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

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Date:   Fri, 10 Mar 2023 16:22:42 -0800
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Zhi Wang <zhi.a.wang@...el.com>
Cc:     kvm@...r.kernel.org, intel-gvt-dev@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Yan Zhao <yan.y.zhao@...el.com>,
        Ben Gardon <bgardon@...gle.com>
Subject: [PATCH v2 11/27] KVM: x86/mmu: Don't rely on page-track mechanism to
 flush on memslot change

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@...el.com>
Link: https://lore.kernel.org/r/20221110014821.1548347-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@...gle.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 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);
 }
 
-- 
2.40.0.rc1.284.g88254d51c5-goog