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

[Daniel P. Berrange]

On Mon, Mar 12, 2012 at 03:53:38PM +0200, Gleb Natapov wrote:
> On Mon, Mar 12, 2012 at 01:50:18PM +0000, Daniel P. Berrange wrote:
> > On Mon, Mar 12, 2012 at 03:15:32PM +0200, Gleb Natapov wrote:
> > > On Mon, Mar 12, 2012 at 01:04:19PM +0000, Daniel P. Berrange wrote:
> > > > On Mon, Mar 12, 2012 at 09:52:27AM -0300, Eduardo Habkost wrote:
> > > > > On Sun, Mar 11, 2012 at 09:12:58AM -0500, Anthony Liguori wrote:
> > > > > > On 03/11/2012 08:27 AM, Gleb Natapov wrote:
> > > > > > >On Sat, Mar 10, 2012 at 12:24:47PM -0600, Anthony Liguori wrote:
> > > > > > >>Let's step back here.
> > > > > > >>
> > > > > > >>Why are you writing these patches?  It's probably not because you
> > > > > > >>have a desire to say -cpu Westmere when you run QEMU on your laptop.
> > > > > > >>I'd wager to say that no human has ever done that or that if they
> > > > > > >>had, they did so by accident because they read documentation and
> > > > > > >>thought they had to.
> > > > > 
> > > > > No, it's because libvirt doesn't handle all the tiny small details
> > > > > involved in specifying a CPU. All libvirty knows about are a set of CPU
> > > > > flag bits, but it knows nothing about 'level', 'family', and 'xlevel',
> > > > > but we would like to allow it to expose a Westmere-like CPU to the
> > > > > guest.
> > > > 
> > > > This is easily fixable in libvirt - so for the point of going discussion,
> > > > IMHO, we can assume libvirt will support level, family, xlevel, etc.
> > > > 
> > > And fill in all cpuid leafs by querying /dev/kvm when needed or, if TCG
> > > is used, replicating QEMU logic? And since QEMU should be usable without
> > > libvirt the same logic should be implemented in QEMU anyway.
> > 
> > I'm not refering to that. I'm saying that any data QEMU has in its
> > config file (/etc/qemu/target-x86_64.conf) should be represented
> > in the libvirt CPU XML. family, model, stepping, xlevel and
> > model_id are currently in QEMU CPU configs, but not in libvirt XML,
> > which is something we will fix. The other issues you mention are
> > completely independant of that.
> > 
> Eduardo is going to extend what can be configured in /etc/qemu/target-x86_64.conf
> and make CPU models name per machine type. What QEMU has now is not
> good enough. I doubt libvirt goal is to be as bad as QEMU :)

Of course not - libvirt will obviously be extended to cope with this
too


Daniel
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