KVM: inject #UD if instruction emulation fails and exit to userspace

Do not kill VM when instruction emulation fails. Inject #UD and report
failure to userspace instead. Userspace may choose to reenter guest if
vcpu is in userspace (cpl == 3) in which case guest OS will kill
offending process and continue running.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 1 insertions, 4 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index be981b1f1881..4a02dee1f2b5 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2814,11 +2814,8 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u32 error_code)
                 return 1;
         case EMULATE_DO_MMIO:
                 ++vcpu->stat.mmio_exits;
-                return 0;
+                /* fall through */
         case EMULATE_FAIL:
-                vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
-                vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
-                vcpu->run->internal.ndata = 0;
                 return 0;
         default:
                 BUG();