linux-kernel - Re: [PATCH 1/9] mm/maccess: fix unaligned copy_{from,to}_kernel

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Message-ID: <CACRpkdYZw11rJce-Wn_b0xfs-SQKNUQiO84UhxGK9MDfSD7M-w@mail.gmail.com>
Date:   Sun, 27 Sep 2020 11:25:25 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Christoph Hellwig <hch@....de>,
        Russell King <rmk@....linux.org.uk>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        "linux-kernel@...r.kernel.org" <kernel@...r.kernel.org>,
        linux-arch@...r.kernel.org,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>, linux-mm@...ck.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/9] mm/maccess: fix unaligned copy_{from,to}_kernel_nofault

On Mon, Sep 7, 2020 at 5:37 PM Arnd Bergmann <arnd@...db.de> wrote:

> On machines such as ARMv5 that trap unaligned accesses, these
> two functions can be slow when each access needs to be emulated,
> or they might not work at all.
>
> Change them so that each loop is only used when both the src
> and dst pointers are naturally aligned.
>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

That's a clever optimization idea, nice!
Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

Yours,
Linus Walleij