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Date:   Fri, 23 Apr 2021 21:57:54 +0200
From:   Borislav Petkov <bp@alien8.de>
To:     Len Brown <lenb@kernel.org>
Cc:     Willy Tarreau <w@1wt.eu>, Andy Lutomirski <luto@kernel.org>,
        Florian Weimer <fweimer@redhat.com>,
        "Bae, Chang Seok" <chang.seok.bae@intel.com>,
        Dave Hansen <dave.hansen@intel.com>, X86 ML <x86@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>, linux-abi@vger.kernel.org,
        "libc-alpha@sourceware.org" <libc-alpha@sourceware.org>,
        Rich Felker <dalias@libc.org>, Kyle Huey <me@kylehuey.com>,
        Keno Fischer <keno@juliacomputing.com>
Subject: Re: Candidate Linux ABI for Intel AMX and hypothetical new related
 features
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On Fri, Apr 23, 2021 at 03:35:30PM -0400, Len Brown wrote:
> Yes.  If a library decides to execute AMX instructions on behalf
> of a task, the kernel will allocate an 8KB context switch buffer
> on behalf of that task.

Again, the library should ask the kernel first whether it supports AMX.
And the process should decide whether to use AMX - not the library on
its own, on behalf of the process.

> Granted, if you find a reason to dislike AMX, the mechanisms to disable
> it today are on a system-wide basis, not on a process or task basis.

Again, I don't dislike the feature. I don't want libraries jumping on
new features without asking the process or the kernel first especially
when those features have performance implications and need kernel
support.

-- 
Regards/Gruss,
    Boris.

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