[libvirt] Unable to start Nehalem VM on Nehalem host

[Jiri Denemark]

On Mon, Mar 10, 2014 at 15:58:01 +0100, Ruben Kerkhof wrote:
> Hi list,
> 
> I'm trying to debug a strange issue I have, and I'd appreciate some help.
> 
> I've upgraded libvirt to 1.2.2, on Scientific Linux, with qemu-kvm-0.12.1.2-2.415.el6_5.3
> 
> cpuModellsAllowed then does a strcmp between “Nehalem” and "Nehalem  Intel Core i7 9xx (Nehalem Class Core i7)” which fails, and the vm fails to start with:
> 2014-03-10 14:56:16.917+0000: 8328: info : qemuDomainDefineXML:6231 : Creating domain '530df8bd-7b64-4553-b4f4-18922e1327bf'
> 2014-03-10 14:56:17.114+0000: 8329: warning : x86Decode:1515 : Preferred CPU model Nehalem not allowed by hypervisor; closest supported model will be used
> 2014-03-10 14:56:17.114+0000: 8329: error : x86Decode:1571 : internal error: Cannot find suitable CPU model for given data

Yeah, this is a result of using upstream libvirt with downstream
qemu-kvm. The change that made qemu's list of supported CPU models more
verbose was backported from upstream to qemu-kvm-0.12.1.2-* and thus
downstream libvirt had to be fixed to correctly handle that. However,
upstream QEMU made the output more verbose after libvirt switched to
using QMP for checking supported CPU models. See [1] thread for a patch
and a discussion which resulted in not applying the patch.

[1] https://www.redhat.com/archives/libvir-list/2012-October/msg00251.html

Jirka