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

[Michael Ellerman]

John Paul Adrian Glaubitz <glaubitz at physik.fu-berlin.de> writes:
> Hi Michael!
>
> On 10/28/21 08:39, Michael Ellerman wrote:
>> That completed fine on my BE VM here.
>> 
>> I ran these in two tmux windows:
>>   $ sbuild -d sid --arch=powerpc --no-arch-all gcc-11_11.2.0-10.dsc
>>   $ sbuild -d sid --arch=ppc64 --no-arch-all gcc-11_11.2.0-10.dsc
>
> Could you try gcc-10 instead? It's testsuite has crashed the host for me
> with a patched kernel twice now.
>
> $ dget -u https://deb.debian.org/debian/pool/main/g/gcc-10/gcc-10_10.3.0-12.dsc
> $ sbuild -d sid --arch=powerpc --no-arch-all gcc-10_10.3.0-12.dsc
> $ sbuild -d sid --arch=ppc64 --no-arch-all gcc-10_10.3.0-12.dsc

Sure, will give that a try.

I was able to crash my machine over the weekend, building openjdk, but I
haven't been able to reproduce it for ~24 hours now (I didn't change
anything).


Can you try running your guests with no SMT threads?

I think one of your guests was using:

  -smp 32,sockets=1,dies=1,cores=8,threads=4

Can you change that to:

  -smp 8,sockets=1,dies=1,cores=8,threads=1


And something similar for the other guest(s).

If the system is stable with those settings that would be useful
information, and would also mean you could use the system without it
crashing semi regularly.

cheers