[v9,3/6] iommufd: Add iommufd_access_change_ioas helper
Commit Message
The complication of the mutex and refcount will be amplified after we
introduce the replace support for access. So, add a preparatory change
of a constitutive helper iommufd_access_change_ioas(), to take care of
the existing iommufd_access_attach() and iommufd_access_detach().
Also, update the unprotect routine in iommufd_access_destroy_object()
to calling the new iommufd_access_change_ioas() helper.
Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
drivers/iommu/iommufd/device.c | 112 ++++++++++++++++++++-------------
1 file changed, 69 insertions(+), 43 deletions(-)
Comments
On Thu, Jul 27, 2023 at 12:23:08AM -0700, Nicolin Chen wrote:
> The complication of the mutex and refcount will be amplified after we
> introduce the replace support for access. So, add a preparatory change
> of a constitutive helper iommufd_access_change_ioas(), to take care of
> the existing iommufd_access_attach() and iommufd_access_detach().
>
> Also, update the unprotect routine in iommufd_access_destroy_object()
> to calling the new iommufd_access_change_ioas() helper.
>
> Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
> ---
> drivers/iommu/iommufd/device.c | 112 ++++++++++++++++++++-------------
> 1 file changed, 69 insertions(+), 43 deletions(-)
>
> diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
> index 7a3e8660b902..d9680a247e1c 100644
> --- a/drivers/iommu/iommufd/device.c
> +++ b/drivers/iommu/iommufd/device.c
> @@ -684,17 +684,69 @@ void iommufd_device_detach(struct iommufd_device *idev)
> }
> EXPORT_SYMBOL_NS_GPL(iommufd_device_detach, IOMMUFD);
>
> +static int iommufd_access_change_ioas(struct iommufd_access *access,
> + struct iommufd_ioas *new_ioas)
> +{
> + u32 iopt_access_list_id = access->iopt_access_list_id;
> + struct iommufd_ioas *cur_ioas = access->ioas;
> + int rc;
> +
> + lockdep_assert_held(&access->ioas_lock);
> +
> + /* We are racing with a concurrent detach, bail */
> + if (cur_ioas != access->ioas_unpin)
> + return -EBUSY;
> +
> + if (IS_ERR(new_ioas))
> + return PTR_ERR(new_ioas);
> +
> + if (cur_ioas == new_ioas) {
> + /* Do not forget to put since we allow a duplication */
> + iommufd_put_object(&new_ioas->obj);
> + return 0;
> + }
> +
> + /*
> + * Set ioas to NULL to block any further iommufd_access_pin_pages().
> + * iommufd_access_unpin_pages() can continue using access->ioas_unpin.
> + */
> + access->ioas = NULL;
> +
> + if (new_ioas) {
> + rc = iopt_add_access(&new_ioas->iopt, access);
> + if (rc) {
> + iommufd_put_object(&new_ioas->obj);
> + access->ioas = cur_ioas;
> + return rc;
> + }
> + iommufd_ref_to_users(&new_ioas->obj);
Kevin's suggestion to just open code the refcount_inc here
And have a wrapper func that does:
iommufd_access_change_ioas_id(struct iommufd_access *access, u32 id)
{
struct iommufd_ioas *ioas = iommufd_get_ioas(ictx, ioas_id);
int rc;
if (IS_ERR(ioas))
return PTR_ERR(ioas);
rc = iommufd_access_change_ioas(access, ioas);
iommufd_put_object(&ioas->obj);
return rc;
}
Does looks cleaner
Then we delete iommufd_ref_to_users() as there are no users (once all
the branches are merged).
Logic looks OK otherwise
Jason
On Thu, Jul 27, 2023 at 11:40:17AM -0300, Jason Gunthorpe wrote:
> On Thu, Jul 27, 2023 at 12:23:08AM -0700, Nicolin Chen wrote:
> > + if (new_ioas) {
> > + rc = iopt_add_access(&new_ioas->iopt, access);
> > + if (rc) {
> > + iommufd_put_object(&new_ioas->obj);
> > + access->ioas = cur_ioas;
> > + return rc;
> > + }
> > + iommufd_ref_to_users(&new_ioas->obj);
>
> Kevin's suggestion to just open code the refcount_inc here
Will replace this iommufd_ref_to_users with a refcount_inc in v10.
> And have a wrapper func that does:
>
> iommufd_access_change_ioas_id(struct iommufd_access *access, u32 id)
> {
> struct iommufd_ioas *ioas = iommufd_get_ioas(ictx, ioas_id);
> int rc;
>
> if (IS_ERR(ioas))
> return PTR_ERR(ioas);
> rc = iommufd_access_change_ioas(access, ioas);
> iommufd_put_object(&ioas->obj);
> return rc;
> }
>
> Does looks cleaner
I see. So we can drop iommufd_put_object(&new_ioas->obj) in
iommufd_access_change_ioas().
> Then we delete iommufd_ref_to_users() as there are no users (once all
> the branches are merged).
Ack.
Nicolin
@@ -684,17 +684,69 @@ void iommufd_device_detach(struct iommufd_device *idev)
}
EXPORT_SYMBOL_NS_GPL(iommufd_device_detach, IOMMUFD);
+static int iommufd_access_change_ioas(struct iommufd_access *access,
+ struct iommufd_ioas *new_ioas)
+{
+ u32 iopt_access_list_id = access->iopt_access_list_id;
+ struct iommufd_ioas *cur_ioas = access->ioas;
+ int rc;
+
+ lockdep_assert_held(&access->ioas_lock);
+
+ /* We are racing with a concurrent detach, bail */
+ if (cur_ioas != access->ioas_unpin)
+ return -EBUSY;
+
+ if (IS_ERR(new_ioas))
+ return PTR_ERR(new_ioas);
+
+ if (cur_ioas == new_ioas) {
+ /* Do not forget to put since we allow a duplication */
+ iommufd_put_object(&new_ioas->obj);
+ return 0;
+ }
+
+ /*
+ * Set ioas to NULL to block any further iommufd_access_pin_pages().
+ * iommufd_access_unpin_pages() can continue using access->ioas_unpin.
+ */
+ access->ioas = NULL;
+
+ if (new_ioas) {
+ rc = iopt_add_access(&new_ioas->iopt, access);
+ if (rc) {
+ iommufd_put_object(&new_ioas->obj);
+ access->ioas = cur_ioas;
+ return rc;
+ }
+ iommufd_ref_to_users(&new_ioas->obj);
+ }
+
+ if (cur_ioas) {
+ if (access->ops->unmap) {
+ mutex_unlock(&access->ioas_lock);
+ access->ops->unmap(access->data, 0, ULONG_MAX);
+ mutex_lock(&access->ioas_lock);
+ }
+ iopt_remove_access(&cur_ioas->iopt, access, iopt_access_list_id);
+ refcount_dec(&cur_ioas->obj.users);
+ }
+
+ access->ioas = new_ioas;
+ access->ioas_unpin = new_ioas;
+
+ return 0;
+}
+
void iommufd_access_destroy_object(struct iommufd_object *obj)
{
struct iommufd_access *access =
container_of(obj, struct iommufd_access, obj);
- if (access->ioas) {
- iopt_remove_access(&access->ioas->iopt, access,
- access->iopt_access_list_id);
- refcount_dec(&access->ioas->obj.users);
- access->ioas = NULL;
- }
+ mutex_lock(&access->ioas_lock);
+ if (access->ioas)
+ WARN_ON(iommufd_access_change_ioas(access, NULL));
+ mutex_unlock(&access->ioas_lock);
iommufd_ctx_put(access->ictx);
}
@@ -761,60 +813,34 @@ EXPORT_SYMBOL_NS_GPL(iommufd_access_destroy, IOMMUFD);
void iommufd_access_detach(struct iommufd_access *access)
{
- struct iommufd_ioas *cur_ioas = access->ioas;
+ int rc;
mutex_lock(&access->ioas_lock);
- if (WARN_ON(!access->ioas))
- goto out;
- /*
- * Set ioas to NULL to block any further iommufd_access_pin_pages().
- * iommufd_access_unpin_pages() can continue using access->ioas_unpin.
- */
- access->ioas = NULL;
-
- if (access->ops->unmap) {
+ if (WARN_ON(!access->ioas)) {
mutex_unlock(&access->ioas_lock);
- access->ops->unmap(access->data, 0, ULONG_MAX);
- mutex_lock(&access->ioas_lock);
+ return;
}
- iopt_remove_access(&cur_ioas->iopt, access,
- access->iopt_access_list_id);
- refcount_dec(&cur_ioas->obj.users);
-out:
- access->ioas_unpin = NULL;
+ rc = iommufd_access_change_ioas(access, NULL);
+ WARN_ON(rc);
mutex_unlock(&access->ioas_lock);
}
EXPORT_SYMBOL_NS_GPL(iommufd_access_detach, IOMMUFD);
int iommufd_access_attach(struct iommufd_access *access, u32 ioas_id)
{
- struct iommufd_ioas *new_ioas;
- int rc = 0;
+ struct iommufd_ctx *ictx = access->ictx;
+ int rc;
mutex_lock(&access->ioas_lock);
- if (WARN_ON(access->ioas || access->ioas_unpin)) {
+ if (WARN_ON(access->ioas)) {
mutex_unlock(&access->ioas_lock);
return -EINVAL;
}
- new_ioas = iommufd_get_ioas(access->ictx, ioas_id);
- if (IS_ERR(new_ioas)) {
- mutex_unlock(&access->ioas_lock);
- return PTR_ERR(new_ioas);
- }
-
- rc = iopt_add_access(&new_ioas->iopt, access);
- if (rc) {
- mutex_unlock(&access->ioas_lock);
- iommufd_put_object(&new_ioas->obj);
- return rc;
- }
- iommufd_ref_to_users(&new_ioas->obj);
-
- access->ioas = new_ioas;
- access->ioas_unpin = new_ioas;
+ rc = iommufd_access_change_ioas(access,
+ iommufd_get_ioas(ictx, ioas_id));
mutex_unlock(&access->ioas_lock);
- return 0;
+ return rc;
}
EXPORT_SYMBOL_NS_GPL(iommufd_access_attach, IOMMUFD);