KVM: arm64: Refuse illegal KVM_ARM_VCPU_PMU_V3 at reset time

We accept to configure a PMU when a vcpu is created, even if the
HW (or the host) doesn't support it. This results in failures
when attributes get set, which is a bit odd as we should have
failed the vcpu creation the first place.

Move the check to the point where we check the vcpu feature set,
and fail early if we cannot support a PMU. This further simplifies
the attribute handling.
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>

arch/arm64/kvm/pmu-emul.c

@@ -913,7 +913,7 @@ static bool pmu_irq_is_valid(struct kvm *kvm, int irq)
 
 int kvm_arm_pmu_v3_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
 {
-	if (!kvm_arm_support_pmu_v3() || !kvm_vcpu_has_pmu(vcpu))
+	if (!kvm_vcpu_has_pmu(vcpu))
 		return -ENODEV;
 
 	if (vcpu->arch.pmu.created)
@@ -1034,7 +1034,7 @@ int kvm_arm_pmu_v3_has_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
 	case KVM_ARM_VCPU_PMU_V3_IRQ:
 	case KVM_ARM_VCPU_PMU_V3_INIT:
 	case KVM_ARM_VCPU_PMU_V3_FILTER:
-		if (kvm_arm_support_pmu_v3() && kvm_vcpu_has_pmu(vcpu))
+		if (kvm_vcpu_has_pmu(vcpu))
 			return 0;
 	}
 

arch/arm64/kvm/reset.c

@@ -285,6 +285,10 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
 			pstate = VCPU_RESET_PSTATE_EL1;
 		}
 
+		if (kvm_vcpu_has_pmu(vcpu) && !kvm_arm_support_pmu_v3()) {
+			ret = -EINVAL;
+			goto out;
+		}
 		break;
 	}