KVM: Replace pending exception by PF if it happens serially

Replace previous exception with a new one in a hope that instruction
re-execution will regenerate lost exception.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 13 insertions, 7 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 30492f0ba4ea..a066876f1373 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -181,16 +181,22 @@ void kvm_inject_page_fault(struct kvm_vcpu *vcpu, unsigned long addr,
         ++vcpu->stat.pf_guest;
 
         if (vcpu->arch.exception.pending) {
-                if (vcpu->arch.exception.nr == PF_VECTOR) {
-                        printk(KERN_DEBUG "kvm: inject_page_fault:"
-                                        " double fault 0x%lx\n", addr);
-                        vcpu->arch.exception.nr = DF_VECTOR;
-                        vcpu->arch.exception.error_code = 0;
-                } else if (vcpu->arch.exception.nr == DF_VECTOR) {
+                switch(vcpu->arch.exception.nr) {
+                case DF_VECTOR:
                         /* triple fault -> shutdown */
                         set_bit(KVM_REQ_TRIPLE_FAULT, &vcpu->requests);
+                        return;
+                case PF_VECTOR:
+                        vcpu->arch.exception.nr = DF_VECTOR;
+                        vcpu->arch.exception.error_code = 0;
+                        return;
+                default:
+                        /* replace previous exception with a new one in a hope
+                           that instruction re-execution will regenerate lost
+                           exception */
+                        vcpu->arch.exception.pending = false;
+                        break;
                 }
-                return;
         }
         vcpu->arch.cr2 = addr;
         kvm_queue_exception_e(vcpu, PF_VECTOR, error_code);