[libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt

Gleb Natapov gleb at redhat.com
Sun Dec 18 09:58:16 UTC 2011

On Thu, Dec 15, 2011 at 03:42:44PM +0000, Daniel P. Berrange wrote:
> On Thu, Dec 15, 2011 at 03:54:15PM +0100, Jiri Denemark wrote:
> > Hi,
> > 
> > Recently I realized that all modern CPU models defined in
> > /etc/qemu/target-x86_64.conf are useless when qemu is used through libvirt.
> > That's because we start qemu with -nodefconfig which results in qemu ignoring
> > that file with CPU model definitions. We have a very good reason for using
> > -nodefconfig because we need to control the ABI presented to a guest OS and we
> > don't want any configuration file that can contain lots of things including
> > device definitions to be read by qemu. However, we would really like the new
> > CPU models to be understood by qemu even if used through libvirt. What would
> > be the best way to solve this?
> Ideally libvirt would just write out a config file with the CPU
> that was configured in libvirt and pass -readconfig /var/lib/libvirt/qemu/guestcpu.conf
> That way libvirt can configure CPU models without regard for
> what the particular QEMU version might have in its config.
And how libvirt would know that particular QEMU/kvm version can create
this CPU. Managing cpuid shouldn't be libvirt busyness.


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