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From: Arnd Bergmann <arnd@arndb.de>
To: Vincent Chen <deanbo422@gmail.com>
Cc: Greentime Hu <green.hu@gmail.com>,
	Greentime <greentime@andestech.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-arch <linux-arch@vger.kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Jason Cooper <jason@lakedaemon.net>,
	Marc Zyngier <marc.zyngier@arm.com>,
	Rob Herring <robh+dt@kernel.org>,
	Networking <netdev@vger.kernel.org>,
	DTML <devicetree@vger.kernel.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	David Howells <dhowells@redhat.com>,
	Will Deacon <will.deacon@arm.com>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	linux-serial@vger.kernel.org,
	Geert Uytterhoeven <geert.uytterhoeven@gmail.com>,
	Linus Walleij <linus.walleij@linaro.org>,
	Mark Rutland <mark.rutland@arm.com>, Greg KH <greg@kroah.com>,
	Guo Ren <ren_guo@c-sky.com>, Randy Dunlap <rdunlap@infradead.org>,
	David Miller <davem@davemloft.net>,
	Jonas Bonn <jonas@southpole.se>,
	Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>,
	Stafford Horne <shorne@gmail.com>,
	Vincent Chen <vincentc@andestech.com>
Subject: Re: [PATCH v6 07/36] nds32: Exception handling
Date: Tue, 30 Jan 2018 14:33:03 +0100	[thread overview]
Message-ID: <CAK8P3a1iv=10_pfvtfvDwD9YH1HRAXwDy_m8SC=tV59HEDuSsg@mail.gmail.com> (raw)
In-Reply-To: <CAJsyPhx090fPsdhkydoKDHDw+LwByT66JHJNT4Tb5N0s_O7MPw@mail.gmail.com>

On Tue, Jan 30, 2018 at 11:01 AM, Vincent Chen <deanbo422@gmail.com> wrote:
> 2018-01-24 19:10 GMT+08:00 Arnd Bergmann <arnd@arndb.de>:
>> On Wed, Jan 24, 2018 at 12:09 PM, Arnd Bergmann <arnd@arndb.de> wrote:
>>> On Wed, Jan 24, 2018 at 11:53 AM, Vincent Chen <deanbo422@gmail.com> wrote:
>>>> 2018-01-18 18:14 GMT+08:00 Arnd Bergmann <arnd@arndb.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.

I'm not really following that logic, let's go through that again so I understand
the situation better.

CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS should be set if and
only if you have a CPU that does not need to trap on unaligned accesses.

What are the hardware capabilities on nds32? Do you have all three
categories:

a) some CPUs that always trap on unaligned access
b) some CPUs that never trap on unaligned access
c) some CPUs that can be configured to either trap or not trap by
    the kernel?

        Arnd

  reply	other threads:[~2018-01-30 13:33 UTC|newest]

Thread overview: 111+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-15  5:53 [PATCH v6 00/36] Andes(nds32) Linux Kernel Port Greentime Hu
2018-01-15  5:53 ` [PATCH v6 01/36] asm-generic/io.h: move ioremap_nocache/ioremap_uc/ioremap_wc/ioremap_wt out of ifndef CONFIG_MMU Greentime Hu
2018-01-15  5:53 ` [PATCH v6 02/36] openrisc: add ioremap_nocache declaration before include asm-generic/io.h and sync ioremap prototype with it Greentime Hu
2018-01-15 13:07   ` Stafford Horne
2018-01-15 13:28     ` Greentime Hu
2018-01-15  5:53 ` [PATCH v6 03/36] sparc: io: To use the define of ioremap_[nocache|wc|wb] in asm-generic/io.h Greentime Hu
2018-01-18  9:56   ` Arnd Bergmann
2018-01-19 12:50     ` Greentime Hu
2018-01-15  5:53 ` [PATCH v6 04/36] earlycon: add reg-offset to physical address before mapping Greentime Hu
2018-01-18 10:00   ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 05/36] nds32: Assembly macros and definitions Greentime Hu
2018-01-18 10:01   ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 06/36] nds32: Kernel booting and initialization Greentime Hu
2018-01-18 10:11   ` Arnd Bergmann
2018-01-19 16:34     ` Greentime Hu
2018-01-19 16:41       ` Arnd Bergmann
2018-01-22  9:49         ` Greentime Hu
2018-01-22  9:53           ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 07/36] nds32: Exception handling Greentime Hu
2018-01-18 10:14   ` Arnd Bergmann
2018-01-24 10:53     ` Vincent Chen
2018-01-24 11:09       ` Arnd Bergmann
2018-01-24 11:10         ` Arnd Bergmann
2018-01-30 10:01           ` Vincent Chen
2018-01-30 13:33             ` Arnd Bergmann [this message]
2018-01-30 14:49               ` Greentime Hu
2018-01-30 15:27                 ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 08/36] nds32: MMU definitions Greentime Hu
2018-01-18 10:14   ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 09/36] nds32: MMU initialization Greentime Hu
2018-01-18 10:16   ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 10/36] nds32: MMU fault handling and page table management Greentime Hu
2018-01-18 10:16   ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 11/36] nds32: Cache and TLB routines Greentime Hu
2018-01-18 10:17   ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 12/36] nds32: Process management Greentime Hu
2018-01-18 10:22   ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 13/36] nds32: IRQ handling Greentime Hu
2018-01-18 10:22   ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 14/36] nds32: Atomic operations Greentime Hu
2018-01-18 10:23   ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 15/36] nds32: Device specific operations Greentime Hu
2018-01-18 10:25   ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 16/36] nds32: DMA mapping API Greentime Hu
2018-01-18 10:26   ` Arnd Bergmann
2018-01-23  8:23     ` Greentime Hu
2018-01-23 11:52       ` Greentime Hu
2018-01-24 11:36         ` Arnd Bergmann
2018-01-25  3:45           ` Greentime Hu
2018-01-25 10:42             ` Arnd Bergmann
2018-01-25 13:48               ` Greentime Hu
2018-01-15  5:53 ` [PATCH v6 17/36] nds32: ELF definitions Greentime Hu
2018-01-18 10:27   ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 18/36] nds32: System calls handling Greentime Hu
2018-01-18 10:27   ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 19/36] nds32: VDSO support Greentime Hu
2018-01-18 10:28   ` Arnd Bergmann
2018-02-06  7:41     ` Vincent Chen
2018-02-06  8:48       ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 20/36] nds32: Signal handling support Greentime Hu
2018-01-18 10:30   ` Arnd Bergmann
2018-01-24  0:56     ` Vincent Chen
2018-01-24 11:13       ` Arnd Bergmann
2018-02-06  6:39         ` Vincent Chen
2018-01-15  5:53 ` [PATCH v6 21/36] nds32: Library functions Greentime Hu
2018-01-18 10:31   ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 22/36] nds32: Debugging support Greentime Hu
2018-01-18 10:37   ` Arnd Bergmann
2018-01-23  7:28     ` Vincent Chen
2018-01-23  8:21       ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 23/36] nds32: L2 cache support Greentime Hu
2018-01-18 10:37   ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 24/36] nds32: Loadable modules Greentime Hu
2018-01-18 10:41   ` Arnd Bergmann
2018-01-19 14:26     ` Greentime Hu
2018-01-15  5:53 ` [PATCH v6 25/36] nds32: Generic timers support Greentime Hu
2018-01-18 10:41   ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 26/36] nds32: Device tree support Greentime Hu
2018-01-18 10:43   ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 27/36] nds32: Miscellaneous header files Greentime Hu
2018-01-18 10:46   ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 28/36] nds32: defconfig Greentime Hu
2018-01-18 10:44   ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 29/36] nds32: Build infrastructure Greentime Hu
2018-01-18 11:00   ` Arnd Bergmann
2018-01-22 15:20     ` Greentime Hu
2018-01-22 15:38       ` Arnd Bergmann
2018-01-22 16:00         ` Greentime Hu
2018-01-15  5:53 ` [PATCH v6 30/36] MAINTAINERS: Add nds32 Greentime Hu
2018-01-18 10:45   ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 31/36] dt-bindings: nds32 CPU Bindings Greentime Hu
2018-01-18 11:02   ` Arnd Bergmann
2018-01-19 14:32     ` Greentime Hu
2018-01-19 14:52       ` Arnd Bergmann
2018-01-19 15:18         ` Greentime Hu
2018-01-19 15:29           ` Geert Uytterhoeven
2018-01-19 15:35             ` Greentime Hu
2018-01-19 15:37               ` Geert Uytterhoeven
2018-01-22  9:53                 ` Greentime Hu
2018-01-22 11:15                   ` Arnd Bergmann
2018-01-22 13:55                     ` Greentime Hu
2018-01-15  5:53 ` [PATCH v6 32/36] dt-bindings: nds32 L2 cache controller Bindings Greentime Hu
2018-01-18 10:45   ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 33/36] dt-bindings: nds32 SoC Bindings Greentime Hu
2018-01-18 11:03   ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 34/36] dt-bindings: interrupt-controller: Andestech Internal Vector Interrupt Controller Greentime Hu
2018-01-18 10:46   ` Arnd Bergmann
2018-01-15  5:53 ` [PATCH v6 35/36] irqchip: Andestech Internal Vector Interrupt Controller driver Greentime Hu
2018-01-15  5:53 ` [PATCH v6 36/36] net: faraday add nds32 support Greentime Hu
2018-01-18 11:02   ` Arnd Bergmann
2018-01-18  9:49 ` [PATCH v6 00/36] Andes(nds32) Linux Kernel Port Arnd Bergmann

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