Re: NetBSD dom0 PVH: hardware interrupts stalls

[Manuel Bouyer <bouyer@xxxxxxxxxxxxxxx>]

On Fri, Nov 27, 2020 at 02:18:54PM +0100, Jan Beulich wrote:
> On 27.11.2020 14:13, Manuel Bouyer wrote:
> > On Fri, Nov 27, 2020 at 12:29:35PM +0100, Jan Beulich wrote:
> >> On 27.11.2020 11:59, Roger Pau Monné wrote:
> >>> --- a/xen/arch/x86/hvm/irq.c
> >>> +++ b/xen/arch/x86/hvm/irq.c
> >>> @@ -187,6 +187,10 @@ void hvm_gsi_assert(struct domain *d, unsigned int 
> >>> gsi)
> >>>       * to know if the GSI is pending or not.
> >>>       */
> >>>      spin_lock(&d->arch.hvm.irq_lock);
> >>> +    if ( gsi == TRACK_IRQ )
> >>> +        debugtrace_printk("hvm_gsi_assert irq %u trig %u assert count 
> >>> %u\n",
> >>> +                          gsi, trig, hvm_irq->gsi_assert_count[gsi]);
> >>
> >> This produces
> >>
> >> 81961 hvm_gsi_assert irq 34 trig 1 assert count 1
> >>
> >> Since the logging occurs ahead of the call to assert_gsi(), it
> >> means we don't signal anything to Dom0, because according to our
> >> records there's still an IRQ in flight. Unfortunately we only
> >> see the tail of the trace, so it's not possible to tell how / when
> >> we got into this state.
> >>
> >> Manuel - is this the only patch you have in place? Or did you keep
> >> any prior ones? Iirc there once was one where Roger also suppressed
> >> some de-assert call.
> > 
> > Yes, I have some of the previous patches (otherwise Xen panics).
> > Attached is the diffs I currently have 
> 
> I think you want to delete the hunk dropping the call to
> hvm_gsi_deassert() from pt_irq_time_out(). Iirc it was that
> addition which changed the behavior to just a single IRQ ever
> making it into Dom0. And it ought to be only the change to
> msix_write() which is needed to avoid the panic.

yes, I did keep the hvm_gsi_deassert() patch because I expected it
to make things easier, as it allows to interract with Xen without changing
interrupt states.
I removed it, here's a new trace

http://www-soc.lip6.fr/~bouyer/xen-log12.txt

-- 
Manuel Bouyer <bouyer@xxxxxxxxxxxxxxx>
     NetBSD: 26 ans d'experience feront toujours la difference
--