Re: [PATCH] KVM: x86/pmu: Don't retry a counter whose config was rejected

[Absandze, Luka]

On 2026-09-18 09:16, Sean Christopherson wrote:
> Hmm, would it instead make more sense to explicitly check for -EBUSY?  -EINVAL
> isn't the only fatal error code.
> 
> diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
> index a7d60c8785cd..5296ee8f32af 100644
> --- a/arch/x86/kvm/pmu.c
> +++ b/arch/x86/kvm/pmu.c
> @@ -681,7 +681,7 @@ void kvm_pmu_handle_event(struct kvm_vcpu *vcpu)
>                  * PMU refresh.  Don't make a new request as doing so can stall
>                  * the guest if reprogramming repeatedly fails.
>                  */
> -               if (reprogram_counter(pmc))
> +               if (reprogram_counter(pmc) == -EBUSY)
>                         set_bit(pmc->idx, pmu->reprogram_pmi);
>         }
> 
> Though I guess one could argue -ENOMEM is also transient?

I had contemplated this, but could not convince myself at a glance that
perf and KVM agreed on what constituted a transient error.
I have now concluded I was seeing ghosts :)

> E.g. this? (completely untested)
> [diff]

Tested against the fault described in the linked patch and selftests on
AMD Zen 3 (although I don't think there's much coverage in this regard).

If no other objections, would you be fine with taking the diff you
provided into the tree or would you prefer a v2?