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

[Marcin Gibuła]

> 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?

--
mg