KVM: MMU: ignore zapped root pagetables

Mark zapped root pagetables as invalid and ignore such pages during lookup.

This is a problem with the cr3-target feature, where a zapped root table fools
the faulting code into creating a read-only mapping. The result is a lockup
if the instruction can't be emulated.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0dd038e7392..e8e64927bdd 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2658,6 +2658,10 @@ preempted:
                 kvm_x86_ops->guest_debug_pre(vcpu);
 
 again:
+        if (vcpu->requests)
+                if (test_and_clear_bit(KVM_REQ_MMU_RELOAD, &vcpu->requests))
+                        kvm_mmu_unload(vcpu);
+
         r = kvm_mmu_reload(vcpu);
         if (unlikely(r))
                 goto out;
@@ -2689,6 +2693,14 @@ again:
                 goto out;
         }
 
+        if (vcpu->requests)
+                if (test_bit(KVM_REQ_MMU_RELOAD, &vcpu->requests)) {
+                        local_irq_enable();
+                        preempt_enable();
+                        r = 1;
+                        goto out;
+                }
+
         if (signal_pending(current)) {
                 local_irq_enable();
                 preempt_enable();