[Qemu-devel] Re: [PATCH] introduce kvm64 CPU

[Andre Przywara]

Glauber Costa wrote:
> On Fri, Aug 21, 2009 at 12:41 PM, Avi Kivity<address@hidden> wrote:
> > On 08/21/2009 12:34 AM, Andre Przywara wrote:
> > > In addition to the TCG based qemu64 type let's introduce a kvm64 CPU type,
> > > which is the least common denominator of all KVM-capable x86-CPUs
> > > (based on Intel Pentium 4 Prescott). It can be used as a base type
> > > for migration.
> > Typically users will want more specialized greatest common denomiator cpu
> > types; if a site has standardized on recent hardware they will want the
> > features of that hardware exposed.
> >
> > I think this is best left to management software, which has more information
> > about the migration pool.
> I believe what we want is an automatic tool that will connect to a
> list of machines,and determine which qemu cpu type we should use.
> Doesn't sound like black magic...
I already have such a basic tool. It uses ssh (with pubkey) to connect 
to the target machine, then uses dd on /dev/cpu/0/cpuid to get the CPUID 
info. This requires cpuid.ko to be loaded and the permissions on the 
device file to be sufficient (the appropriate udev patch is already 
upstream). It then computes the least common denominator bits from 
several machines.
Were you thinking of that approach or do you want to include this host 
CPUID functionality into QEMU (somehow embedded in the migration handler)?

Regards,
Andre.

--
Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany
Tel: +49 351 488-3567-12
----to satisfy European Law for business letters:
Advanced Micro Devices GmbH
Karl-Hammerschmidt-Str. 34, 85609 Dornach b. Muenchen
Geschaeftsfuehrer: Jochen Polster; Thomas M. McCoy; Giuliano Meroni
Sitz: Dornach, Gemeinde Aschheim, Landkreis Muenchen
Registergericht Muenchen, HRB Nr. 43632