arm64: KVM: PMU: Inject UNDEF on non-privileged accesses

access_pminten() and access_pmuserenr() can only be accessed when
the CPU is in a priviledged mode. If it is not, let's inject an
UNDEF exception.
Reviewed-by: Christoffer Dall <cdall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

arch/arm64/kvm/sys_regs.c

@@ -709,8 +709,10 @@ static bool access_pminten(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 	if (!kvm_arm_pmu_v3_ready(vcpu))
 		return trap_raz_wi(vcpu, p, r);
 
-	if (!vcpu_mode_priv(vcpu))
+	if (!vcpu_mode_priv(vcpu)) {
+		kvm_inject_undefined(vcpu);
 		return false;
+	}
 
 	if (p->is_write) {
 		u64 val = p->regval & mask;
@@ -780,8 +782,10 @@ static bool access_pmuserenr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 		return trap_raz_wi(vcpu, p, r);
 
 	if (p->is_write) {
-		if (!vcpu_mode_priv(vcpu))
+		if (!vcpu_mode_priv(vcpu)) {
+			kvm_inject_undefined(vcpu);
 			return false;
+		}
 
 		vcpu_sys_reg(vcpu, PMUSERENR_EL0) = p->regval
 						    & ARMV8_PMU_USERENR_MASK;