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From: Arnd Bergmann <arnd@kernel.org>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: linux-arch <linux-arch@vger.kernel.org>,
	Vineet Gupta <vgupta@synopsys.com>,
	linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Paul Mackerras <paulus@samba.org>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH v2 05/13] powerpc: use linux/unaligned/le_struct.h on LE power7
Date: Fri, 14 May 2021 15:02:43 +0200	[thread overview]
Message-ID: <CAK8P3a04OZzSwV0039GiA0x=Kmp_mUvNz_CEyVFo8NJHTv2smg@mail.gmail.com> (raw)
In-Reply-To: <20210514114813.GJ10366@gate.crashing.org>

On Fri, May 14, 2021 at 1:48 PM Segher Boessenkool
<segher@kernel.crashing.org> wrote:
> On Fri, May 14, 2021 at 12:00:53PM +0200, Arnd Bergmann wrote:
> > Little-endian POWER7 kernels disable
> > CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS because that is not supported on
> > the hardware, but the kernel still uses direct load/store for explicti
> > get_unaligned()/put_unaligned().
> >
> > I assume this is a mistake that leads to power7 having to trap and fix
> > up all these unaligned accesses at a noticeable performance cost.
> >
> > The fix is completely trivial, just remove the file and use the
> > generic version that gets it right.
>
> LE p7 isn't supported (it requires special firmware), and no one uses it
> anymore, also not for development.  It was used for powerpc64le-linux
> development before p8 was widely available.

Ok, thanks for the clarification.

Should we just remove the Kconfig option for it then as further cleanup?
Is there any other code such as alignment trap handling that could be
removed if LE POWER7 gets dropped?

      Arnd

  reply	other threads:[~2021-05-14 13:03 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-14 10:00 [PATCH v2 00/13] Unify asm/unaligned.h around struct helper Arnd Bergmann
2021-05-14 10:00 ` [PATCH v2 01/13] asm-generic: use asm-generic/unaligned.h for most architectures Arnd Bergmann
2021-05-14 10:00 ` [PATCH v2 02/13] openrisc: always use unaligned-struct header Arnd Bergmann
2021-05-14 10:00 ` [PATCH v2 03/13] sh: remove unaligned access for sh4a Arnd Bergmann
2021-05-14 10:34   ` John Paul Adrian Glaubitz
2021-05-14 12:22     ` Arnd Bergmann
2021-05-15 15:36       ` John Paul Adrian Glaubitz
2021-05-15 20:10         ` Arnd Bergmann
2021-05-14 10:00 ` [PATCH v2 04/13] m68k: select CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS Arnd Bergmann
2021-05-14 10:00 ` [PATCH v2 05/13] powerpc: use linux/unaligned/le_struct.h on LE power7 Arnd Bergmann
2021-05-14 11:48   ` Segher Boessenkool
2021-05-14 13:02     ` Arnd Bergmann [this message]
2021-05-14 10:00 ` [PATCH v2 06/13] asm-generic: unaligned: remove byteshift helpers Arnd Bergmann
2021-05-14 10:00 ` [PATCH v2 07/13] asm-generic: unaligned always use struct helpers Arnd Bergmann
2021-05-17 21:53   ` Eric Biggers
2021-05-18  7:25     ` Arnd Bergmann
2021-05-18 14:56       ` Linus Torvalds
2021-05-18 15:41         ` Arnd Bergmann
2021-05-18 16:12           ` Linus Torvalds
2021-05-18 18:09             ` Jason A. Donenfeld
2021-05-18 20:51             ` Arnd Bergmann
2021-05-18 21:31               ` Eric Biggers
2021-05-18 21:14         ` David Laight
2021-05-14 10:00 ` [PATCH v2 08/13] partitions: msdos: fix one-byte get_unaligned() Arnd Bergmann
2021-05-17 10:28   ` Christoph Hellwig
2021-05-17 10:44     ` Arnd Bergmann
2021-05-14 10:00 ` [PATCH v2 09/13] apparmor: use get_unaligned() only for multi-byte words Arnd Bergmann
2021-05-14 10:00 ` [PATCH v2 10/13] mwifiex: re-fix for unaligned accesses Arnd Bergmann
2021-05-15  6:22   ` Kalle Valo
2021-05-15  9:01     ` Arnd Bergmann
2021-05-15 18:23       ` Kalle Valo
2021-05-14 10:00 ` [PATCH v2 11/13] netpoll: avoid put_unaligned() on single character Arnd Bergmann
2021-05-14 10:01 ` [PATCH v2 12/13] asm-generic: uaccess: 1-byte access is always aligned Arnd Bergmann
2021-05-15 18:41   ` Randy Dunlap
2021-05-15 20:16     ` Arnd Bergmann
2021-05-14 10:01 ` [PATCH v2 13/13] asm-generic: simplify asm/unaligned.h Arnd Bergmann
2021-05-14 10:35   ` David Laight
2021-05-14 17:32 ` [PATCH v2 00/13] Unify asm/unaligned.h around struct helper Linus Torvalds
2021-05-14 18:51   ` Vineet Gupta
2021-05-14 19:22     ` Linus Torvalds
2021-05-14 19:45       ` Vineet Gupta
2021-05-14 20:19         ` Linus Torvalds
2021-05-14 19:31   ` Arnd Bergmann
2021-12-16 17:29 ` Ard Biesheuvel
2021-12-16 17:42   ` Linus Torvalds
2021-12-16 17:49   ` David Laight
2021-12-16 18:56   ` Segher Boessenkool
2021-12-17 12:34     ` David Laight
2021-12-17 13:35       ` Segher Boessenkool

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