Do not stop VM if emulation failed in userspace.

Continue vcpu execution in case emulation failure happened while vcpu
was in userspace. In this case #UD will be injected into the guest
allowing guest OS to kill offending process and continue.
Signed-off-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

kvm-all.c

@@ -764,6 +764,8 @@ static void kvm_handle_internal_error(CPUState *env, struct kvm_run *run)
     cpu_dump_state(env, stderr, fprintf, 0);
     if (run->internal.suberror == KVM_INTERNAL_ERROR_EMULATION) {
         fprintf(stderr, "emulation failure\n");
+        if (!kvm_arch_stop_on_emulation_error(env))
+		return;
     }
     /* FIXME: Should trigger a qmp message to let management know
      * something went wrong.

kvm.h

@@ -140,6 +140,8 @@ void kvm_arch_remove_all_hw_breakpoints(void);
 
 void kvm_arch_update_guest_debug(CPUState *env, struct kvm_guest_debug *dbg);
 
+bool kvm_arch_stop_on_emulation_error(CPUState *env);
+
 int kvm_check_extension(KVMState *s, unsigned int extension);
 
 uint32_t kvm_arch_get_supported_cpuid(CPUState *env, uint32_t function,

target-i386/kvm.c

@@ -1289,3 +1289,10 @@ void kvm_arch_update_guest_debug(CPUState *env, struct kvm_guest_debug *dbg)
     }
 }
 #endif /* KVM_CAP_SET_GUEST_DEBUG */
+
+bool kvm_arch_stop_on_emulation_error(CPUState *env)
+{
+      return !(env->cr[0] & CR0_PE_MASK) ||
+              ((env->segs[R_CS].selector  & 3) != 3);
+}
+

target-ppc/kvm.c

@@ -326,3 +326,8 @@ uint32_t kvmppc_get_tbfreq(void)
     retval = atoi(ns);
     return retval;
 }
+
+bool kvm_arch_stop_on_emulation_error(CPUState *env)
+{
+    return true;
+}

target-s390x/kvm.c

@@ -485,3 +485,8 @@ int kvm_arch_handle_exit(CPUState *env, struct kvm_run *run)
 
     return ret;
 }
+
+bool kvm_arch_stop_on_emulation_error(CPUState *env)
+{
+    return true;
+}