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

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Date:   Sat, 27 Mar 2021 10:58:52 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Len Brown <lenb@...nel.org>
Cc:     Andy Lutomirski <luto@...nel.org>,
        "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

On Fri, Mar 26, 2021 at 11:39:18PM -0400, Len Brown wrote:
> Hi Andy,
> 
> Say a mainline links with a math library that uses AMX without the
> knowledge of the mainline.

What does this mean?  What happened to the context here?

> Say the mainline is also linked with a userspace threading library
> that thinks it has a concept of XSAVE area size.

How can the kernel (what I think you mean by "mainline" here) be linked
with a userspace library at all?

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

Shouldn't that be the job of the kernel and not userspace?

totally confused,

greg k-h