All of lore.kernel.org
 help / color / mirror / Atom feed
From: Christoph Hellwig <hch@lst.de>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Christoph Hellwig <hch@lst.de>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-riscv <linux-riscv@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	linux-arch <linux-arch@vger.kernel.org>
Subject: Re: [PATCH 3/8] asm-generic: fix unaligned access hamdling in raw_copy_{from,to}_user
Date: Sat, 5 Sep 2020 09:14:47 +0200	[thread overview]
Message-ID: <20200905071447.GA13228@lst.de> (raw)
In-Reply-To: <CAK8P3a1=udSEq8kpsmLk-b7ye0p=6eKTvBV74jBoGYmufL2oEw@mail.gmail.com>

On Fri, Sep 04, 2020 at 08:04:34PM +0200, Arnd Bergmann wrote:
> >         if (__builtin_constant_p(n)) {
> >                 switch(n) {
> >                 case 1:
> > -                       *(u8 *)to = *(u8 __force *)from;
> > +                       *(u8 *)to = get_unaligned((u8 __force *)from);
> >                         return 0;
> >                 case 2:
> > -                       *(u16 *)to = *(u16 __force *)from;
> > +                       *(u16 *)to = get_unaligned((u16 __force *)from);
> >                         return 0;
> 
> The change look correct and necessary, but I wonder if this could be done
> in a way that is a little easier on the compiler than the nested switch/case.
> 
> If I see it right, __put_user() and __get_user() can probably
> be reduced to a plain put_unaligned() and get_unaligned() here,
> which would simplify these a lot.
> 
> In turn it seems that the generic raw_copy_to_user() can just be the
> a plain memcpy(), IIRC the optimization for small sizes should also
> be done by modern compilers whenever they can.

Sure, I can look into that.

WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Arnd Bergmann <arnd@arndb.de>
Cc: linux-arch <linux-arch@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	linux-riscv <linux-riscv@lists.infradead.org>,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 3/8] asm-generic: fix unaligned access hamdling in raw_copy_{from,to}_user
Date: Sat, 5 Sep 2020 09:14:47 +0200	[thread overview]
Message-ID: <20200905071447.GA13228@lst.de> (raw)
In-Reply-To: <CAK8P3a1=udSEq8kpsmLk-b7ye0p=6eKTvBV74jBoGYmufL2oEw@mail.gmail.com>

On Fri, Sep 04, 2020 at 08:04:34PM +0200, Arnd Bergmann wrote:
> >         if (__builtin_constant_p(n)) {
> >                 switch(n) {
> >                 case 1:
> > -                       *(u8 *)to = *(u8 __force *)from;
> > +                       *(u8 *)to = get_unaligned((u8 __force *)from);
> >                         return 0;
> >                 case 2:
> > -                       *(u16 *)to = *(u16 __force *)from;
> > +                       *(u16 *)to = get_unaligned((u16 __force *)from);
> >                         return 0;
> 
> The change look correct and necessary, but I wonder if this could be done
> in a way that is a little easier on the compiler than the nested switch/case.
> 
> If I see it right, __put_user() and __get_user() can probably
> be reduced to a plain put_unaligned() and get_unaligned() here,
> which would simplify these a lot.
> 
> In turn it seems that the generic raw_copy_to_user() can just be the
> a plain memcpy(), IIRC the optimization for small sizes should also
> be done by modern compilers whenever they can.

Sure, I can look into that.

_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

  reply	other threads:[~2020-09-05  7:14 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-04 16:52 remove set_fs for riscv Christoph Hellwig
2020-09-04 16:52 ` Christoph Hellwig
2020-09-04 16:52 ` [PATCH 1/8] maccess: add a generic __{get,put}_kernel_nofault for nommu Christoph Hellwig
2020-09-04 16:52   ` [PATCH 1/8] maccess: add a generic __{get, put}_kernel_nofault " Christoph Hellwig
2020-09-04 16:52 ` [PATCH 2/8] uaccess: provide a generic TASK_SIZE_MAX definition Christoph Hellwig
2020-09-04 16:52   ` Christoph Hellwig
2020-09-04 16:52 ` [PATCH 3/8] asm-generic: fix unaligned access hamdling in raw_copy_{from,to}_user Christoph Hellwig
2020-09-04 16:52   ` [PATCH 3/8] asm-generic: fix unaligned access hamdling in raw_copy_{from, to}_user Christoph Hellwig
2020-09-04 18:04   ` [PATCH 3/8] asm-generic: fix unaligned access hamdling in raw_copy_{from,to}_user Arnd Bergmann
2020-09-04 18:04     ` [PATCH 3/8] asm-generic: fix unaligned access hamdling in raw_copy_{from, to}_user Arnd Bergmann
2020-09-05  7:14     ` Christoph Hellwig [this message]
2020-09-05  7:14       ` [PATCH 3/8] asm-generic: fix unaligned access hamdling in raw_copy_{from,to}_user Christoph Hellwig
2020-09-04 18:06   ` Al Viro
2020-09-04 18:06     ` Al Viro
2020-09-04 22:35     ` Al Viro
2020-09-04 22:35       ` Al Viro
2020-09-05 14:41       ` Al Viro
2020-09-05 14:41         ` Al Viro
2020-09-07  8:07       ` Arnd Bergmann
2020-09-07  8:07         ` [PATCH 3/8] asm-generic: fix unaligned access hamdling in raw_copy_{from, to}_user Arnd Bergmann
2020-09-07 19:00   ` Sean Anderson
2020-09-07 19:00     ` Sean Anderson
2020-09-04 16:52 ` [PATCH 4/8] asm-generic: prepare uaccess.h for a set_fs-less world Christoph Hellwig
2020-09-04 16:52   ` Christoph Hellwig
2020-09-04 16:52 ` [PATCH 5/8] riscv: use memcpy based uaccess for nommu again Christoph Hellwig
2020-09-04 16:52   ` Christoph Hellwig
2020-09-04 16:52 ` [PATCH 6/8] riscv: refactor __get_user and __put_user Christoph Hellwig
2020-09-04 16:52   ` Christoph Hellwig
2020-09-04 16:52 ` [PATCH 7/8] riscv: implement __get_kernel_nofault and __put_user_nofault Christoph Hellwig
2020-09-04 16:52   ` Christoph Hellwig
2020-09-04 16:52 ` [PATCH 8/8] riscv: remove address space overrides using set_fs() Christoph Hellwig
2020-09-04 16:52   ` Christoph Hellwig
2020-09-04 18:15 ` remove set_fs for riscv Arnd Bergmann
2020-09-04 18:15   ` Arnd Bergmann
2020-09-05  7:17   ` Christoph Hellwig
2020-09-05  7:17     ` Christoph Hellwig
2020-09-05 12:17     ` Arnd Bergmann
2020-09-05 12:17       ` Arnd Bergmann
2020-09-06 22:14     ` Arnd Bergmann
2020-09-06 22:14       ` Arnd Bergmann
2020-09-07  6:03       ` Christoph Hellwig
2020-09-07  6:03         ` Christoph Hellwig
2020-09-07 14:58         ` Arnd Bergmann
2020-09-07 14:58           ` Arnd Bergmann

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200905071447.GA13228@lst.de \
    --to=hch@lst.de \
    --cc=arnd@arndb.de \
    --cc=linux-arch@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-riscv@lists.infradead.org \
    --cc=palmer@dabbelt.com \
    --cc=paul.walmsley@sifive.com \
    --cc=viro@zeniv.linux.org.uk \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.