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

John Paul Adrian Glaubitz [off-list ref] writes:

Hi Michael!

Sorry for the long time without any responses. Shall we continue debugging this?

Yes!

Sorry also that I haven't been able to fix it yet, I had to stop chasing
this bug and work on other things before the end of the year.

We're currently running 5.15.x on the host system and the guests and the testsuite
for gcc-9 still reproducibly kills the KVM host.

Have you been able to try the different -smp options I suggested?

Can you separately test with (on the host):

 # echo 0 > /sys/module/kvm_hv/parameters/dynamic_mt_modes


cheers

On 11/1/21 07:53, Michael Ellerman wrote:

quoted

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

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz@debian.org
`. `'   Freie Universitaet Berlin - glaubitz@physik.fu-berlin.de
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