Re: [PATCH v4] KVM: s390: fix gisa destroy operation might lead to cpu stalls

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Quoting Michael Mueller (2023-09-01 12:58:23)
[...]
> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
> index 9bd0a873f3b1..96450e5c4b6f 100644
> --- a/arch/s390/kvm/interrupt.c
> +++ b/arch/s390/kvm/interrupt.c
[...]
>  static inline void gisa_set_ipm_gisc(struct kvm_s390_gisa *gisa, u32 gisc)
>  {
>         set_bit_inv(IPM_BIT_OFFSET + gisc, (unsigned long *) gisa);
> @@ -3202,11 +3197,12 @@ void kvm_s390_gisa_destroy(struct kvm *kvm)
>  
>         if (!gi->origin)
>                 return;
> -       if (gi->alert.mask)
> -               KVM_EVENT(3, "vm 0x%pK has unexpected iam 0x%02x",
> -                         kvm, gi->alert.mask);
> -       while (gisa_in_alert_list(gi->origin))
> -               cpu_relax();
> +       WARN(gi->alert.mask != 0x00,
> +            "unexpected non zero alert.mask 0x%02x",
> +            gi->alert.mask);
> +       gi->alert.mask = 0x00;
> +       if (gisa_set_iam(gi->origin, gi->alert.mask))
> +               process_gib_alert_list();

I am not an expert for the GISA, so excuse my possibly stupid question:
process_gib_alert_list() starts the timer. So can gisa_vcpu_kicker()
already be running before we reach hrtimer_cancel() below? Is this fine?

>         hrtimer_cancel(&gi->timer);
>         gi->origin = NULL;
>         VM_EVENT(kvm, 3, "gisa 0x%pK destroyed", gisa);




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