Open Stack

On Thu, Jul 09, 2015 at 12:00:15PM -0600, David Medberry wrote:
> Hi,
> 
> When trying to live-migrate between two distinct CPUs, I kind of expect
> there to be issues. Which is why openstack supports the "cpu_mode=custom",
> "cpu_model=MODELNAME" flags for libvirt.
> 
> When I set those to some Lowest Common Denominator (and restart
> everything), I still git the issue. I've set both systems to SandyBridge
> and tested as well as Conroe. The actual CPUs are Ivy Bridge and Haswell
> (newer than SandyBridge and supersets thereof.)
> 
> The Older->Newer migration works fine (even without setting a cpu_model)
> but the newer to older never works.
> 
> Specfics:
> OpenStack Juno.2
> LibVirt: 1.2.2
> 
> Older: model name : Intel(R) Xeon(R) CPU E5-2650 v2 @ 2.60GHz (Ivy Bridge)
> Newer: model name : Intel(R) Xeon(R) CPU E5-2650 v3 @ 2.30GHz (Haswell)
> 
> Daniel, Operators: Any ideas?

In versions of Nova prior to Liberty, nova did an incorrect CPU model
comparison. It checks the source *host* CPU model against the dest
host CPU model, instead of checking the *guest* CPU model against the
dest host CPU model.

This is fixed in Liberty, provided you have the cpu_mode=custom and
cpu_modelk=MODELNAME parameters set. Unfortunately the fix will only
work for guests that are launched under Liberty codebase as it needed
a database addition. So if you have existing running guests from Juno
those need restarting after upgrade.

Regards,
Daniel
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