linux-kernel - Re: [BUG] from x86: Support kmap

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Date:   Wed, 6 Jan 2021 20:16:45 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Willem de Bruijn <willemb@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        David Miller <davem@...emloft.net>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Christoph Hellwig <hch@....de>,
        Matthew Wilcox <willy@...radead.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux-MM <linux-mm@...ck.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Netdev <netdev@...r.kernel.org>
Subject: Re: [BUG] from x86: Support kmap_local() forced debugging

On Wed, 6 Jan 2021 17:03:48 -0800
Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> (although I wonder how/why the heck you've enabled
> CC_OPTIMIZE_FOR_SIZE=y, which is what causes "memcpy()" to be done as
> that "rep movsb". I thought we disabled it because it's so bad on most
> cpus).

Why?

Because to test x86_32, I have a Fedora Core 13 (yes 13!) partition
(baremetal) that I use. And the .config I use for it hasn't changed
since that time ;-) (except to add new features that I want to test on
x86_32).

Anyway, I'll test out your patch. Thanks for investigating this.

-- Steve