New CPUID/MSR driver; virtualization hooks

H. Peter Anvin hpa at
Thu Apr 5 14:59:34 PDT 2007

Jeremy Fitzhardinge wrote:
> Zachary Amsden wrote:
>> Or implement anything useful at all ... perhaps it might be useful to
>> simply wrap them with an -ENOSYS in some cases.
>> Rusty, Jeremy. Chris - any feedback on MSR support?
> I've looked at hpa's patch a bit, but I don't quite get what the point
> is yet.  Is it that rdmsr/wrmsr can use multiple random registers, so
> its necessary to haul them all around?  And that cpuid might use more
> beyond the current eax-edx?

Yes, pretty much.  There are enough evidence that you can't trust CPU 
architecture to stay sane.  Inside Transmeta it was a constant battle, 
and we were a small company.

> Xen will trap and emulate any rd/wrmsr instructions, so I don't think it
> needs anything beyond native support.

If that's true for all hypervisors, then that's obviously the easiest 
all around.


More information about the Virtualization mailing list