Re: [tip: x86/fpu] x86/arch_prctl: Add AMX feature numbers as ABI constants

[Chang S. Bae]

On 3/22/2023 1:14 PM, tip-bot2 for Chang S. Bae wrote:
> The following commit has been merged into the x86/fpu branch of tip:
>
> x86/arch_prctl: Add AMX feature numbers as ABI constants
>
> Each distinct XSAVE feature has a number assigned to it.  Among other
> things, the number determines the ordering of features in the XSAVE
> buffer and is also used to generate XSAVE bitmasks like the value
> for XCR0.
>
> AMX state is dynamically enabled by the architecture-specific prctl().
> This prctl() takes one XSAVE feature number as an argument.  However, the
> feature numbers are not defined in any readily available userspace headers.
> The means that each userspace app trying to use dynamic feature prctl()s
> will likely end up defining their own constants for each feature.
>
> Since these feature numbers are a part of the uabi, expose them in the
> prctl() uabi header.  Save everyone the trouble of looking them up and
> defining their own.
>
> [ dhansen: expand changelog a bit ]

Sorry, it looks like I was not diligent enough to explain what those 
numbers are and that they are now part of the ABI.

Thank you for the write-up.

Chang