>> This was an intentional decision, since in this specific case it
>> seems to
>> be more readable than the alternatives.
>>
>> However, if we consider this to be a hard rule, which we never ever
>> break,
>> I'm fine changing it too.
> 
> With the errors, sooner or later they are going to start generate
> patches to "fix" them. In this particular case also Xe CI is
> complaining and abort building when I submit the Xe adaptation, so it'd
> be good to be checkpatch.pl conformant IMHO.

Ok, I will change this one.

However, in general my opinion on coding style is that we should preserve us
the privilege to deviate from it when we agree it makes sense and improves
the code quality.

Having a CI forcing people to *blindly* follow certain rules and even abort
building isn't very beneficial in that respect.

Also, consider patches which partially change a line of code that already
contains a coding style "issue" - the CI would also block you on that one I
guess. Besides that it seems to block you on unrelated code, note that the
assignment in question is from Nouveau and not from GPUVM.

- Danilo

> 
> Thanks,
> Thomas
> 
> 
> 
> 
>>
>>>
>>> Thanks,
>>> Thomas
>>>
>>
>
  

Hi, Danilo,

On Tue, 2023-10-31 at 18:52 +0100, Danilo Krummrich wrote:
> On 10/31/23 17:45, Thomas Hellström wrote:
> > On Tue, 2023-10-31 at 17:39 +0100, Danilo Krummrich wrote:
> > > On 10/31/23 12:25, Thomas Hellström wrote:
> > > > On Mon, 2023-10-23 at 22:16 +0200, Danilo Krummrich wrote:
> > > > > Add an abstraction layer between the drm_gpuva mappings of a
> > > > > particular
> > > > > drm_gem_object and this GEM object itself. The abstraction
> > > > > represents
> > > > > a
> > > > > combination of a drm_gem_object and drm_gpuvm. The
> > > > > drm_gem_object
> > > > > holds
> > > > > a list of drm_gpuvm_bo structures (the structure representing
> > > > > this
> > > > > abstraction), while each drm_gpuvm_bo contains list of
> > > > > mappings
> > > > > of
> > > > > this
> > > > > GEM object.
> > > > > 
> > > > > This has multiple advantages:
> > > > > 
> > > > > 1) We can use the drm_gpuvm_bo structure to attach it to
> > > > > various
> > > > > lists
> > > > >      of the drm_gpuvm. This is useful for tracking external
> > > > > and
> > > > > evicted
> > > > >      objects per VM, which is introduced in subsequent
> > > > > patches.
> > > > > 
> > > > > 2) Finding mappings of a certain drm_gem_object mapped in a
> > > > > certain
> > > > >      drm_gpuvm becomes much cheaper.
> > > > > 
> > > > > 3) Drivers can derive and extend the structure to easily
> > > > > represent
> > > > >      driver specific states of a BO for a certain GPUVM.
> > > > > 
> > > > > The idea of this abstraction was taken from amdgpu, hence the
> > > > > credit
> > > > > for
> > > > > this idea goes to the developers of amdgpu.
> > > > > 
> > > > > Cc: Christian König <christian.koenig@amd.com>
> > > > > Signed-off-by: Danilo Krummrich <dakr@redhat.com>
> > > > > ---
> > > > >    drivers/gpu/drm/drm_gpuvm.c            | 335
> > > > > +++++++++++++++++++++--
> > > > > --
> > > > >    drivers/gpu/drm/nouveau/nouveau_uvmm.c |  64 +++--
> > > > >    include/drm/drm_gem.h                  |  32 +--
> > > > >    include/drm/drm_gpuvm.h                | 188
> > > > > +++++++++++++-
> > > > >    4 files changed, 533 insertions(+), 86 deletions(-)
> > > > 
> > > > That checkpatch.pl error still remains as well.
> > > 
> > > I guess you refer to:
> > > 
> > > ERROR: do not use assignment in if condition
> > > #633: FILE: drivers/gpu/drm/nouveau/nouveau_uvmm.c:1165:
> > > +                       if (!(op->gem.obj = obj))
> > > 
> > > This was an intentional decision, since in this specific case it
> > > seems to
> > > be more readable than the alternatives.
> > > 
> > > However, if we consider this to be a hard rule, which we never
> > > ever
> > > break,
> > > I'm fine changing it too.
> > 
> > With the errors, sooner or later they are going to start generate
> > patches to "fix" them. In this particular case also Xe CI is
> > complaining and abort building when I submit the Xe adaptation, so
> > it'd
> > be good to be checkpatch.pl conformant IMHO.
> 
> Ok, I will change this one.
> 
> However, in general my opinion on coding style is that we should
> preserve us
> the privilege to deviate from it when we agree it makes sense and
> improves
> the code quality.
> 
> Having a CI forcing people to *blindly* follow certain rules and even
> abort
> building isn't very beneficial in that respect.
> 
> Also, consider patches which partially change a line of code that
> already
> contains a coding style "issue" - the CI would also block you on that
> one I
> guess. Besides that it seems to block you on unrelated code, note
> that the
> assignment in question is from Nouveau and not from GPUVM.

Yes, I completely agree that having CI enforce error free coding style
checks is bad, and I'll see if I can get that changed on Xe CI. To my
Knowledge It hasn't always been like that.

But OTOH my take on this is that if there are coding style rules and
recommendations we should try to follow them unless there are *strong*
reasons not to. Sometimes that may result in code that may be a little
harder to read, but OTOH a reviewer won't have to read up on the
component's style flavor before reviewing and it will avoid future
style fix patches.

Thanks,
Thomas


> 
> - Danilo
> 
> > 
> > Thanks,
> > Thomas
> > 
> > 
> > 
> > 
> > > 
> > > > 
> > > > Thanks,
> > > > Thomas
> > > > 
> > > 
> > 
>
  

On Wed, 2023-11-01 at 10:41 +0100, Thomas Hellström wrote:
> Hi, Danilo,
> 
> On Tue, 2023-10-31 at 18:52 +0100, Danilo Krummrich wrote:
> > On 10/31/23 17:45, Thomas Hellström wrote:
> > > On Tue, 2023-10-31 at 17:39 +0100, Danilo Krummrich wrote:
> > > > On 10/31/23 12:25, Thomas Hellström wrote:
> > > > > On Mon, 2023-10-23 at 22:16 +0200, Danilo Krummrich wrote:
> > > > > > Add an abstraction layer between the drm_gpuva mappings of
> > > > > > a
> > > > > > particular
> > > > > > drm_gem_object and this GEM object itself. The abstraction
> > > > > > represents
> > > > > > a
> > > > > > combination of a drm_gem_object and drm_gpuvm. The
> > > > > > drm_gem_object
> > > > > > holds
> > > > > > a list of drm_gpuvm_bo structures (the structure
> > > > > > representing
> > > > > > this
> > > > > > abstraction), while each drm_gpuvm_bo contains list of
> > > > > > mappings
> > > > > > of
> > > > > > this
> > > > > > GEM object.
> > > > > > 
> > > > > > This has multiple advantages:
> > > > > > 
> > > > > > 1) We can use the drm_gpuvm_bo structure to attach it to
> > > > > > various
> > > > > > lists
> > > > > >      of the drm_gpuvm. This is useful for tracking external
> > > > > > and
> > > > > > evicted
> > > > > >      objects per VM, which is introduced in subsequent
> > > > > > patches.
> > > > > > 
> > > > > > 2) Finding mappings of a certain drm_gem_object mapped in a
> > > > > > certain
> > > > > >      drm_gpuvm becomes much cheaper.
> > > > > > 
> > > > > > 3) Drivers can derive and extend the structure to easily
> > > > > > represent
> > > > > >      driver specific states of a BO for a certain GPUVM.
> > > > > > 
> > > > > > The idea of this abstraction was taken from amdgpu, hence
> > > > > > the
> > > > > > credit
> > > > > > for
> > > > > > this idea goes to the developers of amdgpu.
> > > > > > 
> > > > > > Cc: Christian König <christian.koenig@amd.com>
> > > > > > Signed-off-by: Danilo Krummrich <dakr@redhat.com>
> > > > > > ---
> > > > > >    drivers/gpu/drm/drm_gpuvm.c            | 335
> > > > > > +++++++++++++++++++++--
> > > > > > --
> > > > > >    drivers/gpu/drm/nouveau/nouveau_uvmm.c |  64 +++--
> > > > > >    include/drm/drm_gem.h                  |  32 +--
> > > > > >    include/drm/drm_gpuvm.h                | 188
> > > > > > +++++++++++++-
> > > > > >    4 files changed, 533 insertions(+), 86 deletions(-)
> > > > > 
> > > > > That checkpatch.pl error still remains as well.
> > > > 
> > > > I guess you refer to:
> > > > 
> > > > ERROR: do not use assignment in if condition
> > > > #633: FILE: drivers/gpu/drm/nouveau/nouveau_uvmm.c:1165:
> > > > +                       if (!(op->gem.obj = obj))
> > > > 
> > > > This was an intentional decision, since in this specific case
> > > > it
> > > > seems to
> > > > be more readable than the alternatives.
> > > > 
> > > > However, if we consider this to be a hard rule, which we never
> > > > ever
> > > > break,
> > > > I'm fine changing it too.
> > > 
> > > With the errors, sooner or later they are going to start generate
> > > patches to "fix" them. In this particular case also Xe CI is
> > > complaining and abort building when I submit the Xe adaptation,
> > > so
> > > it'd
> > > be good to be checkpatch.pl conformant IMHO.
> > 
> > Ok, I will change this one.
> > 
> > However, in general my opinion on coding style is that we should
> > preserve us
> > the privilege to deviate from it when we agree it makes sense and
> > improves
> > the code quality.
> > 
> > Having a CI forcing people to *blindly* follow certain rules and
> > even
> > abort
> > building isn't very beneficial in that respect.
> > 
> > Also, consider patches which partially change a line of code that
> > already
> > contains a coding style "issue" - the CI would also block you on
> > that
> > one I
> > guess. Besides that it seems to block you on unrelated code, note
> > that the
> > assignment in question is from Nouveau and not from GPUVM.
> 
> Yes, I completely agree that having CI enforce error free coding
> style
> checks is bad, and I'll see if I can get that changed on Xe CI. To my
> Knowledge It hasn't always been like that.
> 
> But OTOH my take on this is that if there are coding style rules and
> recommendations we should try to follow them unless there are
> *strong*
> reasons not to. Sometimes that may result in code that may be a
> little
> harder to read, but OTOH a reviewer won't have to read up on the
> component's style flavor before reviewing and it will avoid future
> style fix patches.

Basically meaning I'll continue to point those out when reviewing in
case the author made an oversight, but won't require fixing for an R-B
if the component owner thinks otherwise.

Thanks,
Thomas

> 
> Thanks,
> Thomas
> 
> 
> > 
> > - Danilo
> > 
> > > 
> > > Thanks,
> > > Thomas
> > > 
> > > 
> > > 
> > > 
> > > > 
> > > > > 
> > > > > Thanks,
> > > > > Thomas
> > > > > 
> > > > 
> > > 
> > 
>
  

On Tue, 2023-10-31 at 18:38 +0100, Danilo Krummrich wrote:
> On 10/31/23 11:32, Thomas Hellström wrote:
> > On Mon, 2023-10-23 at 22:16 +0200, Danilo Krummrich wrote:
> > > Add an abstraction layer between the drm_gpuva mappings of a
> > > particular
> > > drm_gem_object and this GEM object itself. The abstraction
> > > represents
> > > a
> > > combination of a drm_gem_object and drm_gpuvm. The drm_gem_object
> > > holds
> > > a list of drm_gpuvm_bo structures (the structure representing
> > > this
> > > abstraction), while each drm_gpuvm_bo contains list of mappings
> > > of
> > > this
> > > GEM object.
> > > 
> > > This has multiple advantages:
> > > 
> > > 1) We can use the drm_gpuvm_bo structure to attach it to various
> > > lists
> > >     of the drm_gpuvm. This is useful for tracking external and
> > > evicted
> > >     objects per VM, which is introduced in subsequent patches.
> > > 
> > > 2) Finding mappings of a certain drm_gem_object mapped in a
> > > certain
> > >     drm_gpuvm becomes much cheaper.
> > > 
> > > 3) Drivers can derive and extend the structure to easily
> > > represent
> > >     driver specific states of a BO for a certain GPUVM.
> > > 
> > > The idea of this abstraction was taken from amdgpu, hence the
> > > credit
> > > for
> > > this idea goes to the developers of amdgpu.
> > > 
> > > Cc: Christian König <christian.koenig@amd.com>
> > > Signed-off-by: Danilo Krummrich <dakr@redhat.com>
> > > ---
> > >   drivers/gpu/drm/drm_gpuvm.c            | 335
> > > +++++++++++++++++++++--
> > > --
> > >   drivers/gpu/drm/nouveau/nouveau_uvmm.c |  64 +++--
> > >   include/drm/drm_gem.h                  |  32 +--
> > >   include/drm/drm_gpuvm.h                | 188 +++++++++++++-
> > >   4 files changed, 533 insertions(+), 86 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/drm_gpuvm.c
> > > b/drivers/gpu/drm/drm_gpuvm.c
> > > index c03332883432..7f4f5919f84c 100644
> > > --- a/drivers/gpu/drm/drm_gpuvm.c
> > > +++ b/drivers/gpu/drm/drm_gpuvm.c
> > > @@ -70,6 +70,18 @@
> > >    * &drm_gem_object, such as the &drm_gem_object containing the
> > > root
> > > page table,
> > >    * but it can also be a 'dummy' object, which can be allocated
> > > with
> > >    * drm_gpuvm_resv_object_alloc().
> > > + *
> > > + * In order to connect a struct drm_gpuva its backing
> > > &drm_gem_object each
> > > + * &drm_gem_object maintains a list of &drm_gpuvm_bo structures,
> > > and
> > > each
> > > + * &drm_gpuvm_bo contains a list of &drm_gpuva structures.
> > > + *
> > > + * A &drm_gpuvm_bo is an abstraction that represents a
> > > combination
> > > of a
> > > + * &drm_gpuvm and a &drm_gem_object. Every such combination
> > > should
> > > be unique.
> > > + * This is ensured by the API through drm_gpuvm_bo_obtain() and
> > > + * drm_gpuvm_bo_obtain_prealloc() which first look into the
> > > corresponding
> > > + * &drm_gem_object list of &drm_gpuvm_bos for an existing
> > > instance
> > > of this
> > > + * particular combination. If not existent a new instance is
> > > created
> > > and linked
> > > + * to the &drm_gem_object.
> > >    */
> > >   
> > >   /**
> > > @@ -395,21 +407,28 @@
> > >   /**
> > >    * DOC: Locking
> > >    *
> > > - * Generally, the GPU VA manager does not take care of locking
> > > itself, it is
> > > - * the drivers responsibility to take care about locking.
> > > Drivers
> > > might want to
> > > - * protect the following operations: inserting, removing and
> > > iterating
> > > - * &drm_gpuva objects as well as generating all kinds of
> > > operations,
> > > such as
> > > - * split / merge or prefetch.
> > > - *
> > > - * The GPU VA manager also does not take care of the locking of
> > > the
> > > backing
> > > - * &drm_gem_object buffers GPU VA lists by itself; drivers are
> > > responsible to
> > > - * enforce mutual exclusion using either the GEMs dma_resv lock
> > > or
> > > alternatively
> > > - * a driver specific external lock. For the latter see also
> > > - * drm_gem_gpuva_set_lock().
> > > - *
> > > - * However, the GPU VA manager contains lockdep checks to ensure
> > > callers of its
> > > - * API hold the corresponding lock whenever the &drm_gem_objects
> > > GPU
> > > VA list is
> > > - * accessed by functions such as drm_gpuva_link() or
> > > drm_gpuva_unlink().
> > > + * In terms of managing &drm_gpuva entries DRM GPUVM does not
> > > take
> > > care of
> > > + * locking itself, it is the drivers responsibility to take care
> > > about locking.
> > > + * Drivers might want to protect the following operations:
> > > inserting, removing
> > > + * and iterating &drm_gpuva objects as well as generating all
> > > kinds
> > > of
> > > + * operations, such as split / merge or prefetch.
> > > + *
> > > + * DRM GPUVM also does not take care of the locking of the
> > > backing
> > > + * &drm_gem_object buffers GPU VA lists and &drm_gpuvm_bo
> > > abstractions by
> > > + * itself; drivers are responsible to enforce mutual exclusion
> > > using
> > > either the
> > > + * GEMs dma_resv lock or alternatively a driver specific
> > > external
> > > lock. For the
> > > + * latter see also drm_gem_gpuva_set_lock().
> > > + *
> > > + * However, DRM GPUVM contains lockdep checks to ensure callers
> > > of
> > > its API hold
> > > + * the corresponding lock whenever the &drm_gem_objects GPU VA
> > > list
> > > is accessed
> > > + * by functions such as drm_gpuva_link() or drm_gpuva_unlink(),
> > > but
> > > also
> > > + * drm_gpuvm_bo_obtain() and drm_gpuvm_bo_put().
> > > + *
> > > + * The latter is required since on creation and destruction of a
> > > &drm_gpuvm_bo
> > > + * the &drm_gpuvm_bo is attached / removed from the
> > > &drm_gem_objects
> > > gpuva list.
> > > + * Subsequent calls to drm_gpuvm_bo_obtain() for the same
> > > &drm_gpuvm
> > > and
> > > + * &drm_gem_object must be able to observe previous creations
> > > and
> > > destructions
> > > + * of &drm_gpuvm_bos in order to keep instances unique.
> > >    */
> > >   
> > >   /**
> > > @@ -439,6 +458,7 @@
> > >    *     {
> > >    *             struct drm_gpuva_ops *ops;
> > >    *             struct drm_gpuva_op *op
> > > + *             struct drm_gpuvm_bo *vm_bo;
> > >    *
> > >    *             driver_lock_va_space();
> > >    *             ops = drm_gpuvm_sm_map_ops_create(gpuvm, addr,
> > > range,
> > > @@ -446,6 +466,10 @@
> > >    *             if (IS_ERR(ops))
> > >    *                     return PTR_ERR(ops);
> > >    *
> > > + *             vm_bo = drm_gpuvm_bo_obtain(gpuvm, obj);
> > > + *             if (IS_ERR(vm_bo))
> > > + *                     return PTR_ERR(vm_bo);
> > > + *
> > >    *             drm_gpuva_for_each_op(op, ops) {
> > >    *                     struct drm_gpuva *va;
> > >    *
> > > @@ -458,7 +482,7 @@
> > >    *
> > >    *                             driver_vm_map();
> > >    *                             drm_gpuva_map(gpuvm, va, &op-
> > > >map);
> > > - *                             drm_gpuva_link(va);
> > > + *                             drm_gpuva_link(va, vm_bo);
> > >    *
> > >    *                             break;
> > >    *                     case DRM_GPUVA_OP_REMAP: {
> > > @@ -485,11 +509,11 @@
> > >    *                             driver_vm_remap();
> > >    *                             drm_gpuva_remap(prev, next, &op-
> > > > remap);
> > >    *
> > > - *                             drm_gpuva_unlink(va);
> > >    *                             if (prev)
> > > - *                                     drm_gpuva_link(prev);
> > > + *                                     drm_gpuva_link(prev, va-
> > > > vm_bo);
> > >    *                             if (next)
> > > - *                                     drm_gpuva_link(next);
> > > + *                                     drm_gpuva_link(next, va-
> > > > vm_bo);
> > > + *                             drm_gpuva_unlink(va);
> > >    *
> > >    *                             break;
> > >    *                     }
> > > @@ -505,6 +529,7 @@
> > >    *                             break;
> > >    *                     }
> > >    *             }
> > > + *             drm_gpuvm_bo_put(vm_bo);
> > >    *             driver_unlock_va_space();
> > >    *
> > >    *             return 0;
> > > @@ -514,6 +539,7 @@
> > >    *
> > >    *     struct driver_context {
> > >    *             struct drm_gpuvm *gpuvm;
> > > + *             struct drm_gpuvm_bo *vm_bo;
> > >    *             struct drm_gpuva *new_va;
> > >    *             struct drm_gpuva *prev_va;
> > >    *             struct drm_gpuva *next_va;
> > > @@ -534,6 +560,7 @@
> > >    *                               struct drm_gem_object *obj,
> > > u64
> > > offset)
> > >    *     {
> > >    *             struct driver_context ctx;
> > > + *             struct drm_gpuvm_bo *vm_bo;
> > >    *             struct drm_gpuva_ops *ops;
> > >    *             struct drm_gpuva_op *op;
> > >    *             int ret = 0;
> > > @@ -543,16 +570,23 @@
> > >    *             ctx.new_va = kzalloc(sizeof(*ctx.new_va),
> > > GFP_KERNEL);
> > >    *             ctx.prev_va = kzalloc(sizeof(*ctx.prev_va),
> > > GFP_KERNEL);
> > >    *             ctx.next_va = kzalloc(sizeof(*ctx.next_va),
> > > GFP_KERNEL);
> > > - *             if (!ctx.new_va || !ctx.prev_va || !ctx.next_va)
> > > {
> > > + *             ctx.vm_bo = drm_gpuvm_bo_create(gpuvm, obj);
> > > + *             if (!ctx.new_va || !ctx.prev_va || !ctx.next_va
> > > ||
> > > !vm_bo) {
> > >    *                     ret = -ENOMEM;
> > >    *                     goto out;
> > >    *             }
> > >    *
> > > + *             // Typically protected with a driver specific GEM
> > > gpuva lock
> > > + *             // used in the fence signaling path for
> > > drm_gpuva_link() and
> > > + *             // drm_gpuva_unlink(), hence pre-allocate.
> > > + *             ctx.vm_bo =
> > > drm_gpuvm_bo_obtain_prealloc(ctx.vm_bo);
> > > + *
> > >    *             driver_lock_va_space();
> > >    *             ret = drm_gpuvm_sm_map(gpuvm, &ctx, addr, range,
> > > obj,
> > > offset);
> > >    *             driver_unlock_va_space();
> > >    *
> > >    *     out:
> > > + *             drm_gpuvm_bo_put(ctx.vm_bo);
> > >    *             kfree(ctx.new_va);
> > >    *             kfree(ctx.prev_va);
> > >    *             kfree(ctx.next_va);
> > > @@ -565,7 +599,7 @@
> > >    *
> > >    *             drm_gpuva_map(ctx->vm, ctx->new_va, &op->map);
> > >    *
> > > - *             drm_gpuva_link(ctx->new_va);
> > > + *             drm_gpuva_link(ctx->new_va, ctx->vm_bo);
> > >    *
> > >    *             // prevent the new GPUVA from being freed in
> > >    *             // driver_mapping_create()
> > > @@ -577,22 +611,23 @@
> > >    *     int driver_gpuva_remap(struct drm_gpuva_op *op, void
> > > *__ctx)
> > >    *     {
> > >    *             struct driver_context *ctx = __ctx;
> > > + *             struct drm_gpuva *va = op->remap.unmap->va;
> > >    *
> > >    *             drm_gpuva_remap(ctx->prev_va, ctx->next_va, &op-
> > > > remap);
> > >    *
> > > - *             drm_gpuva_unlink(op->remap.unmap->va);
> > > - *             kfree(op->remap.unmap->va);
> > > - *
> > >    *             if (op->remap.prev) {
> > > - *                     drm_gpuva_link(ctx->prev_va);
> > > + *                     drm_gpuva_link(ctx->prev_va, va->vm_bo);
> > >    *                     ctx->prev_va = NULL;
> > >    *             }
> > >    *
> > >    *             if (op->remap.next) {
> > > - *                     drm_gpuva_link(ctx->next_va);
> > > + *                     drm_gpuva_link(ctx->next_va, va->vm_bo);
> > >    *                     ctx->next_va = NULL;
> > >    *             }
> > >    *
> > > + *             drm_gpuva_unlink(va);
> > > + *             kfree(va);
> > > + *
> > >    *             return 0;
> > >    *     }
> > >    *
> > > @@ -774,6 +809,194 @@ drm_gpuvm_destroy(struct drm_gpuvm *gpuvm)
> > >   }
> > >   EXPORT_SYMBOL_GPL(drm_gpuvm_destroy);
> > >   
> > > +/**
> > > + * drm_gpuvm_bo_create() - create a new instance of struct
> > > drm_gpuvm_bo
> > > + * @gpuvm: The &drm_gpuvm the @obj is mapped in.
> > > + * @obj: The &drm_gem_object being mapped in the @gpuvm.
> > > + *
> > > + * If provided by the driver, this function uses the
> > > &drm_gpuvm_ops
> > > + * vm_bo_alloc() callback to allocate.
> > > + *
> > > + * Returns: a pointer to the &drm_gpuvm_bo on success, NULL on
> > 
> > Still needs s/Returns:/Return:/g
> > 
> > > failure
> > > + */
> > > +struct drm_gpuvm_bo *
> > > +drm_gpuvm_bo_create(struct drm_gpuvm *gpuvm,
> > > +                   struct drm_gem_object *obj)
> > > +{
> > > +       const struct drm_gpuvm_ops *ops = gpuvm->ops;
> > > +       struct drm_gpuvm_bo *vm_bo;
> > > +
> > > +       if (ops && ops->vm_bo_alloc)
> > > +               vm_bo = ops->vm_bo_alloc();
> > > +       else
> > > +               vm_bo = kzalloc(sizeof(*vm_bo), GFP_KERNEL);
> > > +
> > > +       if (unlikely(!vm_bo))
> > > +               return NULL;
> > > +
> > > +       vm_bo->vm = gpuvm;
> > > +       vm_bo->obj = obj;
> > > +       drm_gem_object_get(obj);
> > > +
> > > +       kref_init(&vm_bo->kref);
> > > +       INIT_LIST_HEAD(&vm_bo->list.gpuva);
> > > +       INIT_LIST_HEAD(&vm_bo->list.entry.gem);
> > > +
> > > +       return vm_bo;
> > > +}
> > > +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_create);
> > > +
> > > +static void
> > > +drm_gpuvm_bo_destroy(struct kref *kref)
> > > +{
> > > +       struct drm_gpuvm_bo *vm_bo = container_of(kref, struct
> > > drm_gpuvm_bo,
> > > +                                                 kref);
> > > +       struct drm_gpuvm *gpuvm = vm_bo->vm;
> > > +       const struct drm_gpuvm_ops *ops = gpuvm->ops;
> > > +       struct drm_gem_object *obj = vm_bo->obj;
> > > +       bool lock = !drm_gpuvm_resv_protected(gpuvm);
> > > +
> > > +       if (!lock)
> > > +               drm_gpuvm_resv_assert_held(gpuvm);
> > > +
> > > +       drm_gem_gpuva_assert_lock_held(obj);
> > > +       list_del(&vm_bo->list.entry.gem);
> > > +
> > > +       if (ops && ops->vm_bo_free)
> > > +               ops->vm_bo_free(vm_bo);
> > > +       else
> > > +               kfree(vm_bo);
> > > +
> > > +       drm_gem_object_put(obj);
> > > +}
> > > +
> > > +/**
> > > + * drm_gpuvm_bo_put() - drop a struct drm_gpuvm_bo reference
> > > + * @vm_bo: the &drm_gpuvm_bo to release the reference of
> > > + *
> > > + * This releases a reference to @vm_bo.
> > > + *
> > > + * If the reference count drops to zero, the &gpuvm_bo is
> > > destroyed,
> > > which
> > > + * includes removing it from the GEMs gpuva list. Hence, if a
> > > call
> > > to this
> > > + * function can potentially let the reference count to zero the
> > > caller must
> > > + * hold the dma-resv or driver specific GEM gpuva lock.
> > > + */
> > > +void
> > > +drm_gpuvm_bo_put(struct drm_gpuvm_bo *vm_bo)
> > > +{
> > > +       if (vm_bo)
> > > +               kref_put(&vm_bo->kref, drm_gpuvm_bo_destroy);
> > > +}
> > > +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_put);
> > > +
> > > +static struct drm_gpuvm_bo *
> > > +__drm_gpuvm_bo_find(struct drm_gpuvm *gpuvm,
> > > +                   struct drm_gem_object *obj)
> > > +{
> > > +       struct drm_gpuvm_bo *vm_bo;
> > > +
> > > +       drm_gem_gpuva_assert_lock_held(obj);
> > > +       drm_gem_for_each_gpuvm_bo(vm_bo, obj)
> > > +               if (vm_bo->vm == gpuvm)
> > > +                       return vm_bo;
> > > +
> > > +       return NULL;
> > > +}
> > > +
> > > +/**
> > > + * drm_gpuvm_bo_find() - find the &drm_gpuvm_bo for the given
> > > + * &drm_gpuvm and &drm_gem_object
> > > + * @gpuvm: The &drm_gpuvm the @obj is mapped in.
> > > + * @obj: The &drm_gem_object being mapped in the @gpuvm.
> > > + *
> > > + * Find the &drm_gpuvm_bo representing the combination of the
> > > given
> > > + * &drm_gpuvm and &drm_gem_object. If found, increases the
> > > reference
> > > + * count of the &drm_gpuvm_bo accordingly.
> > > + *
> > > + * Returns: a pointer to the &drm_gpuvm_bo on success, NULL on
> > > failure
> > > + */
> > > +struct drm_gpuvm_bo *
> > > +drm_gpuvm_bo_find(struct drm_gpuvm *gpuvm,
> > > +                 struct drm_gem_object *obj)
> > > +{
> > > +       struct drm_gpuvm_bo *vm_bo = __drm_gpuvm_bo_find(gpuvm,
> > > obj);
> > > +
> > > +       return vm_bo ? drm_gpuvm_bo_get(vm_bo) : NULL;
> > > +}
> > > +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_find);
> > > +
> > > +/**
> > > + * drm_gpuvm_bo_obtain() - obtains and instance of the
> > > &drm_gpuvm_bo
> > > for the
> > > + * given &drm_gpuvm and &drm_gem_object
> > > + * @gpuvm: The &drm_gpuvm the @obj is mapped in.
> > > + * @obj: The &drm_gem_object being mapped in the @gpuvm.
> > > + *
> > > + * Find the &drm_gpuvm_bo representing the combination of the
> > > given
> > > + * &drm_gpuvm and &drm_gem_object. If found, increases the
> > > reference
> > > + * count of the &drm_gpuvm_bo accordingly. If not found,
> > > allocates a
> > > new
> > > + * &drm_gpuvm_bo.
> > > + *
> > > + * A new &drm_gpuvm_bo is added to the GEMs gpuva list.
> > > + *
> > > + * Returns: a pointer to the &drm_gpuvm_bo on success, an
> > > ERR_PTR on
> > > failure
> > > + */
> > > +struct drm_gpuvm_bo *
> > > +drm_gpuvm_bo_obtain(struct drm_gpuvm *gpuvm,
> > > +                   struct drm_gem_object *obj)
> > > +{
> > > +       struct drm_gpuvm_bo *vm_bo;
> > > +
> > > +       vm_bo = drm_gpuvm_bo_find(gpuvm, obj);
> > > +       if (vm_bo)
> > > +               return vm_bo;
> > > +
> > > +       vm_bo = drm_gpuvm_bo_create(gpuvm, obj);
> > > +       if (!vm_bo)
> > > +               return ERR_PTR(-ENOMEM);
> > > +
> > > +       drm_gem_gpuva_assert_lock_held(obj);
> > > +       list_add_tail(&vm_bo->list.entry.gem, &obj->gpuva.list);
> > > +
> > > +       return vm_bo;
> > > +}
> > > +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_obtain);
> > > +
> > > +/**
> > > + * drm_gpuvm_bo_obtain_prealloc() - obtains and instance of the
> > > &drm_gpuvm_bo
> > > + * for the given &drm_gpuvm and &drm_gem_object
> > > + * @__vm_bo: A pre-allocated struct drm_gpuvm_bo.
> > > + *
> > > + * Find the &drm_gpuvm_bo representing the combination of the
> > > given
> > > + * &drm_gpuvm and &drm_gem_object. If found, increases the
> > > reference
> > > + * count of the found &drm_gpuvm_bo accordingly, while the
> > > @__vm_bo
> > > reference
> > > + * count is decreased. If not found @__vm_bo is returned without
> > > further
> > > + * increase of the reference count.
> > > + *
> > > + * A new &drm_gpuvm_bo is added to the GEMs gpuva list.
> > > + *
> > > + * Returns: a pointer to the found &drm_gpuvm_bo or @__vm_bo if
> > > no
> > > existing
> > > + * &drm_gpuvm_bo was found
> > > + */
> > > +struct drm_gpuvm_bo *
> > > +drm_gpuvm_bo_obtain_prealloc(struct drm_gpuvm_bo *__vm_bo)
> > > +{
> > > +       struct drm_gpuvm *gpuvm = __vm_bo->vm;
> > > +       struct drm_gem_object *obj = __vm_bo->obj;
> > > +       struct drm_gpuvm_bo *vm_bo;
> > > +
> > > +       vm_bo = drm_gpuvm_bo_find(gpuvm, obj);
> > > +       if (vm_bo) {
> > > +               drm_gpuvm_bo_put(__vm_bo);
> > > +               return vm_bo;
> > > +       }
> > > +
> > > +       drm_gem_gpuva_assert_lock_held(obj);
> > > +       list_add_tail(&__vm_bo->list.entry.gem, &obj-
> > > >gpuva.list);
> > > +
> > > +       return __vm_bo;
> > > +}
> > > +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_obtain_prealloc);
> > > +
> > >   static int
> > >   __drm_gpuva_insert(struct drm_gpuvm *gpuvm,
> > >                     struct drm_gpuva *va)
> > > @@ -864,24 +1087,33 @@ EXPORT_SYMBOL_GPL(drm_gpuva_remove);
> > >   /**
> > >    * drm_gpuva_link() - link a &drm_gpuva
> > >    * @va: the &drm_gpuva to link
> > > + * @vm_bo: the &drm_gpuvm_bo to add the &drm_gpuva to
> > >    *
> > > - * This adds the given &va to the GPU VA list of the
> > > &drm_gem_object
> > > it is
> > > - * associated with.
> > > + * This adds the given &va to the GPU VA list of the
> > > &drm_gpuvm_bo
> > > and the
> > > + * &drm_gpuvm_bo to the &drm_gem_object it is associated with.
> > > + *
> > > + * For every &drm_gpuva entry added to the &drm_gpuvm_bo an
> > > additional
> > > + * reference of the latter is taken.
> > >    *
> > >    * This function expects the caller to protect the GEM's GPUVA
> > > list
> > > against
> > > - * concurrent access using the GEMs dma_resv lock.
> > > + * concurrent access using either the GEMs dma_resv lock or a
> > > driver
> > > specific
> > > + * lock set through drm_gem_gpuva_set_lock().
> > >    */
> > >   void
> > > -drm_gpuva_link(struct drm_gpuva *va)
> > > +drm_gpuva_link(struct drm_gpuva *va, struct drm_gpuvm_bo *vm_bo)
> > >   {
> > >          struct drm_gem_object *obj = va->gem.obj;
> > > +       struct drm_gpuvm *gpuvm = va->vm;
> > >   
> > >          if (unlikely(!obj))
> > >                  return;
> > >   
> > > -       drm_gem_gpuva_assert_lock_held(obj);
> > > +       drm_WARN_ON(gpuvm->drm, obj != vm_bo->obj);
> > >   
> > > -       list_add_tail(&va->gem.entry, &obj->gpuva.list);
> > > +       va->vm_bo = drm_gpuvm_bo_get(vm_bo);
> > > +
> > > +       drm_gem_gpuva_assert_lock_held(obj);
> > > +       list_add_tail(&va->gem.entry, &vm_bo->list.gpuva);
> > >   }
> > >   EXPORT_SYMBOL_GPL(drm_gpuva_link);
> > >   
> > > @@ -892,20 +1124,31 @@ EXPORT_SYMBOL_GPL(drm_gpuva_link);
> > >    * This removes the given &va from the GPU VA list of the
> > > &drm_gem_object it is
> > >    * associated with.
> > >    *
> > > + * This removes the given &va from the GPU VA list of the
> > > &drm_gpuvm_bo and
> > > + * the &drm_gpuvm_bo from the &drm_gem_object it is associated
> > > with
> > > in case
> > > + * this call unlinks the last &drm_gpuva from the &drm_gpuvm_bo.
> > > + *
> > > + * For every &drm_gpuva entry removed from the &drm_gpuvm_bo a
> > > reference of
> > > + * the latter is dropped.
> > > + *
> > >    * This function expects the caller to protect the GEM's GPUVA
> > > list
> > > against
> > > - * concurrent access using the GEMs dma_resv lock.
> > > + * concurrent access using either the GEMs dma_resv lock or a
> > > driver
> > > specific
> > > + * lock set through drm_gem_gpuva_set_lock().
> > >    */
> > >   void
> > >   drm_gpuva_unlink(struct drm_gpuva *va)
> > >   {
> > >          struct drm_gem_object *obj = va->gem.obj;
> > > +       struct drm_gpuvm_bo *vm_bo = va->vm_bo;
> > >   
> > >          if (unlikely(!obj))
> > >                  return;
> > >   
> > >          drm_gem_gpuva_assert_lock_held(obj);
> > > -
> > >          list_del_init(&va->gem.entry);
> > > +
> > > +       va->vm_bo = NULL;
> > > +       drm_gpuvm_bo_put(vm_bo);
> > >   }
> > >   EXPORT_SYMBOL_GPL(drm_gpuva_unlink);
> > >   
> > > @@ -1050,10 +1293,10 @@ drm_gpuva_remap(struct drm_gpuva *prev,
> > >                  struct drm_gpuva *next,
> > >                  struct drm_gpuva_op_remap *op)
> > >   {
> > > -       struct drm_gpuva *curr = op->unmap->va;
> > > -       struct drm_gpuvm *gpuvm = curr->vm;
> > > +       struct drm_gpuva *va = op->unmap->va;
> > > +       struct drm_gpuvm *gpuvm = va->vm;
> > >   
> > > -       drm_gpuva_remove(curr);
> > > +       drm_gpuva_remove(va);
> > >   
> > >          if (op->prev) {
> > >                  drm_gpuva_init_from_op(prev, op->prev);
> > > @@ -1695,9 +1938,8 @@ drm_gpuvm_prefetch_ops_create(struct
> > > drm_gpuvm
> > > *gpuvm,
> > >   EXPORT_SYMBOL_GPL(drm_gpuvm_prefetch_ops_create);
> > >   
> > >   /**
> > > - * drm_gpuvm_gem_unmap_ops_create() - creates the &drm_gpuva_ops
> > > to
> > > unmap a GEM
> > > - * @gpuvm: the &drm_gpuvm representing the GPU VA space
> > > - * @obj: the &drm_gem_object to unmap
> > > + * drm_gpuvm_bo_unmap_ops_create() - creates the &drm_gpuva_ops
> > > to
> > > unmap a GEM
> > > + * @vm_bo: the &drm_gpuvm_bo abstraction
> > >    *
> > >    * This function creates a list of operations to perform
> > > unmapping
> > > for every
> > >    * GPUVA attached to a GEM.
> > > @@ -1714,15 +1956,14 @@
> > > EXPORT_SYMBOL_GPL(drm_gpuvm_prefetch_ops_create);
> > >    * Returns: a pointer to the &drm_gpuva_ops on success, an
> > > ERR_PTR
> > > on failure
> > >    */
> > >   struct drm_gpuva_ops *
> > > -drm_gpuvm_gem_unmap_ops_create(struct drm_gpuvm *gpuvm,
> > > -                              struct drm_gem_object *obj)
> > > +drm_gpuvm_bo_unmap_ops_create(struct drm_gpuvm_bo *vm_bo)
> > >   {
> > >          struct drm_gpuva_ops *ops;
> > >          struct drm_gpuva_op *op;
> > >          struct drm_gpuva *va;
> > >          int ret;
> > >   
> > > -       drm_gem_gpuva_assert_lock_held(obj);
> > > +       drm_gem_gpuva_assert_lock_held(vm_bo->obj);
> > >   
> > >          ops = kzalloc(sizeof(*ops), GFP_KERNEL);
> > >          if (!ops)
> > > @@ -1730,8 +1971,8 @@ drm_gpuvm_gem_unmap_ops_create(struct
> > > drm_gpuvm
> > > *gpuvm,
> > >   
> > >          INIT_LIST_HEAD(&ops->list);
> > >   
> > > -       drm_gem_for_each_gpuva(va, obj) {
> > > -               op = gpuva_op_alloc(gpuvm);
> > > +       drm_gpuvm_bo_for_each_va(va, vm_bo) {
> > > +               op = gpuva_op_alloc(vm_bo->vm);
> > >                  if (!op) {
> > >                          ret = -ENOMEM;
> > >                          goto err_free_ops;
> > > @@ -1745,10 +1986,10 @@ drm_gpuvm_gem_unmap_ops_create(struct
> > > drm_gpuvm *gpuvm,
> > >          return ops;
> > >   
> > >   err_free_ops:
> > > -       drm_gpuva_ops_free(gpuvm, ops);
> > > +       drm_gpuva_ops_free(vm_bo->vm, ops);
> > >          return ERR_PTR(ret);
> > >   }
> > > -EXPORT_SYMBOL_GPL(drm_gpuvm_gem_unmap_ops_create);
> > > +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_unmap_ops_create);
> > >   
> > >   /**
> > >    * drm_gpuva_ops_free() - free the given &drm_gpuva_ops
> > > diff --git a/drivers/gpu/drm/nouveau/nouveau_uvmm.c
> > > b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
> > > index ed439bf4032f..1e95b0a1b047 100644
> > > --- a/drivers/gpu/drm/nouveau/nouveau_uvmm.c
> > > +++ b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
> > > @@ -62,6 +62,8 @@ struct bind_job_op {
> > >          enum vm_bind_op op;
> > >          u32 flags;
> > >   
> > > +       struct drm_gpuvm_bo *vm_bo;
> > > +
> > >          struct {
> > >                  u64 addr;
> > >                  u64 range;
> > > @@ -1113,22 +1115,28 @@ bind_validate_region(struct nouveau_job
> > > *job)
> > >   }
> > >   
> > >   static void
> > > -bind_link_gpuvas(struct drm_gpuva_ops *ops, struct
> > > nouveau_uvma_prealloc *new)
> > > +bind_link_gpuvas(struct bind_job_op *bop)
> > >   {
> > > +       struct nouveau_uvma_prealloc *new = &bop->new;
> > > +       struct drm_gpuvm_bo *vm_bo = bop->vm_bo;
> > > +       struct drm_gpuva_ops *ops = bop->ops;
> > >          struct drm_gpuva_op *op;
> > >   
> > >          drm_gpuva_for_each_op(op, ops) {
> > >                  switch (op->op) {
> > >                  case DRM_GPUVA_OP_MAP:
> > > -                       drm_gpuva_link(&new->map->va);
> > > +                       drm_gpuva_link(&new->map->va, vm_bo);
> > >                          break;
> > > -               case DRM_GPUVA_OP_REMAP:
> > > +               case DRM_GPUVA_OP_REMAP: {
> > > +                       struct drm_gpuva *va = op->remap.unmap-
> > > >va;
> > > +
> > >                          if (op->remap.prev)
> > > -                               drm_gpuva_link(&new->prev->va);
> > > +                               drm_gpuva_link(&new->prev->va,
> > > va-
> > > > vm_bo);
> > >                          if (op->remap.next)
> > > -                               drm_gpuva_link(&new->next->va);
> > > -                       drm_gpuva_unlink(op->remap.unmap->va);
> > > +                               drm_gpuva_link(&new->next->va,
> > > va-
> > > > vm_bo);
> > > +                       drm_gpuva_unlink(va);
> > >                          break;
> > > +               }
> > >                  case DRM_GPUVA_OP_UNMAP:
> > >                          drm_gpuva_unlink(op->unmap.va);
> > >                          break;
> > > @@ -1150,10 +1158,18 @@ nouveau_uvmm_bind_job_submit(struct
> > > nouveau_job *job)
> > >   
> > >          list_for_each_op(op, &bind_job->ops) {
> > >                  if (op->op == OP_MAP) {
> > > -                       op->gem.obj = drm_gem_object_lookup(job-
> > > > file_priv,
> > > -                                                           op-
> > > > gem.handle);
> > > -                       if (!op->gem.obj)
> > > +                       struct drm_gem_object *obj;
> > > +
> > > +                       obj = drm_gem_object_lookup(job-
> > > >file_priv,
> > > +                                                   op-
> > > >gem.handle);
> > > +                       if (!(op->gem.obj = obj))
> > >                                  return -ENOENT;
> > > +
> > > +                       dma_resv_lock(obj->resv, NULL);
> > > +                       op->vm_bo = drm_gpuvm_bo_obtain(&uvmm-
> > > >base,
> > > obj);
> > > +                       dma_resv_unlock(obj->resv);
> > > +                       if (IS_ERR(op->vm_bo))
> > > +                               return PTR_ERR(op->vm_bo);
> > >                  }
> > >   
> > >                  ret = bind_validate_op(job, op);
> > > @@ -1364,7 +1380,7 @@ nouveau_uvmm_bind_job_submit(struct
> > > nouveau_job
> > > *job)
> > >                  case OP_UNMAP_SPARSE:
> > >                  case OP_MAP:
> > >                  case OP_UNMAP:
> > > -                       bind_link_gpuvas(op->ops, &op->new);
> > > +                       bind_link_gpuvas(op);
> > >                          break;
> > >                  default:
> > >                          break;
> > > @@ -1511,6 +1527,12 @@ nouveau_uvmm_bind_job_free_work_fn(struct
> > > work_struct *work)
> > >                  if (!IS_ERR_OR_NULL(op->ops))
> > >                          drm_gpuva_ops_free(&uvmm->base, op-
> > > >ops);
> > >   
> > > +               if (!IS_ERR_OR_NULL(op->vm_bo)) {
> > > +                       dma_resv_lock(obj->resv, NULL);
> > > +                       drm_gpuvm_bo_put(op->vm_bo);
> > > +                       dma_resv_unlock(obj->resv);
> > > +               }
> > > +
> > >                  if (obj)
> > >                          drm_gem_object_put(obj);
> > >          }
> > > @@ -1776,15 +1798,18 @@ void
> > >   nouveau_uvmm_bo_map_all(struct nouveau_bo *nvbo, struct
> > > nouveau_mem
> > > *mem)
> > >   {
> > >          struct drm_gem_object *obj = &nvbo->bo.base;
> > > +       struct drm_gpuvm_bo *vm_bo;
> > >          struct drm_gpuva *va;
> > >   
> > >          dma_resv_assert_held(obj->resv);
> > >   
> > > -       drm_gem_for_each_gpuva(va, obj) {
> > > -               struct nouveau_uvma *uvma = uvma_from_va(va);
> > > +       drm_gem_for_each_gpuvm_bo(vm_bo, obj) {
> > > +               drm_gpuvm_bo_for_each_va(va, vm_bo) {
> > > +                       struct nouveau_uvma *uvma =
> > > uvma_from_va(va);
> > >   
> > > -               nouveau_uvma_map(uvma, mem);
> > > -               drm_gpuva_invalidate(va, false);
> > > +                       nouveau_uvma_map(uvma, mem);
> > > +                       drm_gpuva_invalidate(va, false);
> > > +               }
> > >          }
> > >   }
> > >   
> > > @@ -1792,15 +1817,18 @@ void
> > >   nouveau_uvmm_bo_unmap_all(struct nouveau_bo *nvbo)
> > >   {
> > >          struct drm_gem_object *obj = &nvbo->bo.base;
> > > +       struct drm_gpuvm_bo *vm_bo;
> > >          struct drm_gpuva *va;
> > >   
> > >          dma_resv_assert_held(obj->resv);
> > >   
> > > -       drm_gem_for_each_gpuva(va, obj) {
> > > -               struct nouveau_uvma *uvma = uvma_from_va(va);
> > > +       drm_gem_for_each_gpuvm_bo(vm_bo, obj) {
> > > +               drm_gpuvm_bo_for_each_va(va, vm_bo) {
> > > +                       struct nouveau_uvma *uvma =
> > > uvma_from_va(va);
> > >   
> > > -         ��     nouveau_uvma_unmap(uvma);
> > > -               drm_gpuva_invalidate(va, true);
> > > +                       nouveau_uvma_unmap(uvma);
> > > +                       drm_gpuva_invalidate(va, true);
> > > +               }
> > >          }
> > >   }
> > >   
> > > diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
> > > index 16364487fde9..369505447acd 100644
> > > --- a/include/drm/drm_gem.h
> > > +++ b/include/drm/drm_gem.h
> > > @@ -580,7 +580,7 @@ int drm_gem_evict(struct drm_gem_object
> > > *obj);
> > >    * drm_gem_gpuva_init() - initialize the gpuva list of a GEM
> > > object
> > >    * @obj: the &drm_gem_object
> > >    *
> > > - * This initializes the &drm_gem_object's &drm_gpuva list.
> > > + * This initializes the &drm_gem_object's &drm_gpuvm_bo list.
> > >    *
> > >    * Calling this function is only necessary for drivers
> > > intending to
> > > support the
> > >    * &drm_driver_feature DRIVER_GEM_GPUVA.
> > > @@ -593,28 +593,28 @@ static inline void
> > > drm_gem_gpuva_init(struct
> > > drm_gem_object *obj)
> > >   }
> > >   
> > >   /**
> > > - * drm_gem_for_each_gpuva() - iternator to walk over a list of
> > > gpuvas
> > > - * @entry__: &drm_gpuva structure to assign to in each iteration
> > > step
> > > - * @obj__: the &drm_gem_object the &drm_gpuvas to walk are
> > > associated with
> > > + * drm_gem_for_each_gpuvm_bo() - iterator to walk over a list of
> > > &drm_gpuvm_bo
> > > + * @entry__: &drm_gpuvm_bo structure to assign to in each
> > > iteration
> > > step
> > > + * @obj__: the &drm_gem_object the &drm_gpuvm_bo to walk are
> > > associated with
> > >    *
> > > - * This iterator walks over all &drm_gpuva structures associated
> > > with the
> > > - * &drm_gpuva_manager.
> > > + * This iterator walks over all &drm_gpuvm_bo structures
> > > associated
> > > with the
> > > + * &drm_gem_object.
> > >    */
> > > -#define drm_gem_for_each_gpuva(entry__, obj__) \
> > > -       list_for_each_entry(entry__, &(obj__)->gpuva.list,
> > > gem.entry)
> > > +#define drm_gem_for_each_gpuvm_bo(entry__, obj__) \
> > > +       list_for_each_entry(entry__, &(obj__)->gpuva.list,
> > > list.entry.gem)
> > >   
> > >   /**
> > > - * drm_gem_for_each_gpuva_safe() - iternator to safely walk over
> > > a
> > > list of
> > > - * gpuvas
> > > - * @entry__: &drm_gpuva structure to assign to in each iteration
> > > step
> > > - * @next__: &next &drm_gpuva to store the next step
> > > - * @obj__: the &drm_gem_object the &drm_gpuvas to walk are
> > > associated with
> > > + * drm_gem_for_each_gpuvm_bo_safe() - iterator to safely walk
> > > over a
> > > list of
> > > + * &drm_gpuvm_bo
> > > + * @entry__: &drm_gpuvm_bostructure to assign to in each
> > > iteration
> > > step
> > > + * @next__: &next &drm_gpuvm_bo to store the next step
> > > + * @obj__: the &drm_gem_object the &drm_gpuvm_bo to walk are
> > > associated with
> > >    *
> > > - * This iterator walks over all &drm_gpuva structures associated
> > > with the
> > > + * This iterator walks over all &drm_gpuvm_bo structures
> > > associated
> > > with the
> > >    * &drm_gem_object. It is implemented with
> > > list_for_each_entry_safe(), hence
> > >    * it is save against removal of elements.
> > >    */
> > > -#define drm_gem_for_each_gpuva_safe(entry__, next__, obj__) \
> > > -       list_for_each_entry_safe(entry__, next__, &(obj__)-
> > > > gpuva.list, gem.entry)
> > > +#define drm_gem_for_each_gpuvm_bo_safe(entry__, next__, obj__) \
> > > +       list_for_each_entry_safe(entry__, next__, &(obj__)-
> > > > gpuva.list, list.entry.gem)
> > >   
> > >   #endif /* __DRM_GEM_H__ */
> > > diff --git a/include/drm/drm_gpuvm.h b/include/drm/drm_gpuvm.h
> > > index 47cbacb244b9..466fdd76c71a 100644
> > > --- a/include/drm/drm_gpuvm.h
> > > +++ b/include/drm/drm_gpuvm.h
> > > @@ -25,6 +25,7 @@
> > >    * OTHER DEALINGS IN THE SOFTWARE.
> > >    */
> > >   
> > > +#include <linux/dma-resv.h>
> > >   #include <linux/list.h>
> > >   #include <linux/rbtree.h>
> > >   #include <linux/types.h>
> > > @@ -33,6 +34,7 @@
> > >   #include <drm/drm_gem.h>
> > >   
> > >   struct drm_gpuvm;
> > > +struct drm_gpuvm_bo;
> > >   struct drm_gpuvm_ops;
> > >   
> > >   /**
> > > @@ -73,6 +75,12 @@ struct drm_gpuva {
> > >           */
> > >          struct drm_gpuvm *vm;
> > >   
> > > +       /**
> > > +        * @vm_bo: the &drm_gpuvm_bo abstraction for the mapped
> > > +        * &drm_gem_object
> > > +        */
> > > +       struct drm_gpuvm_bo *vm_bo;
> > > +
> > >          /**
> > >           * @flags: the &drm_gpuva_flags for this mapping
> > >           */
> > > @@ -108,7 +116,7 @@ struct drm_gpuva {
> > >                  struct drm_gem_object *obj;
> > >   
> > >                  /**
> > > -                * @entry: the &list_head to attach this object
> > > to a
> > > &drm_gem_object
> > > +                * @entry: the &list_head to attach this object
> > > to a
> > > &drm_gpuvm_bo
> > >                   */
> > >                  struct list_head entry;
> > >          } gem;
> > > @@ -141,7 +149,7 @@ struct drm_gpuva {
> > >   int drm_gpuva_insert(struct drm_gpuvm *gpuvm, struct drm_gpuva
> > > *va);
> > >   void drm_gpuva_remove(struct drm_gpuva *va);
> > >   
> > > -void drm_gpuva_link(struct drm_gpuva *va);
> > > +void drm_gpuva_link(struct drm_gpuva *va, struct drm_gpuvm_bo
> > > *vm_bo);
> > >   void drm_gpuva_unlink(struct drm_gpuva *va);
> > >   
> > >   struct drm_gpuva *drm_gpuva_find(struct drm_gpuvm *gpuvm,
> > > @@ -188,10 +196,16 @@ static inline bool
> > > drm_gpuva_invalidated(struct
> > > drm_gpuva *va)
> > >    * enum drm_gpuvm_flags - flags for struct drm_gpuvm
> > >    */
> > >   enum drm_gpuvm_flags {
> > > +       /**
> > > +        * @DRM_GPUVM_RESV_PROTECTED: GPUVM is protected
> > > externally
> > > by the
> > > +        * GPUVM's &dma_resv lock
> > > +        */
> > > +       DRM_GPUVM_RESV_PROTECTED = BIT(0),
> > > +
> > >          /**
> > >           * @DRM_GPUVM_USERBITS: user defined bits
> > >           */
> > > -       DRM_GPUVM_USERBITS = BIT(0),
> > > +       DRM_GPUVM_USERBITS = BIT(1),
> > >   };
> > >   
> > >   /**
> > > @@ -280,6 +294,19 @@ bool drm_gpuvm_interval_empty(struct
> > > drm_gpuvm
> > > *gpuvm, u64 addr, u64 range);
> > >   struct drm_gem_object *
> > >   drm_gpuvm_resv_object_alloc(struct drm_device *drm);
> > >   
> > > +/**
> > > + * drm_gpuvm_resv_protected() - indicates whether
> > > &DRM_GPUVM_RESV_PROTECTED is
> > > + * set
> > > + * @gpuvm: the &drm_gpuvm
> > > + *
> > > + * Returns: true if &DRM_GPUVM_RESV_PROTECTED is set, false
> > > otherwise.
> > > + */
> > > +static inline bool
> > > +drm_gpuvm_resv_protected(struct drm_gpuvm *gpuvm)
> > > +{
> > > +       return gpuvm->flags & DRM_GPUVM_RESV_PROTECTED;
> > > +}
> > > +
> > >   /**
> > >    * drm_gpuvm_resv() - returns the &drm_gpuvm's &dma_resv
> > >    * @gpuvm__: the &drm_gpuvm
> > > @@ -298,6 +325,12 @@ drm_gpuvm_resv_object_alloc(struct
> > > drm_device
> > > *drm);
> > >    */
> > >   #define drm_gpuvm_resv_obj(gpuvm__) ((gpuvm__)->r_obj)
> > >   
> > > +#define drm_gpuvm_resv_held(gpuvm__) \
> > > +       dma_resv_held(drm_gpuvm_resv(gpuvm__))
> > > +
> > > +#define drm_gpuvm_resv_assert_held(gpuvm__) \
> > > +       dma_resv_assert_held(drm_gpuvm_resv(gpuvm__))
> > > +
> > >   #define drm_gpuvm_resv_held(gpuvm__) \
> > >          dma_resv_held(drm_gpuvm_resv(gpuvm__))
> > >   
> > > @@ -382,6 +415,128 @@ __drm_gpuva_next(struct drm_gpuva *va)
> > >   #define drm_gpuvm_for_each_va_safe(va__, next__, gpuvm__) \
> > >          list_for_each_entry_safe(va__, next__, &(gpuvm__)-
> > > >rb.list,
> > > rb.entry)
> > >   
> > > +/**
> > > + * struct drm_gpuvm_bo - structure representing a &drm_gpuvm and
> > > + * &drm_gem_object combination
> > > + *
> > > + * This structure is an abstraction representing a &drm_gpuvm
> > > and
> > > + * &drm_gem_object combination. It serves as an indirection to
> > > accelerate
> > > + * iterating all &drm_gpuvas within a &drm_gpuvm backed by the
> > > same
> > > + * &drm_gem_object.
> > > + *
> > > + * Furthermore it is used cache evicted GEM objects for a
> > > certain
> > > GPU-VM to
> > > + * accelerate validation.
> > > + *
> > > + * Typically, drivers want to create an instance of a struct
> > > drm_gpuvm_bo once
> > > + * a GEM object is mapped first in a GPU-VM and release the
> > > instance
> > > once the
> > > + * last mapping of the GEM object in this GPU-VM is unmapped.
> > > + */
> > > +struct drm_gpuvm_bo {
> > > +       /**
> > > +        * @vm: The &drm_gpuvm the @obj is mapped in. This
> > > pointer is
> > > not
> > > +        * reference counted.
> > > +        *
> > > +        * A struct drm_gpuvm_bo is not allowed to out-live its
> > > &drm_gpuvm
> > > +        * context. Implicitly, this is ensured by the fact that
> > > the
> > > driver is
> > > +        * responsible to ensure the VM doesn't contain mappings
> > > once
> > > it's
> > > +        * freed, since a struct drm_gpuvm_bo should be freed
> > > once
> > > the last
> > > +        * mapping being backed by the corresponding buffer
> > > object is
> > > unmapped.
> > > +        */
> > 
> > 
> > I don't think the above is completely true. Let's assume in the
> > !RESV_PROTECTED case that a reference is grabbed on the
> > drm_gpuvm_bo
> > during an iteration over a list. Then user-space closes the vm and
> > all
> > vmas are unlinked, but this reference remains but the vm pointer
> > becomes stale. In the RESV_PROTECTED case this is ensured not to
> > happen
> > if by the vm->resv being grabbed during unlink, but in the
> > !RESV_PROTECTED case, the above wording isn't sufficient. The
> > caller
> > needs to ensure the vm stays alive using some sort of similar rule
> > or
> > use kref_get_unless_zero() on the vm under the spinlock if
> > dereferenced.
> 
> The list is part of the GPUVM. Hence, the caller *must* either
> already hold
> a reference to the GPUVM or otherwise ensure it's not freed while
> iterating
> this list. All the drm_gpuvm_bo structures within this list can't
> have a
> pointer to another VM than this one by definition.
> 
> Anyway, I recognize that this isn't very obvious. Hence, I think we
> should
> probably reference count GPUVMs as well. I'd think of the same way we
> do it
> with drm_gem_objects. However, I'd prefer to introduce this with a
> subsequent
> patch.

Well, I think we should actually be OK in most cases, and refcounting
here would probably result in circular dependencies.

I think to do this properly one would document that this pointer is not
refecounted and that dereferencing that pointer requires a strong vm
reference from elsewhere, or holding the bo resv and verifying that the
gpuvm_bo is on the gem object's gpuvm_bo list.

We've had a lot of tricky lifetime problems of vms and vmas in the i915
driver so that's why I think clearly documenting the rules for
dereferencing is important. In particular if we, in the future provide
some sort of iteration over the gem object's gpvum_bo list, dropping
the lock while iterating, that will blow up.

/Thomas


> 
> > 
> > > +       struct drm_gpuvm *vm;
> > > +
> > > +       /**
> > > +        * @obj: The &drm_gem_object being mapped in @vm. This is
> > > a
> > > reference
> > > +        * counted pointer.
> > > +        */
> > > +       struct drm_gem_object *obj;
> > > +
> > > +       /**
> > > +        * @kref: The reference count for this &drm_gpuvm_bo.
> > > +        */
> > > +       struct kref kref;
> > > +
> > > +       /**
> > > +        * @list: Structure containing all &list_heads.
> > > +        */
> > > +       struct {
> > > +               /**
> > > +                * @gpuva: The list of linked &drm_gpuvas.
> > > +                */
> > > +               struct list_head gpuva;
> > 
> > Still missing doc on how the @gpuva stays alive during iteration
> > over
> > the list?
> 
> Thanks for pointing this out again, I missed that one.
> 
> - Danilo
> 
> > 
> > 
> > 
> > 8<-------------------------------------------------------------
> > 
> > Thanks,
> > Thomas
> > 
>
  

On 11/1/23 17:38, Thomas Hellström wrote:
> On Tue, 2023-10-31 at 18:38 +0100, Danilo Krummrich wrote:
>> On 10/31/23 11:32, Thomas Hellström wrote:
>>> On Mon, 2023-10-23 at 22:16 +0200, Danilo Krummrich wrote:
>>>> Add an abstraction layer between the drm_gpuva mappings of a
>>>> particular
>>>> drm_gem_object and this GEM object itself. The abstraction
>>>> represents
>>>> a
>>>> combination of a drm_gem_object and drm_gpuvm. The drm_gem_object
>>>> holds
>>>> a list of drm_gpuvm_bo structures (the structure representing
>>>> this
>>>> abstraction), while each drm_gpuvm_bo contains list of mappings
>>>> of
>>>> this
>>>> GEM object.
>>>>
>>>> This has multiple advantages:
>>>>
>>>> 1) We can use the drm_gpuvm_bo structure to attach it to various
>>>> lists
>>>>      of the drm_gpuvm. This is useful for tracking external and
>>>> evicted
>>>>      objects per VM, which is introduced in subsequent patches.
>>>>
>>>> 2) Finding mappings of a certain drm_gem_object mapped in a
>>>> certain
>>>>      drm_gpuvm becomes much cheaper.
>>>>
>>>> 3) Drivers can derive and extend the structure to easily
>>>> represent
>>>>      driver specific states of a BO for a certain GPUVM.
>>>>
>>>> The idea of this abstraction was taken from amdgpu, hence the
>>>> credit
>>>> for
>>>> this idea goes to the developers of amdgpu.
>>>>
>>>> Cc: Christian König <christian.koenig@amd.com>
>>>> Signed-off-by: Danilo Krummrich <dakr@redhat.com>
>>>> ---
>>>>    drivers/gpu/drm/drm_gpuvm.c            | 335
>>>> +++++++++++++++++++++--
>>>> --
>>>>    drivers/gpu/drm/nouveau/nouveau_uvmm.c |  64 +++--
>>>>    include/drm/drm_gem.h                  |  32 +--
>>>>    include/drm/drm_gpuvm.h                | 188 +++++++++++++-
>>>>    4 files changed, 533 insertions(+), 86 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/drm_gpuvm.c
>>>> b/drivers/gpu/drm/drm_gpuvm.c
>>>> index c03332883432..7f4f5919f84c 100644
>>>> --- a/drivers/gpu/drm/drm_gpuvm.c
>>>> +++ b/drivers/gpu/drm/drm_gpuvm.c
>>>> @@ -70,6 +70,18 @@
>>>>     * &drm_gem_object, such as the &drm_gem_object containing the
>>>> root
>>>> page table,
>>>>     * but it can also be a 'dummy' object, which can be allocated
>>>> with
>>>>     * drm_gpuvm_resv_object_alloc().
>>>> + *
>>>> + * In order to connect a struct drm_gpuva its backing
>>>> &drm_gem_object each
>>>> + * &drm_gem_object maintains a list of &drm_gpuvm_bo structures,
>>>> and
>>>> each
>>>> + * &drm_gpuvm_bo contains a list of &drm_gpuva structures.
>>>> + *
>>>> + * A &drm_gpuvm_bo is an abstraction that represents a
>>>> combination
>>>> of a
>>>> + * &drm_gpuvm and a &drm_gem_object. Every such combination
>>>> should
>>>> be unique.
>>>> + * This is ensured by the API through drm_gpuvm_bo_obtain() and
>>>> + * drm_gpuvm_bo_obtain_prealloc() which first look into the
>>>> corresponding
>>>> + * &drm_gem_object list of &drm_gpuvm_bos for an existing
>>>> instance
>>>> of this
>>>> + * particular combination. If not existent a new instance is
>>>> created
>>>> and linked
>>>> + * to the &drm_gem_object.
>>>>     */
>>>>    
>>>>    /**
>>>> @@ -395,21 +407,28 @@
>>>>    /**
>>>>     * DOC: Locking
>>>>     *
>>>> - * Generally, the GPU VA manager does not take care of locking
>>>> itself, it is
>>>> - * the drivers responsibility to take care about locking.
>>>> Drivers
>>>> might want to
>>>> - * protect the following operations: inserting, removing and
>>>> iterating
>>>> - * &drm_gpuva objects as well as generating all kinds of
>>>> operations,
>>>> such as
>>>> - * split / merge or prefetch.
>>>> - *
>>>> - * The GPU VA manager also does not take care of the locking of
>>>> the
>>>> backing
>>>> - * &drm_gem_object buffers GPU VA lists by itself; drivers are
>>>> responsible to
>>>> - * enforce mutual exclusion using either the GEMs dma_resv lock
>>>> or
>>>> alternatively
>>>> - * a driver specific external lock. For the latter see also
>>>> - * drm_gem_gpuva_set_lock().
>>>> - *
>>>> - * However, the GPU VA manager contains lockdep checks to ensure
>>>> callers of its
>>>> - * API hold the corresponding lock whenever the &drm_gem_objects
>>>> GPU
>>>> VA list is
>>>> - * accessed by functions such as drm_gpuva_link() or
>>>> drm_gpuva_unlink().
>>>> + * In terms of managing &drm_gpuva entries DRM GPUVM does not
>>>> take
>>>> care of
>>>> + * locking itself, it is the drivers responsibility to take care
>>>> about locking.
>>>> + * Drivers might want to protect the following operations:
>>>> inserting, removing
>>>> + * and iterating &drm_gpuva objects as well as generating all
>>>> kinds
>>>> of
>>>> + * operations, such as split / merge or prefetch.
>>>> + *
>>>> + * DRM GPUVM also does not take care of the locking of the
>>>> backing
>>>> + * &drm_gem_object buffers GPU VA lists and &drm_gpuvm_bo
>>>> abstractions by
>>>> + * itself; drivers are responsible to enforce mutual exclusion
>>>> using
>>>> either the
>>>> + * GEMs dma_resv lock or alternatively a driver specific
>>>> external
>>>> lock. For the
>>>> + * latter see also drm_gem_gpuva_set_lock().
>>>> + *
>>>> + * However, DRM GPUVM contains lockdep checks to ensure callers
>>>> of
>>>> its API hold
>>>> + * the corresponding lock whenever the &drm_gem_objects GPU VA
>>>> list
>>>> is accessed
>>>> + * by functions such as drm_gpuva_link() or drm_gpuva_unlink(),
>>>> but
>>>> also
>>>> + * drm_gpuvm_bo_obtain() and drm_gpuvm_bo_put().
>>>> + *
>>>> + * The latter is required since on creation and destruction of a
>>>> &drm_gpuvm_bo
>>>> + * the &drm_gpuvm_bo is attached / removed from the
>>>> &drm_gem_objects
>>>> gpuva list.
>>>> + * Subsequent calls to drm_gpuvm_bo_obtain() for the same
>>>> &drm_gpuvm
>>>> and
>>>> + * &drm_gem_object must be able to observe previous creations
>>>> and
>>>> destructions
>>>> + * of &drm_gpuvm_bos in order to keep instances unique.
>>>>     */
>>>>    
>>>>    /**
>>>> @@ -439,6 +458,7 @@
>>>>     *     {
>>>>     *             struct drm_gpuva_ops *ops;
>>>>     *             struct drm_gpuva_op *op
>>>> + *             struct drm_gpuvm_bo *vm_bo;
>>>>     *
>>>>     *             driver_lock_va_space();
>>>>     *             ops = drm_gpuvm_sm_map_ops_create(gpuvm, addr,
>>>> range,
>>>> @@ -446,6 +466,10 @@
>>>>     *             if (IS_ERR(ops))
>>>>     *                     return PTR_ERR(ops);
>>>>     *
>>>> + *             vm_bo = drm_gpuvm_bo_obtain(gpuvm, obj);
>>>> + *             if (IS_ERR(vm_bo))
>>>> + *                     return PTR_ERR(vm_bo);
>>>> + *
>>>>     *             drm_gpuva_for_each_op(op, ops) {
>>>>     *                     struct drm_gpuva *va;
>>>>     *
>>>> @@ -458,7 +482,7 @@
>>>>     *
>>>>     *                             driver_vm_map();
>>>>     *                             drm_gpuva_map(gpuvm, va, &op-
>>>>> map);
>>>> - *                             drm_gpuva_link(va);
>>>> + *                             drm_gpuva_link(va, vm_bo);
>>>>     *
>>>>     *                             break;
>>>>     *                     case DRM_GPUVA_OP_REMAP: {
>>>> @@ -485,11 +509,11 @@
>>>>     *                             driver_vm_remap();
>>>>     *                             drm_gpuva_remap(prev, next, &op-
>>>>> remap);
>>>>     *
>>>> - *                             drm_gpuva_unlink(va);
>>>>     *                             if (prev)
>>>> - *                                     drm_gpuva_link(prev);
>>>> + *                                     drm_gpuva_link(prev, va-
>>>>> vm_bo);
>>>>     *                             if (next)
>>>> - *                                     drm_gpuva_link(next);
>>>> + *                                     drm_gpuva_link(next, va-
>>>>> vm_bo);
>>>> + *                             drm_gpuva_unlink(va);
>>>>     *
>>>>     *                             break;
>>>>     *                     }
>>>> @@ -505,6 +529,7 @@
>>>>     *                             break;
>>>>     *                     }
>>>>     *             }
>>>> + *             drm_gpuvm_bo_put(vm_bo);
>>>>     *             driver_unlock_va_space();
>>>>     *
>>>>     *             return 0;
>>>> @@ -514,6 +539,7 @@
>>>>     *
>>>>     *     struct driver_context {
>>>>     *             struct drm_gpuvm *gpuvm;
>>>> + *             struct drm_gpuvm_bo *vm_bo;
>>>>     *             struct drm_gpuva *new_va;
>>>>     *             struct drm_gpuva *prev_va;
>>>>     *             struct drm_gpuva *next_va;
>>>> @@ -534,6 +560,7 @@
>>>>     *                               struct drm_gem_object *obj,
>>>> u64
>>>> offset)
>>>>     *     {
>>>>     *             struct driver_context ctx;
>>>> + *             struct drm_gpuvm_bo *vm_bo;
>>>>     *             struct drm_gpuva_ops *ops;
>>>>     *             struct drm_gpuva_op *op;
>>>>     *             int ret = 0;
>>>> @@ -543,16 +570,23 @@
>>>>     *             ctx.new_va = kzalloc(sizeof(*ctx.new_va),
>>>> GFP_KERNEL);
>>>>     *             ctx.prev_va = kzalloc(sizeof(*ctx.prev_va),
>>>> GFP_KERNEL);
>>>>     *             ctx.next_va = kzalloc(sizeof(*ctx.next_va),
>>>> GFP_KERNEL);
>>>> - *             if (!ctx.new_va || !ctx.prev_va || !ctx.next_va)
>>>> {
>>>> + *             ctx.vm_bo = drm_gpuvm_bo_create(gpuvm, obj);
>>>> + *             if (!ctx.new_va || !ctx.prev_va || !ctx.next_va
>>>> ||
>>>> !vm_bo) {
>>>>     *                     ret = -ENOMEM;
>>>>     *                     goto out;
>>>>     *             }
>>>>     *
>>>> + *             // Typically protected with a driver specific GEM
>>>> gpuva lock
>>>> + *             // used in the fence signaling path for
>>>> drm_gpuva_link() and
>>>> + *             // drm_gpuva_unlink(), hence pre-allocate.
>>>> + *             ctx.vm_bo =
>>>> drm_gpuvm_bo_obtain_prealloc(ctx.vm_bo);
>>>> + *
>>>>     *             driver_lock_va_space();
>>>>     *             ret = drm_gpuvm_sm_map(gpuvm, &ctx, addr, range,
>>>> obj,
>>>> offset);
>>>>     *             driver_unlock_va_space();
>>>>     *
>>>>     *     out:
>>>> + *             drm_gpuvm_bo_put(ctx.vm_bo);
>>>>     *             kfree(ctx.new_va);
>>>>     *             kfree(ctx.prev_va);
>>>>     *             kfree(ctx.next_va);
>>>> @@ -565,7 +599,7 @@
>>>>     *
>>>>     *             drm_gpuva_map(ctx->vm, ctx->new_va, &op->map);
>>>>     *
>>>> - *             drm_gpuva_link(ctx->new_va);
>>>> + *             drm_gpuva_link(ctx->new_va, ctx->vm_bo);
>>>>     *
>>>>     *             // prevent the new GPUVA from being freed in
>>>>     *             // driver_mapping_create()
>>>> @@ -577,22 +611,23 @@
>>>>     *     int driver_gpuva_remap(struct drm_gpuva_op *op, void
>>>> *__ctx)
>>>>     *     {
>>>>     *             struct driver_context *ctx = __ctx;
>>>> + *             struct drm_gpuva *va = op->remap.unmap->va;
>>>>     *
>>>>     *             drm_gpuva_remap(ctx->prev_va, ctx->next_va, &op-
>>>>> remap);
>>>>     *
>>>> - *             drm_gpuva_unlink(op->remap.unmap->va);
>>>> - *             kfree(op->remap.unmap->va);
>>>> - *
>>>>     *             if (op->remap.prev) {
>>>> - *                     drm_gpuva_link(ctx->prev_va);
>>>> + *                     drm_gpuva_link(ctx->prev_va, va->vm_bo);
>>>>     *                     ctx->prev_va = NULL;
>>>>     *             }
>>>>     *
>>>>     *             if (op->remap.next) {
>>>> - *                     drm_gpuva_link(ctx->next_va);
>>>> + *                     drm_gpuva_link(ctx->next_va, va->vm_bo);
>>>>     *                     ctx->next_va = NULL;
>>>>     *             }
>>>>     *
>>>> + *             drm_gpuva_unlink(va);
>>>> + *             kfree(va);
>>>> + *
>>>>     *             return 0;
>>>>     *     }
>>>>     *
>>>> @@ -774,6 +809,194 @@ drm_gpuvm_destroy(struct drm_gpuvm *gpuvm)
>>>>    }
>>>>    EXPORT_SYMBOL_GPL(drm_gpuvm_destroy);
>>>>    
>>>> +/**
>>>> + * drm_gpuvm_bo_create() - create a new instance of struct
>>>> drm_gpuvm_bo
>>>> + * @gpuvm: The &drm_gpuvm the @obj is mapped in.
>>>> + * @obj: The &drm_gem_object being mapped in the @gpuvm.
>>>> + *
>>>> + * If provided by the driver, this function uses the
>>>> &drm_gpuvm_ops
>>>> + * vm_bo_alloc() callback to allocate.
>>>> + *
>>>> + * Returns: a pointer to the &drm_gpuvm_bo on success, NULL on
>>>
>>> Still needs s/Returns:/Return:/g
>>>
>>>> failure
>>>> + */
>>>> +struct drm_gpuvm_bo *
>>>> +drm_gpuvm_bo_create(struct drm_gpuvm *gpuvm,
>>>> +                   struct drm_gem_object *obj)
>>>> +{
>>>> +       const struct drm_gpuvm_ops *ops = gpuvm->ops;
>>>> +       struct drm_gpuvm_bo *vm_bo;
>>>> +
>>>> +       if (ops && ops->vm_bo_alloc)
>>>> +               vm_bo = ops->vm_bo_alloc();
>>>> +       else
>>>> +               vm_bo = kzalloc(sizeof(*vm_bo), GFP_KERNEL);
>>>> +
>>>> +       if (unlikely(!vm_bo))
>>>> +               return NULL;
>>>> +
>>>> +       vm_bo->vm = gpuvm;
>>>> +       vm_bo->obj = obj;
>>>> +       drm_gem_object_get(obj);
>>>> +
>>>> +       kref_init(&vm_bo->kref);
>>>> +       INIT_LIST_HEAD(&vm_bo->list.gpuva);
>>>> +       INIT_LIST_HEAD(&vm_bo->list.entry.gem);
>>>> +
>>>> +       return vm_bo;
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_create);
>>>> +
>>>> +static void
>>>> +drm_gpuvm_bo_destroy(struct kref *kref)
>>>> +{
>>>> +       struct drm_gpuvm_bo *vm_bo = container_of(kref, struct
>>>> drm_gpuvm_bo,
>>>> +                                                 kref);
>>>> +       struct drm_gpuvm *gpuvm = vm_bo->vm;
>>>> +       const struct drm_gpuvm_ops *ops = gpuvm->ops;
>>>> +       struct drm_gem_object *obj = vm_bo->obj;
>>>> +       bool lock = !drm_gpuvm_resv_protected(gpuvm);
>>>> +
>>>> +       if (!lock)
>>>> +               drm_gpuvm_resv_assert_held(gpuvm);
>>>> +
>>>> +       drm_gem_gpuva_assert_lock_held(obj);
>>>> +       list_del(&vm_bo->list.entry.gem);
>>>> +
>>>> +       if (ops && ops->vm_bo_free)
>>>> +               ops->vm_bo_free(vm_bo);
>>>> +       else
>>>> +               kfree(vm_bo);
>>>> +
>>>> +       drm_gem_object_put(obj);
>>>> +}
>>>> +
>>>> +/**
>>>> + * drm_gpuvm_bo_put() - drop a struct drm_gpuvm_bo reference
>>>> + * @vm_bo: the &drm_gpuvm_bo to release the reference of
>>>> + *
>>>> + * This releases a reference to @vm_bo.
>>>> + *
>>>> + * If the reference count drops to zero, the &gpuvm_bo is
>>>> destroyed,
>>>> which
>>>> + * includes removing it from the GEMs gpuva list. Hence, if a
>>>> call
>>>> to this
>>>> + * function can potentially let the reference count to zero the
>>>> caller must
>>>> + * hold the dma-resv or driver specific GEM gpuva lock.
>>>> + */
>>>> +void
>>>> +drm_gpuvm_bo_put(struct drm_gpuvm_bo *vm_bo)
>>>> +{
>>>> +       if (vm_bo)
>>>> +               kref_put(&vm_bo->kref, drm_gpuvm_bo_destroy);
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_put);
>>>> +
>>>> +static struct drm_gpuvm_bo *
>>>> +__drm_gpuvm_bo_find(struct drm_gpuvm *gpuvm,
>>>> +                   struct drm_gem_object *obj)
>>>> +{
>>>> +       struct drm_gpuvm_bo *vm_bo;
>>>> +
>>>> +       drm_gem_gpuva_assert_lock_held(obj);
>>>> +       drm_gem_for_each_gpuvm_bo(vm_bo, obj)
>>>> +               if (vm_bo->vm == gpuvm)
>>>> +                       return vm_bo;
>>>> +
>>>> +       return NULL;
>>>> +}
>>>> +
>>>> +/**
>>>> + * drm_gpuvm_bo_find() - find the &drm_gpuvm_bo for the given
>>>> + * &drm_gpuvm and &drm_gem_object
>>>> + * @gpuvm: The &drm_gpuvm the @obj is mapped in.
>>>> + * @obj: The &drm_gem_object being mapped in the @gpuvm.
>>>> + *
>>>> + * Find the &drm_gpuvm_bo representing the combination of the
>>>> given
>>>> + * &drm_gpuvm and &drm_gem_object. If found, increases the
>>>> reference
>>>> + * count of the &drm_gpuvm_bo accordingly.
>>>> + *
>>>> + * Returns: a pointer to the &drm_gpuvm_bo on success, NULL on
>>>> failure
>>>> + */
>>>> +struct drm_gpuvm_bo *
>>>> +drm_gpuvm_bo_find(struct drm_gpuvm *gpuvm,
>>>> +                 struct drm_gem_object *obj)
>>>> +{
>>>> +       struct drm_gpuvm_bo *vm_bo = __drm_gpuvm_bo_find(gpuvm,
>>>> obj);
>>>> +
>>>> +       return vm_bo ? drm_gpuvm_bo_get(vm_bo) : NULL;
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_find);
>>>> +
>>>> +/**
>>>> + * drm_gpuvm_bo_obtain() - obtains and instance of the
>>>> &drm_gpuvm_bo
>>>> for the
>>>> + * given &drm_gpuvm and &drm_gem_object
>>>> + * @gpuvm: The &drm_gpuvm the @obj is mapped in.
>>>> + * @obj: The &drm_gem_object being mapped in the @gpuvm.
>>>> + *
>>>> + * Find the &drm_gpuvm_bo representing the combination of the
>>>> given
>>>> + * &drm_gpuvm and &drm_gem_object. If found, increases the
>>>> reference
>>>> + * count of the &drm_gpuvm_bo accordingly. If not found,
>>>> allocates a
>>>> new
>>>> + * &drm_gpuvm_bo.
>>>> + *
>>>> + * A new &drm_gpuvm_bo is added to the GEMs gpuva list.
>>>> + *
>>>> + * Returns: a pointer to the &drm_gpuvm_bo on success, an
>>>> ERR_PTR on
>>>> failure
>>>> + */
>>>> +struct drm_gpuvm_bo *
>>>> +drm_gpuvm_bo_obtain(struct drm_gpuvm *gpuvm,
>>>> +                   struct drm_gem_object *obj)
>>>> +{
>>>> +       struct drm_gpuvm_bo *vm_bo;
>>>> +
>>>> +       vm_bo = drm_gpuvm_bo_find(gpuvm, obj);
>>>> +       if (vm_bo)
>>>> +               return vm_bo;
>>>> +
>>>> +       vm_bo = drm_gpuvm_bo_create(gpuvm, obj);
>>>> +       if (!vm_bo)
>>>> +               return ERR_PTR(-ENOMEM);
>>>> +
>>>> +       drm_gem_gpuva_assert_lock_held(obj);
>>>> +       list_add_tail(&vm_bo->list.entry.gem, &obj->gpuva.list);
>>>> +
>>>> +       return vm_bo;
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_obtain);
>>>> +
>>>> +/**
>>>> + * drm_gpuvm_bo_obtain_prealloc() - obtains and instance of the
>>>> &drm_gpuvm_bo
>>>> + * for the given &drm_gpuvm and &drm_gem_object
>>>> + * @__vm_bo: A pre-allocated struct drm_gpuvm_bo.
>>>> + *
>>>> + * Find the &drm_gpuvm_bo representing the combination of the
>>>> given
>>>> + * &drm_gpuvm and &drm_gem_object. If found, increases the
>>>> reference
>>>> + * count of the found &drm_gpuvm_bo accordingly, while the
>>>> @__vm_bo
>>>> reference
>>>> + * count is decreased. If not found @__vm_bo is returned without
>>>> further
>>>> + * increase of the reference count.
>>>> + *
>>>> + * A new &drm_gpuvm_bo is added to the GEMs gpuva list.
>>>> + *
>>>> + * Returns: a pointer to the found &drm_gpuvm_bo or @__vm_bo if
>>>> no
>>>> existing
>>>> + * &drm_gpuvm_bo was found
>>>> + */
>>>> +struct drm_gpuvm_bo *
>>>> +drm_gpuvm_bo_obtain_prealloc(struct drm_gpuvm_bo *__vm_bo)
>>>> +{
>>>> +       struct drm_gpuvm *gpuvm = __vm_bo->vm;
>>>> +       struct drm_gem_object *obj = __vm_bo->obj;
>>>> +       struct drm_gpuvm_bo *vm_bo;
>>>> +
>>>> +       vm_bo = drm_gpuvm_bo_find(gpuvm, obj);
>>>> +       if (vm_bo) {
>>>> +               drm_gpuvm_bo_put(__vm_bo);
>>>> +               return vm_bo;
>>>> +       }
>>>> +
>>>> +       drm_gem_gpuva_assert_lock_held(obj);
>>>> +       list_add_tail(&__vm_bo->list.entry.gem, &obj-
>>>>> gpuva.list);
>>>> +
>>>> +       return __vm_bo;
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_obtain_prealloc);
>>>> +
>>>>    static int
>>>>    __drm_gpuva_insert(struct drm_gpuvm *gpuvm,
>>>>                      struct drm_gpuva *va)
>>>> @@ -864,24 +1087,33 @@ EXPORT_SYMBOL_GPL(drm_gpuva_remove);
>>>>    /**
>>>>     * drm_gpuva_link() - link a &drm_gpuva
>>>>     * @va: the &drm_gpuva to link
>>>> + * @vm_bo: the &drm_gpuvm_bo to add the &drm_gpuva to
>>>>     *
>>>> - * This adds the given &va to the GPU VA list of the
>>>> &drm_gem_object
>>>> it is
>>>> - * associated with.
>>>> + * This adds the given &va to the GPU VA list of the
>>>> &drm_gpuvm_bo
>>>> and the
>>>> + * &drm_gpuvm_bo to the &drm_gem_object it is associated with.
>>>> + *
>>>> + * For every &drm_gpuva entry added to the &drm_gpuvm_bo an
>>>> additional
>>>> + * reference of the latter is taken.
>>>>     *
>>>>     * This function expects the caller to protect the GEM's GPUVA
>>>> list
>>>> against
>>>> - * concurrent access using the GEMs dma_resv lock.
>>>> + * concurrent access using either the GEMs dma_resv lock or a
>>>> driver
>>>> specific
>>>> + * lock set through drm_gem_gpuva_set_lock().
>>>>     */
>>>>    void
>>>> -drm_gpuva_link(struct drm_gpuva *va)
>>>> +drm_gpuva_link(struct drm_gpuva *va, struct drm_gpuvm_bo *vm_bo)
>>>>    {
>>>>           struct drm_gem_object *obj = va->gem.obj;
>>>> +       struct drm_gpuvm *gpuvm = va->vm;
>>>>    
>>>>           if (unlikely(!obj))
>>>>                   return;
>>>>    
>>>> -       drm_gem_gpuva_assert_lock_held(obj);
>>>> +       drm_WARN_ON(gpuvm->drm, obj != vm_bo->obj);
>>>>    
>>>> -       list_add_tail(&va->gem.entry, &obj->gpuva.list);
>>>> +       va->vm_bo = drm_gpuvm_bo_get(vm_bo);
>>>> +
>>>> +       drm_gem_gpuva_assert_lock_held(obj);
>>>> +       list_add_tail(&va->gem.entry, &vm_bo->list.gpuva);
>>>>    }
>>>>    EXPORT_SYMBOL_GPL(drm_gpuva_link);
>>>>    
>>>> @@ -892,20 +1124,31 @@ EXPORT_SYMBOL_GPL(drm_gpuva_link);
>>>>     * This removes the given &va from the GPU VA list of the
>>>> &drm_gem_object it is
>>>>     * associated with.
>>>>     *
>>>> + * This removes the given &va from the GPU VA list of the
>>>> &drm_gpuvm_bo and
>>>> + * the &drm_gpuvm_bo from the &drm_gem_object it is associated
>>>> with
>>>> in case
>>>> + * this call unlinks the last &drm_gpuva from the &drm_gpuvm_bo.
>>>> + *
>>>> + * For every &drm_gpuva entry removed from the &drm_gpuvm_bo a
>>>> reference of
>>>> + * the latter is dropped.
>>>> + *
>>>>     * This function expects the caller to protect the GEM's GPUVA
>>>> list
>>>> against
>>>> - * concurrent access using the GEMs dma_resv lock.
>>>> + * concurrent access using either the GEMs dma_resv lock or a
>>>> driver
>>>> specific
>>>> + * lock set through drm_gem_gpuva_set_lock().
>>>>     */
>>>>    void
>>>>    drm_gpuva_unlink(struct drm_gpuva *va)
>>>>    {
>>>>           struct drm_gem_object *obj = va->gem.obj;
>>>> +       struct drm_gpuvm_bo *vm_bo = va->vm_bo;
>>>>    
>>>>           if (unlikely(!obj))
>>>>                   return;
>>>>    
>>>>           drm_gem_gpuva_assert_lock_held(obj);
>>>> -
>>>>           list_del_init(&va->gem.entry);
>>>> +
>>>> +       va->vm_bo = NULL;
>>>> +       drm_gpuvm_bo_put(vm_bo);
>>>>    }
>>>>    EXPORT_SYMBOL_GPL(drm_gpuva_unlink);
>>>>    
>>>> @@ -1050,10 +1293,10 @@ drm_gpuva_remap(struct drm_gpuva *prev,
>>>>                   struct drm_gpuva *next,
>>>>                   struct drm_gpuva_op_remap *op)
>>>>    {
>>>> -       struct drm_gpuva *curr = op->unmap->va;
>>>> -       struct drm_gpuvm *gpuvm = curr->vm;
>>>> +       struct drm_gpuva *va = op->unmap->va;
>>>> +       struct drm_gpuvm *gpuvm = va->vm;
>>>>    
>>>> -       drm_gpuva_remove(curr);
>>>> +       drm_gpuva_remove(va);
>>>>    
>>>>           if (op->prev) {
>>>>                   drm_gpuva_init_from_op(prev, op->prev);
>>>> @@ -1695,9 +1938,8 @@ drm_gpuvm_prefetch_ops_create(struct
>>>> drm_gpuvm
>>>> *gpuvm,
>>>>    EXPORT_SYMBOL_GPL(drm_gpuvm_prefetch_ops_create);
>>>>    
>>>>    /**
>>>> - * drm_gpuvm_gem_unmap_ops_create() - creates the &drm_gpuva_ops
>>>> to
>>>> unmap a GEM
>>>> - * @gpuvm: the &drm_gpuvm representing the GPU VA space
>>>> - * @obj: the &drm_gem_object to unmap
>>>> + * drm_gpuvm_bo_unmap_ops_create() - creates the &drm_gpuva_ops
>>>> to
>>>> unmap a GEM
>>>> + * @vm_bo: the &drm_gpuvm_bo abstraction
>>>>     *
>>>>     * This function creates a list of operations to perform
>>>> unmapping
>>>> for every
>>>>     * GPUVA attached to a GEM.
>>>> @@ -1714,15 +1956,14 @@
>>>> EXPORT_SYMBOL_GPL(drm_gpuvm_prefetch_ops_create);
>>>>     * Returns: a pointer to the &drm_gpuva_ops on success, an
>>>> ERR_PTR
>>>> on failure
>>>>     */
>>>>    struct drm_gpuva_ops *
>>>> -drm_gpuvm_gem_unmap_ops_create(struct drm_gpuvm *gpuvm,
>>>> -                              struct drm_gem_object *obj)
>>>> +drm_gpuvm_bo_unmap_ops_create(struct drm_gpuvm_bo *vm_bo)
>>>>    {
>>>>           struct drm_gpuva_ops *ops;
>>>>           struct drm_gpuva_op *op;
>>>>           struct drm_gpuva *va;
>>>>           int ret;
>>>>    
>>>> -       drm_gem_gpuva_assert_lock_held(obj);
>>>> +       drm_gem_gpuva_assert_lock_held(vm_bo->obj);
>>>>    
>>>>           ops = kzalloc(sizeof(*ops), GFP_KERNEL);
>>>>           if (!ops)
>>>> @@ -1730,8 +1971,8 @@ drm_gpuvm_gem_unmap_ops_create(struct
>>>> drm_gpuvm
>>>> *gpuvm,
>>>>    
>>>>           INIT_LIST_HEAD(&ops->list);
>>>>    
>>>> -       drm_gem_for_each_gpuva(va, obj) {
>>>> -               op = gpuva_op_alloc(gpuvm);
>>>> +       drm_gpuvm_bo_for_each_va(va, vm_bo) {
>>>> +               op = gpuva_op_alloc(vm_bo->vm);
>>>>                   if (!op) {
>>>>                           ret = -ENOMEM;
>>>>                           goto err_free_ops;
>>>> @@ -1745,10 +1986,10 @@ drm_gpuvm_gem_unmap_ops_create(struct
>>>> drm_gpuvm *gpuvm,
>>>>           return ops;
>>>>    
>>>>    err_free_ops:
>>>> -       drm_gpuva_ops_free(gpuvm, ops);
>>>> +       drm_gpuva_ops_free(vm_bo->vm, ops);
>>>>           return ERR_PTR(ret);
>>>>    }
>>>> -EXPORT_SYMBOL_GPL(drm_gpuvm_gem_unmap_ops_create);
>>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_unmap_ops_create);
>>>>    
>>>>    /**
>>>>     * drm_gpuva_ops_free() - free the given &drm_gpuva_ops
>>>> diff --git a/drivers/gpu/drm/nouveau/nouveau_uvmm.c
>>>> b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
>>>> index ed439bf4032f..1e95b0a1b047 100644
>>>> --- a/drivers/gpu/drm/nouveau/nouveau_uvmm.c
>>>> +++ b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
>>>> @@ -62,6 +62,8 @@ struct bind_job_op {
>>>>           enum vm_bind_op op;
>>>>           u32 flags;
>>>>    
>>>> +       struct drm_gpuvm_bo *vm_bo;
>>>> +
>>>>           struct {
>>>>                   u64 addr;
>>>>                   u64 range;
>>>> @@ -1113,22 +1115,28 @@ bind_validate_region(struct nouveau_job
>>>> *job)
>>>>    }
>>>>    
>>>>    static void
>>>> -bind_link_gpuvas(struct drm_gpuva_ops *ops, struct
>>>> nouveau_uvma_prealloc *new)
>>>> +bind_link_gpuvas(struct bind_job_op *bop)
>>>>    {
>>>> +       struct nouveau_uvma_prealloc *new = &bop->new;
>>>> +       struct drm_gpuvm_bo *vm_bo = bop->vm_bo;
>>>> +       struct drm_gpuva_ops *ops = bop->ops;
>>>>           struct drm_gpuva_op *op;
>>>>    
>>>>           drm_gpuva_for_each_op(op, ops) {
>>>>                   switch (op->op) {
>>>>                   case DRM_GPUVA_OP_MAP:
>>>> -                       drm_gpuva_link(&new->map->va);
>>>> +                       drm_gpuva_link(&new->map->va, vm_bo);
>>>>                           break;
>>>> -               case DRM_GPUVA_OP_REMAP:
>>>> +               case DRM_GPUVA_OP_REMAP: {
>>>> +                       struct drm_gpuva *va = op->remap.unmap-
>>>>> va;
>>>> +
>>>>                           if (op->remap.prev)
>>>> -                               drm_gpuva_link(&new->prev->va);
>>>> +                               drm_gpuva_link(&new->prev->va,
>>>> va-
>>>>> vm_bo);
>>>>                           if (op->remap.next)
>>>> -                               drm_gpuva_link(&new->next->va);
>>>> -                       drm_gpuva_unlink(op->remap.unmap->va);
>>>> +                               drm_gpuva_link(&new->next->va,
>>>> va-
>>>>> vm_bo);
>>>> +                       drm_gpuva_unlink(va);
>>>>                           break;
>>>> +               }
>>>>                   case DRM_GPUVA_OP_UNMAP:
>>>>                           drm_gpuva_unlink(op->unmap.va);
>>>>                           break;
>>>> @@ -1150,10 +1158,18 @@ nouveau_uvmm_bind_job_submit(struct
>>>> nouveau_job *job)
>>>>    
>>>>           list_for_each_op(op, &bind_job->ops) {
>>>>                   if (op->op == OP_MAP) {
>>>> -                       op->gem.obj = drm_gem_object_lookup(job-
>>>>> file_priv,
>>>> -                                                           op-
>>>>> gem.handle);
>>>> -                       if (!op->gem.obj)
>>>> +                       struct drm_gem_object *obj;
>>>> +
>>>> +                       obj = drm_gem_object_lookup(job-
>>>>> file_priv,
>>>> +                                                   op-
>>>>> gem.handle);
>>>> +                       if (!(op->gem.obj = obj))
>>>>                                   return -ENOENT;
>>>> +
>>>> +                       dma_resv_lock(obj->resv, NULL);
>>>> +                       op->vm_bo = drm_gpuvm_bo_obtain(&uvmm-
>>>>> base,
>>>> obj);
>>>> +                       dma_resv_unlock(obj->resv);
>>>> +                       if (IS_ERR(op->vm_bo))
>>>> +                               return PTR_ERR(op->vm_bo);
>>>>                   }
>>>>    
>>>>                   ret = bind_validate_op(job, op);
>>>> @@ -1364,7 +1380,7 @@ nouveau_uvmm_bind_job_submit(struct
>>>> nouveau_job
>>>> *job)
>>>>                   case OP_UNMAP_SPARSE:
>>>>                   case OP_MAP:
>>>>                   case OP_UNMAP:
>>>> -                       bind_link_gpuvas(op->ops, &op->new);
>>>> +                       bind_link_gpuvas(op);
>>>>                           break;
>>>>                   default:
>>>>                           break;
>>>> @@ -1511,6 +1527,12 @@ nouveau_uvmm_bind_job_free_work_fn(struct
>>>> work_struct *work)
>>>>                   if (!IS_ERR_OR_NULL(op->ops))
>>>>                           drm_gpuva_ops_free(&uvmm->base, op-
>>>>> ops);
>>>>    
>>>> +               if (!IS_ERR_OR_NULL(op->vm_bo)) {
>>>> +                       dma_resv_lock(obj->resv, NULL);
>>>> +                       drm_gpuvm_bo_put(op->vm_bo);
>>>> +                       dma_resv_unlock(obj->resv);
>>>> +               }
>>>> +
>>>>                   if (obj)
>>>>                           drm_gem_object_put(obj);
>>>>           }
>>>> @@ -1776,15 +1798,18 @@ void
>>>>    nouveau_uvmm_bo_map_all(struct nouveau_bo *nvbo, struct
>>>> nouveau_mem
>>>> *mem)
>>>>    {
>>>>           struct drm_gem_object *obj = &nvbo->bo.base;
>>>> +       struct drm_gpuvm_bo *vm_bo;
>>>>        ��  struct drm_gpuva *va;
>>>>    
>>>>           dma_resv_assert_held(obj->resv);
>>>>    
>>>> -       drm_gem_for_each_gpuva(va, obj) {
>>>> -               struct nouveau_uvma *uvma = uvma_from_va(va);
>>>> +       drm_gem_for_each_gpuvm_bo(vm_bo, obj) {
>>>> +               drm_gpuvm_bo_for_each_va(va, vm_bo) {
>>>> +                       struct nouveau_uvma *uvma =
>>>> uvma_from_va(va);
>>>>    
>>>> -               nouveau_uvma_map(uvma, mem);
>>>> -               drm_gpuva_invalidate(va, false);
>>>> +                       nouveau_uvma_map(uvma, mem);
>>>> +                       drm_gpuva_invalidate(va, false);
>>>> +               }
>>>>           }
>>>>    }
>>>>    
>>>> @@ -1792,15 +1817,18 @@ void
>>>>    nouveau_uvmm_bo_unmap_all(struct nouveau_bo *nvbo)
>>>>    {
>>>>           struct drm_gem_object *obj = &nvbo->bo.base;
>>>> +       struct drm_gpuvm_bo *vm_bo;
>>>>           struct drm_gpuva *va;
>>>>    
>>>>           dma_resv_assert_held(obj->resv);
>>>>    
>>>> -       drm_gem_for_each_gpuva(va, obj) {
>>>> -               struct nouveau_uvma *uvma = uvma_from_va(va);
>>>> +       drm_gem_for_each_gpuvm_bo(vm_bo, obj) {
>>>> +               drm_gpuvm_bo_for_each_va(va, vm_bo) {
>>>> +                       struct nouveau_uvma *uvma =
>>>> uvma_from_va(va);
>>>>    
>>>> -         ��     nouveau_uvma_unmap(uvma);
>>>> -               drm_gpuva_invalidate(va, true);
>>>> +                       nouveau_uvma_unmap(uvma);
>>>> +                       drm_gpuva_invalidate(va, true);
>>>> +               }
>>>>           }
>>>>    }
>>>>    
>>>> diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
>>>> index 16364487fde9..369505447acd 100644
>>>> --- a/include/drm/drm_gem.h
>>>> +++ b/include/drm/drm_gem.h
>>>> @@ -580,7 +580,7 @@ int drm_gem_evict(struct drm_gem_object
>>>> *obj);
>>>>     * drm_gem_gpuva_init() - initialize the gpuva list of a GEM
>>>> object
>>>>     * @obj: the &drm_gem_object
>>>>     *
>>>> - * This initializes the &drm_gem_object's &drm_gpuva list.
>>>> + * This initializes the &drm_gem_object's &drm_gpuvm_bo list.
>>>>     *
>>>>     * Calling this function is only necessary for drivers
>>>> intending to
>>>> support the
>>>>     * &drm_driver_feature DRIVER_GEM_GPUVA.
>>>> @@ -593,28 +593,28 @@ static inline void
>>>> drm_gem_gpuva_init(struct
>>>> drm_gem_object *obj)
>>>>    }
>>>>    
>>>>    /**
>>>> - * drm_gem_for_each_gpuva() - iternator to walk over a list of
>>>> gpuvas
>>>> - * @entry__: &drm_gpuva structure to assign to in each iteration
>>>> step
>>>> - * @obj__: the &drm_gem_object the &drm_gpuvas to walk are
>>>> associated with
>>>> + * drm_gem_for_each_gpuvm_bo() - iterator to walk over a list of
>>>> &drm_gpuvm_bo
>>>> + * @entry__: &drm_gpuvm_bo structure to assign to in each
>>>> iteration
>>>> step
>>>> + * @obj__: the &drm_gem_object the &drm_gpuvm_bo to walk are
>>>> associated with
>>>>     *
>>>> - * This iterator walks over all &drm_gpuva structures associated
>>>> with the
>>>> - * &drm_gpuva_manager.
>>>> + * This iterator walks over all &drm_gpuvm_bo structures
>>>> associated
>>>> with the
>>>> + * &drm_gem_object.
>>>>     */
>>>> -#define drm_gem_for_each_gpuva(entry__, obj__) \
>>>> -       list_for_each_entry(entry__, &(obj__)->gpuva.list,
>>>> gem.entry)
>>>> +#define drm_gem_for_each_gpuvm_bo(entry__, obj__) \
>>>> +       list_for_each_entry(entry__, &(obj__)->gpuva.list,
>>>> list.entry.gem)
>>>>    
>>>>    /**
>>>> - * drm_gem_for_each_gpuva_safe() - iternator to safely walk over
>>>> a
>>>> list of
>>>> - * gpuvas
>>>> - * @entry__: &drm_gpuva structure to assign to in each iteration
>>>> step
>>>> - * @next__: &next &drm_gpuva to store the next step
>>>> - * @obj__: the &drm_gem_object the &drm_gpuvas to walk are
>>>> associated with
>>>> + * drm_gem_for_each_gpuvm_bo_safe() - iterator to safely walk
>>>> over a
>>>> list of
>>>> + * &drm_gpuvm_bo
>>>> + * @entry__: &drm_gpuvm_bostructure to assign to in each
>>>> iteration
>>>> step
>>>> + * @next__: &next &drm_gpuvm_bo to store the next step
>>>> + * @obj__: the &drm_gem_object the &drm_gpuvm_bo to walk are
>>>> associated with
>>>>     *
>>>> - * This iterator walks over all &drm_gpuva structures associated
>>>> with the
>>>> + * This iterator walks over all &drm_gpuvm_bo structures
>>>> associated
>>>> with the
>>>>     * &drm_gem_object. It is implemented with
>>>> list_for_each_entry_safe(), hence
>>>>     * it is save against removal of elements.
>>>>     */
>>>> -#define drm_gem_for_each_gpuva_safe(entry__, next__, obj__) \
>>>> -       list_for_each_entry_safe(entry__, next__, &(obj__)-
>>>>> gpuva.list, gem.entry)
>>>> +#define drm_gem_for_each_gpuvm_bo_safe(entry__, next__, obj__) \
>>>> +       list_for_each_entry_safe(entry__, next__, &(obj__)-
>>>>> gpuva.list, list.entry.gem)
>>>>    
>>>>    #endif /* __DRM_GEM_H__ */
>>>> diff --git a/include/drm/drm_gpuvm.h b/include/drm/drm_gpuvm.h
>>>> index 47cbacb244b9..466fdd76c71a 100644
>>>> --- a/include/drm/drm_gpuvm.h
>>>> +++ b/include/drm/drm_gpuvm.h
>>>> @@ -25,6 +25,7 @@
>>>>     * OTHER DEALINGS IN THE SOFTWARE.
>>>>     */
>>>>    
>>>> +#include <linux/dma-resv.h>
>>>>    #include <linux/list.h>
>>>>    #include <linux/rbtree.h>
>>>>    #include <linux/types.h>
>>>> @@ -33,6 +34,7 @@
>>>>    #include <drm/drm_gem.h>
>>>>    
>>>>    struct drm_gpuvm;
>>>> +struct drm_gpuvm_bo;
>>>>    struct drm_gpuvm_ops;
>>>>    
>>>>    /**
>>>> @@ -73,6 +75,12 @@ struct drm_gpuva {
>>>>            */
>>>>           struct drm_gpuvm *vm;
>>>>    
>>>> +       /**
>>>> +        * @vm_bo: the &drm_gpuvm_bo abstraction for the mapped
>>>> +        * &drm_gem_object
>>>> +        */
>>>> +       struct drm_gpuvm_bo *vm_bo;
>>>> +
>>>>           /**
>>>>            * @flags: the &drm_gpuva_flags for this mapping
>>>>            */
>>>> @@ -108,7 +116,7 @@ struct drm_gpuva {
>>>>                   struct drm_gem_object *obj;
>>>>    
>>>>                   /**
>>>> -                * @entry: the &list_head to attach this object
>>>> to a
>>>> &drm_gem_object
>>>> +                * @entry: the &list_head to attach this object
>>>> to a
>>>> &drm_gpuvm_bo
>>>>                    */
>>>>                   struct list_head entry;
>>>>           } gem;
>>>> @@ -141,7 +149,7 @@ struct drm_gpuva {
>>>>    int drm_gpuva_insert(struct drm_gpuvm *gpuvm, struct drm_gpuva
>>>> *va);
>>>>    void drm_gpuva_remove(struct drm_gpuva *va);
>>>>    
>>>> -void drm_gpuva_link(struct drm_gpuva *va);
>>>> +void drm_gpuva_link(struct drm_gpuva *va, struct drm_gpuvm_bo
>>>> *vm_bo);
>>>>    void drm_gpuva_unlink(struct drm_gpuva *va);
>>>>    
>>>>    struct drm_gpuva *drm_gpuva_find(struct drm_gpuvm *gpuvm,
>>>> @@ -188,10 +196,16 @@ static inline bool
>>>> drm_gpuva_invalidated(struct
>>>> drm_gpuva *va)
>>>>     * enum drm_gpuvm_flags - flags for struct drm_gpuvm
>>>>     */
>>>>    enum drm_gpuvm_flags {
>>>> +       /**
>>>> +        * @DRM_GPUVM_RESV_PROTECTED: GPUVM is protected
>>>> externally
>>>> by the
>>>> +        * GPUVM's &dma_resv lock
>>>> +        */
>>>> +       DRM_GPUVM_RESV_PROTECTED = BIT(0),
>>>> +
>>>>           /**
>>>>            * @DRM_GPUVM_USERBITS: user defined bits
>>>>            */
>>>> -       DRM_GPUVM_USERBITS = BIT(0),
>>>> +       DRM_GPUVM_USERBITS = BIT(1),
>>>>    };
>>>>    
>>>>    /**
>>>> @@ -280,6 +294,19 @@ bool drm_gpuvm_interval_empty(struct
>>>> drm_gpuvm
>>>> *gpuvm, u64 addr, u64 range);
>>>>    struct drm_gem_object *
>>>>    drm_gpuvm_resv_object_alloc(struct drm_device *drm);
>>>>    
>>>> +/**
>>>> + * drm_gpuvm_resv_protected() - indicates whether
>>>> &DRM_GPUVM_RESV_PROTECTED is
>>>> + * set
>>>> + * @gpuvm: the &drm_gpuvm
>>>> + *
>>>> + * Returns: true if &DRM_GPUVM_RESV_PROTECTED is set, false
>>>> otherwise.
>>>> + */
>>>> +static inline bool
>>>> +drm_gpuvm_resv_protected(struct drm_gpuvm *gpuvm)
>>>> +{
>>>> +       return gpuvm->flags & DRM_GPUVM_RESV_PROTECTED;
>>>> +}
>>>> +
>>>>    /**
>>>>     * drm_gpuvm_resv() - returns the &drm_gpuvm's &dma_resv
>>>>     * @gpuvm__: the &drm_gpuvm
>>>> @@ -298,6 +325,12 @@ drm_gpuvm_resv_object_alloc(struct
>>>> drm_device
>>>> *drm);
>>>>     */
>>>>    #define drm_gpuvm_resv_obj(gpuvm__) ((gpuvm__)->r_obj)
>>>>    
>>>> +#define drm_gpuvm_resv_held(gpuvm__) \
>>>> +       dma_resv_held(drm_gpuvm_resv(gpuvm__))
>>>> +
>>>> +#define drm_gpuvm_resv_assert_held(gpuvm__) \
>>>> +       dma_resv_assert_held(drm_gpuvm_resv(gpuvm__))
>>>> +
>>>>    #define drm_gpuvm_resv_held(gpuvm__) \
>>>>           dma_resv_held(drm_gpuvm_resv(gpuvm__))
>>>>    
>>>> @@ -382,6 +415,128 @@ __drm_gpuva_next(struct drm_gpuva *va)
>>>>    #define drm_gpuvm_for_each_va_safe(va__, next__, gpuvm__) \
>>>>           list_for_each_entry_safe(va__, next__, &(gpuvm__)-
>>>>> rb.list,
>>>> rb.entry)
>>>>    
>>>> +/**
>>>> + * struct drm_gpuvm_bo - structure representing a &drm_gpuvm and
>>>> + * &drm_gem_object combination
>>>> + *
>>>> + * This structure is an abstraction representing a &drm_gpuvm
>>>> and
>>>> + * &drm_gem_object combination. It serves as an indirection to
>>>> accelerate
>>>> + * iterating all &drm_gpuvas within a &drm_gpuvm backed by the
>>>> same
>>>> + * &drm_gem_object.
>>>> + *
>>>> + * Furthermore it is used cache evicted GEM objects for a
>>>> certain
>>>> GPU-VM to
>>>> + * accelerate validation.
>>>> + *
>>>> + * Typically, drivers want to create an instance of a struct
>>>> drm_gpuvm_bo once
>>>> + * a GEM object is mapped first in a GPU-VM and release the
>>>> instance
>>>> once the
>>>> + * last mapping of the GEM object in this GPU-VM is unmapped.
>>>> + */
>>>> +struct drm_gpuvm_bo {
>>>> +       /**
>>>> +        * @vm: The &drm_gpuvm the @obj is mapped in. This
>>>> pointer is
>>>> not
>>>> +        * reference counted.
>>>> +        *
>>>> +        * A struct drm_gpuvm_bo is not allowed to out-live its
>>>> &drm_gpuvm
>>>> +        * context. Implicitly, this is ensured by the fact that
>>>> the
>>>> driver is
>>>> +        * responsible to ensure the VM doesn't contain mappings
>>>> once
>>>> it's
>>>> +        * freed, since a struct drm_gpuvm_bo should be freed
>>>> once
>>>> the last
>>>> +        * mapping being backed by the corresponding buffer
>>>> object is
>>>> unmapped.
>>>> +        */
>>>
>>>
>>> I don't think the above is completely true. Let's assume in the
>>> !RESV_PROTECTED case that a reference is grabbed on the
>>> drm_gpuvm_bo
>>> during an iteration over a list. Then user-space closes the vm and
>>> all
>>> vmas are unlinked, but this reference remains but the vm pointer
>>> becomes stale. In the RESV_PROTECTED case this is ensured not to
>>> happen
>>> if by the vm->resv being grabbed during unlink, but in the
>>> !RESV_PROTECTED case, the above wording isn't sufficient. The
>>> caller
>>> needs to ensure the vm stays alive using some sort of similar rule
>>> or
>>> use kref_get_unless_zero() on the vm under the spinlock if
>>> dereferenced.
>>
>> The list is part of the GPUVM. Hence, the caller *must* either
>> already hold
>> a reference to the GPUVM or otherwise ensure it's not freed while
>> iterating
>> this list. All the drm_gpuvm_bo structures within this list can't
>> have a
>> pointer to another VM than this one by definition.
>>
>> Anyway, I recognize that this isn't very obvious. Hence, I think we
>> should
>> probably reference count GPUVMs as well. I'd think of the same way we
>> do it
>> with drm_gem_objects. However, I'd prefer to introduce this with a
>> subsequent
>> patch.
> 
> Well, I think we should actually be OK in most cases, and refcounting
> here would probably result in circular dependencies.

Where would you see a circular dependency with reference counted GPUVMs?

Actually, I already started implementing it, because I think it's really
what we should do.

> 
> I think to do this properly one would document that this pointer is not
> refecounted and that dereferencing that pointer requires a strong vm
> reference from elsewhere, or holding the bo resv and verifying that the
> gpuvm_bo is on the gem object's gpuvm_bo list.

Yeah, I think the comment above coveres that. However, I probably even want
to introduce reference counting already in this series, hence this and the
below would just go away.

> 
> We've had a lot of tricky lifetime problems of vms and vmas in the i915
> driver so that's why I think clearly documenting the rules for
> dereferencing is important. In particular if we, in the future provide
> some sort of iteration over the gem object's gpvum_bo list, dropping
> the lock while iterating, that will blow up.
> 
> /Thomas
> 
> 
>>
>>>
>>>> +       struct drm_gpuvm *vm;
>>>> +
>>>> +       /**
>>>> +        * @obj: The &drm_gem_object being mapped in @vm. This is
>>>> a
>>>> reference
>>>> +        * counted pointer.
>>>> +        */
>>>> +       struct drm_gem_object *obj;
>>>> +
>>>> +       /**
>>>> +        * @kref: The reference count for this &drm_gpuvm_bo.
>>>> +        */
>>>> +       struct kref kref;
>>>> +
>>>> +       /**
>>>> +        * @list: Structure containing all &list_heads.
>>>> +        */
>>>> +       struct {
>>>> +               /**
>>>> +                * @gpuva: The list of linked &drm_gpuvas.
>>>> +                */
>>>> +               struct list_head gpuva;
>>>
>>> Still missing doc on how the @gpuva stays alive during iteration
>>> over
>>> the list?
>>
>> Thanks for pointing this out again, I missed that one.
>>
>> - Danilo
>>
>>>
>>>
>>>
>>> 8<-------------------------------------------------------------
>>>
>>> Thanks,
>>> Thomas
>>>
>>
>
  

On 11/1/23 10:56, Thomas Hellström wrote:
> On Wed, 2023-11-01 at 10:41 +0100, Thomas Hellström wrote:
>> Hi, Danilo,
>>
>> On Tue, 2023-10-31 at 18:52 +0100, Danilo Krummrich wrote:
>>> On 10/31/23 17:45, Thomas Hellström wrote:
>>>> On Tue, 2023-10-31 at 17:39 +0100, Danilo Krummrich wrote:
>>>>> On 10/31/23 12:25, Thomas Hellström wrote:
>>>>>> On Mon, 2023-10-23 at 22:16 +0200, Danilo Krummrich wrote:
>>>>>>> Add an abstraction layer between the drm_gpuva mappings of
>>>>>>> a
>>>>>>> particular
>>>>>>> drm_gem_object and this GEM object itself. The abstraction
>>>>>>> represents
>>>>>>> a
>>>>>>> combination of a drm_gem_object and drm_gpuvm. The
>>>>>>> drm_gem_object
>>>>>>> holds
>>>>>>> a list of drm_gpuvm_bo structures (the structure
>>>>>>> representing
>>>>>>> this
>>>>>>> abstraction), while each drm_gpuvm_bo contains list of
>>>>>>> mappings
>>>>>>> of
>>>>>>> this
>>>>>>> GEM object.
>>>>>>>
>>>>>>> This has multiple advantages:
>>>>>>>
>>>>>>> 1) We can use the drm_gpuvm_bo structure to attach it to
>>>>>>> various
>>>>>>> lists
>>>>>>>       of the drm_gpuvm. This is useful for tracking external
>>>>>>> and
>>>>>>> evicted
>>>>>>>       objects per VM, which is introduced in subsequent
>>>>>>> patches.
>>>>>>>
>>>>>>> 2) Finding mappings of a certain drm_gem_object mapped in a
>>>>>>> certain
>>>>>>>       drm_gpuvm becomes much cheaper.
>>>>>>>
>>>>>>> 3) Drivers can derive and extend the structure to easily
>>>>>>> represent
>>>>>>>       driver specific states of a BO for a certain GPUVM.
>>>>>>>
>>>>>>> The idea of this abstraction was taken from amdgpu, hence
>>>>>>> the
>>>>>>> credit
>>>>>>> for
>>>>>>> this idea goes to the developers of amdgpu.
>>>>>>>
>>>>>>> Cc: Christian König <christian.koenig@amd.com>
>>>>>>> Signed-off-by: Danilo Krummrich <dakr@redhat.com>
>>>>>>> ---
>>>>>>>     drivers/gpu/drm/drm_gpuvm.c            | 335
>>>>>>> +++++++++++++++++++++--
>>>>>>> --
>>>>>>>     drivers/gpu/drm/nouveau/nouveau_uvmm.c |  64 +++--
>>>>>>>     include/drm/drm_gem.h                  |  32 +--
>>>>>>>     include/drm/drm_gpuvm.h                | 188
>>>>>>> +++++++++++++-
>>>>>>>     4 files changed, 533 insertions(+), 86 deletions(-)
>>>>>>
>>>>>> That checkpatch.pl error still remains as well.
>>>>>
>>>>> I guess you refer to:
>>>>>
>>>>> ERROR: do not use assignment in if condition
>>>>> #633: FILE: drivers/gpu/drm/nouveau/nouveau_uvmm.c:1165:
>>>>> +                       if (!(op->gem.obj = obj))
>>>>>
>>>>> This was an intentional decision, since in this specific case
>>>>> it
>>>>> seems to
>>>>> be more readable than the alternatives.
>>>>>
>>>>> However, if we consider this to be a hard rule, which we never
>>>>> ever
>>>>> break,
>>>>> I'm fine changing it too.
>>>>
>>>> With the errors, sooner or later they are going to start generate
>>>> patches to "fix" them. In this particular case also Xe CI is
>>>> complaining and abort building when I submit the Xe adaptation,
>>>> so
>>>> it'd
>>>> be good to be checkpatch.pl conformant IMHO.
>>>
>>> Ok, I will change this one.
>>>
>>> However, in general my opinion on coding style is that we should
>>> preserve us
>>> the privilege to deviate from it when we agree it makes sense and
>>> improves
>>> the code quality.
>>>
>>> Having a CI forcing people to *blindly* follow certain rules and
>>> even
>>> abort
>>> building isn't very beneficial in that respect.
>>>
>>> Also, consider patches which partially change a line of code that
>>> already
>>> contains a coding style "issue" - the CI would also block you on
>>> that
>>> one I
>>> guess. Besides that it seems to block you on unrelated code, note
>>> that the
>>> assignment in question is from Nouveau and not from GPUVM.
>>
>> Yes, I completely agree that having CI enforce error free coding
>> style
>> checks is bad, and I'll see if I can get that changed on Xe CI. To my
>> Knowledge It hasn't always been like that.
>>
>> But OTOH my take on this is that if there are coding style rules and
>> recommendations we should try to follow them unless there are
>> *strong*
>> reasons not to. Sometimes that may result in code that may be a
>> little
>> harder to read, but OTOH a reviewer won't have to read up on the
>> component's style flavor before reviewing and it will avoid future
>> style fix patches.
> 
> Basically meaning I'll continue to point those out when reviewing in
> case the author made an oversight, but won't require fixing for an R-B
> if the component owner thinks otherwise.

Yeah, I fully agree on that. That's why I changed it. I still think it was
better as it was, but clearly way too minor to break the rules.

- Danilo

> 
> Thanks,
> Thomas
> 
>>
>> Thanks,
>> Thomas
>>
>>
>>>
>>> - Danilo
>>>
>>>>
>>>> Thanks,
>>>> Thomas
>>>>
>>>>
>>>>
>>>>
>>>>>
>>>>>>
>>>>>> Thanks,
>>>>>> Thomas
>>>>>>
>>>>>
>>>>
>>>
>>
>
  

On Wed, 2023-11-01 at 18:21 +0100, Danilo Krummrich wrote:
> On 11/1/23 17:38, Thomas Hellström wrote:
> > On Tue, 2023-10-31 at 18:38 +0100, Danilo Krummrich wrote:
> > > On 10/31/23 11:32, Thomas Hellström wrote:
> > > > On Mon, 2023-10-23 at 22:16 +0200, Danilo Krummrich wrote:
> > > > > Add an abstraction layer between the drm_gpuva mappings of a
> > > > > particular
> > > > > drm_gem_object and this GEM object itself. The abstraction
> > > > > represents
> > > > > a
> > > > > combination of a drm_gem_object and drm_gpuvm. The
> > > > > drm_gem_object
> > > > > holds
> > > > > a list of drm_gpuvm_bo structures (the structure representing
> > > > > this
> > > > > abstraction), while each drm_gpuvm_bo contains list of
> > > > > mappings
> > > > > of
> > > > > this
> > > > > GEM object.
> > > > > 
> > > > > This has multiple advantages:
> > > > > 
> > > > > 1) We can use the drm_gpuvm_bo structure to attach it to
> > > > > various
> > > > > lists
> > > > >      of the drm_gpuvm. This is useful for tracking external
> > > > > and
> > > > > evicted
> > > > >      objects per VM, which is introduced in subsequent
> > > > > patches.
> > > > > 
> > > > > 2) Finding mappings of a certain drm_gem_object mapped in a
> > > > > certain
> > > > >      drm_gpuvm becomes much cheaper.
> > > > > 
> > > > > 3) Drivers can derive and extend the structure to easily
> > > > > represent
> > > > >      driver specific states of a BO for a certain GPUVM.
> > > > > 
> > > > > The idea of this abstraction was taken from amdgpu, hence the
> > > > > credit
> > > > > for
> > > > > this idea goes to the developers of amdgpu.
> > > > > 
> > > > > Cc: Christian König <christian.koenig@amd.com>
> > > > > Signed-off-by: Danilo Krummrich <dakr@redhat.com>
> > > > > ---
> > > > >    drivers/gpu/drm/drm_gpuvm.c            | 335
> > > > > +++++++++++++++++++++--
> > > > > --
> > > > >    drivers/gpu/drm/nouveau/nouveau_uvmm.c |  64 +++--
> > > > >    include/drm/drm_gem.h                  |  32 +--
> > > > >    include/drm/drm_gpuvm.h                | 188
> > > > > +++++++++++++-
> > > > >    4 files changed, 533 insertions(+), 86 deletions(-)
> > > > > 
> > > > > diff --git a/drivers/gpu/drm/drm_gpuvm.c
> > > > > b/drivers/gpu/drm/drm_gpuvm.c
> > > > > index c03332883432..7f4f5919f84c 100644
> > > > > --- a/drivers/gpu/drm/drm_gpuvm.c
> > > > > +++ b/drivers/gpu/drm/drm_gpuvm.c
> > > > > @@ -70,6 +70,18 @@
> > > > >     * &drm_gem_object, such as the &drm_gem_object containing
> > > > > the
> > > > > root
> > > > > page table,
> > > > >     * but it can also be a 'dummy' object, which can be
> > > > > allocated
> > > > > with
> > > > >     * drm_gpuvm_resv_object_alloc().
> > > > > + *
> > > > > + * In order to connect a struct drm_gpuva its backing
> > > > > &drm_gem_object each
> > > > > + * &drm_gem_object maintains a list of &drm_gpuvm_bo
> > > > > structures,
> > > > > and
> > > > > each
> > > > > + * &drm_gpuvm_bo contains a list of &drm_gpuva structures.
> > > > > + *
> > > > > + * A &drm_gpuvm_bo is an abstraction that represents a
> > > > > combination
> > > > > of a
> > > > > + * &drm_gpuvm and a &drm_gem_object. Every such combination
> > > > > should
> > > > > be unique.
> > > > > + * This is ensured by the API through drm_gpuvm_bo_obtain()
> > > > > and
> > > > > + * drm_gpuvm_bo_obtain_prealloc() which first look into the
> > > > > corresponding
> > > > > + * &drm_gem_object list of &drm_gpuvm_bos for an existing
> > > > > instance
> > > > > of this
> > > > > + * particular combination. If not existent a new instance is
> > > > > created
> > > > > and linked
> > > > > + * to the &drm_gem_object.
> > > > >     */
> > > > >    
> > > > >    /**
> > > > > @@ -395,21 +407,28 @@
> > > > >    /**
> > > > >     * DOC: Locking
> > > > >     *
> > > > > - * Generally, the GPU VA manager does not take care of
> > > > > locking
> > > > > itself, it is
> > > > > - * the drivers responsibility to take care about locking.
> > > > > Drivers
> > > > > might want to
> > > > > - * protect the following operations: inserting, removing and
> > > > > iterating
> > > > > - * &drm_gpuva objects as well as generating all kinds of
> > > > > operations,
> > > > > such as
> > > > > - * split / merge or prefetch.
> > > > > - *
> > > > > - * The GPU VA manager also does not take care of the locking
> > > > > of
> > > > > the
> > > > > backing
> > > > > - * &drm_gem_object buffers GPU VA lists by itself; drivers
> > > > > are
> > > > > responsible to
> > > > > - * enforce mutual exclusion using either the GEMs dma_resv
> > > > > lock
> > > > > or
> > > > > alternatively
> > > > > - * a driver specific external lock. For the latter see also
> > > > > - * drm_gem_gpuva_set_lock().
> > > > > - *
> > > > > - * However, the GPU VA manager contains lockdep checks to
> > > > > ensure
> > > > > callers of its
> > > > > - * API hold the corresponding lock whenever the
> > > > > &drm_gem_objects
> > > > > GPU
> > > > > VA list is
> > > > > - * accessed by functions such as drm_gpuva_link() or
> > > > > drm_gpuva_unlink().
> > > > > + * In terms of managing &drm_gpuva entries DRM GPUVM does
> > > > > not
> > > > > take
> > > > > care of
> > > > > + * locking itself, it is the drivers responsibility to take
> > > > > care
> > > > > about locking.
> > > > > + * Drivers might want to protect the following operations:
> > > > > inserting, removing
> > > > > + * and iterating &drm_gpuva objects as well as generating
> > > > > all
> > > > > kinds
> > > > > of
> > > > > + * operations, such as split / merge or prefetch.
> > > > > + *
> > > > > + * DRM GPUVM also does not take care of the locking of the
> > > > > backing
> > > > > + * &drm_gem_object buffers GPU VA lists and &drm_gpuvm_bo
> > > > > abstractions by
> > > > > + * itself; drivers are responsible to enforce mutual
> > > > > exclusion
> > > > > using
> > > > > either the
> > > > > + * GEMs dma_resv lock or alternatively a driver specific
> > > > > external
> > > > > lock. For the
> > > > > + * latter see also drm_gem_gpuva_set_lock().
> > > > > + *
> > > > > + * However, DRM GPUVM contains lockdep checks to ensure
> > > > > callers
> > > > > of
> > > > > its API hold
> > > > > + * the corresponding lock whenever the &drm_gem_objects GPU
> > > > > VA
> > > > > list
> > > > > is accessed
> > > > > + * by functions such as drm_gpuva_link() or
> > > > > drm_gpuva_unlink(),
> > > > > but
> > > > > also
> > > > > + * drm_gpuvm_bo_obtain() and drm_gpuvm_bo_put().
> > > > > + *
> > > > > + * The latter is required since on creation and destruction
> > > > > of a
> > > > > &drm_gpuvm_bo
> > > > > + * the &drm_gpuvm_bo is attached / removed from the
> > > > > &drm_gem_objects
> > > > > gpuva list.
> > > > > + * Subsequent calls to drm_gpuvm_bo_obtain() for the same
> > > > > &drm_gpuvm
> > > > > and
> > > > > + * &drm_gem_object must be able to observe previous
> > > > > creations
> > > > > and
> > > > > destructions
> > > > > + * of &drm_gpuvm_bos in order to keep instances unique.
> > > > >     */
> > > > >    
> > > > >    /**
> > > > > @@ -439,6 +458,7 @@
> > > > >     *     {
> > > > >     *             struct drm_gpuva_ops *ops;
> > > > >     *             struct drm_gpuva_op *op
> > > > > + *             struct drm_gpuvm_bo *vm_bo;
> > > > >     *
> > > > >     *             driver_lock_va_space();
> > > > >     *             ops = drm_gpuvm_sm_map_ops_create(gpuvm,
> > > > > addr,
> > > > > range,
> > > > > @@ -446,6 +466,10 @@
> > > > >     *             if (IS_ERR(ops))
> > > > >     *                     return PTR_ERR(ops);
> > > > >     *
> > > > > + *             vm_bo = drm_gpuvm_bo_obtain(gpuvm, obj);
> > > > > + *             if (IS_ERR(vm_bo))
> > > > > + *                     return PTR_ERR(vm_bo);
> > > > > + *
> > > > >     *             drm_gpuva_for_each_op(op, ops) {
> > > > >     *                     struct drm_gpuva *va;
> > > > >     *
> > > > > @@ -458,7 +482,7 @@
> > > > >     *
> > > > >     *                             driver_vm_map();
> > > > >     *                             drm_gpuva_map(gpuvm, va,
> > > > > &op-
> > > > > > map);
> > > > > - *                             drm_gpuva_link(va);
> > > > > + *                             drm_gpuva_link(va, vm_bo);
> > > > >     *
> > > > >     *                             break;
> > > > >     *                     case DRM_GPUVA_OP_REMAP: {
> > > > > @@ -485,11 +509,11 @@
> > > > >     *                             driver_vm_remap();
> > > > >     *                             drm_gpuva_remap(prev, next,
> > > > > &op-
> > > > > > remap);
> > > > >     *
> > > > > - *                             drm_gpuva_unlink(va);
> > > > >     *                             if (prev)
> > > > > - *                                     drm_gpuva_link(prev);
> > > > > + *                                     drm_gpuva_link(prev,
> > > > > va-
> > > > > > vm_bo);
> > > > >     *                             if (next)
> > > > > - *                                     drm_gpuva_link(next);
> > > > > + *                                     drm_gpuva_link(next,
> > > > > va-
> > > > > > vm_bo);
> > > > > + *                             drm_gpuva_unlink(va);
> > > > >     *
> > > > >     *                             break;
> > > > >     *                     }
> > > > > @@ -505,6 +529,7 @@
> > > > >     *                             break;
> > > > >     *                     }
> > > > >     *             }
> > > > > + *             drm_gpuvm_bo_put(vm_bo);
> > > > >     *             driver_unlock_va_space();
> > > > >     *
> > > > >     *             return 0;
> > > > > @@ -514,6 +539,7 @@
> > > > >     *
> > > > >     *     struct driver_context {
> > > > >     *             struct drm_gpuvm *gpuvm;
> > > > > + *             struct drm_gpuvm_bo *vm_bo;
> > > > >     *             struct drm_gpuva *new_va;
> > > > >     *             struct drm_gpuva *prev_va;
> > > > >     *             struct drm_gpuva *next_va;
> > > > > @@ -534,6 +560,7 @@
> > > > >     *                               struct drm_gem_object
> > > > > *obj,
> > > > > u64
> > > > > offset)
> > > > >     *     {
> > > > >     *             struct driver_context ctx;
> > > > > + *             struct drm_gpuvm_bo *vm_bo;
> > > > >     *             struct drm_gpuva_ops *ops;
> > > > >     *             struct drm_gpuva_op *op;
> > > > >     *             int ret = 0;
> > > > > @@ -543,16 +570,23 @@
> > > > >     *             ctx.new_va = kzalloc(sizeof(*ctx.new_va),
> > > > > GFP_KERNEL);
> > > > >     *             ctx.prev_va = kzalloc(sizeof(*ctx.prev_va),
> > > > > GFP_KERNEL);
> > > > >     *             ctx.next_va = kzalloc(sizeof(*ctx.next_va),
> > > > > GFP_KERNEL);
> > > > > - *             if (!ctx.new_va || !ctx.prev_va ||
> > > > > !ctx.next_va)
> > > > > {
> > > > > + *             ctx.vm_bo = drm_gpuvm_bo_create(gpuvm, obj);
> > > > > + *             if (!ctx.new_va || !ctx.prev_va ||
> > > > > !ctx.next_va
> > > > > > > 
> > > > > !vm_bo) {
> > > > >     *                     ret = -ENOMEM;
> > > > >     *                     goto out;
> > > > >     *             }
> > > > >     *
> > > > > + *             // Typically protected with a driver specific
> > > > > GEM
> > > > > gpuva lock
> > > > > + *             // used in the fence signaling path for
> > > > > drm_gpuva_link() and
> > > > > + *             // drm_gpuva_unlink(), hence pre-allocate.
> > > > > + *             ctx.vm_bo =
> > > > > drm_gpuvm_bo_obtain_prealloc(ctx.vm_bo);
> > > > > + *
> > > > >     *             driver_lock_va_space();
> > > > >     *             ret = drm_gpuvm_sm_map(gpuvm, &ctx, addr,
> > > > > range,
> > > > > obj,
> > > > > offset);
> > > > >     *             driver_unlock_va_space();
> > > > >     *
> > > > >     *     out:
> > > > > + *             drm_gpuvm_bo_put(ctx.vm_bo);
> > > > >     *             kfree(ctx.new_va);
> > > > >     *             kfree(ctx.prev_va);
> > > > >     *             kfree(ctx.next_va);
> > > > > @@ -565,7 +599,7 @@
> > > > >     *
> > > > >     *             drm_gpuva_map(ctx->vm, ctx->new_va, &op-
> > > > > >map);
> > > > >     *
> > > > > - *             drm_gpuva_link(ctx->new_va);
> > > > > + *             drm_gpuva_link(ctx->new_va, ctx->vm_bo);
> > > > >     *
> > > > >     *             // prevent the new GPUVA from being freed
> > > > > in
> > > > >     *             // driver_mapping_create()
> > > > > @@ -577,22 +611,23 @@
> > > > >     *     int driver_gpuva_remap(struct drm_gpuva_op *op,
> > > > > void
> > > > > *__ctx)
> > > > >     *     {
> > > > >     *             struct driver_context *ctx = __ctx;
> > > > > + *             struct drm_gpuva *va = op->remap.unmap->va;
> > > > >     *
> > > > >     *             drm_gpuva_remap(ctx->prev_va, ctx->next_va,
> > > > > &op-
> > > > > > remap);
> > > > >     *
> > > > > - *             drm_gpuva_unlink(op->remap.unmap->va);
> > > > > - *             kfree(op->remap.unmap->va);
> > > > > - *
> > > > >     *             if (op->remap.prev) {
> > > > > - *                     drm_gpuva_link(ctx->prev_va);
> > > > > + *                     drm_gpuva_link(ctx->prev_va, va-
> > > > > >vm_bo);
> > > > >     *                     ctx->prev_va = NULL;
> > > > >     *             }
> > > > >     *
> > > > >     *             if (op->remap.next) {
> > > > > - *                     drm_gpuva_link(ctx->next_va);
> > > > > + *                     drm_gpuva_link(ctx->next_va, va-
> > > > > >vm_bo);
> > > > >     *                     ctx->next_va = NULL;
> > > > >     *             }
> > > > >     *
> > > > > + *             drm_gpuva_unlink(va);
> > > > > + *             kfree(va);
> > > > > + *
> > > > >     *             return 0;
> > > > >     *     }
> > > > >     *
> > > > > @@ -774,6 +809,194 @@ drm_gpuvm_destroy(struct drm_gpuvm
> > > > > *gpuvm)
> > > > >    }
> > > > >    EXPORT_SYMBOL_GPL(drm_gpuvm_destroy);
> > > > >    
> > > > > +/**
> > > > > + * drm_gpuvm_bo_create() - create a new instance of struct
> > > > > drm_gpuvm_bo
> > > > > + * @gpuvm: The &drm_gpuvm the @obj is mapped in.
> > > > > + * @obj: The &drm_gem_object being mapped in the @gpuvm.
> > > > > + *
> > > > > + * If provided by the driver, this function uses the
> > > > > &drm_gpuvm_ops
> > > > > + * vm_bo_alloc() callback to allocate.
> > > > > + *
> > > > > + * Returns: a pointer to the &drm_gpuvm_bo on success, NULL
> > > > > on
> > > > 
> > > > Still needs s/Returns:/Return:/g
> > > > 
> > > > > failure
> > > > > + */
> > > > > +struct drm_gpuvm_bo *
> > > > > +drm_gpuvm_bo_create(struct drm_gpuvm *gpuvm,
> > > > > +                   struct drm_gem_object *obj)
> > > > > +{
> > > > > +       const struct drm_gpuvm_ops *ops = gpuvm->ops;
> > > > > +       struct drm_gpuvm_bo *vm_bo;
> > > > > +
> > > > > +       if (ops && ops->vm_bo_alloc)
> > > > > +               vm_bo = ops->vm_bo_alloc();
> > > > > +       else
> > > > > +               vm_bo = kzalloc(sizeof(*vm_bo), GFP_KERNEL);
> > > > > +
> > > > > +       if (unlikely(!vm_bo))
> > > > > +               return NULL;
> > > > > +
> > > > > +       vm_bo->vm = gpuvm;
> > > > > +       vm_bo->obj = obj;
> > > > > +       drm_gem_object_get(obj);
> > > > > +
> > > > > +       kref_init(&vm_bo->kref);
> > > > > +       INIT_LIST_HEAD(&vm_bo->list.gpuva);
> > > > > +       INIT_LIST_HEAD(&vm_bo->list.entry.gem);
> > > > > +
> > > > > +       return vm_bo;
> > > > > +}
> > > > > +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_create);
> > > > > +
> > > > > +static void
> > > > > +drm_gpuvm_bo_destroy(struct kref *kref)
> > > > > +{
> > > > > +       struct drm_gpuvm_bo *vm_bo = container_of(kref,
> > > > > struct
> > > > > drm_gpuvm_bo,
> > > > > +                                                 kref);
> > > > > +       struct drm_gpuvm *gpuvm = vm_bo->vm;
> > > > > +       const struct drm_gpuvm_ops *ops = gpuvm->ops;
> > > > > +       struct drm_gem_object *obj = vm_bo->obj;
> > > > > +       bool lock = !drm_gpuvm_resv_protected(gpuvm);
> > > > > +
> > > > > +       if (!lock)
> > > > > +               drm_gpuvm_resv_assert_held(gpuvm);
> > > > > +
> > > > > +       drm_gem_gpuva_assert_lock_held(obj);
> > > > > +       list_del(&vm_bo->list.entry.gem);
> > > > > +
> > > > > +       if (ops && ops->vm_bo_free)
> > > > > +               ops->vm_bo_free(vm_bo);
> > > > > +       else
> > > > > +               kfree(vm_bo);
> > > > > +
> > > > > +       drm_gem_object_put(obj);
> > > > > +}
> > > > > +
> > > > > +/**
> > > > > + * drm_gpuvm_bo_put() - drop a struct drm_gpuvm_bo reference
> > > > > + * @vm_bo: the &drm_gpuvm_bo to release the reference of
> > > > > + *
> > > > > + * This releases a reference to @vm_bo.
> > > > > + *
> > > > > + * If the reference count drops to zero, the &gpuvm_bo is
> > > > > destroyed,
> > > > > which
> > > > > + * includes removing it from the GEMs gpuva list. Hence, if
> > > > > a
> > > > > call
> > > > > to this
> > > > > + * function can potentially let the reference count to zero
> > > > > the
> > > > > caller must
> > > > > + * hold the dma-resv or driver specific GEM gpuva lock.
> > > > > + */
> > > > > +void
> > > > > +drm_gpuvm_bo_put(struct drm_gpuvm_bo *vm_bo)
> > > > > +{
> > > > > +       if (vm_bo)
> > > > > +               kref_put(&vm_bo->kref, drm_gpuvm_bo_destroy);
> > > > > +}
> > > > > +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_put);
> > > > > +
> > > > > +static struct drm_gpuvm_bo *
> > > > > +__drm_gpuvm_bo_find(struct drm_gpuvm *gpuvm,
> > > > > +                   struct drm_gem_object *obj)
> > > > > +{
> > > > > +       struct drm_gpuvm_bo *vm_bo;
> > > > > +
> > > > > +       drm_gem_gpuva_assert_lock_held(obj);
> > > > > +       drm_gem_for_each_gpuvm_bo(vm_bo, obj)
> > > > > +               if (vm_bo->vm == gpuvm)
> > > > > +                       return vm_bo;
> > > > > +
> > > > > +       return NULL;
> > > > > +}
> > > > > +
> > > > > +/**
> > > > > + * drm_gpuvm_bo_find() - find the &drm_gpuvm_bo for the
> > > > > given
> > > > > + * &drm_gpuvm and &drm_gem_object
> > > > > + * @gpuvm: The &drm_gpuvm the @obj is mapped in.
> > > > > + * @obj: The &drm_gem_object being mapped in the @gpuvm.
> > > > > + *
> > > > > + * Find the &drm_gpuvm_bo representing the combination of
> > > > > the
> > > > > given
> > > > > + * &drm_gpuvm and &drm_gem_object. If found, increases the
> > > > > reference
> > > > > + * count of the &drm_gpuvm_bo accordingly.
> > > > > + *
> > > > > + * Returns: a pointer to the &drm_gpuvm_bo on success, NULL
> > > > > on
> > > > > failure
> > > > > + */
> > > > > +struct drm_gpuvm_bo *
> > > > > +drm_gpuvm_bo_find(struct drm_gpuvm *gpuvm,
> > > > > +                 struct drm_gem_object *obj)
> > > > > +{
> > > > > +       struct drm_gpuvm_bo *vm_bo =
> > > > > __drm_gpuvm_bo_find(gpuvm,
> > > > > obj);
> > > > > +
> > > > > +       return vm_bo ? drm_gpuvm_bo_get(vm_bo) : NULL;
> > > > > +}
> > > > > +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_find);
> > > > > +
> > > > > +/**
> > > > > + * drm_gpuvm_bo_obtain() - obtains and instance of the
> > > > > &drm_gpuvm_bo
> > > > > for the
> > > > > + * given &drm_gpuvm and &drm_gem_object
> > > > > + * @gpuvm: The &drm_gpuvm the @obj is mapped in.
> > > > > + * @obj: The &drm_gem_object being mapped in the @gpuvm.
> > > > > + *
> > > > > + * Find the &drm_gpuvm_bo representing the combination of
> > > > > the
> > > > > given
> > > > > + * &drm_gpuvm and &drm_gem_object. If found, increases the
> > > > > reference
> > > > > + * count of the &drm_gpuvm_bo accordingly. If not found,
> > > > > allocates a
> > > > > new
> > > > > + * &drm_gpuvm_bo.
> > > > > + *
> > > > > + * A new &drm_gpuvm_bo is added to the GEMs gpuva list.
> > > > > + *
> > > > > + * Returns: a pointer to the &drm_gpuvm_bo on success, an
> > > > > ERR_PTR on
> > > > > failure
> > > > > + */
> > > > > +struct drm_gpuvm_bo *
> > > > > +drm_gpuvm_bo_obtain(struct drm_gpuvm *gpuvm,
> > > > > +                   struct drm_gem_object *obj)
> > > > > +{
> > > > > +       struct drm_gpuvm_bo *vm_bo;
> > > > > +
> > > > > +       vm_bo = drm_gpuvm_bo_find(gpuvm, obj);
> > > > > +       if (vm_bo)
> > > > > +               return vm_bo;
> > > > > +
> > > > > +       vm_bo = drm_gpuvm_bo_create(gpuvm, obj);
> > > > > +       if (!vm_bo)
> > > > > +               return ERR_PTR(-ENOMEM);
> > > > > +
> > > > > +       drm_gem_gpuva_assert_lock_held(obj);
> > > > > +       list_add_tail(&vm_bo->list.entry.gem, &obj-
> > > > > >gpuva.list);
> > > > > +
> > > > > +       return vm_bo;
> > > > > +}
> > > > > +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_obtain);
> > > > > +
> > > > > +/**
> > > > > + * drm_gpuvm_bo_obtain_prealloc() - obtains and instance of
> > > > > the
> > > > > &drm_gpuvm_bo
> > > > > + * for the given &drm_gpuvm and &drm_gem_object
> > > > > + * @__vm_bo: A pre-allocated struct drm_gpuvm_bo.
> > > > > + *
> > > > > + * Find the &drm_gpuvm_bo representing the combination of
> > > > > the
> > > > > given
> > > > > + * &drm_gpuvm and &drm_gem_object. If found, increases the
> > > > > reference
> > > > > + * count of the found &drm_gpuvm_bo accordingly, while the
> > > > > @__vm_bo
> > > > > reference
> > > > > + * count is decreased. If not found @__vm_bo is returned
> > > > > without
> > > > > further
> > > > > + * increase of the reference count.
> > > > > + *
> > > > > + * A new &drm_gpuvm_bo is added to the GEMs gpuva list.
> > > > > + *
> > > > > + * Returns: a pointer to the found &drm_gpuvm_bo or @__vm_bo
> > > > > if
> > > > > no
> > > > > existing
> > > > > + * &drm_gpuvm_bo was found
> > > > > + */
> > > > > +struct drm_gpuvm_bo *
> > > > > +drm_gpuvm_bo_obtain_prealloc(struct drm_gpuvm_bo *__vm_bo)
> > > > > +{
> > > > > +       struct drm_gpuvm *gpuvm = __vm_bo->vm;
> > > > > +       struct drm_gem_object *obj = __vm_bo->obj;
> > > > > +       struct drm_gpuvm_bo *vm_bo;
> > > > > +
> > > > > +       vm_bo = drm_gpuvm_bo_find(gpuvm, obj);
> > > > > +       if (vm_bo) {
> > > > > +               drm_gpuvm_bo_put(__vm_bo);
> > > > > +               return vm_bo;
> > > > > +       }
> > > > > +
> > > > > +       drm_gem_gpuva_assert_lock_held(obj);
> > > > > +       list_add_tail(&__vm_bo->list.entry.gem, &obj-
> > > > > > gpuva.list);
> > > > > +
> > > > > +       return __vm_bo;
> > > > > +}
> > > > > +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_obtain_prealloc);
> > > > > +
> > > > >    static int
> > > > >    __drm_gpuva_insert(struct drm_gpuvm *gpuvm,
> > > > >                      struct drm_gpuva *va)
> > > > > @@ -864,24 +1087,33 @@ EXPORT_SYMBOL_GPL(drm_gpuva_remove);
> > > > >    /**
> > > > >     * drm_gpuva_link() - link a &drm_gpuva
> > > > >     * @va: the &drm_gpuva to link
> > > > > + * @vm_bo: the &drm_gpuvm_bo to add the &drm_gpuva to
> > > > >     *
> > > > > - * This adds the given &va to the GPU VA list of the
> > > > > &drm_gem_object
> > > > > it is
> > > > > - * associated with.
> > > > > + * This adds the given &va to the GPU VA list of the
> > > > > &drm_gpuvm_bo
> > > > > and the
> > > > > + * &drm_gpuvm_bo to the &drm_gem_object it is associated
> > > > > with.
> > > > > + *
> > > > > + * For every &drm_gpuva entry added to the &drm_gpuvm_bo an
> > > > > additional
> > > > > + * reference of the latter is taken.
> > > > >     *
> > > > >     * This function expects the caller to protect the GEM's
> > > > > GPUVA
> > > > > list
> > > > > against
> > > > > - * concurrent access using the GEMs dma_resv lock.
> > > > > + * concurrent access using either the GEMs dma_resv lock or
> > > > > a
> > > > > driver
> > > > > specific
> > > > > + * lock set through drm_gem_gpuva_set_lock().
> > > > >     */
> > > > >    void
> > > > > -drm_gpuva_link(struct drm_gpuva *va)
> > > > > +drm_gpuva_link(struct drm_gpuva *va, struct drm_gpuvm_bo
> > > > > *vm_bo)
> > > > >    {
> > > > >           struct drm_gem_object *obj = va->gem.obj;
> > > > > +       struct drm_gpuvm *gpuvm = va->vm;
> > > > >    
> > > > >           if (unlikely(!obj))
> > > > >                   return;
> > > > >    
> > > > > -       drm_gem_gpuva_assert_lock_held(obj);
> > > > > +       drm_WARN_ON(gpuvm->drm, obj != vm_bo->obj);
> > > > >    
> > > > > -       list_add_tail(&va->gem.entry, &obj->gpuva.list);
> > > > > +       va->vm_bo = drm_gpuvm_bo_get(vm_bo);
> > > > > +
> > > > > +       drm_gem_gpuva_assert_lock_held(obj);
> > > > > +       list_add_tail(&va->gem.entry, &vm_bo->list.gpuva);
> > > > >    }
> > > > >    EXPORT_SYMBOL_GPL(drm_gpuva_link);
> > > > >    
> > > > > @@ -892,20 +1124,31 @@ EXPORT_SYMBOL_GPL(drm_gpuva_link);
> > > > >     * This removes the given &va from the GPU VA list of the
> > > > > &drm_gem_object it is
> > > > >     * associated with.
> > > > >     *
> > > > > + * This removes the given &va from the GPU VA list of the
> > > > > &drm_gpuvm_bo and
> > > > > + * the &drm_gpuvm_bo from the &drm_gem_object it is
> > > > > associated
> > > > > with
> > > > > in case
> > > > > + * this call unlinks the last &drm_gpuva from the
> > > > > &drm_gpuvm_bo.
> > > > > + *
> > > > > + * For every &drm_gpuva entry removed from the &drm_gpuvm_bo
> > > > > a
> > > > > reference of
> > > > > + * the latter is dropped.
> > > > > + *
> > > > >     * This function expects the caller to protect the GEM's
> > > > > GPUVA
> > > > > list
> > > > > against
> > > > > - * concurrent access using the GEMs dma_resv lock.
> > > > > + * concurrent access using either the GEMs dma_resv lock or
> > > > > a
> > > > > driver
> > > > > specific
> > > > > + * lock set through drm_gem_gpuva_set_lock().
> > > > >     */
> > > > >    void
> > > > >    drm_gpuva_unlink(struct drm_gpuva *va)
> > > > >    {
> > > > >           struct drm_gem_object *obj = va->gem.obj;
> > > > > +       struct drm_gpuvm_bo *vm_bo = va->vm_bo;
> > > > >    
> > > > >           if (unlikely(!obj))
> > > > >                   return;
> > > > >    
> > > > >           drm_gem_gpuva_assert_lock_held(obj);
> > > > > -
> > > > >           list_del_init(&va->gem.entry);
> > > > > +
> > > > > +       va->vm_bo = NULL;
> > > > > +       drm_gpuvm_bo_put(vm_bo);
> > > > >    }
> > > > >    EXPORT_SYMBOL_GPL(drm_gpuva_unlink);
> > > > >    
> > > > > @@ -1050,10 +1293,10 @@ drm_gpuva_remap(struct drm_gpuva
> > > > > *prev,
> > > > >                   struct drm_gpuva *next,
> > > > >                   struct drm_gpuva_op_remap *op)
> > > > >    {
> > > > > -       struct drm_gpuva *curr = op->unmap->va;
> > > > > -       struct drm_gpuvm *gpuvm = curr->vm;
> > > > > +       struct drm_gpuva *va = op->unmap->va;
> > > > > +       struct drm_gpuvm *gpuvm = va->vm;
> > > > >    
> > > > > -       drm_gpuva_remove(curr);
> > > > > +       drm_gpuva_remove(va);
> > > > >    
> > > > >           if (op->prev) {
> > > > >                   drm_gpuva_init_from_op(prev, op->prev);
> > > > > @@ -1695,9 +1938,8 @@ drm_gpuvm_prefetch_ops_create(struct
> > > > > drm_gpuvm
> > > > > *gpuvm,
> > > > >    EXPORT_SYMBOL_GPL(drm_gpuvm_prefetch_ops_create);
> > > > >    
> > > > >    /**
> > > > > - * drm_gpuvm_gem_unmap_ops_create() - creates the
> > > > > &drm_gpuva_ops
> > > > > to
> > > > > unmap a GEM
> > > > > - * @gpuvm: the &drm_gpuvm representing the GPU VA space
> > > > > - * @obj: the &drm_gem_object to unmap
> > > > > + * drm_gpuvm_bo_unmap_ops_create() - creates the
> > > > > &drm_gpuva_ops
> > > > > to
> > > > > unmap a GEM
> > > > > + * @vm_bo: the &drm_gpuvm_bo abstraction
> > > > >     *
> > > > >     * This function creates a list of operations to perform
> > > > > unmapping
> > > > > for every
> > > > >     * GPUVA attached to a GEM.
> > > > > @@ -1714,15 +1956,14 @@
> > > > > EXPORT_SYMBOL_GPL(drm_gpuvm_prefetch_ops_create);
> > > > >     * Returns: a pointer to the &drm_gpuva_ops on success, an
> > > > > ERR_PTR
> > > > > on failure
> > > > >     */
> > > > >    struct drm_gpuva_ops *
> > > > > -drm_gpuvm_gem_unmap_ops_create(struct drm_gpuvm *gpuvm,
> > > > > -                              struct drm_gem_object *obj)
> > > > > +drm_gpuvm_bo_unmap_ops_create(struct drm_gpuvm_bo *vm_bo)
> > > > >    {
> > > > >           struct drm_gpuva_ops *ops;
> > > > >           struct drm_gpuva_op *op;
> > > > >           struct drm_gpuva *va;
> > > > >           int ret;
> > > > >    
> > > > > -       drm_gem_gpuva_assert_lock_held(obj);
> > > > > +       drm_gem_gpuva_assert_lock_held(vm_bo->obj);
> > > > >    
> > > > >           ops = kzalloc(sizeof(*ops), GFP_KERNEL);
> > > > >           if (!ops)
> > > > > @@ -1730,8 +1971,8 @@ drm_gpuvm_gem_unmap_ops_create(struct
> > > > > drm_gpuvm
> > > > > *gpuvm,
> > > > >    
> > > > >           INIT_LIST_HEAD(&ops->list);
> > > > >    
> > > > > -       drm_gem_for_each_gpuva(va, obj) {
> > > > > -               op = gpuva_op_alloc(gpuvm);
> > > > > +       drm_gpuvm_bo_for_each_va(va, vm_bo) {
> > > > > +               op = gpuva_op_alloc(vm_bo->vm);
> > > > >                   if (!op) {
> > > > >                           ret = -ENOMEM;
> > > > >                           goto err_free_ops;
> > > > > @@ -1745,10 +1986,10 @@ drm_gpuvm_gem_unmap_ops_create(struct
> > > > > drm_gpuvm *gpuvm,
> > > > >           return ops;
> > > > >    
> > > > >    err_free_ops:
> > > > > -       drm_gpuva_ops_free(gpuvm, ops);
> > > > > +       drm_gpuva_ops_free(vm_bo->vm, ops);
> > > > >           return ERR_PTR(ret);
> > > > >    }
> > > > > -EXPORT_SYMBOL_GPL(drm_gpuvm_gem_unmap_ops_create);
> > > > > +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_unmap_ops_create);
> > > > >    
> > > > >    /**
> > > > >     * drm_gpuva_ops_free() - free the given &drm_gpuva_ops
> > > > > diff --git a/drivers/gpu/drm/nouveau/nouveau_uvmm.c
> > > > > b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
> > > > > index ed439bf4032f..1e95b0a1b047 100644
> > > > > --- a/drivers/gpu/drm/nouveau/nouveau_uvmm.c
> > > > > +++ b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
> > > > > @@ -62,6 +62,8 @@ struct bind_job_op {
> > > > >           enum vm_bind_op op;
> > > > >           u32 flags;
> > > > >    
> > > > > +       struct drm_gpuvm_bo *vm_bo;
> > > > > +
> > > > >           struct {
> > > > >                   u64 addr;
> > > > >                   u64 range;
> > > > > @@ -1113,22 +1115,28 @@ bind_validate_region(struct
> > > > > nouveau_job
> > > > > *job)
> > > > >    }
> > > > >    
> > > > >    static void
> > > > > -bind_link_gpuvas(struct drm_gpuva_ops *ops, struct
> > > > > nouveau_uvma_prealloc *new)
> > > > > +bind_link_gpuvas(struct bind_job_op *bop)
> > > > >    {
> > > > > +       struct nouveau_uvma_prealloc *new = &bop->new;
> > > > > +       struct drm_gpuvm_bo *vm_bo = bop->vm_bo;
> > > > > +       struct drm_gpuva_ops *ops = bop->ops;
> > > > >           struct drm_gpuva_op *op;
> > > > >    
> > > > >           drm_gpuva_for_each_op(op, ops) {
> > > > >                   switch (op->op) {
> > > > >                   case DRM_GPUVA_OP_MAP:
> > > > > -                       drm_gpuva_link(&new->map->va);
> > > > > +                       drm_gpuva_link(&new->map->va, vm_bo);
> > > > >                           break;
> > > > > -               case DRM_GPUVA_OP_REMAP:
> > > > > +               case DRM_GPUVA_OP_REMAP: {
> > > > > +                       struct drm_gpuva *va = op-
> > > > > >remap.unmap-
> > > > > > va;
> > > > > +
> > > > >                           if (op->remap.prev)
> > > > > -                               drm_gpuva_link(&new->prev-
> > > > > >va);
> > > > > +                               drm_gpuva_link(&new->prev-
> > > > > >va,
> > > > > va-
> > > > > > vm_bo);
> > > > >                           if (op->remap.next)
> > > > > -                               drm_gpuva_link(&new->next-
> > > > > >va);
> > > > > -                       drm_gpuva_unlink(op->remap.unmap-
> > > > > >va);
> > > > > +                               drm_gpuva_link(&new->next-
> > > > > >va,
> > > > > va-
> > > > > > vm_bo);
> > > > > +                       drm_gpuva_unlink(va);
> > > > >                           break;
> > > > > +               }
> > > > >                   case DRM_GPUVA_OP_UNMAP:
> > > > >                           drm_gpuva_unlink(op->unmap.va);
> > > > >                           break;
> > > > > @@ -1150,10 +1158,18 @@ nouveau_uvmm_bind_job_submit(struct
> > > > > nouveau_job *job)
> > > > >    
> > > > >           list_for_each_op(op, &bind_job->ops) {
> > > > >                   if (op->op == OP_MAP) {
> > > > > -                       op->gem.obj =
> > > > > drm_gem_object_lookup(job-
> > > > > > file_priv,
> > > > > -                                                          
> > > > > op-
> > > > > > gem.handle);
> > > > > -                       if (!op->gem.obj)
> > > > > +                       struct drm_gem_object *obj;
> > > > > +
> > > > > +                       obj = drm_gem_object_lookup(job-
> > > > > > file_priv,
> > > > > +                                                   op-
> > > > > > gem.handle);
> > > > > +                       if (!(op->gem.obj = obj))
> > > > >                                   return -ENOENT;
> > > > > +
> > > > > +                       dma_resv_lock(obj->resv, NULL);
> > > > > +                       op->vm_bo =
> > > > > drm_gpuvm_bo_obtain(&uvmm-
> > > > > > base,
> > > > > obj);
> > > > > +                       dma_resv_unlock(obj->resv);
> > > > > +                       if (IS_ERR(op->vm_bo))
> > > > > +                               return PTR_ERR(op->vm_bo);
> > > > >                   }
> > > > >    
> > > > >                   ret = bind_validate_op(job, op);
> > > > > @@ -1364,7 +1380,7 @@ nouveau_uvmm_bind_job_submit(struct
> > > > > nouveau_job
> > > > > *job)
> > > > >                   case OP_UNMAP_SPARSE:
> > > > >                   case OP_MAP:
> > > > >                   case OP_UNMAP:
> > > > > -                       bind_link_gpuvas(op->ops, &op->new);
> > > > > +                       bind_link_gpuvas(op);
> > > > >                           break;
> > > > >                   default:
> > > > >                           break;
> > > > > @@ -1511,6 +1527,12 @@
> > > > > nouveau_uvmm_bind_job_free_work_fn(struct
> > > > > work_struct *work)
> > > > >                   if (!IS_ERR_OR_NULL(op->ops))
> > > > >                           drm_gpuva_ops_free(&uvmm->base, op-
> > > > > > ops);
> > > > >    
> > > > > +               if (!IS_ERR_OR_NULL(op->vm_bo)) {
> > > > > +                       dma_resv_lock(obj->resv, NULL);
> > > > > +                       drm_gpuvm_bo_put(op->vm_bo);
> > > > > +                       dma_resv_unlock(obj->resv);
> > > > > +               }
> > > > > +
> > > > >                   if (obj)
> > > > >                           drm_gem_object_put(obj);
> > > > >           }
> > > > > @@ -1776,15 +1798,18 @@ void
> > > > >    nouveau_uvmm_bo_map_all(struct nouveau_bo *nvbo, struct
> > > > > nouveau_mem
> > > > > *mem)
> > > > >    {
> > > > >           struct drm_gem_object *obj = &nvbo->bo.base;
> > > > > +       struct drm_gpuvm_bo *vm_bo;
> > > > >        ��  struct drm_gpuva *va;
> > > > >    
> > > > >           dma_resv_assert_held(obj->resv);
> > > > >    
> > > > > -       drm_gem_for_each_gpuva(va, obj) {
> > > > > -               struct nouveau_uvma *uvma = uvma_from_va(va);
> > > > > +       drm_gem_for_each_gpuvm_bo(vm_bo, obj) {
> > > > > +               drm_gpuvm_bo_for_each_va(va, vm_bo) {
> > > > > +                       struct nouveau_uvma *uvma =
> > > > > uvma_from_va(va);
> > > > >    
> > > > > -               nouveau_uvma_map(uvma, mem);
> > > > > -               drm_gpuva_invalidate(va, false);
> > > > > +                       nouveau_uvma_map(uvma, mem);
> > > > > +                       drm_gpuva_invalidate(va, false);
> > > > > +               }
> > > > >           }
> > > > >    }
> > > > >    
> > > > > @@ -1792,15 +1817,18 @@ void
> > > > >    nouveau_uvmm_bo_unmap_all(struct nouveau_bo *nvbo)
> > > > >    {
> > > > >           struct drm_gem_object *obj = &nvbo->bo.base;
> > > > > +       struct drm_gpuvm_bo *vm_bo;
> > > > >           struct drm_gpuva *va;
> > > > >    
> > > > >           dma_resv_assert_held(obj->resv);
> > > > >    
> > > > > -       drm_gem_for_each_gpuva(va, obj) {
> > > > > -               struct nouveau_uvma *uvma = uvma_from_va(va);
> > > > > +       drm_gem_for_each_gpuvm_bo(vm_bo, obj) {
> > > > > +               drm_gpuvm_bo_for_each_va(va, vm_bo) {
> > > > > +                       struct nouveau_uvma *uvma =
> > > > > uvma_from_va(va);
> > > > >    
> > > > > -         ��     nouveau_uvma_unmap(uvma);
> > > > > -               drm_gpuva_invalidate(va, true);
> > > > > +                       nouveau_uvma_unmap(uvma);
> > > > > +                       drm_gpuva_invalidate(va, true);
> > > > > +               }
> > > > >           }
> > > > >    }
> > > > >    
> > > > > diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
> > > > > index 16364487fde9..369505447acd 100644
> > > > > --- a/include/drm/drm_gem.h
> > > > > +++ b/include/drm/drm_gem.h
> > > > > @@ -580,7 +580,7 @@ int drm_gem_evict(struct drm_gem_object
> > > > > *obj);
> > > > >     * drm_gem_gpuva_init() - initialize the gpuva list of a
> > > > > GEM
> > > > > object
> > > > >     * @obj: the &drm_gem_object
> > > > >     *
> > > > > - * This initializes the &drm_gem_object's &drm_gpuva list.
> > > > > + * This initializes the &drm_gem_object's &drm_gpuvm_bo
> > > > > list.
> > > > >     *
> > > > >     * Calling this function is only necessary for drivers
> > > > > intending to
> > > > > support the
> > > > >     * &drm_driver_feature DRIVER_GEM_GPUVA.
> > > > > @@ -593,28 +593,28 @@ static inline void
> > > > > drm_gem_gpuva_init(struct
> > > > > drm_gem_object *obj)
> > > > >    }
> > > > >    
> > > > >    /**
> > > > > - * drm_gem_for_each_gpuva() - iternator to walk over a list
> > > > > of
> > > > > gpuvas
> > > > > - * @entry__: &drm_gpuva structure to assign to in each
> > > > > iteration
> > > > > step
> > > > > - * @obj__: the &drm_gem_object the &drm_gpuvas to walk are
> > > > > associated with
> > > > > + * drm_gem_for_each_gpuvm_bo() - iterator to walk over a
> > > > > list of
> > > > > &drm_gpuvm_bo
> > > > > + * @entry__: &drm_gpuvm_bo structure to assign to in each
> > > > > iteration
> > > > > step
> > > > > + * @obj__: the &drm_gem_object the &drm_gpuvm_bo to walk are
> > > > > associated with
> > > > >     *
> > > > > - * This iterator walks over all &drm_gpuva structures
> > > > > associated
> > > > > with the
> > > > > - * &drm_gpuva_manager.
> > > > > + * This iterator walks over all &drm_gpuvm_bo structures
> > > > > associated
> > > > > with the
> > > > > + * &drm_gem_object.
> > > > >     */
> > > > > -#define drm_gem_for_each_gpuva(entry__, obj__) \
> > > > > -       list_for_each_entry(entry__, &(obj__)->gpuva.list,
> > > > > gem.entry)
> > > > > +#define drm_gem_for_each_gpuvm_bo(entry__, obj__) \
> > > > > +       list_for_each_entry(entry__, &(obj__)->gpuva.list,
> > > > > list.entry.gem)
> > > > >    
> > > > >    /**
> > > > > - * drm_gem_for_each_gpuva_safe() - iternator to safely walk
> > > > > over
> > > > > a
> > > > > list of
> > > > > - * gpuvas
> > > > > - * @entry__: &drm_gpuva structure to assign to in each
> > > > > iteration
> > > > > step
> > > > > - * @next__: &next &drm_gpuva to store the next step
> > > > > - * @obj__: the &drm_gem_object the &drm_gpuvas to walk are
> > > > > associated with
> > > > > + * drm_gem_for_each_gpuvm_bo_safe() - iterator to safely
> > > > > walk
> > > > > over a
> > > > > list of
> > > > > + * &drm_gpuvm_bo
> > > > > + * @entry__: &drm_gpuvm_bostructure to assign to in each
> > > > > iteration
> > > > > step
> > > > > + * @next__: &next &drm_gpuvm_bo to store the next step
> > > > > + * @obj__: the &drm_gem_object the &drm_gpuvm_bo to walk are
> > > > > associated with
> > > > >     *
> > > > > - * This iterator walks over all &drm_gpuva structures
> > > > > associated
> > > > > with the
> > > > > + * This iterator walks over all &drm_gpuvm_bo structures
> > > > > associated
> > > > > with the
> > > > >     * &drm_gem_object. It is implemented with
> > > > > list_for_each_entry_safe(), hence
> > > > >     * it is save against removal of elements.
> > > > >     */
> > > > > -#define drm_gem_for_each_gpuva_safe(entry__, next__, obj__)
> > > > > \
> > > > > -       list_for_each_entry_safe(entry__, next__, &(obj__)-
> > > > > > gpuva.list, gem.entry)
> > > > > +#define drm_gem_for_each_gpuvm_bo_safe(entry__, next__,
> > > > > obj__) \
> > > > > +       list_for_each_entry_safe(entry__, next__, &(obj__)-
> > > > > > gpuva.list, list.entry.gem)
> > > > >    
> > > > >    #endif /* __DRM_GEM_H__ */
> > > > > diff --git a/include/drm/drm_gpuvm.h
> > > > > b/include/drm/drm_gpuvm.h
> > > > > index 47cbacb244b9..466fdd76c71a 100644
> > > > > --- a/include/drm/drm_gpuvm.h
> > > > > +++ b/include/drm/drm_gpuvm.h
> > > > > @@ -25,6 +25,7 @@
> > > > >     * OTHER DEALINGS IN THE SOFTWARE.
> > > > >     */
> > > > >    
> > > > > +#include <linux/dma-resv.h>
> > > > >    #include <linux/list.h>
> > > > >    #include <linux/rbtree.h>
> > > > >    #include <linux/types.h>
> > > > > @@ -33,6 +34,7 @@
> > > > >    #include <drm/drm_gem.h>
> > > > >    
> > > > >    struct drm_gpuvm;
> > > > > +struct drm_gpuvm_bo;
> > > > >    struct drm_gpuvm_ops;
> > > > >    
> > > > >    /**
> > > > > @@ -73,6 +75,12 @@ struct drm_gpuva {
> > > > >            */
> > > > >           struct drm_gpuvm *vm;
> > > > >    
> > > > > +       /**
> > > > > +        * @vm_bo: the &drm_gpuvm_bo abstraction for the
> > > > > mapped
> > > > > +        * &drm_gem_object
> > > > > +        */
> > > > > +       struct drm_gpuvm_bo *vm_bo;
> > > > > +
> > > > >           /**
> > > > >            * @flags: the &drm_gpuva_flags for this mapping
> > > > >            */
> > > > > @@ -108,7 +116,7 @@ struct drm_gpuva {
> > > > >                   struct drm_gem_object *obj;
> > > > >    
> > > > >                   /**
> > > > > -                * @entry: the &list_head to attach this
> > > > > object
> > > > > to a
> > > > > &drm_gem_object
> > > > > +                * @entry: the &list_head to attach this
> > > > > object
> > > > > to a
> > > > > &drm_gpuvm_bo
> > > > >                    */
> > > > >                   struct list_head entry;
> > > > >           } gem;
> > > > > @@ -141,7 +149,7 @@ struct drm_gpuva {
> > > > >    int drm_gpuva_insert(struct drm_gpuvm *gpuvm, struct
> > > > > drm_gpuva
> > > > > *va);
> > > > >    void drm_gpuva_remove(struct drm_gpuva *va);
> > > > >    
> > > > > -void drm_gpuva_link(struct drm_gpuva *va);
> > > > > +void drm_gpuva_link(struct drm_gpuva *va, struct
> > > > > drm_gpuvm_bo
> > > > > *vm_bo);
> > > > >    void drm_gpuva_unlink(struct drm_gpuva *va);
> > > > >    
> > > > >    struct drm_gpuva *drm_gpuva_find(struct drm_gpuvm *gpuvm,
> > > > > @@ -188,10 +196,16 @@ static inline bool
> > > > > drm_gpuva_invalidated(struct
> > > > > drm_gpuva *va)
> > > > >     * enum drm_gpuvm_flags - flags for struct drm_gpuvm
> > > > >     */
> > > > >    enum drm_gpuvm_flags {
> > > > > +       /**
> > > > > +        * @DRM_GPUVM_RESV_PROTECTED: GPUVM is protected
> > > > > externally
> > > > > by the
> > > > > +        * GPUVM's &dma_resv lock
> > > > > +        */
> > > > > +       DRM_GPUVM_RESV_PROTECTED = BIT(0),
> > > > > +
> > > > >           /**
> > > > >            * @DRM_GPUVM_USERBITS: user defined bits
> > > > >            */
> > > > > -       DRM_GPUVM_USERBITS = BIT(0),
> > > > > +       DRM_GPUVM_USERBITS = BIT(1),
> > > > >    };
> > > > >    
> > > > >    /**
> > > > > @@ -280,6 +294,19 @@ bool drm_gpuvm_interval_empty(struct
> > > > > drm_gpuvm
> > > > > *gpuvm, u64 addr, u64 range);
> > > > >    struct drm_gem_object *
> > > > >    drm_gpuvm_resv_object_alloc(struct drm_device *drm);
> > > > >    
> > > > > +/**
> > > > > + * drm_gpuvm_resv_protected() - indicates whether
> > > > > &DRM_GPUVM_RESV_PROTECTED is
> > > > > + * set
> > > > > + * @gpuvm: the &drm_gpuvm
> > > > > + *
> > > > > + * Returns: true if &DRM_GPUVM_RESV_PROTECTED is set, false
> > > > > otherwise.
> > > > > + */
> > > > > +static inline bool
> > > > > +drm_gpuvm_resv_protected(struct drm_gpuvm *gpuvm)
> > > > > +{
> > > > > +       return gpuvm->flags & DRM_GPUVM_RESV_PROTECTED;
> > > > > +}
> > > > > +
> > > > >    /**
> > > > >     * drm_gpuvm_resv() - returns the &drm_gpuvm's &dma_resv
> > > > >     * @gpuvm__: the &drm_gpuvm
> > > > > @@ -298,6 +325,12 @@ drm_gpuvm_resv_object_alloc(struct
> > > > > drm_device
> > > > > *drm);
> > > > >     */
> > > > >    #define drm_gpuvm_resv_obj(gpuvm__) ((gpuvm__)->r_obj)
> > > > >    
> > > > > +#define drm_gpuvm_resv_held(gpuvm__) \
> > > > > +       dma_resv_held(drm_gpuvm_resv(gpuvm__))
> > > > > +
> > > > > +#define drm_gpuvm_resv_assert_held(gpuvm__) \
> > > > > +       dma_resv_assert_held(drm_gpuvm_resv(gpuvm__))
> > > > > +
> > > > >    #define drm_gpuvm_resv_held(gpuvm__) \
> > > > >           dma_resv_held(drm_gpuvm_resv(gpuvm__))
> > > > >    
> > > > > @@ -382,6 +415,128 @@ __drm_gpuva_next(struct drm_gpuva *va)
> > > > >    #define drm_gpuvm_for_each_va_safe(va__, next__, gpuvm__)
> > > > > \
> > > > >           list_for_each_entry_safe(va__, next__, &(gpuvm__)-
> > > > > > rb.list,
> > > > > rb.entry)
> > > > >    
> > > > > +/**
> > > > > + * struct drm_gpuvm_bo - structure representing a &drm_gpuvm
> > > > > and
> > > > > + * &drm_gem_object combination
> > > > > + *
> > > > > + * This structure is an abstraction representing a
> > > > > &drm_gpuvm
> > > > > and
> > > > > + * &drm_gem_object combination. It serves as an indirection
> > > > > to
> > > > > accelerate
> > > > > + * iterating all &drm_gpuvas within a &drm_gpuvm backed by
> > > > > the
> > > > > same
> > > > > + * &drm_gem_object.
> > > > > + *
> > > > > + * Furthermore it is used cache evicted GEM objects for a
> > > > > certain
> > > > > GPU-VM to
> > > > > + * accelerate validation.
> > > > > + *
> > > > > + * Typically, drivers want to create an instance of a struct
> > > > > drm_gpuvm_bo once
> > > > > + * a GEM object is mapped first in a GPU-VM and release the
> > > > > instance
> > > > > once the
> > > > > + * last mapping of the GEM object in this GPU-VM is
> > > > > unmapped.
> > > > > + */
> > > > > +struct drm_gpuvm_bo {
> > > > > +       /**
> > > > > +        * @vm: The &drm_gpuvm the @obj is mapped in. This
> > > > > pointer is
> > > > > not
> > > > > +        * reference counted.
> > > > > +        *
> > > > > +        * A struct drm_gpuvm_bo is not allowed to out-live
> > > > > its
> > > > > &drm_gpuvm
> > > > > +        * context. Implicitly, this is ensured by the fact
> > > > > that
> > > > > the
> > > > > driver is
> > > > > +        * responsible to ensure the VM doesn't contain
> > > > > mappings
> > > > > once
> > > > > it's
> > > > > +        * freed, since a struct drm_gpuvm_bo should be freed
> > > > > once
> > > > > the last
> > > > > +        * mapping being backed by the corresponding buffer
> > > > > object is
> > > > > unmapped.
> > > > > +        */
> > > > 
> > > > 
> > > > I don't think the above is completely true. Let's assume in the
> > > > !RESV_PROTECTED case that a reference is grabbed on the
> > > > drm_gpuvm_bo
> > > > during an iteration over a list. Then user-space closes the vm
> > > > and
> > > > all
> > > > vmas are unlinked, but this reference remains but the vm
> > > > pointer
> > > > becomes stale. In the RESV_PROTECTED case this is ensured not
> > > > to
> > > > happen
> > > > if by the vm->resv being grabbed during unlink, but in the
> > > > !RESV_PROTECTED case, the above wording isn't sufficient. The
> > > > caller
> > > > needs to ensure the vm stays alive using some sort of similar
> > > > rule
> > > > or
> > > > use kref_get_unless_zero() on the vm under the spinlock if
> > > > dereferenced.
> > > 
> > > The list is part of the GPUVM. Hence, the caller *must* either
> > > already hold
> > > a reference to the GPUVM or otherwise ensure it's not freed while
> > > iterating
> > > this list. All the drm_gpuvm_bo structures within this list can't
> > > have a
> > > pointer to another VM than this one by definition.
> > > 
> > > Anyway, I recognize that this isn't very obvious. Hence, I think
> > > we
> > > should
> > > probably reference count GPUVMs as well. I'd think of the same
> > > way we
> > > do it
> > > with drm_gem_objects. However, I'd prefer to introduce this with
> > > a
> > > subsequent
> > > patch.
> > 
> > Well, I think we should actually be OK in most cases, and
> > refcounting
> > here would probably result in circular dependencies.
> 
> Where would you see a circular dependency with reference counted
> GPUVMs?

It'd be if you call any va_unlink() from the vm destructor. Then the
destructor will never get called because of the corresponding gpuvm_bo
vm reference. (IIRC the same argument was made with the vm's resv_bo by
Christian?)

However if there is a vm_close(), that does all the va_unlink(), that
will resolve that circular depencency. We do have it in Xe, not sure
about other drivers.

/Thomas
  

On 11/1/23 20:45, Thomas Hellström wrote:
> On Wed, 2023-11-01 at 18:21 +0100, Danilo Krummrich wrote:
>> On 11/1/23 17:38, Thomas Hellström wrote:
>>> On Tue, 2023-10-31 at 18:38 +0100, Danilo Krummrich wrote:
>>>> On 10/31/23 11:32, Thomas Hellström wrote:
>>>>> On Mon, 2023-10-23 at 22:16 +0200, Danilo Krummrich wrote:
>>>>>> Add an abstraction layer between the drm_gpuva mappings of a
>>>>>> particular
>>>>>> drm_gem_object and this GEM object itself. The abstraction
>>>>>> represents
>>>>>> a
>>>>>> combination of a drm_gem_object and drm_gpuvm. The
>>>>>> drm_gem_object
>>>>>> holds
>>>>>> a list of drm_gpuvm_bo structures (the structure representing
>>>>>> this
>>>>>> abstraction), while each drm_gpuvm_bo contains list of
>>>>>> mappings
>>>>>> of
>>>>>> this
>>>>>> GEM object.
>>>>>>
>>>>>> This has multiple advantages:
>>>>>>
>>>>>> 1) We can use the drm_gpuvm_bo structure to attach it to
>>>>>> various
>>>>>> lists
>>>>>>       of the drm_gpuvm. This is useful for tracking external
>>>>>> and
>>>>>> evicted
>>>>>>       objects per VM, which is introduced in subsequent
>>>>>> patches.
>>>>>>
>>>>>> 2) Finding mappings of a certain drm_gem_object mapped in a
>>>>>> certain
>>>>>>       drm_gpuvm becomes much cheaper.
>>>>>>
>>>>>> 3) Drivers can derive and extend the structure to easily
>>>>>> represent
>>>>>>       driver specific states of a BO for a certain GPUVM.
>>>>>>
>>>>>> The idea of this abstraction was taken from amdgpu, hence the
>>>>>> credit
>>>>>> for
>>>>>> this idea goes to the developers of amdgpu.
>>>>>>
>>>>>> Cc: Christian König <christian.koenig@amd.com>
>>>>>> Signed-off-by: Danilo Krummrich <dakr@redhat.com>
>>>>>> ---
>>>>>>     drivers/gpu/drm/drm_gpuvm.c            | 335
>>>>>> +++++++++++++++++++++--
>>>>>> --
>>>>>>     drivers/gpu/drm/nouveau/nouveau_uvmm.c |  64 +++--
>>>>>>     include/drm/drm_gem.h                  |  32 +--
>>>>>>     include/drm/drm_gpuvm.h                | 188
>>>>>> +++++++++++++-
>>>>>>     4 files changed, 533 insertions(+), 86 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/drm_gpuvm.c
>>>>>> b/drivers/gpu/drm/drm_gpuvm.c
>>>>>> index c03332883432..7f4f5919f84c 100644
>>>>>> --- a/drivers/gpu/drm/drm_gpuvm.c
>>>>>> +++ b/drivers/gpu/drm/drm_gpuvm.c
>>>>>> @@ -70,6 +70,18 @@
>>>>>>      * &drm_gem_object, such as the &drm_gem_object containing
>>>>>> the
>>>>>> root
>>>>>> page table,
>>>>>>      * but it can also be a 'dummy' object, which can be
>>>>>> allocated
>>>>>> with
>>>>>>      * drm_gpuvm_resv_object_alloc().
>>>>>> + *
>>>>>> + * In order to connect a struct drm_gpuva its backing
>>>>>> &drm_gem_object each
>>>>>> + * &drm_gem_object maintains a list of &drm_gpuvm_bo
>>>>>> structures,
>>>>>> and
>>>>>> each
>>>>>> + * &drm_gpuvm_bo contains a list of &drm_gpuva structures.
>>>>>> + *
>>>>>> + * A &drm_gpuvm_bo is an abstraction that represents a
>>>>>> combination
>>>>>> of a
>>>>>> + * &drm_gpuvm and a &drm_gem_object. Every such combination
>>>>>> should
>>>>>> be unique.
>>>>>> + * This is ensured by the API through drm_gpuvm_bo_obtain()
>>>>>> and
>>>>>> + * drm_gpuvm_bo_obtain_prealloc() which first look into the
>>>>>> corresponding
>>>>>> + * &drm_gem_object list of &drm_gpuvm_bos for an existing
>>>>>> instance
>>>>>> of this
>>>>>> + * particular combination. If not existent a new instance is
>>>>>> created
>>>>>> and linked
>>>>>> + * to the &drm_gem_object.
>>>>>>      */
>>>>>>     
>>>>>>     /**
>>>>>> @@ -395,21 +407,28 @@
>>>>>>     /**
>>>>>>      * DOC: Locking
>>>>>>      *
>>>>>> - * Generally, the GPU VA manager does not take care of
>>>>>> locking
>>>>>> itself, it is
>>>>>> - * the drivers responsibility to take care about locking.
>>>>>> Drivers
>>>>>> might want to
>>>>>> - * protect the following operations: inserting, removing and
>>>>>> iterating
>>>>>> - * &drm_gpuva objects as well as generating all kinds of
>>>>>> operations,
>>>>>> such as
>>>>>> - * split / merge or prefetch.
>>>>>> - *
>>>>>> - * The GPU VA manager also does not take care of the locking
>>>>>> of
>>>>>> the
>>>>>> backing
>>>>>> - * &drm_gem_object buffers GPU VA lists by itself; drivers
>>>>>> are
>>>>>> responsible to
>>>>>> - * enforce mutual exclusion using either the GEMs dma_resv
>>>>>> lock
>>>>>> or
>>>>>> alternatively
>>>>>> - * a driver specific external lock. For the latter see also
>>>>>> - * drm_gem_gpuva_set_lock().
>>>>>> - *
>>>>>> - * However, the GPU VA manager contains lockdep checks to
>>>>>> ensure
>>>>>> callers of its
>>>>>> - * API hold the corresponding lock whenever the
>>>>>> &drm_gem_objects
>>>>>> GPU
>>>>>> VA list is
>>>>>> - * accessed by functions such as drm_gpuva_link() or
>>>>>> drm_gpuva_unlink().
>>>>>> + * In terms of managing &drm_gpuva entries DRM GPUVM does
>>>>>> not
>>>>>> take
>>>>>> care of
>>>>>> + * locking itself, it is the drivers responsibility to take
>>>>>> care
>>>>>> about locking.
>>>>>> + * Drivers might want to protect the following operations:
>>>>>> inserting, removing
>>>>>> + * and iterating &drm_gpuva objects as well as generating
>>>>>> all
>>>>>> kinds
>>>>>> of
>>>>>> + * operations, such as split / merge or prefetch.
>>>>>> + *
>>>>>> + * DRM GPUVM also does not take care of the locking of the
>>>>>> backing
>>>>>> + * &drm_gem_object buffers GPU VA lists and &drm_gpuvm_bo
>>>>>> abstractions by
>>>>>> + * itself; drivers are responsible to enforce mutual
>>>>>> exclusion
>>>>>> using
>>>>>> either the
>>>>>> + * GEMs dma_resv lock or alternatively a driver specific
>>>>>> external
>>>>>> lock. For the
>>>>>> + * latter see also drm_gem_gpuva_set_lock().
>>>>>> + *
>>>>>> + * However, DRM GPUVM contains lockdep checks to ensure
>>>>>> callers
>>>>>> of
>>>>>> its API hold
>>>>>> + * the corresponding lock whenever the &drm_gem_objects GPU
>>>>>> VA
>>>>>> list
>>>>>> is accessed
>>>>>> + * by functions such as drm_gpuva_link() or
>>>>>> drm_gpuva_unlink(),
>>>>>> but
>>>>>> also
>>>>>> + * drm_gpuvm_bo_obtain() and drm_gpuvm_bo_put().
>>>>>> + *
>>>>>> + * The latter is required since on creation and destruction
>>>>>> of a
>>>>>> &drm_gpuvm_bo
>>>>>> + * the &drm_gpuvm_bo is attached / removed from the
>>>>>> &drm_gem_objects
>>>>>> gpuva list.
>>>>>> + * Subsequent calls to drm_gpuvm_bo_obtain() for the same
>>>>>> &drm_gpuvm
>>>>>> and
>>>>>> + * &drm_gem_object must be able to observe previous
>>>>>> creations
>>>>>> and
>>>>>> destructions
>>>>>> + * of &drm_gpuvm_bos in order to keep instances unique.
>>>>>>      */
>>>>>>     
>>>>>>     /**
>>>>>> @@ -439,6 +458,7 @@
>>>>>>      *     {
>>>>>>      *             struct drm_gpuva_ops *ops;
>>>>>>      *             struct drm_gpuva_op *op
>>>>>> + *             struct drm_gpuvm_bo *vm_bo;
>>>>>>      *
>>>>>>      *             driver_lock_va_space();
>>>>>>      *             ops = drm_gpuvm_sm_map_ops_create(gpuvm,
>>>>>> addr,
>>>>>> range,
>>>>>> @@ -446,6 +466,10 @@
>>>>>>      *             if (IS_ERR(ops))
>>>>>>      *                     return PTR_ERR(ops);
>>>>>>      *
>>>>>> + *             vm_bo = drm_gpuvm_bo_obtain(gpuvm, obj);
>>>>>> + *             if (IS_ERR(vm_bo))
>>>>>> + *                     return PTR_ERR(vm_bo);
>>>>>> + *
>>>>>>      *             drm_gpuva_for_each_op(op, ops) {
>>>>>>      *                     struct drm_gpuva *va;
>>>>>>      *
>>>>>> @@ -458,7 +482,7 @@
>>>>>>      *
>>>>>>      *                             driver_vm_map();
>>>>>>      *                             drm_gpuva_map(gpuvm, va,
>>>>>> &op-
>>>>>>> map);
>>>>>> - *                             drm_gpuva_link(va);
>>>>>> + *                             drm_gpuva_link(va, vm_bo);
>>>>>>      *
>>>>>>      *                             break;
>>>>>>      *                     case DRM_GPUVA_OP_REMAP: {
>>>>>> @@ -485,11 +509,11 @@
>>>>>>      *                             driver_vm_remap();
>>>>>>      *                             drm_gpuva_remap(prev, next,
>>>>>> &op-
>>>>>>> remap);
>>>>>>      *
>>>>>> - *                             drm_gpuva_unlink(va);
>>>>>>      *                             if (prev)
>>>>>> - *                                     drm_gpuva_link(prev);
>>>>>> + *                                     drm_gpuva_link(prev,
>>>>>> va-
>>>>>>> vm_bo);
>>>>>>      *                             if (next)
>>>>>> - *                                     drm_gpuva_link(next);
>>>>>> + *                                     drm_gpuva_link(next,
>>>>>> va-
>>>>>>> vm_bo);
>>>>>> + *                             drm_gpuva_unlink(va);
>>>>>>      *
>>>>>>      *                             break;
>>>>>>      *                     }
>>>>>> @@ -505,6 +529,7 @@
>>>>>>      *                             break;
>>>>>>      *                     }
>>>>>>      *             }
>>>>>> + *             drm_gpuvm_bo_put(vm_bo);
>>>>>>      *             driver_unlock_va_space();
>>>>>>      *
>>>>>>      *             return 0;
>>>>>> @@ -514,6 +539,7 @@
>>>>>>      *
>>>>>>      *     struct driver_context {
>>>>>>      *             struct drm_gpuvm *gpuvm;
>>>>>> + *             struct drm_gpuvm_bo *vm_bo;
>>>>>>      *             struct drm_gpuva *new_va;
>>>>>>      *             struct drm_gpuva *prev_va;
>>>>>>      *             struct drm_gpuva *next_va;
>>>>>> @@ -534,6 +560,7 @@
>>>>>>      *                               struct drm_gem_object
>>>>>> *obj,
>>>>>> u64
>>>>>> offset)
>>>>>>      *     {
>>>>>>      *             struct driver_context ctx;
>>>>>> + *             struct drm_gpuvm_bo *vm_bo;
>>>>>>      *             struct drm_gpuva_ops *ops;
>>>>>>      *             struct drm_gpuva_op *op;
>>>>>>      *             int ret = 0;
>>>>>> @@ -543,16 +570,23 @@
>>>>>>      *             ctx.new_va = kzalloc(sizeof(*ctx.new_va),
>>>>>> GFP_KERNEL);
>>>>>>      *             ctx.prev_va = kzalloc(sizeof(*ctx.prev_va),
>>>>>> GFP_KERNEL);
>>>>>>      *             ctx.next_va = kzalloc(sizeof(*ctx.next_va),
>>>>>> GFP_KERNEL);
>>>>>> - *             if (!ctx.new_va || !ctx.prev_va ||
>>>>>> !ctx.next_va)
>>>>>> {
>>>>>> + *             ctx.vm_bo = drm_gpuvm_bo_create(gpuvm, obj);
>>>>>> + *             if (!ctx.new_va || !ctx.prev_va ||
>>>>>> !ctx.next_va
>>>>>>>>
>>>>>> !vm_bo) {
>>>>>>      *                     ret = -ENOMEM;
>>>>>>      *                     goto out;
>>>>>>      *             }
>>>>>>      *
>>>>>> + *             // Typically protected with a driver specific
>>>>>> GEM
>>>>>> gpuva lock
>>>>>> + *             // used in the fence signaling path for
>>>>>> drm_gpuva_link() and
>>>>>> + *             // drm_gpuva_unlink(), hence pre-allocate.
>>>>>> + *             ctx.vm_bo =
>>>>>> drm_gpuvm_bo_obtain_prealloc(ctx.vm_bo);
>>>>>> + *
>>>>>>      *             driver_lock_va_space();
>>>>>>      *             ret = drm_gpuvm_sm_map(gpuvm, &ctx, addr,
>>>>>> range,
>>>>>> obj,
>>>>>> offset);
>>>>>>      *             driver_unlock_va_space();
>>>>>>      *
>>>>>>      *     out:
>>>>>> + *             drm_gpuvm_bo_put(ctx.vm_bo);
>>>>>>      *             kfree(ctx.new_va);
>>>>>>      *             kfree(ctx.prev_va);
>>>>>>      *             kfree(ctx.next_va);
>>>>>> @@ -565,7 +599,7 @@
>>>>>>      *
>>>>>>      *             drm_gpuva_map(ctx->vm, ctx->new_va, &op-
>>>>>>> map);
>>>>>>      *
>>>>>> - *             drm_gpuva_link(ctx->new_va);
>>>>>> + *             drm_gpuva_link(ctx->new_va, ctx->vm_bo);
>>>>>>      *
>>>>>>      *             // prevent the new GPUVA from being freed
>>>>>> in
>>>>>>      *             // driver_mapping_create()
>>>>>> @@ -577,22 +611,23 @@
>>>>>>      *     int driver_gpuva_remap(struct drm_gpuva_op *op,
>>>>>> void
>>>>>> *__ctx)
>>>>>>      *     {
>>>>>>      *             struct driver_context *ctx = __ctx;
>>>>>> + *             struct drm_gpuva *va = op->remap.unmap->va;
>>>>>>      *
>>>>>>      *             drm_gpuva_remap(ctx->prev_va, ctx->next_va,
>>>>>> &op-
>>>>>>> remap);
>>>>>>      *
>>>>>> - *             drm_gpuva_unlink(op->remap.unmap->va);
>>>>>> - *             kfree(op->remap.unmap->va);
>>>>>> - *
>>>>>>      *             if (op->remap.prev) {
>>>>>> - *                     drm_gpuva_link(ctx->prev_va);
>>>>>> + *                     drm_gpuva_link(ctx->prev_va, va-
>>>>>>> vm_bo);
>>>>>>      *                     ctx->prev_va = NULL;
>>>>>>      *             }
>>>>>>      *
>>>>>>      *             if (op->remap.next) {
>>>>>> - *                     drm_gpuva_link(ctx->next_va);
>>>>>> + *                     drm_gpuva_link(ctx->next_va, va-
>>>>>>> vm_bo);
>>>>>>      *                     ctx->next_va = NULL;
>>>>>>      *             }
>>>>>>      *
>>>>>> + *             drm_gpuva_unlink(va);
>>>>>> + *             kfree(va);
>>>>>> + *
>>>>>>      *             return 0;
>>>>>>      *     }
>>>>>>      *
>>>>>> @@ -774,6 +809,194 @@ drm_gpuvm_destroy(struct drm_gpuvm
>>>>>> *gpuvm)
>>>>>>     }
>>>>>>     EXPORT_SYMBOL_GPL(drm_gpuvm_destroy);
>>>>>>     
>>>>>> +/**
>>>>>> + * drm_gpuvm_bo_create() - create a new instance of struct
>>>>>> drm_gpuvm_bo
>>>>>> + * @gpuvm: The &drm_gpuvm the @obj is mapped in.
>>>>>> + * @obj: The &drm_gem_object being mapped in the @gpuvm.
>>>>>> + *
>>>>>> + * If provided by the driver, this function uses the
>>>>>> &drm_gpuvm_ops
>>>>>> + * vm_bo_alloc() callback to allocate.
>>>>>> + *
>>>>>> + * Returns: a pointer to the &drm_gpuvm_bo on success, NULL
>>>>>> on
>>>>>
>>>>> Still needs s/Returns:/Return:/g
>>>>>
>>>>>> failure
>>>>>> + */
>>>>>> +struct drm_gpuvm_bo *
>>>>>> +drm_gpuvm_bo_create(struct drm_gpuvm *gpuvm,
>>>>>> +                   struct drm_gem_object *obj)
>>>>>> +{
>>>>>> +       const struct drm_gpuvm_ops *ops = gpuvm->ops;
>>>>>> +       struct drm_gpuvm_bo *vm_bo;
>>>>>> +
>>>>>> +       if (ops && ops->vm_bo_alloc)
>>>>>> +               vm_bo = ops->vm_bo_alloc();
>>>>>> +       else
>>>>>> +               vm_bo = kzalloc(sizeof(*vm_bo), GFP_KERNEL);
>>>>>> +
>>>>>> +       if (unlikely(!vm_bo))
>>>>>> +               return NULL;
>>>>>> +
>>>>>> +       vm_bo->vm = gpuvm;
>>>>>> +       vm_bo->obj = obj;
>>>>>> +       drm_gem_object_get(obj);
>>>>>> +
>>>>>> +       kref_init(&vm_bo->kref);
>>>>>> +       INIT_LIST_HEAD(&vm_bo->list.gpuva);
>>>>>> +       INIT_LIST_HEAD(&vm_bo->list.entry.gem);
>>>>>> +
>>>>>> +       return vm_bo;
>>>>>> +}
>>>>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_create);
>>>>>> +
>>>>>> +static void
>>>>>> +drm_gpuvm_bo_destroy(struct kref *kref)
>>>>>> +{
>>>>>> +       struct drm_gpuvm_bo *vm_bo = container_of(kref,
>>>>>> struct
>>>>>> drm_gpuvm_bo,
>>>>>> +                                                 kref);
>>>>>> +       struct drm_gpuvm *gpuvm = vm_bo->vm;
>>>>>> +       const struct drm_gpuvm_ops *ops = gpuvm->ops;
>>>>>> +       struct drm_gem_object *obj = vm_bo->obj;
>>>>>> +       bool lock = !drm_gpuvm_resv_protected(gpuvm);
>>>>>> +
>>>>>> +       if (!lock)
>>>>>> +               drm_gpuvm_resv_assert_held(gpuvm);
>>>>>> +
>>>>>> +       drm_gem_gpuva_assert_lock_held(obj);
>>>>>> +       list_del(&vm_bo->list.entry.gem);
>>>>>> +
>>>>>> +       if (ops && ops->vm_bo_free)
>>>>>> +               ops->vm_bo_free(vm_bo);
>>>>>> +       else
>>>>>> +               kfree(vm_bo);
>>>>>> +
>>>>>> +       drm_gem_object_put(obj);
>>>>>> +}
>>>>>> +
>>>>>> +/**
>>>>>> + * drm_gpuvm_bo_put() - drop a struct drm_gpuvm_bo reference
>>>>>> + * @vm_bo: the &drm_gpuvm_bo to release the reference of
>>>>>> + *
>>>>>> + * This releases a reference to @vm_bo.
>>>>>> + *
>>>>>> + * If the reference count drops to zero, the &gpuvm_bo is
>>>>>> destroyed,
>>>>>> which
>>>>>> + * includes removing it from the GEMs gpuva list. Hence, if
>>>>>> a
>>>>>> call
>>>>>> to this
>>>>>> + * function can potentially let the reference count to zero
>>>>>> the
>>>>>> caller must
>>>>>> + * hold the dma-resv or driver specific GEM gpuva lock.
>>>>>> + */
>>>>>> +void
>>>>>> +drm_gpuvm_bo_put(struct drm_gpuvm_bo *vm_bo)
>>>>>> +{
>>>>>> +       if (vm_bo)
>>>>>> +               kref_put(&vm_bo->kref, drm_gpuvm_bo_destroy);
>>>>>> +}
>>>>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_put);
>>>>>> +
>>>>>> +static struct drm_gpuvm_bo *
>>>>>> +__drm_gpuvm_bo_find(struct drm_gpuvm *gpuvm,
>>>>>> +                   struct drm_gem_object *obj)
>>>>>> +{
>>>>>> +       struct drm_gpuvm_bo *vm_bo;
>>>>>> +
>>>>>> +       drm_gem_gpuva_assert_lock_held(obj);
>>>>>> +       drm_gem_for_each_gpuvm_bo(vm_bo, obj)
>>>>>> +               if (vm_bo->vm == gpuvm)
>>>>>> +                       return vm_bo;
>>>>>> +
>>>>>> +       return NULL;
>>>>>> +}
>>>>>> +
>>>>>> +/**
>>>>>> + * drm_gpuvm_bo_find() - find the &drm_gpuvm_bo for the
>>>>>> given
>>>>>> + * &drm_gpuvm and &drm_gem_object
>>>>>> + * @gpuvm: The &drm_gpuvm the @obj is mapped in.
>>>>>> + * @obj: The &drm_gem_object being mapped in the @gpuvm.
>>>>>> + *
>>>>>> + * Find the &drm_gpuvm_bo representing the combination of
>>>>>> the
>>>>>> given
>>>>>> + * &drm_gpuvm and &drm_gem_object. If found, increases the
>>>>>> reference
>>>>>> + * count of the &drm_gpuvm_bo accordingly.
>>>>>> + *
>>>>>> + * Returns: a pointer to the &drm_gpuvm_bo on success, NULL
>>>>>> on
>>>>>> failure
>>>>>> + */
>>>>>> +struct drm_gpuvm_bo *
>>>>>> +drm_gpuvm_bo_find(struct drm_gpuvm *gpuvm,
>>>>>> +                 struct drm_gem_object *obj)
>>>>>> +{
>>>>>> +       struct drm_gpuvm_bo *vm_bo =
>>>>>> __drm_gpuvm_bo_find(gpuvm,
>>>>>> obj);
>>>>>> +
>>>>>> +       return vm_bo ? drm_gpuvm_bo_get(vm_bo) : NULL;
>>>>>> +}
>>>>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_find);
>>>>>> +
>>>>>> +/**
>>>>>> + * drm_gpuvm_bo_obtain() - obtains and instance of the
>>>>>> &drm_gpuvm_bo
>>>>>> for the
>>>>>> + * given &drm_gpuvm and &drm_gem_object
>>>>>> + * @gpuvm: The &drm_gpuvm the @obj is mapped in.
>>>>>> + * @obj: The &drm_gem_object being mapped in the @gpuvm.
>>>>>> + *
>>>>>> + * Find the &drm_gpuvm_bo representing the combination of
>>>>>> the
>>>>>> given
>>>>>> + * &drm_gpuvm and &drm_gem_object. If found, increases the
>>>>>> reference
>>>>>> + * count of the &drm_gpuvm_bo accordingly. If not found,
>>>>>> allocates a
>>>>>> new
>>>>>> + * &drm_gpuvm_bo.
>>>>>> + *
>>>>>> + * A new &drm_gpuvm_bo is added to the GEMs gpuva list.
>>>>>> + *
>>>>>> + * Returns: a pointer to the &drm_gpuvm_bo on success, an
>>>>>> ERR_PTR on
>>>>>> failure
>>>>>> + */
>>>>>> +struct drm_gpuvm_bo *
>>>>>> +drm_gpuvm_bo_obtain(struct drm_gpuvm *gpuvm,
>>>>>> +                   struct drm_gem_object *obj)
>>>>>> +{
>>>>>> +       struct drm_gpuvm_bo *vm_bo;
>>>>>> +
>>>>>> +       vm_bo = drm_gpuvm_bo_find(gpuvm, obj);
>>>>>> +       if (vm_bo)
>>>>>> +               return vm_bo;
>>>>>> +
>>>>>> +       vm_bo = drm_gpuvm_bo_create(gpuvm, obj);
>>>>>> +       if (!vm_bo)
>>>>>> +               return ERR_PTR(-ENOMEM);
>>>>>> +
>>>>>> +       drm_gem_gpuva_assert_lock_held(obj);
>>>>>> +       list_add_tail(&vm_bo->list.entry.gem, &obj-
>>>>>>> gpuva.list);
>>>>>> +
>>>>>> +       return vm_bo;
>>>>>> +}
>>>>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_obtain);
>>>>>> +
>>>>>> +/**
>>>>>> + * drm_gpuvm_bo_obtain_prealloc() - obtains and instance of
>>>>>> the
>>>>>> &drm_gpuvm_bo
>>>>>> + * for the given &drm_gpuvm and &drm_gem_object
>>>>>> + * @__vm_bo: A pre-allocated struct drm_gpuvm_bo.
>>>>>> + *
>>>>>> + * Find the &drm_gpuvm_bo representing the combination of
>>>>>> the
>>>>>> given
>>>>>> + * &drm_gpuvm and &drm_gem_object. If found, increases the
>>>>>> reference
>>>>>> + * count of the found &drm_gpuvm_bo accordingly, while the
>>>>>> @__vm_bo
>>>>>> reference
>>>>>> + * count is decreased. If not found @__vm_bo is returned
>>>>>> without
>>>>>> further
>>>>>> + * increase of the reference count.
>>>>>> + *
>>>>>> + * A new &drm_gpuvm_bo is added to the GEMs gpuva list.
>>>>>> + *
>>>>>> + * Returns: a pointer to the found &drm_gpuvm_bo or @__vm_bo
>>>>>> if
>>>>>> no
>>>>>> existing
>>>>>> + * &drm_gpuvm_bo was found
>>>>>> + */
>>>>>> +struct drm_gpuvm_bo *
>>>>>> +drm_gpuvm_bo_obtain_prealloc(struct drm_gpuvm_bo *__vm_bo)
>>>>>> +{
>>>>>> +       struct drm_gpuvm *gpuvm = __vm_bo->vm;
>>>>>> +       struct drm_gem_object *obj = __vm_bo->obj;
>>>>>> +       struct drm_gpuvm_bo *vm_bo;
>>>>>> +
>>>>>> +       vm_bo = drm_gpuvm_bo_find(gpuvm, obj);
>>>>>> +       if (vm_bo) {
>>>>>> +               drm_gpuvm_bo_put(__vm_bo);
>>>>>> +               return vm_bo;
>>>>>> +       }
>>>>>> +
>>>>>> +       drm_gem_gpuva_assert_lock_held(obj);
>>>>>> +       list_add_tail(&__vm_bo->list.entry.gem, &obj-
>>>>>>> gpuva.list);
>>>>>> +
>>>>>> +       return __vm_bo;
>>>>>> +}
>>>>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_obtain_prealloc);
>>>>>> +
>>>>>>     static int
>>>>>>     __drm_gpuva_insert(struct drm_gpuvm *gpuvm,
>>>>>>                       struct drm_gpuva *va)
>>>>>> @@ -864,24 +1087,33 @@ EXPORT_SYMBOL_GPL(drm_gpuva_remove);
>>>>>>     /**
>>>>>>      * drm_gpuva_link() - link a &drm_gpuva
>>>>>>      * @va: the &drm_gpuva to link
>>>>>> + * @vm_bo: the &drm_gpuvm_bo to add the &drm_gpuva to
>>>>>>      *
>>>>>> - * This adds the given &va to the GPU VA list of the
>>>>>> &drm_gem_object
>>>>>> it is
>>>>>> - * associated with.
>>>>>> + * This adds the given &va to the GPU VA list of the
>>>>>> &drm_gpuvm_bo
>>>>>> and the
>>>>>> + * &drm_gpuvm_bo to the &drm_gem_object it is associated
>>>>>> with.
>>>>>> + *
>>>>>> + * For every &drm_gpuva entry added to the &drm_gpuvm_bo an
>>>>>> additional
>>>>>> + * reference of the latter is taken.
>>>>>>      *
>>>>>>      * This function expects the caller to protect the GEM's
>>>>>> GPUVA
>>>>>> list
>>>>>> against
>>>>>> - * concurrent access using the GEMs dma_resv lock.
>>>>>> + * concurrent access using either the GEMs dma_resv lock or
>>>>>> a
>>>>>> driver
>>>>>> specific
>>>>>> + * lock set through drm_gem_gpuva_set_lock().
>>>>>>      */
>>>>>>     void
>>>>>> -drm_gpuva_link(struct drm_gpuva *va)
>>>>>> +drm_gpuva_link(struct drm_gpuva *va, struct drm_gpuvm_bo
>>>>>> *vm_bo)
>>>>>>     {
>>>>>>            struct drm_gem_object *obj = va->gem.obj;
>>>>>> +       struct drm_gpuvm *gpuvm = va->vm;
>>>>>>     
>>>>>>            if (unlikely(!obj))
>>>>>>                    return;
>>>>>>     
>>>>>> -       drm_gem_gpuva_assert_lock_held(obj);
>>>>>> +       drm_WARN_ON(gpuvm->drm, obj != vm_bo->obj);
>>>>>>     
>>>>>> -       list_add_tail(&va->gem.entry, &obj->gpuva.list);
>>>>>> +       va->vm_bo = drm_gpuvm_bo_get(vm_bo);
>>>>>> +
>>>>>> +       drm_gem_gpuva_assert_lock_held(obj);
>>>>>> +       list_add_tail(&va->gem.entry, &vm_bo->list.gpuva);
>>>>>>     }
>>>>>>     EXPORT_SYMBOL_GPL(drm_gpuva_link);
>>>>>>     
>>>>>> @@ -892,20 +1124,31 @@ EXPORT_SYMBOL_GPL(drm_gpuva_link);
>>>>>>      * This removes the given &va from the GPU VA list of the
>>>>>> &drm_gem_object it is
>>>>>>      * associated with.
>>>>>>      *
>>>>>> + * This removes the given &va from the GPU VA list of the
>>>>>> &drm_gpuvm_bo and
>>>>>> + * the &drm_gpuvm_bo from the &drm_gem_object it is
>>>>>> associated
>>>>>> with
>>>>>> in case
>>>>>> + * this call unlinks the last &drm_gpuva from the
>>>>>> &drm_gpuvm_bo.
>>>>>> + *
>>>>>> + * For every &drm_gpuva entry removed from the &drm_gpuvm_bo
>>>>>> a
>>>>>> reference of
>>>>>> + * the latter is dropped.
>>>>>> + *
>>>>>>      * This function expects the caller to protect the GEM's
>>>>>> GPUVA
>>>>>> list
>>>>>> against
>>>>>> - * concurrent access using the GEMs dma_resv lock.
>>>>>> + * concurrent access using either the GEMs dma_resv lock or
>>>>>> a
>>>>>> driver
>>>>>> specific
>>>>>> + * lock set through drm_gem_gpuva_set_lock().
>>>>>>      */
>>>>>>     void
>>>>>>     drm_gpuva_unlink(struct drm_gpuva *va)
>>>>>>     {
>>>>>>            struct drm_gem_object *obj = va->gem.obj;
>>>>>> +       struct drm_gpuvm_bo *vm_bo = va->vm_bo;
>>>>>>     
>>>>>>            if (unlikely(!obj))
>>>>>>                    return;
>>>>>>     
>>>>>>            drm_gem_gpuva_assert_lock_held(obj);
>>>>>> -
>>>>>>            list_del_init(&va->gem.entry);
>>>>>> +
>>>>>> +       va->vm_bo = NULL;
>>>>>> +       drm_gpuvm_bo_put(vm_bo);
>>>>>>     }
>>>>>>     EXPORT_SYMBOL_GPL(drm_gpuva_unlink);
>>>>>>     
>>>>>> @@ -1050,10 +1293,10 @@ drm_gpuva_remap(struct drm_gpuva
>>>>>> *prev,
>>>>>>                    struct drm_gpuva *next,
>>>>>>                    struct drm_gpuva_op_remap *op)
>>>>>>     {
>>>>>> -       struct drm_gpuva *curr = op->unmap->va;
>>>>>> -       struct drm_gpuvm *gpuvm = curr->vm;
>>>>>> +       struct drm_gpuva *va = op->unmap->va;
>>>>>> +       struct drm_gpuvm *gpuvm = va->vm;
>>>>>>     
>>>>>> -       drm_gpuva_remove(curr);
>>>>>> +       drm_gpuva_remove(va);
>>>>>>     
>>>>>>            if (op->prev) {
>>>>>>                    drm_gpuva_init_from_op(prev, op->prev);
>>>>>> @@ -1695,9 +1938,8 @@ drm_gpuvm_prefetch_ops_create(struct
>>>>>> drm_gpuvm
>>>>>> *gpuvm,
>>>>>>     EXPORT_SYMBOL_GPL(drm_gpuvm_prefetch_ops_create);
>>>>>>     
>>>>>>     /**
>>>>>> - * drm_gpuvm_gem_unmap_ops_create() - creates the
>>>>>> &drm_gpuva_ops
>>>>>> to
>>>>>> unmap a GEM
>>>>>> - * @gpuvm: the &drm_gpuvm representing the GPU VA space
>>>>>> - * @obj: the &drm_gem_object to unmap
>>>>>> + * drm_gpuvm_bo_unmap_ops_create() - creates the
>>>>>> &drm_gpuva_ops
>>>>>> to
>>>>>> unmap a GEM
>>>>>> + * @vm_bo: the &drm_gpuvm_bo abstraction
>>>>>>      *
>>>>>>      * This function creates a list of operations to perform
>>>>>> unmapping
>>>>>> for every
>>>>>>      * GPUVA attached to a GEM.
>>>>>> @@ -1714,15 +1956,14 @@
>>>>>> EXPORT_SYMBOL_GPL(drm_gpuvm_prefetch_ops_create);
>>>>>>      * Returns: a pointer to the &drm_gpuva_ops on success, an
>>>>>> ERR_PTR
>>>>>> on failure
>>>>>>      */
>>>>>>     struct drm_gpuva_ops *
>>>>>> -drm_gpuvm_gem_unmap_ops_create(struct drm_gpuvm *gpuvm,
>>>>>> -                              struct drm_gem_object *obj)
>>>>>> +drm_gpuvm_bo_unmap_ops_create(struct drm_gpuvm_bo *vm_bo)
>>>>>>     {
>>>>>>            struct drm_gpuva_ops *ops;
>>>>>>            struct drm_gpuva_op *op;
>>>>>>            struct drm_gpuva *va;
>>>>>>            int ret;
>>>>>>     
>>>>>> -       drm_gem_gpuva_assert_lock_held(obj);
>>>>>> +       drm_gem_gpuva_assert_lock_held(vm_bo->obj);
>>>>>>     
>>>>>>            ops = kzalloc(sizeof(*ops), GFP_KERNEL);
>>>>>>            if (!ops)
>>>>>> @@ -1730,8 +1971,8 @@ drm_gpuvm_gem_unmap_ops_create(struct
>>>>>> drm_gpuvm
>>>>>> *gpuvm,
>>>>>>     
>>>>>>            INIT_LIST_HEAD(&ops->list);
>>>>>>     
>>>>>> -       drm_gem_for_each_gpuva(va, obj) {
>>>>>> -               op = gpuva_op_alloc(gpuvm);
>>>>>> +       drm_gpuvm_bo_for_each_va(va, vm_bo) {
>>>>>> +               op = gpuva_op_alloc(vm_bo->vm);
>>>>>>                    if (!op) {
>>>>>>                            ret = -ENOMEM;
>>>>>>                            goto err_free_ops;
>>>>>> @@ -1745,10 +1986,10 @@ drm_gpuvm_gem_unmap_ops_create(struct
>>>>>> drm_gpuvm *gpuvm,
>>>>>>            return ops;
>>>>>>     
>>>>>>     err_free_ops:
>>>>>> -       drm_gpuva_ops_free(gpuvm, ops);
>>>>>> +       drm_gpuva_ops_free(vm_bo->vm, ops);
>>>>>>            return ERR_PTR(ret);
>>>>>>     }
>>>>>> -EXPORT_SYMBOL_GPL(drm_gpuvm_gem_unmap_ops_create);
>>>>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_unmap_ops_create);
>>>>>>     
>>>>>>     /**
>>>>>>      * drm_gpuva_ops_free() - free the given &drm_gpuva_ops
>>>>>> diff --git a/drivers/gpu/drm/nouveau/nouveau_uvmm.c
>>>>>> b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
>>>>>> index ed439bf4032f..1e95b0a1b047 100644
>>>>>> --- a/drivers/gpu/drm/nouveau/nouveau_uvmm.c
>>>>>> +++ b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
>>>>>> @@ -62,6 +62,8 @@ struct bind_job_op {
>>>>>>            enum vm_bind_op op;
>>>>>>            u32 flags;
>>>>>>     
>>>>>> +       struct drm_gpuvm_bo *vm_bo;
>>>>>> +
>>>>>>            struct {
>>>>>>                    u64 addr;
>>>>>>                    u64 range;
>>>>>> @@ -1113,22 +1115,28 @@ bind_validate_region(struct
>>>>>> nouveau_job
>>>>>> *job)
>>>>>>     }
>>>>>>     
>>>>>>     static void
>>>>>> -bind_link_gpuvas(struct drm_gpuva_ops *ops, struct
>>>>>> nouveau_uvma_prealloc *new)
>>>>>> +bind_link_gpuvas(struct bind_job_op *bop)
>>>>>>     {
>>>>>> +       struct nouveau_uvma_prealloc *new = &bop->new;
>>>>>> +       struct drm_gpuvm_bo *vm_bo = bop->vm_bo;
>>>>>> +       struct drm_gpuva_ops *ops = bop->ops;
>>>>>>            struct drm_gpuva_op *op;
>>>>>>     
>>>>>>            drm_gpuva_for_each_op(op, ops) {
>>>>>>                    switch (op->op) {
>>>>>>                    case DRM_GPUVA_OP_MAP:
>>>>>> -                       drm_gpuva_link(&new->map->va);
>>>>>> +                       drm_gpuva_link(&new->map->va, vm_bo);
>>>>>>                            break;
>>>>>> -               case DRM_GPUVA_OP_REMAP:
>>>>>> +               case DRM_GPUVA_OP_REMAP: {
>>>>>> +                       struct drm_gpuva *va = op-
>>>>>>> remap.unmap-
>>>>>>> va;
>>>>>> +
>>>>>>                            if (op->remap.prev)
>>>>>> -                               drm_gpuva_link(&new->prev-
>>>>>>> va);
>>>>>> +                               drm_gpuva_link(&new->prev-
>>>>>>> va,
>>>>>> va-
>>>>>>> vm_bo);
>>>>>>                            if (op->remap.next)
>>>>>> -                               drm_gpuva_link(&new->next-
>>>>>>> va);
>>>>>> -                       drm_gpuva_unlink(op->remap.unmap-
>>>>>>> va);
>>>>>> +                               drm_gpuva_link(&new->next-
>>>>>>> va,
>>>>>> va-
>>>>>>> vm_bo);
>>>>>> +                       drm_gpuva_unlink(va);
>>>>>>                            break;
>>>>>> +               }
>>>>>>                    case DRM_GPUVA_OP_UNMAP:
>>>>>>                            drm_gpuva_unlink(op->unmap.va);
>>>>>>                            break;
>>>>>> @@ -1150,10 +1158,18 @@ nouveau_uvmm_bind_job_submit(struct
>>>>>> nouveau_job *job)
>>>>>>     
>>>>>>            list_for_each_op(op, &bind_job->ops) {
>>>>>>                    if (op->op == OP_MAP) {
>>>>>> -                       op->gem.obj =
>>>>>> drm_gem_object_lookup(job-
>>>>>>> file_priv,
>>>>>> -
>>>>>> op-
>>>>>>> gem.handle);
>>>>>> -                       if (!op->gem.obj)
>>>>>> +                       struct drm_gem_object *obj;
>>>>>> +
>>>>>> +                       obj = drm_gem_object_lookup(job-
>>>>>>> file_priv,
>>>>>> +                                                   op-
>>>>>>> gem.handle);
>>>>>> +                       if (!(op->gem.obj = obj))
>>>>>>                                    return -ENOENT;
>>>>>> +
>>>>>> +                       dma_resv_lock(obj->resv, NULL);
>>>>>> +                       op->vm_bo =
>>>>>> drm_gpuvm_bo_obtain(&uvmm-
>>>>>>> base,
>>>>>> obj);
>>>>>> +                       dma_resv_unlock(obj->resv);
>>>>>> +                       if (IS_ERR(op->vm_bo))
>>>>>> +                               return PTR_ERR(op->vm_bo);
>>>>>>                    }
>>>>>>     
>>>>>>                    ret = bind_validate_op(job, op);
>>>>>> @@ -1364,7 +1380,7 @@ nouveau_uvmm_bind_job_submit(struct
>>>>>> nouveau_job
>>>>>> *job)
>>>>>>                    case OP_UNMAP_SPARSE:
>>>>>>                    case OP_MAP:
>>>>>>                    case OP_UNMAP:
>>>>>> -                       bind_link_gpuvas(op->ops, &op->new);
>>>>>> +                       bind_link_gpuvas(op);
>>>>>>                            break;
>>>>>>                    default:
>>>>>>                            break;
>>>>>> @@ -1511,6 +1527,12 @@
>>>>>> nouveau_uvmm_bind_job_free_work_fn(struct
>>>>>> work_struct *work)
>>>>>>                    if (!IS_ERR_OR_NULL(op->ops))
>>>>>>                            drm_gpuva_ops_free(&uvmm->base, op-
>>>>>>> ops);
>>>>>>     
>>>>>> +               if (!IS_ERR_OR_NULL(op->vm_bo)) {
>>>>>> +                       dma_resv_lock(obj->resv, NULL);
>>>>>> +                       drm_gpuvm_bo_put(op->vm_bo);
>>>>>> +                       dma_resv_unlock(obj->resv);
>>>>>> +               }
>>>>>> +
>>>>>>                    if (obj)
>>>>>>                            drm_gem_object_put(obj);
>>>>>>            }
>>>>>> @@ -1776,15 +1798,18 @@ void
>>>>>>     nouveau_uvmm_bo_map_all(struct nouveau_bo *nvbo, struct
>>>>>> nouveau_mem
>>>>>> *mem)
>>>>>>     {
>>>>>>            struct drm_gem_object *obj = &nvbo->bo.base;
>>>>>> +       struct drm_gpuvm_bo *vm_bo;
>>>>>>         ��  struct drm_gpuva *va;
>>>>>>     
>>>>>>            dma_resv_assert_held(obj->resv);
>>>>>>     
>>>>>> -       drm_gem_for_each_gpuva(va, obj) {
>>>>>> -               struct nouveau_uvma *uvma = uvma_from_va(va);
>>>>>> +       drm_gem_for_each_gpuvm_bo(vm_bo, obj) {
>>>>>> +               drm_gpuvm_bo_for_each_va(va, vm_bo) {
>>>>>> +                       struct nouveau_uvma *uvma =
>>>>>> uvma_from_va(va);
>>>>>>     
>>>>>> -               nouveau_uvma_map(uvma, mem);
>>>>>> -               drm_gpuva_invalidate(va, false);
>>>>>> +                       nouveau_uvma_map(uvma, mem);
>>>>>> +                       drm_gpuva_invalidate(va, false);
>>>>>> +               }
>>>>>>            }
>>>>>>     }
>>>>>>     
>>>>>> @@ -1792,15 +1817,18 @@ void
>>>>>>     nouveau_uvmm_bo_unmap_all(struct nouveau_bo *nvbo)
>>>>>>     {
>>>>>>            struct drm_gem_object *obj = &nvbo->bo.base;
>>>>>> +       struct drm_gpuvm_bo *vm_bo;
>>>>>>            struct drm_gpuva *va;
>>>>>>     
>>>>>>            dma_resv_assert_held(obj->resv);
>>>>>>     
>>>>>> -       drm_gem_for_each_gpuva(va, obj) {
>>>>>> -               struct nouveau_uvma *uvma = uvma_from_va(va);
>>>>>> +       drm_gem_for_each_gpuvm_bo(vm_bo, obj) {
>>>>>> +               drm_gpuvm_bo_for_each_va(va, vm_bo) {
>>>>>> +                       struct nouveau_uvma *uvma =
>>>>>> uvma_from_va(va);
>>>>>>     
>>>>>> -         ��     nouveau_uvma_unmap(uvma);
>>>>>> -               drm_gpuva_invalidate(va, true);
>>>>>> +                       nouveau_uvma_unmap(uvma);
>>>>>> +                       drm_gpuva_invalidate(va, true);
>>>>>> +               }
>>>>>>            }
>>>>>>     }
>>>>>>     
>>>>>> diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
>>>>>> index 16364487fde9..369505447acd 100644
>>>>>> --- a/include/drm/drm_gem.h
>>>>>> +++ b/include/drm/drm_gem.h
>>>>>> @@ -580,7 +580,7 @@ int drm_gem_evict(struct drm_gem_object
>>>>>> *obj);
>>>>>>      * drm_gem_gpuva_init() - initialize the gpuva list of a
>>>>>> GEM
>>>>>> object
>>>>>>      * @obj: the &drm_gem_object
>>>>>>      *
>>>>>> - * This initializes the &drm_gem_object's &drm_gpuva list.
>>>>>> + * This initializes the &drm_gem_object's &drm_gpuvm_bo
>>>>>> list.
>>>>>>      *
>>>>>>      * Calling this function is only necessary for drivers
>>>>>> intending to
>>>>>> support the
>>>>>>      * &drm_driver_feature DRIVER_GEM_GPUVA.
>>>>>> @@ -593,28 +593,28 @@ static inline void
>>>>>> drm_gem_gpuva_init(struct
>>>>>> drm_gem_object *obj)
>>>>>>     }
>>>>>>     
>>>>>>     /**
>>>>>> - * drm_gem_for_each_gpuva() - iternator to walk over a list
>>>>>> of
>>>>>> gpuvas
>>>>>> - * @entry__: &drm_gpuva structure to assign to in each
>>>>>> iteration
>>>>>> step
>>>>>> - * @obj__: the &drm_gem_object the &drm_gpuvas to walk are
>>>>>> associated with
>>>>>> + * drm_gem_for_each_gpuvm_bo() - iterator to walk over a
>>>>>> list of
>>>>>> &drm_gpuvm_bo
>>>>>> + * @entry__: &drm_gpuvm_bo structure to assign to in each
>>>>>> iteration
>>>>>> step
>>>>>> + * @obj__: the &drm_gem_object the &drm_gpuvm_bo to walk are
>>>>>> associated with
>>>>>>      *
>>>>>> - * This iterator walks over all &drm_gpuva structures
>>>>>> associated
>>>>>> with the
>>>>>> - * &drm_gpuva_manager.
>>>>>> + * This iterator walks over all &drm_gpuvm_bo structures
>>>>>> associated
>>>>>> with the
>>>>>> + * &drm_gem_object.
>>>>>>      */
>>>>>> -#define drm_gem_for_each_gpuva(entry__, obj__) \
>>>>>> -       list_for_each_entry(entry__, &(obj__)->gpuva.list,
>>>>>> gem.entry)
>>>>>> +#define drm_gem_for_each_gpuvm_bo(entry__, obj__) \
>>>>>> +       list_for_each_entry(entry__, &(obj__)->gpuva.list,
>>>>>> list.entry.gem)
>>>>>>     
>>>>>>     /**
>>>>>> - * drm_gem_for_each_gpuva_safe() - iternator to safely walk
>>>>>> over
>>>>>> a
>>>>>> list of
>>>>>> - * gpuvas
>>>>>> - * @entry__: &drm_gpuva structure to assign to in each
>>>>>> iteration
>>>>>> step
>>>>>> - * @next__: &next &drm_gpuva to store the next step
>>>>>> - * @obj__: the &drm_gem_object the &drm_gpuvas to walk are
>>>>>> associated with
>>>>>> + * drm_gem_for_each_gpuvm_bo_safe() - iterator to safely
>>>>>> walk
>>>>>> over a
>>>>>> list of
>>>>>> + * &drm_gpuvm_bo
>>>>>> + * @entry__: &drm_gpuvm_bostructure to assign to in each
>>>>>> iteration
>>>>>> step
>>>>>> + * @next__: &next &drm_gpuvm_bo to store the next step
>>>>>> + * @obj__: the &drm_gem_object the &drm_gpuvm_bo to walk are
>>>>>> associated with
>>>>>>      *
>>>>>> - * This iterator walks over all &drm_gpuva structures
>>>>>> associated
>>>>>> with the
>>>>>> + * This iterator walks over all &drm_gpuvm_bo structures
>>>>>> associated
>>>>>> with the
>>>>>>      * &drm_gem_object. It is implemented with
>>>>>> list_for_each_entry_safe(), hence
>>>>>>      * it is save against removal of elements.
>>>>>>      */
>>>>>> -#define drm_gem_for_each_gpuva_safe(entry__, next__, obj__)
>>>>>> \
>>>>>> -       list_for_each_entry_safe(entry__, next__, &(obj__)-
>>>>>>> gpuva.list, gem.entry)
>>>>>> +#define drm_gem_for_each_gpuvm_bo_safe(entry__, next__,
>>>>>> obj__) \
>>>>>> +       list_for_each_entry_safe(entry__, next__, &(obj__)-
>>>>>>> gpuva.list, list.entry.gem)
>>>>>>     
>>>>>>     #endif /* __DRM_GEM_H__ */
>>>>>> diff --git a/include/drm/drm_gpuvm.h
>>>>>> b/include/drm/drm_gpuvm.h
>>>>>> index 47cbacb244b9..466fdd76c71a 100644
>>>>>> --- a/include/drm/drm_gpuvm.h
>>>>>> +++ b/include/drm/drm_gpuvm.h
>>>>>> @@ -25,6 +25,7 @@
>>>>>>      * OTHER DEALINGS IN THE SOFTWARE.
>>>>>>      */
>>>>>>     
>>>>>> +#include <linux/dma-resv.h>
>>>>>>     #include <linux/list.h>
>>>>>>     #include <linux/rbtree.h>
>>>>>>     #include <linux/types.h>
>>>>>> @@ -33,6 +34,7 @@
>>>>>>     #include <drm/drm_gem.h>
>>>>>>     
>>>>>>     struct drm_gpuvm;
>>>>>> +struct drm_gpuvm_bo;
>>>>>>     struct drm_gpuvm_ops;
>>>>>>     
>>>>>>     /**
>>>>>> @@ -73,6 +75,12 @@ struct drm_gpuva {
>>>>>>             */
>>>>>>            struct drm_gpuvm *vm;
>>>>>>     
>>>>>> +       /**
>>>>>> +        * @vm_bo: the &drm_gpuvm_bo abstraction for the
>>>>>> mapped
>>>>>> +        * &drm_gem_object
>>>>>> +        */
>>>>>> +       struct drm_gpuvm_bo *vm_bo;
>>>>>> +
>>>>>>            /**
>>>>>>             * @flags: the &drm_gpuva_flags for this mapping
>>>>>>             */
>>>>>> @@ -108,7 +116,7 @@ struct drm_gpuva {
>>>>>>                    struct drm_gem_object *obj;
>>>>>>     
>>>>>>                    /**
>>>>>> -                * @entry: the &list_head to attach this
>>>>>> object
>>>>>> to a
>>>>>> &drm_gem_object
>>>>>> +                * @entry: the &list_head to attach this
>>>>>> object
>>>>>> to a
>>>>>> &drm_gpuvm_bo
>>>>>>                     */
>>>>>>                    struct list_head entry;
>>>>>>            } gem;
>>>>>> @@ -141,7 +149,7 @@ struct drm_gpuva {
>>>>>>     int drm_gpuva_insert(struct drm_gpuvm *gpuvm, struct
>>>>>> drm_gpuva
>>>>>> *va);
>>>>>>     void drm_gpuva_remove(struct drm_gpuva *va);
>>>>>>     
>>>>>> -void drm_gpuva_link(struct drm_gpuva *va);
>>>>>> +void drm_gpuva_link(struct drm_gpuva *va, struct
>>>>>> drm_gpuvm_bo
>>>>>> *vm_bo);
>>>>>>     void drm_gpuva_unlink(struct drm_gpuva *va);
>>>>>>     
>>>>>>     struct drm_gpuva *drm_gpuva_find(struct drm_gpuvm *gpuvm,
>>>>>> @@ -188,10 +196,16 @@ static inline bool
>>>>>> drm_gpuva_invalidated(struct
>>>>>> drm_gpuva *va)
>>>>>>      * enum drm_gpuvm_flags - flags for struct drm_gpuvm
>>>>>>      */
>>>>>>     enum drm_gpuvm_flags {
>>>>>> +       /**
>>>>>> +        * @DRM_GPUVM_RESV_PROTECTED: GPUVM is protected
>>>>>> externally
>>>>>> by the
>>>>>> +        * GPUVM's &dma_resv lock
>>>>>> +        */
>>>>>> +       DRM_GPUVM_RESV_PROTECTED = BIT(0),
>>>>>> +
>>>>>>            /**
>>>>>>             * @DRM_GPUVM_USERBITS: user defined bits
>>>>>>             */
>>>>>> -       DRM_GPUVM_USERBITS = BIT(0),
>>>>>> +       DRM_GPUVM_USERBITS = BIT(1),
>>>>>>     };
>>>>>>     
>>>>>>     /**
>>>>>> @@ -280,6 +294,19 @@ bool drm_gpuvm_interval_empty(struct
>>>>>> drm_gpuvm
>>>>>> *gpuvm, u64 addr, u64 range);
>>>>>>     struct drm_gem_object *
>>>>>>     drm_gpuvm_resv_object_alloc(struct drm_device *drm);
>>>>>>     
>>>>>> +/**
>>>>>> + * drm_gpuvm_resv_protected() - indicates whether
>>>>>> &DRM_GPUVM_RESV_PROTECTED is
>>>>>> + * set
>>>>>> + * @gpuvm: the &drm_gpuvm
>>>>>> + *
>>>>>> + * Returns: true if &DRM_GPUVM_RESV_PROTECTED is set, false
>>>>>> otherwise.
>>>>>> + */
>>>>>> +static inline bool
>>>>>> +drm_gpuvm_resv_protected(struct drm_gpuvm *gpuvm)
>>>>>> +{
>>>>>> +       return gpuvm->flags & DRM_GPUVM_RESV_PROTECTED;
>>>>>> +}
>>>>>> +
>>>>>>     /**
>>>>>>      * drm_gpuvm_resv() - returns the &drm_gpuvm's &dma_resv
>>>>>>      * @gpuvm__: the &drm_gpuvm
>>>>>> @@ -298,6 +325,12 @@ drm_gpuvm_resv_object_alloc(struct
>>>>>> drm_device
>>>>>> *drm);
>>>>>>      */
>>>>>>     #define drm_gpuvm_resv_obj(gpuvm__) ((gpuvm__)->r_obj)
>>>>>>     
>>>>>> +#define drm_gpuvm_resv_held(gpuvm__) \
>>>>>> +       dma_resv_held(drm_gpuvm_resv(gpuvm__))
>>>>>> +
>>>>>> +#define drm_gpuvm_resv_assert_held(gpuvm__) \
>>>>>> +       dma_resv_assert_held(drm_gpuvm_resv(gpuvm__))
>>>>>> +
>>>>>>     #define drm_gpuvm_resv_held(gpuvm__) \
>>>>>>            dma_resv_held(drm_gpuvm_resv(gpuvm__))
>>>>>>     
>>>>>> @@ -382,6 +415,128 @@ __drm_gpuva_next(struct drm_gpuva *va)
>>>>>>     #define drm_gpuvm_for_each_va_safe(va__, next__, gpuvm__)
>>>>>> \
>>>>>>            list_for_each_entry_safe(va__, next__, &(gpuvm__)-
>>>>>>> rb.list,
>>>>>> rb.entry)
>>>>>>     
>>>>>> +/**
>>>>>> + * struct drm_gpuvm_bo - structure representing a &drm_gpuvm
>>>>>> and
>>>>>> + * &drm_gem_object combination
>>>>>> + *
>>>>>> + * This structure is an abstraction representing a
>>>>>> &drm_gpuvm
>>>>>> and
>>>>>> + * &drm_gem_object combination. It serves as an indirection
>>>>>> to
>>>>>> accelerate
>>>>>> + * iterating all &drm_gpuvas within a &drm_gpuvm backed by
>>>>>> the
>>>>>> same
>>>>>> + * &drm_gem_object.
>>>>>> + *
>>>>>> + * Furthermore it is used cache evicted GEM objects for a
>>>>>> certain
>>>>>> GPU-VM to
>>>>>> + * accelerate validation.
>>>>>> + *
>>>>>> + * Typically, drivers want to create an instance of a struct
>>>>>> drm_gpuvm_bo once
>>>>>> + * a GEM object is mapped first in a GPU-VM and release the
>>>>>> instance
>>>>>> once the
>>>>>> + * last mapping of the GEM object in this GPU-VM is
>>>>>> unmapped.
>>>>>> + */
>>>>>> +struct drm_gpuvm_bo {
>>>>>> +       /**
>>>>>> +        * @vm: The &drm_gpuvm the @obj is mapped in. This
>>>>>> pointer is
>>>>>> not
>>>>>> +        * reference counted.
>>>>>> +        *
>>>>>> +        * A struct drm_gpuvm_bo is not allowed to out-live
>>>>>> its
>>>>>> &drm_gpuvm
>>>>>> +        * context. Implicitly, this is ensured by the fact
>>>>>> that
>>>>>> the
>>>>>> driver is
>>>>>> +        * responsible to ensure the VM doesn't contain
>>>>>> mappings
>>>>>> once
>>>>>> it's
>>>>>> +        * freed, since a struct drm_gpuvm_bo should be freed
>>>>>> once
>>>>>> the last
>>>>>> +        * mapping being backed by the corresponding buffer
>>>>>> object is
>>>>>> unmapped.
>>>>>> +        */
>>>>>
>>>>>
>>>>> I don't think the above is completely true. Let's assume in the
>>>>> !RESV_PROTECTED case that a reference is grabbed on the
>>>>> drm_gpuvm_bo
>>>>> during an iteration over a list. Then user-space closes the vm
>>>>> and
>>>>> all
>>>>> vmas are unlinked, but this reference remains but the vm
>>>>> pointer
>>>>> becomes stale. In the RESV_PROTECTED case this is ensured not
>>>>> to
>>>>> happen
>>>>> if by the vm->resv being grabbed during unlink, but in the
>>>>> !RESV_PROTECTED case, the above wording isn't sufficient. The
>>>>> caller
>>>>> needs to ensure the vm stays alive using some sort of similar
>>>>> rule
>>>>> or
>>>>> use kref_get_unless_zero() on the vm under the spinlock if
>>>>> dereferenced.
>>>>
>>>> The list is part of the GPUVM. Hence, the caller *must* either
>>>> already hold
>>>> a reference to the GPUVM or otherwise ensure it's not freed while
>>>> iterating
>>>> this list. All the drm_gpuvm_bo structures within this list can't
>>>> have a
>>>> pointer to another VM than this one by definition.
>>>>
>>>> Anyway, I recognize that this isn't very obvious. Hence, I think
>>>> we
>>>> should
>>>> probably reference count GPUVMs as well. I'd think of the same
>>>> way we
>>>> do it
>>>> with drm_gem_objects. However, I'd prefer to introduce this with
>>>> a
>>>> subsequent
>>>> patch.
>>>
>>> Well, I think we should actually be OK in most cases, and
>>> refcounting
>>> here would probably result in circular dependencies.
>>
>> Where would you see a circular dependency with reference counted
>> GPUVMs?
> 
> It'd be if you call any va_unlink() from the vm destructor. Then the
> destructor will never get called because of the corresponding gpuvm_bo
> vm reference. (IIRC the same argument was made with the vm's resv_bo by
> Christian?)

Well, if that is a use-case it's simply not what the GPUVM's reference
count is intended for. Drivers are free to maintain a driver specific
reference count, counting whatever they want and unlink/remove remaining
stuff this reference counter's callback.

> 
> However if there is a vm_close(), that does all the va_unlink(), that
> will resolve that circular depencency. We do have it in Xe, not sure
> about other drivers.

That's what Nouveau does as well.

> 
> /Thomas
>