Re: [RFC PATCH 22/22] x86/fpu/xstate: Introduce boot-parameters for control some state component support

[Andy Lutomirski]

On Thu, Oct 1, 2020 at 1:43 PM Chang S. Bae <chang.seok.bae@xxxxxxxxx> wrote:
>
> "xstate.disable=0x6000" will disable AMX on a system that has AMX compiled
> into XFEATURE_MASK_USER_SUPPORTED.

Can we please use words for this?  Perhaps:

xstate.disable=amx,zmm

and maybe add a list in /proc/cpuinfo or somewhere in /proc or /sys
that shows all the currently enabled xsave states.

>
> "xstate.enable=0x6000" will enable AMX on a system that does NOT have AMX
> compiled into XFEATURE_MASK_USER_SUPPORTED (assuming the kernel is new
> enough to support this feature).

This sounds like it will be quite confusing to anyone reading the
kernel code to discover that a feature that is not "SUPPORTED" is
nonetheless enabled.