1 files changed, 21 insertions, 4 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 388a2ef83911..65f2400b8268 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4309,15 +4309,32 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot)
                         if (*rmapp)
                                 __rmap_write_protect(kvm, rmapp, false);
 
-                        if (need_resched() || spin_needbreak(&kvm->mmu_lock)) {
-                                kvm_flush_remote_tlbs(kvm);
+                        if (need_resched() || spin_needbreak(&kvm->mmu_lock))
                                 cond_resched_lock(&kvm->mmu_lock);
-                        }
                 }
         }
 
-        kvm_flush_remote_tlbs(kvm);
         spin_unlock(&kvm->mmu_lock);
+
+        /*
+         * kvm_mmu_slot_remove_write_access() and kvm_vm_ioctl_get_dirty_log()
+         * which do tlb flush out of mmu-lock should be serialized by
+         * kvm->slots_lock otherwise tlb flush would be missed.
+         */
+        lockdep_assert_held(&kvm->slots_lock);
+
+        /*
+         * We can flush all the TLBs out of the mmu lock without TLB
+         * corruption since we just change the spte from writable to
+         * readonly so that we only need to care the case of changing
+         * spte from present to present (changing the spte from present
+         * to nonpresent will flush all the TLBs immediately), in other
+         * words, the only case we care is mmu_spte_update() where we
+         * haved checked SPTE_HOST_WRITEABLE | SPTE_MMU_WRITEABLE
+         * instead of PT_WRITABLE_MASK, that means it does not depend
+         * on PT_WRITABLE_MASK anymore.
+         */
+        kvm_flush_remote_tlbs(kvm);
 }
 
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