V6: [PATCH] x86: Install <sys/platform/x86.h> [BZ #26124]

[Florian Weimer]

* H. J. Lu:

>> One thing I still dislike (sorry) is the asymmetry between the usable
>> and feature checks.  For example, why is there are usability check for
>> VAES, but not for AES?  I believe the reason is that VAES depends on
>> AVX/AVX2, but AES only depends on SSE2.  But even that suggests to me
>> that for 32-bit, there should be a usable gate for that (which is false
>> if SSE2 support has been masked).
>
> CPU with AES must have SSE2.  I don't think we need explicit check
> for SSE2.

But SSE2 needs operating system support, so we get the usable vs
available distinction this way.  I think.

Thanks,
Florian