Re: [RFC] CPUID usage for interaction between Hypervisors and Linux.

[Anthony Liguori]

Jeremy Fitzhardinge wrote:
> Alok Kataria wrote:
>
> I guess, but the bulk of the uses of this stuff are going to be 
> hypervisor-specific.  You're hard-pressed to come up with any other 
> generic uses beyond tsc.

And arguably, storing TSC frequency in CPUID is a terrible interface 
because the TSC frequency can change any time a guest is entered.  It 
really should be a shared memory area so that a guest doesn't have to 
vmexit to read it (like it is with the Xen/KVM paravirt clock).

Regards,

Anthony Liguori

>   In general, if a hypervisor is going to put something in a special 
> cpuid leaf, its because there's no other good way to represent it.  
> Generic things are generally going to appear as an emulated piece of 
> the virtualized platform, in ACPI, DMI, a hardware-defined cpuid leaf, 
> etc...

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