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

From: Jason Andryuk <jandryuk@gmail.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
	Aaron Janse <aaron@ajanse.me>,
	xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [Xen-devel] [BUG] panic: "IO-APIC + timer doesn't work" - several people have reproduced
Date: Tue, 17 Mar 2020 09:48:28 -0400	[thread overview]
Message-ID: <CAKf6xpu+YC9zcwZr7rWSz37RE20GQ0dpsMBSqQh6+oPDuYQXuQ@mail.gmail.com> (raw)
In-Reply-To: <CAKf6xpsh3y_JpD15JLv52mgZOAVSu_Rp3EZOgGOmuS8_P5OsVQ@mail.gmail.com>

On Wed, Mar 4, 2020 at 11:06 AM Jason Andryuk <jandryuk@gmail.com> wrote:
>
> On Wed, Feb 19, 2020 at 3:25 AM Jan Beulich <jbeulich@suse.com> 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@citrix.com> wrote:
> > >>> On 17/02/2020 20:41, Jason Andryuk wrote:
> > >>>> On Mon, Feb 17, 2020 at 2:46 PM Andrew Cooper <andrew.cooper3@citrix.com> 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?

I got it to boot past "IO-APIC + timer doesn't work".  I programmed
the HPET to provide a periodic timer in hpet_resume() on T0.  When I
actually got it programmed properly, it worked to increment
pit0_ticks.  I also made timer_interrupt() unconditionally
pit0_ticks++ though that may not matter.

Now it panics in pv_destroy_gdt() when it fails "ASSERT(v == current
|| !vcpu_cpu_dirty(v));" when building dom0.  I haven't investigated
that yet.

Regards,
Jason

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