From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57282) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WLGcn-0002mz-9k for qemu-devel@nongnu.org; Wed, 05 Mar 2014 13:33:09 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WLGcg-0006ar-0Z for qemu-devel@nongnu.org; Wed, 05 Mar 2014 13:33:01 -0500 Received: from mail-qg0-f51.google.com ([209.85.192.51]:63655) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WLGcf-0006af-Sl for qemu-devel@nongnu.org; Wed, 05 Mar 2014 13:32:53 -0500 Received: by mail-qg0-f51.google.com with SMTP id q108so3959571qgd.10 for ; Wed, 05 Mar 2014 10:32:53 -0800 (PST) From: Neil Skrypuch Date: Wed, 05 Mar 2014 13:32:51 -0500 Message-ID: <6723641.sIsB0JMXJF@skrypuch> In-Reply-To: <531749DC.6090402@suse.de> References: <1729828.TVLplOUlZS@skrypuch> <531749DC.6090402@suse.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="ISO-8859-1" Subject: Re: [Qemu-devel] Live migration results in non-working virtio-net device (sometimes) List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Andreas =?ISO-8859-1?Q?F=E4rber?= Cc: qemu-devel@nongnu.org, Stefan Hajnoczi , Juan Quintela On Wednesday 05 March 2014 16:59:24 Andreas F=E4rber wrote: > Am 30.01.2014 19:23, schrieb Neil Skrypuch: > > First, let me briefly outline the way we use live migration, as it = is > > probably not typical. We use live migration (with block migration) = to > > make backups of VMs with zero downtime. The basic process goes like= this: > >=20 > > 1) migrate src VM -> dest VM > > 2) migration completes > > 3) cont src VM > > 4) gracefully shut down dest VM > > 5) dest VM's disk image is now a valid backup > >=20 > > In general, this works very well. > >=20 > > Up until now we have been using qemu-kvm 1.1.2 and have not had any= =20 issues > > with the above process. I am now attempting to upgrade us to a newe= r > > version of qemu, but all newer versions I've tried occasionally res= ult in > > the virtio- net device ceasing to function on the src VM after step= 3. >=20 > While I don't know this particular symptom, I can definitely tell you= > that migrating from qemu-kvm to qemu is bound to fail unless you enab= le > at least a version_id change in piix4.c, possibly also in kvmvapic.c.= > Such errors would lead to migration not successfully completing thoug= h, > with cryptic error on the dest side. >=20 > Regards, > Andreas I should clarify, all of these migrations happen from same version to s= ame=20 version (and same host to same host). So 1.7.0 -> 1.7.0, 1.6.0 -> 1.6.0= , etc.=20 What we're looking for out of this is a clean copy of the disk image=20= (consistent and from a graceful shutdown) for backup purposes, without = having=20 to shut down the VM. I expected cross-version migration to be dicey and made a point of avoi= ding=20 it. - Neil