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From: Len Brown <lenb@kernel.org>
Date: Fri, 26 Mar 2021 23:39:18 -0400
Message-ID: <CAJvTdKm8aQPwQMXFQWgVb5dfJ88ds3d0=uHOyWeueUqfya9Nsw@mail.gmail.com>
Subject: Re: Candidate Linux ABI for Intel AMX and hypothetical new related
 features
To: Andy Lutomirski <luto@kernel.org>
Cc: "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>, 
 libc-alpha <libc-alpha@sourceware.org>, Florian Weimer <fweimer@redhat.com>, 
 Rich Felker <dalias@libc.org>, Kyle Huey <me@kylehuey.com>, 
 Keno Fischer <keno@juliacomputing.com>, Linux API <linux-api@vger.kernel.org>
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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