Re: [Intel-gfx] [PATCH v3 12/28] KVM: x86/mmu: Don't rely on page-track mechanism to flush on memslot change

[Yan Zhao]

Reviewed-by: Yan Zhao 

On Fri, May 12, 2023 at 05:35:44PM -0700, Sean Christopherson wrote:
> 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 
> Link: https://lore.kernel.org/r/20221110014821.1548347-2-sea...@google.com
> Signed-off-by: Sean Christopherson 
> ---
>  arch/x86/kvm/mmu/mmu.c | 10 ++
>  1 file changed, 2 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 2e4476d38377..23a79723031b 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -6184,13 +6184,6 @@ static bool kvm_has_zapped_obsolete_pages(struct kvm 
> *kvm)
>   return unlikely(!list_empty_careful(>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 = >arch.mmu_sp_tracker;
> @@ -6208,7 +6201,6 @@ 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;
> @@ -6750,6 +6742,8 @@ 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);
>  }
>  
> -- 
> 2.40.1.606.ga4b1b128d6-goog
> 

[Intel-gfx] [PATCH v3 12/28] KVM: x86/mmu: Don't rely on page-track mechanism to flush on memslot change

[Sean Christopherson]

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 
Link: https://lore.kernel.org/r/20221110014821.1548347-2-sea...@google.com
Signed-off-by: Sean Christopherson 
---
 arch/x86/kvm/mmu/mmu.c | 10 ++
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 2e4476d38377..23a79723031b 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -6184,13 +6184,6 @@ static bool kvm_has_zapped_obsolete_pages(struct kvm 
*kvm)
return unlikely(!list_empty_careful(>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 = >arch.mmu_sp_tracker;
@@ -6208,7 +6201,6 @@ 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;
@@ -6750,6 +6742,8 @@ 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);
 }
 
-- 
2.40.1.606.ga4b1b128d6-goog