[libvirt] [RFC] Support for CPUID masking

Jim Paris jim at jtan.com
Wed Sep 2 15:59:39 UTC 2009


Jiri Denemark wrote:
> Hi,
> 
> We need to provide support for CPU ID masking. Xen and VMware ESX are examples
> of current hypervisors which support such masking.
> 
> My proposal is to define new 'cpuid' feature advertised in guest
> capabilities:
...
> <domain type='xen' id='42'>
>     ...
>     <features>
>         <pae/>
>         <acpi/>
>         <apic/>
>         <cpuid>
>             <mask level='1' register='ebx'>
>                 xxxx:xxxx:0000:1010:xxxx:xxxx:xxxx:xxxx
>             </mask>
...
> What are your opinions about this?

I think it's too low-level, and the structure is x86-specific.  QEMU
and KVM compute their CPUID response based on arguments to the -cpu
argument, e.g.:

   -cpu core2duo,model=23,+ssse3,+lahf_lm

I think a similar structure makes more sense for libvirt, where the
configuration generally avoids big blocks of binary data, and the 
XML format should suit other architectures as well.

-jim




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