[Openstack-operators] qemu 1.x to 2.0

Daniele Venzano daniele.venzano at eurecom.fr
Mon Oct 20 06:46:48 UTC 2014

We have the same setup (Icehouse on Ubuntu 12.04) and had similar 
issues. We downgraded qemu from 2.x to 1.x, as we cannot terminate all 
VMs for all users. We had non-resumable VMs also in the middle of the 
1.x series and nothing was documented in the changlelog.
We had to do the same downgrade with openvswitch, the newest version, 
under heavy load, corrupts packets in-transit, but we do not have the 
time to investigate the issue further.

We plan to warn our users in time for the next major upgrade to Juno 
that all VMs need to be terminated, probably during the Christmas 
holidays. I do not think they will be happy.
Seeing also all the problems we had upgrading Neutron from OVS to ML2, 
terminating all VMs is probably the best policy anyway during an 
OpenStack upgrade. Or you do lots of migrations and upgrade qemu one 
compute host at the time, but if something goes wrong you end-up with an 
angry user and a stuck VM.

It certainly is a big deal.

On 10/20/14 00:59, Joe Topjian wrote:
> Hello,
> We recently upgraded an OpenStack Grizzly environment to Icehouse 
> (doing a quick stop-over at Havana). This environment is still running 
> Ubuntu 12.04.
> The Ubuntu 14.04 release notes 
> <https://wiki.ubuntu.com/TrustyTahr/ReleaseNotes#Ubuntu_Server> make 
> mention of incompatibilities with 12.04 and moving to 14.04 and qemu 
> 2.0. I didn't think that this would apply for upgrades staying on 
> 12.04, but it indeed does.
> We found that existing instances could not be live migrated (as per 
> the release notes). Additionally, instances that were hard-rebooted 
> and had the libvirt xml file rebuilt could no longer start, either.
> The exact error message we saw was:
> "Length mismatch: vga.vram: 1000000 in != 800000"
> I found a few bugs that are related to this, but I don't think they're 
> fully relevant to the issue I ran into:
> https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/1308756
> https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1291321
> https://bugs.launchpad.net/nova/+bug/1312133
> We ended up downgrading to the stock Ubuntu 12.04 qemu 1.0 packages 
> and everything is working nicely.
> I'm wondering if anyone else has run into this issue and how they 
> dealt with it or plan to deal with it.
> Also, I'm curious as to why exactly qemu 1.x to 2.0 are incompatible 
> with each other. Is this just an Ubuntu issue? Or is this native of qemu?
> Unless I'm missing something, this seems like a big deal. If we 
> continue to use Ubuntu's OpenStack packages, we're basically stuck at 
> 12.04 and Icehouse unless we have all users snapshot their instance 
> and re-launch in a new cloud.
> Thanks,
> Joe
> _______________________________________________
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> OpenStack-operators at lists.openstack.org
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