Re: [Xen-devel] [PATCH] xen: mask XSAVE in cpuid since we don't allowguests to use it

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 09/03/2009 11:26, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:

>>>> Jeremy Fitzhardinge <jeremy@xxxxxxxx> 08.03.09 06:31 >>>
>> Mask X86_FEATURE_XSAVE in cpuid leaf 1, ecx, as we don't allow guests to
>> use it (by setting cr4.OSXSAVE).
> 
> I actually disagree to this. The kernel should be dealing with the situation
> by inspecting the OSXSAVE bit in CPUID when running under Xen, since it's
> really Xen that's the 'OS' for that particular feature.
> 
> Then, once Keir gets willing to take Intel xsave patch(es), no further change
> is going to be needed here. And the same kernel will work (assuming it has
> no other dependencies) on older Xen not having this bit masked.

It seems reasonable to mask XSAVE for now though. I don't think it can
usefully be used without some Xen support.

 -- Keir



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