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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <YIMmwhEr46VPAZa4@zn.tnic>
Date:   Fri, 23 Apr 2021 21:57:54 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Len Brown <lenb@...nel.org>
Cc:     Willy Tarreau <w@....eu>, Andy Lutomirski <luto@...nel.org>,
        Florian Weimer <fweimer@...hat.com>,
        "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@...rceware.org" <libc-alpha@...rceware.org>,
        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, 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