KVM: MMU: out of sync shadow core

Allow guest pagetables to go out of sync.  Instead of emulating write
accesses to guest pagetables, or unshadowing them, we un-write-protect
the page table and allow the guest to modify it at will.  We rely on
invlpg executions to synchronize individual ptes, and will synchronize
the entire pagetable on tlb flushes.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index efee85ba07e5..1c5864ac0837 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -101,6 +101,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
         { "mmu_flooded", VM_STAT(mmu_flooded) },
         { "mmu_recycled", VM_STAT(mmu_recycled) },
         { "mmu_cache_miss", VM_STAT(mmu_cache_miss) },
+        { "mmu_unsync", VM_STAT(mmu_unsync) },
         { "remote_tlb_flush", VM_STAT(remote_tlb_flush) },
         { "largepages", VM_STAT(lpages) },
         { NULL }
@@ -3120,6 +3121,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
         if (vcpu->requests) {
                 if (test_and_clear_bit(KVM_REQ_MIGRATE_TIMER, &vcpu->requests))
                         __kvm_migrate_timers(vcpu);
+                if (test_and_clear_bit(KVM_REQ_MMU_SYNC, &vcpu->requests))
+                        kvm_mmu_sync_roots(vcpu);
                 if (test_and_clear_bit(KVM_REQ_TLB_FLUSH, &vcpu->requests))
                         kvm_x86_ops->tlb_flush(vcpu);
                 if (test_and_clear_bit(KVM_REQ_REPORT_TPR_ACCESS,