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

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@physik.fu-berlin.de> wrote:

Hi Michael!

On 1/13/22 01:17, John Paul Adrian Glaubitz wrote:

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On 1/9/22 23:17, John Paul Adrian Glaubitz wrote:

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On 1/7/22 12:20, John Paul Adrian Glaubitz wrote:

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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.

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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

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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

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crashing. However, I have observed on two occasions now that the build

VM is just suddenly

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off as if someone has shut it down using the "force-off" option in the

virt-manager user

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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@debian.org
`. `'   Freie Universitaet Berlin - glaubitz@physik.fu-berlin.de
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