linux-kernel - Re: vhost changes (batched) in linux-next after 12/13 trigger random crashes in KVM guests after reboot

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Date:   Wed, 18 Dec 2019 16:59:02 +0100
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        kvm list <kvm@...r.kernel.org>,
        Halil Pasic <pasic@...ux.ibm.com>
Subject: Re: vhost changes (batched) in linux-next after 12/13 trigger random
 crashes in KVM guests after reboot

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.