[ovirt-users] Going crazy with emory hotplug on 3.6

[Markus Stockhausen]

> Von: Nir Soffer [nsoffer at redhat.com]
> Gesendet: Sonntag, 21. Februar 2016 14:10
> An: Markus Stockhausen; Francesco Romani
> Cc: users
> Betreff: Re: [ovirt-users] Going crazy with emory hotplug on 3.6
> 
> Adding Francesco.
> 
> On Sun, Feb 21, 2016 at 2:19 PM, Markus Stockhausen
> <stockhausen at collogia.de> wrote:
> > Hi there,
> >
> > we upgraded Ovirt to 3.6, added the first Centos 7 host and created a new cluster
> > with compatibility level 3.6 around it. Until now we are running with Fedora nodes.
> > The first Linux VMs are already running in the new cluster. With the first Windows
> > VM migrated over we once again face the old Windows activation problem. The
> > system request us to reactivate the Windows license.
> >
> > To make a long story short: I manually compiled OVirt/Centos qemu 2.3 and enabled
> > the old Fedora machine type pc-1.0. Afterwards I had to lower compatibility level
> > of the cluster to 3.5 because Ovirt tried to start the old machine type with memory
> > hotplug support -> FAIL. Finally everything is up and running.
> >
> > Conclusion: OVirt always tries to start VMs with memory hotplug in a current 3.6
> > cluster. The machine type (e.g. rhel6.6.0) ist not checked and qemu will fail during
> > startup with the message: qemu-kvm: "-memory 'slots|maxmem'" is not supported"
> > Older post on mailing list: http://lists.ovirt.org/pipermail/users/2016-January/037034.html
> >
> > Question: What is the desired way to disable the hotplug qemu parametrization
> > for single VMs in 3.6 cluster? It MUST be possible otherwise it would not make
> > sense to choos older machine types.
> >
> > Markus
> >

Hi Nir & Francesco,

with my qemu modifications in place I wrote a before_vm_start hook. It will remove
memory hotplug from libvirt XML if VM is defined with machine type pc-1.0.

#!/usr/bin/python
import os
import sys
import hooking
import traceback
domxml = hooking.read_domxml()
os = domxml.getElementsByTagName('os')[0]
tp = os.getElementsByTagName('type')[0]
mc = tp.getAttribute('machine')
if mc == 'pc-1.0':
  m = domxml.getElementsByTagName('maxMemory')[0]
  d.removeChild(m)
hooking.write_domxml(domxml)

With this I'm able to start a Fedora cluster 3.5 based Windows VM on a Centos 3.6 cluster. 
And most important: It is still ACTIVATED. 

Just filed a RH BZ: https://bugzilla.redhat.com/show_bug.cgi?id=1310458

Markus
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