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

[Keir Fraser <keir.xen@xxxxxxxxx>]

On 01/07/2013 10:44, "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?
>> 
>> Jan
> 
> Will this not cause a VMexit on each swapgs instruction, as the
> instruction itself does write to MSR 0xC0000102?
> 
> I have looked quite closely through the Intel manuals and cant find
> confirmation one way or another.

Only RDMSR/WRMSR trap on the MSR bitmaps.

> ~Andrew
> 
>> 
>> 
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> 
> 
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