Re: [Xen-devel] (XEN) APIC error on CPU0: 40(00)

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 04.11.15 at 22:09, <securef33d@xxxxxxxxx> wrote:
> On 04/11/2015 17:13, Jan Beulich wrote:
>>>>> On 04.11.15 at 16:15, <securef33d@xxxxxxxxx> wrote:
>>> Hi,
>>> i just build the latest 4.3.0 kernel and ran it on qubes-os with xen
>>> 4.4.3. I get this error just before the reboot:
>>>
>>>  [(XEN) APIC error on CPU0: 40(00)
>> 
>> And this appeared with the switch to kernel 4.3? No other variable
>> (e.g. all config options new in 4.3 turned off)? I ask because the
>> APIC is driven by Xen, not the kernel, and hence the kernel should
>> have no (direct) influence on APIC behavior.
> 
> This started with 4.3.0, with 4.3.0-rc7 the system was booting properly
> (except for the xsave=0 workaround, without that i also get a crash dump
> right before the APIC error).

Now that's a pretty narrow window. I just looked at the source diff,
without spotting anything even just remotely suspicious. Such a
narrow window would of course allow for relatively quick and simple
bisection...

Just to ask the unanswered part of the previous question again:
There were _no_ other changes to the system? I.e. if you go back
to -rc7 now, you don't see the problem anymore?

>>>  (XEN) Resetting with ACPI MEMORY or I/O RESET_REG.

I'm not aware of a code path leading here without any other
Xen messages, and without the reboot having been initiated by
Dom0.

>>> My machine runs on skylake cpu with z170 chipset and the latest bios.
>>> Any ideas on how to fix this?
>> 
>> Not without first figuring out what bad vector is being received
>> by the APIC, which likely will involved quite a bit of debugging
>> and code instrumentation.
> 
> Do you think that this could be caused by some sort of hardware/firmware
> issue?

Unlikely, but not entirely impossible.

Jan


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