linux-kernel - Re: [PATCH v5 28/28] x86/fpu/amx: Clear the AMX state when appropriate

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Message-ID: <CAJvTdKmQjTmOCwUBk+3dhYzOdsZBadqVdqFUPKRMkfcTccJHuA@mail.gmail.com>
Date:   Mon, 24 May 2021 13:32:58 -0400
From:   Len Brown <lenb@...nel.org>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        "Chang S. Bae" <chang.seok.bae@...el.com>,
        Borislav Petkov <bp@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>, X86 ML <x86@...nel.org>,
        "Brown, Len" <len.brown@...el.com>,
        "Liu, Jing2" <jing2.liu@...el.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Chen, Tim C" <tim.c.chen@...el.com>
Subject: Re: [PATCH v5 28/28] x86/fpu/amx: Clear the AMX state when appropriate

On Mon, May 24, 2021 at 10:10 AM Dave Hansen <dave.hansen@...el.com> wrote:

> On 5/23/21 8:13 PM, Andy Lutomirski wrote:
> >
> > Can we do this just when going idle?
>
> Chang, you might also want to talk with folks that do scheduler
> performance work (I've cc'd Tim).  I know we're always fighting to trim
> down the idle and wakeup paths.  There might be no other alternative,
> but unconditionally forcing an AMX XRSTOR on return from idle might be
> considered nasty.

I'm not excited about burdening the generic idle path with a CPU
feature specific check
that would need to be checked on every idle entry.

thanks,
Len Brown, Intel Open Source Technology Center