[libvirt-users] Migration hangs on Gentoo with KVM

[Jonathan Stoppani]

On Aug 1, 2011, at 18:01 , Jonathan Stoppani wrote:

> 
> On Aug 1, 2011, at 16:50 , Jonathan Stoppani wrote:
> 
>> 
>> On Aug 1, 2011, at 16:33 , Eric Blake wrote:
>> 
>>> [re-adding the list]
>> 
>> Sorry about that, still not used to mailman lists which don't put the list address in the reply-to field. ;-)
>> 
>>>> Thanks for the prompt answer Eric! Yes, nc has a q option:
>>>> 
>>>> -q, --hold-timeout=SEC1[:SEC2]   Set hold timeout(s) for local [and remote]
>>> 
>>> Glad to hear that we found root cause to your problems, then.
>>> 
>>>> 
>>>> The bug specifically refers to ssh, does that mean that it should work over tcp?
>>> 
>>> The problem is that libvirt is trying to start a remote nc session over ssh; but looking at http://libvirt.org/remote.html, it looks like ssh is the only protocol using nc in that manner (so yes, you can probably avoid the issue by using tcp or tls).  Meanwhile, I think you can work around it without patching libvirt, by using this as your remote URI:
>>> 
>>> qemu+ssh://user@remotehost/system?netcat=/path/to/nc-wrapper
>>> 
>>> where nc-wrapper is an executable script installed on remotehost, looking like:
>>> 
>>> #!/bin/sh
>>> exec /path/to/real/nc -q0 "$@"
>> 
>> Just tried this, but still hangs; will try tcp and report the results.
>> 
>> ~Jonathan
> 
> Tested using qemu+tcp and it hangs the same. If I interrupt the migration (^C), the domain is correctly destroyed on the destination but left in the paused state on the source. If I try to start it manually, I obtain this error:
> 
> # virsh resume 1
> error: Failed to resume domain 1
> error: Timed out during operation: cannot acquire state change lock
> 
> Any insights?

Can someone shed some light on the libvirt locking possibilities? It seems to me that sanlock is not supported on gentoo (and libvirt is compiled using --without-sanlock); could this be the cause of the problem?

Is there some way to explicitly set the locking mechanism to a noop in the libvirt configuration?

~Jonathan