On Wed, Aug 23, 2023 at 04:09:26PM +0200, Michael Mueller wrote:
>
>
> On 23.08.23 15:23, Alexander Gordeev wrote:
> > 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?
>
> Calling function process_gib_alert_list() guarantees the gisa
> is taken out of the alert list immediately and thus the potential
> endless loop on gisa_in_alert_list() is solved. The issue surfaced
> with the following patch that accidently disabled the GAL interrupt
> processing on the host that normaly handles the alert list.
> The patch has been reverted from devel and will be re-applied in v2.
>
> 88a096a7a460 Revert "s390/airq: remove lsi_mask from airq_struct"
> a9d17c5d8813 s390/airq: remove lsi_mask from airq_struct
>
> Does that make sense for you?
Not really. If process_gib_alert_list() does guarantee the removal,
then it should be a condition, not the loop.
But I am actually not into this code. Just wanted to point out that
cpu_relax() is removed from this loop and the two other loops within
process_gib_alert_list() do not have it either.
So up to Christian, Janosch and Claudio.
