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

[Alexander Gordeev <agordeev@xxxxxxxxxxxxx>]

On Wed, Aug 23, 2023 at 02:41:40PM +0200, Michael Mueller wrote:
...
> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
> index 9bd0a873f3b1..73153bea6c24 100644
> --- a/arch/s390/kvm/interrupt.c
> +++ b/arch/s390/kvm/interrupt.c
> @@ -3205,8 +3205,10 @@ void kvm_s390_gisa_destroy(struct kvm *kvm)
>  	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();
> +	while (gisa_in_alert_list(gi->origin)) {
> +		KVM_EVENT(3, "vm 0x%pK gisa in alert list during destroy", kvm);
> +		process_gib_alert_list();

process_gib_alert_list() has two nested loops and neither of them
does cpu_relax(). I guess, those are needed instead of one you remove?

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