Re: [Qemu-devel] Live migration hangs after migration to remote host

[Eduardo Otubo]

On Tue, Jul 28, 2015 at 04=19=46PM +0100, Dr. David Alan Gilbert wrote:
> * Eduardo Otubo (address@hidden) wrote:
> > Hello all,
> > 
> > I'm facing a weird behavior on my tests: I am able to live migrate
> > between two virtual machines on my localhost, but not to another
> > machine, both using tcp.
> > 
> > * I am using the same arguments on the command line;
> > * Both virtual machines uses the same qcow2 file visible through NFS;
> > * Both machines are in the same subnet;
> > * Migration is being done from intel to intel;
> > * Same version of Qemu (github master - f8787f8723);
> > 
> > Using all above I am able to live migrate on the same host: between two
> > vms on local host or between two vms in the remote host; but when
> > migrating from local to remote, the guest hangs. I still can access its
> > console via ctrl+alt+2, though, and everything seems to be normal. If I
> > issue a reboote via console on the remote, the guest gets back to
> > normal.
> > 
> > Am I missing something here?
> 
> Just checking, but are you saying that as far as qemu is concerned, the 
> migration
> is happy, it's just the guest that's hung?

That's exactly the case. The console (via ctrl+alt+2) is active and
responding to all commands normally, but the screen (ctrl+alt+1) is
frozen and I can't interact with it at all.

> 
> Are the host clocks on the two hosts very close (there are lots of
> weird corner cases with mismatched clocks) - same time zone?

Yep. Both machines are in the same room and have the clock sync'ed.

> 
> Are you using cache=none (given that it's NFS shared)

I wasn't. But I tried again with cache=none and I got exactly the same
thing.

Also, I tried with stable-2.2 branch and got the same behavior. I really
think that's very unlikely to have unstable code of such an important
feature upstream, or on a stable- branch. Most probable thing is that
I have something wrong on my environment.

Anyway, I'll keep tetsing different stable- branches until I find
something that works for me. I'll keep the mailing list posted.

Thanks for the light!

-- 
Eduardo Otubo
ProfitBricks GmbH

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