Re: [PATCH 2/7] xen/events: don't unmask an event channel when an eoi is pending

[Jürgen Groß <jgross@xxxxxxxx>]

On 08.02.21 11:06, Jan Beulich wrote:
> On 06.02.2021 11:49, Juergen Gross wrote:
> > @@ -1798,6 +1818,29 @@ static void mask_ack_dynirq(struct irq_data *data)
> >         ack_dynirq(data);
> >   }
> >   
> > +static void lateeoi_ack_dynirq(struct irq_data *data)
> > +{
> > +       struct irq_info *info = info_for_irq(data->irq);
> > +       evtchn_port_t evtchn = info ? info->evtchn : 0;
> > +
> > +       if (VALID_EVTCHN(evtchn)) {
> > +               info->eoi_pending = true;
> > +               mask_evtchn(evtchn);
> > +       }
> > +}
> > +
> > +static void lateeoi_mask_ack_dynirq(struct irq_data *data)
> > +{
> > +       struct irq_info *info = info_for_irq(data->irq);
> > +       evtchn_port_t evtchn = info ? info->evtchn : 0;
> > +
> > +       if (VALID_EVTCHN(evtchn)) {
> > +               info->masked = true;
> > +               info->eoi_pending = true;
> > +               mask_evtchn(evtchn);
> > +       }
> > +}
> > +
> >   static int retrigger_dynirq(struct irq_data *data)
> >   {
> >         evtchn_port_t evtchn = evtchn_from_irq(data->irq);
> > @@ -2023,8 +2066,8 @@ static struct irq_chip xen_lateeoi_chip __read_mostly = {
> >         .irq_mask               = disable_dynirq,
> >         .irq_unmask             = enable_dynirq,
> >   
> > -	.irq_ack		= mask_ack_dynirq,
> > -       .irq_mask_ack           = mask_ack_dynirq,
> > +       .irq_ack                = lateeoi_ack_dynirq,
> > +       .irq_mask_ack           = lateeoi_mask_ack_dynirq,
> >   
> >   	.irq_set_affinity	= set_affinity_irq,
> >         .irq_retrigger          = retrigger_dynirq,
> Unlike the prior handler the two new ones don't call ack_dynirq()
> anymore, and the description doesn't give a hint towards this
> difference. As a consequence, clear_evtchn() also doesn't get
> called anymore - patch 3 adds the calls, but claims an older
> commit to have been at fault. _If_ ack_dynirq() indeed isn't to
> be called here, shouldn't the clear_evtchn() calls get added
> right here?
There was clearly too much time between writing this patch and looking
at its performance impact. :-(

Somehow I managed to overlook that I just introduced the bug here. This
OTOH explains why there are not tons of complaints with the current
implementation. :-)

Will merge patch 3 into this one.


Juergen

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