Linux kernel: powerpc: KVM guest can trigger host crash on Power8

[Mike]

I just made the huge mistake of hibernating and resuming, I'm going trough
the process of rescue and all, thankfully I had a 2016 cd in the drive.
I'll read up once the sheer panic settles.

-Michael

On Wed, Jan 26, 2022, 21:22 John Paul Adrian Glaubitz <
glaubitz at physik.fu-berlin.de> wrote:

> Hi Michael!
>
> On 1/13/22 01:17, John Paul Adrian Glaubitz wrote:
> > On 1/9/22 23:17, John Paul Adrian Glaubitz wrote:
> >> On 1/7/22 12:20, John Paul Adrian Glaubitz wrote:
> >>>> Can you separately test with (on the host):
> >>>>
> >>>>  # echo 0 > /sys/module/kvm_hv/parameters/dynamic_mt_modes
> >>>
> >>> I'm trying to turn off "dynamic_mt_modes" first and see if that makes
> any difference.
> >>>
> >>> I will report back.
> >>
> >> So far the machine is running stable now and the VM built gcc-9 without
> >> crashing the host. I will continue to monitor the machine and report
> back
> >> if it crashes, but it looks like this could be it.
> >
> > So, it seems that setting "dynamic_mt_modes" actually did the trick, the
> host is no longer
> > crashing. However, I have observed on two occasions now that the build
> VM is just suddenly
> > off as if someone has shut it down using the "force-off" option in the
> virt-manager user
> > interface.
>
> Just as a heads-up. Ever since I set
>
>         echo 0 > /sys/module/kvm_hv/parameters/dynamic_mt_modes
>
> on the host machine, I never saw the crash again. So the issue seems to be
> related to the
> dynamic_mt_modes feature.
>
> Thanks,
> Adrian
>
> --
>  .''`.  John Paul Adrian Glaubitz
> : :' :  Debian Developer - glaubitz at debian.org
> `. `'   Freie Universitaet Berlin - glaubitz at physik.fu-berlin.de
>   `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913
>
>
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