Re: xen 4.17.2 qemu-system-i386 crashes

[Chuck Zmudzinski <brchuckz@xxxxxxxxxxxx>]

On 8/18/2023 10:49 PM, Chuck Zmudzinski wrote:
> On 8/18/2023 7:42 PM, xen@xxxxxxxx wrote:
>> Am 18.08.23 um 02:32 schrieb Chuck Zmudzinski:
>>> On 8/17/23 7:22 PM, xen@xxxxxxxx wrote:
>>>> Hello,
>>>>
>>>> I am using Archlinux. Last month I built and installed xen-4.17.2pre
>>>> which works perfectly. Today I built and installed the newly released
>>>> xen-4.17.2.
>>>> Now qemu-system-i386 crashes.
>>>>
>>>> I attached an excerpt from the log.
>>>>
>>> 
>>> Hmm. I am on Fedora 38, and they just pushed out the 4.17.2 update to me
>>> yesterday and qemu-system-i386 is working fine with it. This is the version
>>> info on Fedora 38 that is working:
>>> 
>>> Xen version info from sudo xl dmesg on Fedora 38:
>>> 
>>> (XEN) Xen version 4.17.2 (mockbuild@) (gcc (GCC) 13.2.1 20230728 (Red Hat 
>>> 13.2.1-1)) debug=n Thu Aug 10 22:11:44 UTC 2023
>>> 
>>> Qemu version info on Fedora 38:
>>> 
>>> [user@fedora ~]$ qemu-system-i386 -version
>>> QEMU emulator version 7.2.1 (qemu-7.2.1-2.fc38)
>>> Copyright (c) 2003-2022 Fabrice Bellard and the QEMU Project developers
>>> [user@fedora ~]$
>>> 
>>> So, I think maybe you are using a different Qemu version that does not
>>> work with Xen 4.17.2.
> 
> With the new data this suggestion I made yesterday seems wrong now.
> 
>> 
>> Xen 4.17.2pre runs on this hardware with both Qemu 8.0.2 and Qemu 8.0.4 
>> without problems> 
>> On older hardware (Intel Haswell processor) Xen 4.17.2 runs without 
>> problems with Qemu 8.0.4. Obviously only my newer hardware is affected.
> 
> My working result is also on older hardware (Intel Haswell processor) so
> we agree the problem you are seeing is related to newer hardware. It
> might help to mention the model of processor in your newer hardware.
> 
> Unfortunately I do not have newer hardware to test my Qemu 7.2.x with
> Xen 4.17.2 so I won't be able to help you out much any more. (Today
> Fedora pushed out Qemu 7.2.4 to me and that also works fine with Xen 4.17.2
> on the Haswell processor).
> 
> With this additional data it seems the changes in Xen (not changes in Qemu)
> are causing the core dump in Qemu on the newer hardware. If no one here
> on xen-users has any ideas you might try posting this bug on the xen-devel
> mailing list instead. Mention Haswell always works, but something goes
> bad with Qemu when upgrading from 4.17.2pre to 4.17.2 on the newer
> hardware, and mention the model of processor of the newer hardware and
> the excerpt from the journal, and maybe some of the developers can help
> you troubleshoot the problem. There presumably are not a lot of changes
> between Xen 4.17.2pre and 4.17.2 so hopefully the developers can find the
> problem and fix it for the next release.

To follow up, I just checked the shortlog of the 4.17 branch on xenbits.xen.org:

https://xenbits.xen.org/gitweb/?p=xen.git;a=shortlog;h=refs/heads/stable-4.17

and there are I think 80 commits (give or take a few) between the 4.17.2pre
version commit and the 4.17.2 release. So you should be able to bisect and
find the offending commit that is causing qemu-system-i386 to crash on your
newer hardware, but it may take a few builds to narrow it down with about
80 commits to check. If you find the offending commit, I suggest you report
it on the xen-devel mailing list so the developers can diagnose the cause
and find a solution.