On Wed, Jul 29, 2015 at 09=11=21AM +0100, Dr. David Alan Gilbert wrote: > * Eduardo Otubo (eduardo.ot...@profitbricks.com) wrote: > > On Tue, Jul 28, 2015 at 04=19=46PM +0100, Dr. David Alan Gilbert wrote: > > > * Eduardo Otubo (eduardo.ot...@profitbricks.com) 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 you driving this via libvirt or using qemu monitor directly? > If the latter, can you please get an 'info migrate' from the source > and an 'info status' from the destination at the end of migrate.
I'm using qemu command line directly. And I got the problem :) See
below.
>
> > > 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.
>
> OK, good.
>
> > >
> > > 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.
>
> OK, and this pair of machines, have you tried both directions - i.e.
> going a->b and b->a - do both directions fail?
> Is the NFS server one of the two machines? If it is, and you're using
> libvirt,
> make sure that the directory the disks are on is an NFS mount on both
> machines; e.g. don't migrate directly from the NFS export.
>
> > 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.
>
> Yes, the challenge is to find what; and if it's something common
> we should try and find a way of spotting it.
>
> > Anyway, I'll keep tetsing different stable- branches until I find
> > something that works for me. I'll keep the mailing list posted.
>
> Could you share the qemu command line so we can see if we can
> spot anything?
Got the problem! I tried to simplify my qemu command line to the
smallest possible, excluding things I thought it could cause the issue.
With no further due, this is the argument:
-cpu 'Opteron_G4'
Without this argument everything works as it should, console responsive
and guest active :)
It says on the documentation[1] that it's possible to migrate between
AMD and Intel, but I think I got a corner case. Apparently I can't
specify the exact CPU model. Is this a known issue? Couldn't find any
reference on bugzilla or launchpad.
[1] - http://www.linux-kvm.org/page/Migration
--
Eduardo Otubo
ProfitBricks GmbH
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