On Thu, Oct 19, 2023 at 3:45 AM Sebastian Ott <sebott@xxxxxxxxxx> wrote:
>
> On Tue, 17 Oct 2023, Raghavendra Rao Ananta wrote:
> > On Tue, Oct 17, 2023 at 8:52 AM Sebastian Ott <sebott@xxxxxxxxxx> wrote:
> >>
> >> 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?
> >>
> > Oh, it's not to break the existing userspace expectations. Before this
> > series, any 'write' from userspace was possible. Returning -EBUSY all
> > of a sudden might tamper with this expectation.
>
> Yes I get that part. What I've meant is why specifically mention -EBUSY?
> You're also not returning -EFAULT nor -EINVAL.
>
> /*
> * Make PMCR immutable once the VM has started running, but do
> * not return an error to meet the existing expectations.
> */
> IMHO provides the same info to the reader and is less confusing
>
Sounds good. I'll apply this.
Thank you.
Raghavendra
> Sebastian
