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, 4 insertions, 24 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 598931734251..a82cfa1e2a40 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3070,7 +3070,7 @@ static int handle_io(struct kvm_vcpu *vcpu)
         ++vcpu->stat.io_exits;
 
         if (string || in)
-                return !(emulate_instruction(vcpu, 0, 0, 0) == EMULATE_DO_MMIO);
+                return emulate_instruction(vcpu, 0, 0, 0) == EMULATE_DONE;
 
         port = exit_qualification >> 16;
         size = (exit_qualification & 7) + 1;
@@ -3327,22 +3327,7 @@ static int handle_wbinvd(struct kvm_vcpu *vcpu)
 
 static int handle_apic_access(struct kvm_vcpu *vcpu)
 {
-        unsigned long exit_qualification;
-        enum emulation_result er;
-        unsigned long offset;
-
-        exit_qualification = vmcs_readl(EXIT_QUALIFICATION);
-        offset = exit_qualification & 0xffful;
-
-        er = emulate_instruction(vcpu, 0, 0, 0);
-
-        if (er !=  EMULATE_DONE) {
-                printk(KERN_ERR
-                       "Fail to handle apic access vmexit! Offset is 0x%lx\n",
-                       offset);
-                return -ENOEXEC;
-        }
-        return 1;
+        return emulate_instruction(vcpu, 0, 0, 0) == EMULATE_DONE;
 }
 
 static int handle_task_switch(struct kvm_vcpu *vcpu)
@@ -3554,13 +3539,8 @@ static int handle_invalid_guest_state(struct kvm_vcpu *vcpu)
                         goto out;
                 }
 
-                if (err != EMULATE_DONE) {
-                        vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
-                        vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
-                        vcpu->run->internal.ndata = 0;
-                        ret = 0;
-                        goto out;
-                }
+                if (err != EMULATE_DONE)
+                        return 0;
 
                 if (signal_pending(current))
                         goto out;