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

[Gleb Natapov <gleb@redhat.com>]

On Mon, Mar 12, 2012 at 01:55:34PM +0000, Daniel P. Berrange wrote:
> 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
> 
So you goal is to follow closely what QEMU does? Fine by me, but then
QEMU design decisions in this ares should not rely on libvirt (as in
"this is libvirt job").

--
			Gleb.