Re: [PATCH] CPUID Masking MSRs

Alexander Graf
2009-01-07T10:10:41Z

On 07.01.2009, at 11:07, Avi Kivity wrote:

> 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.

Right. I keep forgetting about that one ;-).

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

Hum. I'll take a look at it to see if that's as easy to implement then.

Alex