Re: [Qemu-devel] latest rc: virtio-blk hangs forever after migration

[Andrey Korolyov]

On Thu, Jul 17, 2014 at 1:28 AM, Marcin Gibuła <address@hidden> wrote:
>> Tested on iscsi pool, though there are no-cache requirement and rbd
>> with disabled cache may survive one migration but iscsi backend hangs
>> always. As it was before, just rolling back problematic commit fixes
>> the problem and adding cpu_synchronize_all_states to migration.c has
>> no difference at a glance in a VM` behavior. The problem consist at
>> least two separate ones: the current hang and behavior with the
>> unreverted patch from agraf - last one causes live migration with
>> writeback cache to fail, cache=none works well in any variant which
>> survives first condition. Marcin, would you mind to check the current
>> state of the problem on your environments in a spare time? It is
>> probably easier to reproduce on iscsi because of way smaller time
>> needed to set it up, command line and libvirt config attached
>> (v2.1.0-rc2 plus iscsi-1.11.0).
>
>
> Ok, but what exacly do you want me to test?
>
> Just to avoid any confusion, originally there were two problems with
> kvmclock:
>
> 1. Commit a096b3a6732f846ec57dc28b47ee9435aa0609bf fixes problem when clock
> drift (?) caused kvmclock in guest to report time in past which caused guest
> kernel to hang. This is hard to reproduce reliably (probably as it requires
> long time for drift to accumulate).
>
> 2. Commit 9b1786829aefb83f37a8f3135e3ea91c56001b56 fixes regression caused
> by a096b3a6732f846ec57dc28b47ee9435aa0609bf which occured during
> non-migration operations (drive-mirror + pivot), which also caused guest
> kernel to hang. This is trival to reproduce.
>
> I'm using both of them applied on top of 2.0 in production and have no
> problems with them. I'm using NFS exclusively with cache=none.
>
> So, I shall test vm-migration and drive-migration with 2.1.0-rc2 with no
> extra patches applied or reverted, on VM that is running fio, am I correct?
>

Yes, exactly. ISCSI-based setup can take some minutes to deploy, given
prepared image, and I have one hundred percent hit rate for the
original issue with it.

> --
> mg