Re: [Xen-devel] vmx_disable_intercept_for_msr(v, MSR_SHADOW_GS_BASE)

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 01.07.13 at 11:44, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
> On 01/07/13 10:38, Jan Beulich wrote:
>>>>> On 28.06.13 at 23:02, Cyclonus J <cyclonusj@xxxxxxxxx> wrote:
>>> I am wondering if we can disable the VMX interception for
>>> MSR_SHADOW_GS_BASE as AMD is already doing that.
>> I can't immediately see any reason why we shouldn't be permitted
>> to do this, but I also don't think this should be performance critical.
>>
>> If you feel this is important, why don't you contribute a patch,
>> with its description saying under what conditions this can yield
>> measurable benefit?
> 
> Will this not cause a VMexit on each swapgs instruction, as the
> instruction itself does write to MSR 0xC0000102?

No - see the comments in vmx.c around the handling of that MSR.

Jan


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