libvirt users - Jul 2012 - Setting CPU type for a vm

I have a Windows XP vm and would like to know how should I set its cpu 
so it is seen by the vm as a proper 32bit one. In its xml file, I have

   <os>
     <type arch='i686'
machine='rhel6.2.0'>hvm</type>
     <boot dev='cdrom'/>
     <boot dev='hd'/>
     <bootmenu enable='yes'/>
   </os>

And this is the machine I have (an intel i5):

[root at vmhost ~]# virsh nodeinfo
CPU model:           x86_64
CPU(s):              4
CPU frequency:       1600 MHz
CPU socket(s):       1
Core(s) per socket:  4
Thread(s) per core:  1
NUMA cell(s):        1
Memory size:         5904548 kB

and this is what virsh thinks my vm has:

[root at vmhost ~]# virsh vcpuinfo xp
VCPU:           0
CPU:            2
State:          running
CPU time:       521.3s
CPU Affinity:   yyyy

[root at vmhost ~]#

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?

On 07/18/2012 08:45 PM, Mauricio Tavares wrote:
>     I have a Windows XP vm and would like to know how should I set its
> cpu so it is seen by the vm as a proper 32bit one. In its xml file, I have
> 
>   <os>
>     <type arch='i686'
machine='rhel6.2.0'>hvm</type>
That's the correct way.
> and this is what virsh thinks my vm has:
> 
> [root at vmhost ~]# virsh vcpuinfo xp
> VCPU:           0
This looks like a bug - a guest cannot exist without at least one vcpu.
> CPU:            2
That only says your host has 2 cpus that the guest can utilize; it says
nothing about what type of cpu the guest will see.
> 
> 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?

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.

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

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