Re: [PATCH v7 08/12] KVM: arm64: PMU: Allow userspace to limit PMCR_EL0.N for the guest

[Sebastian Ott]

On Mon, 9 Oct 2023, Raghavendra Rao Ananta wrote:
> +static int set_pmcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r,
> +		    u64 val)
> +{
> +	struct kvm *kvm = vcpu->kvm;
> +	u64 new_n, mutable_mask;
> +
> +	mutex_lock(&kvm->arch.config_lock);
> +
> +	/*
> +	 * Make PMCR immutable once the VM has started running, but do
> +	 * not return an error (-EBUSY) to meet the existing expectations.
> +	 */

Why should we mention which error we're _not_ returning?


> +	if (kvm_vm_has_ran_once(vcpu->kvm)) {
> +		mutex_unlock(&kvm->arch.config_lock);
> +		return 0;
> +	}