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

[Itamar Heim]

On 03/12/2012 10:19 PM, Ayal Baron wrote:
> ----- Original Message -----
> > On 03/12/2012 02:12 PM, Itamar Heim wrote:
> > > On 03/12/2012 09:01 PM, Anthony Liguori wrote:
> > > > It's a trade off. From a RAS perspective, it's helpful to have
> > > > information about the host available in the guest.
> > > >
> > > > If you're already exposing a compatible family, exposing the
> > > > actual
> > > > processor seems to be worth the extra effort.
> > >
> > > only if the entire cluster is (and will be?) identical cpu.
> >
> > At least in my experience, this isn't unusual.
>
> I can definitely see places choosing homogeneous hardware and upgrading every 
> few years.
> Giving them max capabilities for their cluster sounds logical to me.
> Esp. cloud providers.

they would get same performance as from the matching "cpu family".
only difference would be if the guest known the name of the host cpu.

> > > or if you don't care about live migration i guess, which could be
> > > hte case for
> > > clouds, then again, not sure a cloud provider would want to expose
> > > the physical
> > > cpu to the tenant.
> >
> > Depends on the type of cloud you're building, I guess.
>
> Wouldn't this affect a simple startup of a VM with a different CPU (if 
> motherboard changed as well cause reactivation issues in windows and fun things 
> like that)?

that's an interesting question, I have to assume this works though, 
since we didn't see issues with changing the cpu family for guests so far.