linux-kernel - Re: Candidate Linux ABI for Intel AMX and hypothetical new related features

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Date:   Wed, 31 Mar 2021 10:24:20 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     "Bae, Chang Seok" <chang.seok.bae@...el.com>,
        Dave Hansen <dave.hansen@...el.com>, X86 ML <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, linux-abi@...r.kernel.org,
        libc-alpha <libc-alpha@...rceware.org>,
        Florian Weimer <fweimer@...hat.com>,
        Rich Felker <dalias@...c.org>, Kyle Huey <me@...ehuey.com>,
        Keno Fischer <keno@...iacomputing.com>
Subject: Re: Candidate Linux ABI for Intel AMX and hypothetical new related
 features

On Fri, Mar 26, 2021 at 04:12:25PM -0700, Andy Lutomirski wrote:
> To detect features and control XCR0, we add some new arch_prctls:
> 
> arch_prctl(ARCH_GET_XCR0_SUPPORT, 0, ...);
> 
> returns the set of XCR0 bits supported on the current kernel.
> 
> arch_prctl(ARCH_GET_XCR0_LAZY_SUPPORT, 0, ...);
> 
> returns 0.  See below.
> 
> arch_prctl(ARCH_SET_XCR0, xcr0, lazy_states, sigsave_states,
> sigclear_states, 0);

Right, but I'd simply replace that "XCR0" arch detail, more or less,
with "XSTATE":

ARCH_GET_XSTATE_SUPPORT
ARCH_GET_XSTATE_LAZY_SUPPORT
ARCH_SET_XSTATE or ARCH_ENABLE_XSTATE or so

to denote that this is controlling XSTATE handling while the XCR0 thing
is the control register and when in the future something else does
control that (XCR0[63] is one provision for that) then we're still
on-point with the naming.

> Thoughts?

FTR, I really like the aspect of apps *requesting* handling of
non-legacy, fat states and latter remaining off otherwise in order to
keep the sanity of everyone involved.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette