Re: [PATCH] CPUID Masking MSRs

Avi Kivity
2009-01-07T10:08:07Z

Alexander Graf wrote:
> Current AMD CPUs support masking of CPUID bits. Using this functionality,
> a VMM can limit what features are exposed to the guest, even if it's not
> using SVM/VMX.
>
> While I'm not aware of any open source hypervisor that uses these MSRs
> atm, VMware ESX does and patches exist for Xen, where trapping CPUID is
> non-trivial.
>
> This patch implements emulation for this masking, which is pretty trivial
> because we're intercepting CPUID anyways.
>
> Because it's so simple and can be pretty effective, I put it into the
> generic code paths, so VMX benefits from it as well.
>
>

Missing save/restore support.

Note that Intel has similar functionality, called FlexMigration IIRC,
likely using different MSRs.

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