Re: [Xen-devel] [BUG] panic: "IO-APIC + timer doesn't work" - several people have reproduced

[Jason Andryuk <jandryuk@xxxxxxxxx>]

On Wed, Feb 19, 2020 at 3:25 AM Jan Beulich <jbeulich@xxxxxxxx> wrote:
>
> On 18.02.2020 22:45, Andrew Cooper wrote:
> > On 18/02/2020 18:43, Jason Andryuk wrote:
> >> On Mon, Feb 17, 2020, 8:22 PM Andrew Cooper <andrew.cooper3@xxxxxxxxxx> 
> >> wrote:
> >>> On 17/02/2020 20:41, Jason Andryuk wrote:
> >>>> On Mon, Feb 17, 2020 at 2:46 PM Andrew Cooper 
> >>>> <andrew.cooper3@xxxxxxxxxx> wrote:
> >>>>> We have multiple bugs.
> >>>>>
> >>>>> First and foremost, Xen seems totally broken when running in ExtINT
> >>>>> mode.  This needs addressing, and ought to be sufficient to let Xen
> >>>>> boot, at which point we can try to figure out why it is trying to fall
> >>>>> back into 486(ish) compatibility mode.
> >> Xen has "enabled ExtINT on CPU#0" while linux has "masked ExtINT on
> >> CPU#0" so linux isn't using ExtINT?
> >
> > It would appear not.  Even more concerningly, on my Kabylake box,
> >
> > # xl dmesg | grep ExtINT
> > (XEN) enabled ExtINT on CPU#0
> > (XEN) masked ExtINT on CPU#1
> > (XEN) masked ExtINT on CPU#2
> > (XEN) masked ExtINT on CPU#3
> > (XEN) masked ExtINT on CPU#4
> > (XEN) masked ExtINT on CPU#5
> > (XEN) masked ExtINT on CPU#6
> > (XEN) masked ExtINT on CPU#7
> >
> > which at first glance suggests that we have something asymmetric being
> > set up.
>
> That's perfectly normal - ExtINT may be enabled on just one CPU,
> and that's CPU0 in our case (until such time that we would want
> to be able to offline CPU0).

Thanks, Jan.  Linux prints masked ExtINT for all 8 CPU threads.

I inserted __print_IO_APIC() before the "IO-APIC + timer doesn't work" panic.

Using vector-based indexing
IRQ to ping mappings:
IRQ240 -> 0:2

where Linux prints
IRQ0 -> 0:2

That may just be the difference between Xen printing the Vector vs.
Linux printing the IRQ number.

Any pointers to what I should investigate?

Regards,
Jason

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