KVM: x86: Exit to user-mode on #UD intercept when emulator requires

Instruction emulation after trapping a #UD exception can result in an
MMIO access, for example when emulating a MOVBE on a processor that
doesn't support the instruction.  In this case, the #UD vmexit handler
must exit to user mode, but there wasn't any code to do so.  Add it for
both VMX and SVM.

Signed-off-by: Liran Alon <[email protected]>
Reviewed-by: Nikita Leshenko <[email protected]>
Reviewed-by: Konrad Rzeszutek Wilk <[email protected]>
Signed-off-by: Konrad Rzeszutek Wilk <[email protected]>
Reviewed-by: Wanpeng Li <[email protected]>
Reviewed-by: Paolo Bonzini <[email protected]>
Cc: [email protected]
Signed-off-by: Radim Krčmář <[email protected]>

2 files changed, 4 insertions, 0 deletions

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 1bf7c09d97e6..eb714f1cdf7e 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -2204,6 +2204,8 @@ static int ud_interception(struct vcpu_svm *svm)
 
 	WARN_ON_ONCE(is_guest_mode(&svm->vcpu));
 	er = emulate_instruction(&svm->vcpu, EMULTYPE_TRAP_UD);
+	if (er == EMULATE_USER_EXIT)
+		return 0;
 	if (er != EMULATE_DONE)
 		kvm_queue_exception(&svm->vcpu, UD_VECTOR);
 	return 1;
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index d319e2666ad5..65f1f06f6aaa 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -5919,6 +5919,8 @@ static int handle_exception(struct kvm_vcpu *vcpu)
 	if (is_invalid_opcode(intr_info)) {
 		WARN_ON_ONCE(is_guest_mode(vcpu));
 		er = emulate_instruction(vcpu, EMULTYPE_TRAP_UD);
+		if (er == EMULATE_USER_EXIT)
+			return 0;
 		if (er != EMULATE_DONE)
 			kvm_queue_exception(vcpu, UD_VECTOR);
 		return 1;