linux-kernel - Re: [PATCH v6 07/36] nds32: Exception handling

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Message-ID: <CAJsyPhx090fPsdhkydoKDHDw+LwByT66JHJNT4Tb5N0s_O7MPw@mail.gmail.com>
Date:   Tue, 30 Jan 2018 18:01:52 +0800
From:   Vincent Chen <deanbo422@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Greentime Hu <green.hu@...il.com>,
        Greentime <greentime@...estech.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <marc.zyngier@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Networking <netdev@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        David Howells <dhowells@...hat.com>,
        Will Deacon <will.deacon@....com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        linux-serial@...r.kernel.org,
        Geert Uytterhoeven <geert.uytterhoeven@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Mark Rutland <mark.rutland@....com>, Greg KH <greg@...ah.com>,
        Guo Ren <ren_guo@...ky.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        David Miller <davem@...emloft.net>,
        Jonas Bonn <jonas@...thpole.se>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Stafford Horne <shorne@...il.com>,
        Vincent Chen <vincentc@...estech.com>
Subject: Re: [PATCH v6 07/36] nds32: Exception handling

2018-01-24 19:10 GMT+08:00 Arnd Bergmann <arnd@...db.de>:
> On Wed, Jan 24, 2018 at 12:09 PM, Arnd Bergmann <arnd@...db.de> wrote:
>> On Wed, Jan 24, 2018 at 11:53 AM, Vincent Chen <deanbo422@...il.com> wrote:
>>> 2018-01-18 18:14 GMT+08:00 Arnd Bergmann <arnd@...db.de>:
>
>> Ok. I still wonder about the kernel part of this though: is it a good idea
>> for user space to configure whether the kernel does unaligned
>> accesses? I would think that the kernel should just be fixed in such
>> a case.
>
> To clarify: I'm asking only about unaligned accesses from kernel code itself,
> which is generally considered a bug when
> CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is disabled.
>
>       Arnd

Thanks for your comments.

For performance, we decide always disable
CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS even if hardware supports
unaligned accessing. Therefore, I will remove kernel unaligned accessing from
nds32/mm/alignment.c. In other words, alignment.c only addresses unaligned
accessing for user space.

Vincent