Linux Virtualization - Dec 2019 - vhost changes (batched) in linux-next after 12/13 trigger random crashes in KVM guests after reboot

Michael,

with 
commit db7286b100b503ef80612884453bed53d74c9a16
(refs/bisect/skip-db7286b100b503ef80612884453bed53d74c9a16)
    vhost: use batched version by default
plus
commit 6bd262d5eafcdf8cdfae491e2e748e4e434dcda6 (HEAD, refs/bisect/bad)
    Revert "vhost/net: add an option to test new code"
to make things compile (your next tree is not easily bisectable, can you fix
that as well?).

I get random crashes in my s390 KVM guests after reboot.
Reverting both patches together with commit decd9b8 "vhost: use vhost_desc
instead of vhost_log" to
make it compile again) on top of linux-next-1218 makes the problem go away.

Looks like the batched version is not yet ready for prime time. Can you drop
these patches until
we have fixed the issues?

Christian

On Wed, Dec 18, 2019 at 03:43:43PM +0100, Christian Borntraeger
wrote:
> Michael,
> 
> with 
> commit db7286b100b503ef80612884453bed53d74c9a16
(refs/bisect/skip-db7286b100b503ef80612884453bed53d74c9a16)
>     vhost: use batched version by default
> plus
> commit 6bd262d5eafcdf8cdfae491e2e748e4e434dcda6 (HEAD, refs/bisect/bad)
>     Revert "vhost/net: add an option to test new code"
> to make things compile (your next tree is not easily bisectable, can you
fix that as well?).
I'll try.
> 
> I get random crashes in my s390 KVM guests after reboot.
> Reverting both patches together with commit decd9b8 "vhost: use
vhost_desc instead of vhost_log" to
> make it compile again) on top of linux-next-1218 makes the problem go away.
> 
> Looks like the batched version is not yet ready for prime time. Can you
drop these patches until
> we have fixed the issues?
> 
> Christian
> 
Will do, thanks for letting me know.

-- 
MST

On 18.12.19 16:10, Michael S. Tsirkin wrote:
> On Wed, Dec 18, 2019 at 03:43:43PM +0100, Christian Borntraeger wrote:
>> Michael,
>>
>> with 
>> commit db7286b100b503ef80612884453bed53d74c9a16
(refs/bisect/skip-db7286b100b503ef80612884453bed53d74c9a16)
>>     vhost: use batched version by default
>> plus
>> commit 6bd262d5eafcdf8cdfae491e2e748e4e434dcda6 (HEAD, refs/bisect/bad)
>>     Revert "vhost/net: add an option to test new code"
>> to make things compile (your next tree is not easily bisectable, can
you fix that as well?).
> 
> I'll try.
> 
>>
>> I get random crashes in my s390 KVM guests after reboot.
>> Reverting both patches together with commit decd9b8 "vhost: use
vhost_desc instead of vhost_log" to
>> make it compile again) on top of linux-next-1218 makes the problem go
away.
>>
>> Looks like the batched version is not yet ready for prime time. Can you
drop these patches until
>> we have fixed the issues?
>>
>> Christian
>>
> 
> Will do, thanks for letting me know.
I have confirmed with the initial reporter (internal test team) that <driver
name='qemu'/>
with a known to be broken linux next kernel also fixes the problem, so it is
really the
vhost changes.