[libvirt-users] Setting CPU type for a vm

[Mauricio Tavares]

On Thu, Jul 19, 2012 at 9:54 AM, Eric Blake <eblake at redhat.com> wrote:
>> But, the vm reports it not only as a 286 but also claims not to have the
>> right drivers for it. How can I make the vm see it as a 686 or something
>> like that?
>
> Huh?  The guest should be seeing it's CPU as a 686.  What is the actual
> error message you are seeing?
>
      When I set it as above and then cpu as qemu32, XP reports it is
a Intel Pentium II Processor. Here is the message seen in Windows
itself (Control Panel->System->Processors):

Windows cannot load the device driver for this hardware. The driver may be
corrupted or missing. (Code 39)

I also tried something like  (still keeping arch='i686' ):

  <cpu match='exact'>
    <model fallback='allow'>coreduo</model>
    <topology sockets='1' cores='2' threads='1'/>
  </cpu>

Which led to

"A driver (service) for this device has been disabled.  An alternate
driver may be providing this functionality. (Code 32)"

> Also, note that you need not constrain your guest cpu to i686 unless you
> specifically plan to migrate your guest to a different host where the
> host is running in 32-bit mode instead of the more typical 64-bit mode;
> all 32-bit operating systems will run equally well on x86_64 cpus.
>
      That is good to know. I was actually wondering if you were
building code inside the VM and asked it to optimize to whatever cpu
you specify, it would do so. Another reason is that some stuff I want
to move into vms is using specific cpus and I want to make the vm as
close to the original setup as I reasonably can.

> --
> Eric Blake   eblake at redhat.com    +1-919-301-3266
> Libvirt virtualization library http://libvirt.org
>