KVM: x86: Avoid zapping mmio sptes twice for generation wraparound

Now that kvm_arch_memslots_updated() catches every increment of the
memslots->generation, checking if the mmio generation has reached its
maximum value is enough.

Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 9e9285a..3a9493a 100644 (file)
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4390,11 +4390,8 @@ void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm)
        /*
         * The very rare case: if the generation-number is round,
         * zap all shadow pages.
-        *
-        * The max value is MMIO_MAX_GEN - 1 since it is not called
-        * when mark memslot invalid.
         */
-       if (unlikely(kvm_current_mmio_generation(kvm) >= (MMIO_MAX_GEN - 1))) {
+       if (unlikely(kvm_current_mmio_generation(kvm) >= MMIO_MAX_GEN)) {
                printk_ratelimited(KERN_INFO "kvm: zapping shadow pages for mmio generation wraparound\n");
                kvm_mmu_invalidate_zap_all_pages(kvm);
        }

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9dd8799..7bea976 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7021,6 +7021,11 @@ out_free:
 
 void kvm_arch_memslots_updated(struct kvm *kvm)
 {
+       /*
+        * memslots->generation has been incremented.
+        * mmio generation may have reached its maximum value.
+        */
+       kvm_mmu_invalidate_mmio_sptes(kvm);
 }
 
 int kvm_arch_prepare_memory_region(struct kvm *kvm,
@@ -7083,11 +7088,6 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
         */
        if ((change != KVM_MR_DELETE) && (mem->flags & KVM_MEM_LOG_DIRTY_PAGES))
                kvm_mmu_slot_remove_write_access(kvm, mem->slot);
-       /*
-        * If memory slot is created, or moved, we need to clear all
-        * mmio sptes.
-        */
-       kvm_mmu_invalidate_mmio_sptes(kvm);
 }
 
 void kvm_arch_flush_shadow_all(struct kvm *kvm)