[PATCH 1/2] KVM: x86/mmu: Don't rely on page-track mechanism to flush on memslot change

Sean Christopherson
2022-11-10T01:48:35Z

Call kvm_mmu_zap_all_fast() directly when flushing a memslot instead of
bounding 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>
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(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 81114a376c4e..382cfffb7e6c 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1765,6 +1765,7 @@ 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 93c389eaf471..0a5ae07a190e 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5943,7 +5943,7 @@ 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);

@@ -5999,13 +5999,6 @@ 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;
@@ -6021,7 +6014,6 @@ int kvm_mmu_init_vm(struct kvm *kvm)
return r;

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 e46e458c5b08..5da86fe3c113 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -12550,6 +12550,8 @@ 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);
}

--
2.38.1.431.g37b22c650d-goog