Re: [Xen-devel] [PATCH] x86/intel: Protect set_cpuidmask() against #GP faults

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 05/06/14 15:56, Jan Beulich wrote:
>>>> On 05.06.14 at 16:24, <andrew.cooper3@xxxxxxxxxx> wrote:
>> On 05/06/14 15:05, Jan Beulich wrote:
>>>>>> On 05.06.14 at 13:19, <andrew.cooper3@xxxxxxxxxx> wrote:
>>>> * Call set_cpuidmask() unconditionally so faulting-capable hardware still 
>>>> gets
>>>>   a log message indicating to the user why their command line arguments are
>>>>   not taking effect.
>>> I don't think Intel will particularly like this part.
>> Why not?
> Because they try to deprecate masking in favor of CPUID faulting as
> much as they can.
>
> Jan
>

And that is a very good thing.

However, masking is only available SandyBridge and older (for a few
generations), whereas faulting is only available on IvyBridge and newer.

If the user tries setting the cpuid_mask_XXX in the hope that masking
occurs, It is kind to give them an error back explaining why nothing is
happening.

~Andrew

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