diff options
| -rw-r--r-- | arch/x86/kvm/mmu/mmu.c | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index e4415e739807..726e5b171543 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -2008,8 +2008,17 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, goto trace_get_page; if (sp->unsync) { - /* The page is good, but __kvm_sync_page might still end - * up zapping it. If so, break in order to rebuild it. + /* + * The page is good, but is stale. __kvm_sync_page does + * get the latest guest state, but (unlike mmu_unsync_children) + * it doesn't write-protect the page or mark it synchronized! + * This way the validity of the mapping is ensured, but the + * overhead of write protection is not incurred until the + * guest invalidates the TLB mapping. This allows multiple + * SPs for a single gfn to be unsync. + * + * If the sync fails, the page is zapped. If so, break + * in order to rebuild it. */ if (!__kvm_sync_page(vcpu, sp, &invalid_list)) break; |