KVM: nSVM: Report NMIs as allowed when in L2 and Exit-on-NMI is set

Report NMIs as allowed when the vCPU is in L2 and L2 is being run with
Exit-on-NMI enabled, as NMIs are always unblocked from L1's perspective
in this case.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm/nested.c

@@ -799,11 +799,6 @@ int nested_svm_check_exception(struct vcpu_svm *svm, unsigned nr,
 	return vmexit;
 }
 
-static bool nested_exit_on_nmi(struct vcpu_svm *svm)
-{
-	return (svm->nested.intercept & (1ULL << INTERCEPT_NMI));
-}
-
 static void nested_svm_nmi(struct vcpu_svm *svm)
 {
 	svm->vmcb->control.exit_code = SVM_EXIT_NMI;

arch/x86/kvm/svm/svm.c

@@ -3071,6 +3071,9 @@ static bool svm_nmi_allowed(struct kvm_vcpu *vcpu)
 	struct vmcb *vmcb = svm->vmcb;
 	bool ret;
 
+	if (is_guest_mode(vcpu) && nested_exit_on_nmi(svm))
+		return true;
+
 	ret = !(vmcb->control.int_state & SVM_INTERRUPT_SHADOW_MASK) &&
 	      !(svm->vcpu.arch.hflags & HF_NMI_MASK);
 	ret = ret && gif_set(svm);

arch/x86/kvm/svm/svm.h

@@ -378,6 +378,11 @@ static inline bool svm_nested_virtualize_tpr(struct kvm_vcpu *vcpu)
 	return is_guest_mode(vcpu) && (vcpu->arch.hflags & HF_VINTR_MASK);
 }
 
+static inline bool nested_exit_on_nmi(struct vcpu_svm *svm)
+{
+	return (svm->nested.intercept & (1ULL << INTERCEPT_NMI));
+}
+
 void enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb_gpa,
 			  struct vmcb *nested_vmcb, struct kvm_host_map *map);
 int nested_svm_vmrun(struct vcpu_svm *svm);