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

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Message-ID: <CAJvTdKm8aQPwQMXFQWgVb5dfJ88ds3d0=uHOyWeueUqfya9Nsw@mail.gmail.com>
Date:   Fri, 26 Mar 2021 23:39:18 -0400
From:   Len Brown <lenb@...nel.org>
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>,
        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>,
        Linux API <linux-api@...r.kernel.org>
Subject: Re: Candidate Linux ABI for Intel AMX and hypothetical new related features

Hi Andy,

Say a mainline links with a math library that uses AMX without the
knowledge of the mainline.
Say the mainline is also linked with a userspace threading library
that thinks it has a concept of XSAVE area size.

Wouldn't the change in XCR0, resulting in XSAVE size change, risk
confusing the threading library?

thanks,
Len Brown, Intel Open Source Technology Center