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

Yan Zhao
2023-05-17T02:32:13Z

Reviewed-by: Yan Zhao <yan.y.zhao@intel.com>

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 <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/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(&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;
> @@ -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
>