diff mbox series

[v2,11/27] KVM: x86/mmu: Don't rely on page-track mechanism to flush on memslot change

Message ID 20230311002258.852397-12-seanjc@google.com
State New
Headers
Series drm/i915/gvt: KVM: KVMGT fixes and page-track cleanups |

Commit Message

Sean Christopherson March 11, 2023, 12:22 a.m. UTC 
  Call kvm_mmu_zap_all_fast() directly when flushing a memslot instead of
bouncing through the page-track mechanism.  KVM (unfortunately) needs to
zap and flush all page tables on memslot DELETE/MOVE irrespective of
whether KVM is shadowing guest page tables.

This will allow changing KVM to register a page-track notifier on the
first shadow root allocation, and will also allow deleting the misguided
kvm_page_track_flush_slot() hook itself once KVM-GT also moves to a
different method for reacting to memslot changes.

No functional change intended.

Cc: Yan Zhao <yan.y.zhao@intel.com>
Link: https://lore.kernel.org/r/20221110014821.1548347-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/include/asm/kvm_host.h |  1 +
 arch/x86/kvm/mmu/mmu.c          | 10 +---------
 arch/x86/kvm/x86.c              |  2 ++
 3 files changed, 4 insertions(+), 9 deletions(-)

Comments

Yan Zhao March 15, 2023, 1:08 a.m. UTC | #1 
On Fri, Mar 10, 2023 at 04:22:42PM -0800, Sean Christopherson wrote:
...
> -static void kvm_mmu_invalidate_zap_pages_in_memslot(struct kvm *kvm,
> -			struct kvm_memory_slot *slot,
> -			struct kvm_page_track_notifier_node *node)
> -{
> -	kvm_mmu_zap_all_fast(kvm);
> -}
> -
>  int kvm_mmu_init_vm(struct kvm *kvm)
>  {
>  	struct kvm_page_track_notifier_node *node = &kvm->arch.mmu_sp_tracker;
> @@ -6110,7 +6103,6 @@ int kvm_mmu_init_vm(struct kvm *kvm)
>  	}
>  
>  	node->track_write = kvm_mmu_pte_write;
> -	node->track_flush_slot = kvm_mmu_invalidate_zap_pages_in_memslot;
>  	kvm_page_track_register_notifier(kvm, node);
>  
>  	kvm->arch.split_page_header_cache.kmem_cache = mmu_page_header_cache;
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index f706621c35b8..29dd6c97d145 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -12662,6 +12662,8 @@ void kvm_arch_flush_shadow_all(struct kvm *kvm)
>  void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
>  				   struct kvm_memory_slot *slot)
>  {
> +	kvm_mmu_zap_all_fast(kvm);
Could we still call kvm_mmu_invalidate_zap_pages_in_memslot() here?
As I know, for TDX, its version of
kvm_mmu_invalidate_zap_pages_in_memslot() is like

static void kvm_mmu_invalidate_zap_pages_in_memslot(struct kvm *kvm,
                        struct kvm_memory_slot *slot,
                        struct kvm_page_track_notifier_node *node)
{
        if (kvm_gfn_shared_mask(kvm))
                kvm_mmu_zap_memslot(kvm, slot);
        else
                kvm_mmu_zap_all_fast(kvm);
}

Maybe this kind of judegment is better to be confined in mmu.c?

Thanks
Yan

> +
>  	kvm_page_track_flush_slot(kvm, slot);
>  }
>
Sean Christopherson March 15, 2023, 3:32 p.m. UTC | #2 
On Wed, Mar 15, 2023, Yan Zhao wrote:
> On Fri, Mar 10, 2023 at 04:22:42PM -0800, Sean Christopherson wrote:
> ...
> > -static void kvm_mmu_invalidate_zap_pages_in_memslot(struct kvm *kvm,
> > -			struct kvm_memory_slot *slot,
> > -			struct kvm_page_track_notifier_node *node)
> > -{
> > -	kvm_mmu_zap_all_fast(kvm);
> > -}
> > -
> >  int kvm_mmu_init_vm(struct kvm *kvm)
> >  {
> >  	struct kvm_page_track_notifier_node *node = &kvm->arch.mmu_sp_tracker;
> > @@ -6110,7 +6103,6 @@ int kvm_mmu_init_vm(struct kvm *kvm)
> >  	}
> >  
> >  	node->track_write = kvm_mmu_pte_write;
> > -	node->track_flush_slot = kvm_mmu_invalidate_zap_pages_in_memslot;
> >  	kvm_page_track_register_notifier(kvm, node);
> >  
> >  	kvm->arch.split_page_header_cache.kmem_cache = mmu_page_header_cache;
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index f706621c35b8..29dd6c97d145 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -12662,6 +12662,8 @@ void kvm_arch_flush_shadow_all(struct kvm *kvm)
> >  void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
> >  				   struct kvm_memory_slot *slot)
> >  {
> > +	kvm_mmu_zap_all_fast(kvm);
> Could we still call kvm_mmu_invalidate_zap_pages_in_memslot() here?
> As I know, for TDX, its version of
> kvm_mmu_invalidate_zap_pages_in_memslot() is like
> 
> static void kvm_mmu_invalidate_zap_pages_in_memslot(struct kvm *kvm,
>                         struct kvm_memory_slot *slot,
>                         struct kvm_page_track_notifier_node *node)
> {
>         if (kvm_gfn_shared_mask(kvm))
>                 kvm_mmu_zap_memslot(kvm, slot);
>         else
>                 kvm_mmu_zap_all_fast(kvm);
> }
> 
> Maybe this kind of judegment is better to be confined in mmu.c?

Hmm, yeah, I agree.  The only reason I exposed kvm_mmu_zap_all_fast() is because
kvm_mmu_zap_all() is already exposed for kvm_arch_flush_shadow_all() and it felt
weird/wrong to split those.  But that's the only usage of kvm_mmu_zap_all(), so
a better approach to maintain consistency would be to move
kvm_arch_flush_shadow_{all,memslot}() into mmu.c.  I'll do that in the next version.
diff mbox series

Patch

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 808c292ad3f4..17281d6825c9 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1844,6 +1844,7 @@  void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm,
 void kvm_mmu_slot_leaf_clear_dirty(struct kvm *kvm,
 				   const struct kvm_memory_slot *memslot);
 void kvm_mmu_zap_all(struct kvm *kvm);
+void kvm_mmu_zap_all_fast(struct kvm *kvm);
 void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm, u64 gen);
 void kvm_mmu_change_mmu_pages(struct kvm *kvm, unsigned long kvm_nr_mmu_pages);
 
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 4685c80e441b..409dabec69df 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -6030,7 +6030,7 @@  static void kvm_zap_obsolete_pages(struct kvm *kvm)
  * not use any resource of the being-deleted slot or all slots
  * after calling the function.
  */
-static void kvm_mmu_zap_all_fast(struct kvm *kvm)
+void kvm_mmu_zap_all_fast(struct kvm *kvm)
 {
 	lockdep_assert_held(&kvm->slots_lock);
 
@@ -6086,13 +6086,6 @@  static bool kvm_has_zapped_obsolete_pages(struct kvm *kvm)
 	return unlikely(!list_empty_careful(&kvm->arch.zapped_obsolete_pages));
 }
 
-static void kvm_mmu_invalidate_zap_pages_in_memslot(struct kvm *kvm,
-			struct kvm_memory_slot *slot,
-			struct kvm_page_track_notifier_node *node)
-{
-	kvm_mmu_zap_all_fast(kvm);
-}
-
 int kvm_mmu_init_vm(struct kvm *kvm)
 {
 	struct kvm_page_track_notifier_node *node = &kvm->arch.mmu_sp_tracker;
@@ -6110,7 +6103,6 @@  int kvm_mmu_init_vm(struct kvm *kvm)
 	}
 
 	node->track_write = kvm_mmu_pte_write;
-	node->track_flush_slot = kvm_mmu_invalidate_zap_pages_in_memslot;
 	kvm_page_track_register_notifier(kvm, node);
 
 	kvm->arch.split_page_header_cache.kmem_cache = mmu_page_header_cache;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f706621c35b8..29dd6c97d145 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -12662,6 +12662,8 @@  void kvm_arch_flush_shadow_all(struct kvm *kvm)
 void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
 				   struct kvm_memory_slot *slot)
 {
+	kvm_mmu_zap_all_fast(kvm);
+
 	kvm_page_track_flush_slot(kvm, slot);
 }