Re: [Patch 3/6] kvm: svm: Add support for XSAVES on AMD

Paolo Bonzini
2019-10-10T16:04:27Z

On 10/10/19 16:42, Aaron Lewis wrote:
>>> Hoist support for IA32_XSS so it can be used for both AMD and Intel,
>>> instead of for just Intel.
>>>
>>> AMD has no equivalent of Intel's "Enable XSAVES/XRSTORS" VM-execution
>>> control. Instead, XSAVES is always available to the guest when supported
>>> on the host.
>>
>> You could add that implement the XSAVES check based on host's features
>> and move the MSR_IA32_XSS msr R/W from Intel only code to the common
>> code.
>
> Isn't this covered by my comments? I mention that we are hoisting
> IA32_XSS to common code in the first comment, then in the second
> comment I say that XSAVES is available in the guest when supported on
> the host.

Yes, I agree.

Perhaps you can add something like "Fortunately, right now Linux does
not use MSR_IA32_XSS so the guest's usage of XSAVES will be a glorified
XSAVEC, and cannot bypass vmexits for MSR loads and stores".

Paolo