Comment 14 for bug 2051965
Revision history for this message
| Sergio Durigan Junior (sergiodj) wrote Re: [Bug 2051965] Re: QEmu with TCG acceleration (without KVM) causes kernel panics with kernels >=6.3 | #14 |
Hey Matthieu,
On Tuesday, February 13 2024, Matthieu Baerts wrote:
>> Right now, I'm trying to reproduce the problem with qemu from Jammy (I
> managed to reproduce it using Mantic). I'm a little bit puzzled to see
> that the qemu crashed quicker on Mantic (I've been running the test on
> Jammy for more than 2 hours now, and it still hasn't crashed). Anyway,
> I'll leave it running overnight.
>
> I also noticed that it was easier to have QEmu crashed on Mantic than on
> Jammy. On the other hand, when I first tried to reproduce the issue on
> Jammy, most of the time, it was taking around 50 iterations to hit the
> kernel panic. Sometimes, it was taking < 10 iterations, but also
> sometimes around ~150/200.
>
>> Huh, the test has just finished on Jammy and the crash didn't happen.
>
> Arf, sorry for that :-/
> I guess 'virtme' was correctly patched not to use KVM, right?
>
> Maybe try with more than 250 iterations by modifying the ".virtme-exec-
> run" file? e.g. 500? Or no limit by using 'run_loop' instead of
> 'run_loop_n 250' and leave it running overnight? It is hard to predict
> when a concurrency bug will happen.
Ah, that did it. Now I can reproduce on Jammy and Mantic, without using
Docker. That's great.
>> Another thing that's concerning is the difference in the codebase from
> qemu 6.2 (the version from Jammy) and 8.x. I started backporting the
> upstream patches into Jammy and noticed that there are non-trivial
> conflicts to be solved.
>
> Thank you for having looked at that! Maybe the QEmu community can help
> for that? I don't know how it usually work.
No problem, I'll figure it out.
>> I apologize for the slow progress here. I'm spread thin across many
> tasks so I have to timebox my work on this bug.
>
> That's OK, take your time. On my side, I have a workaround by using a
> kernel patch. I will be happy to remove it, but I mainly reported the
> issue to help other people also using QEmu < 8.1 without KVM and with a
> guest kernel >= 6.3, because it might not be obvious the issue is due to
> QEmu and not the guest kernel.
Thanks for the patience :-).
Cheers,
--
Sergio
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