From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751515Ab2LTIMh (ORCPT ); Thu, 20 Dec 2012 03:12:37 -0500 Received: from us01smtp3.synopsys.com ([198.182.44.81]:35427 "EHLO hermes.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751069Ab2LTIM3 (ORCPT ); Thu, 20 Dec 2012 03:12:29 -0500 Message-ID: <50D2C78B.4060109@synopsys.com> Date: Thu, 20 Dec 2012 13:38:43 +0530 From: Vineet Gupta User-Agent: Mozilla/5.0 (X11; Linux i686; rv:16.0) Gecko/20121011 Thunderbird/16.0.1 MIME-Version: 1.0 To: Arnd Bergmann CC: , , Subject: Re: [RFC Patch v1 45/55] ARC: unaligned access emulation References: <1352720953-24321-1-git-send-email-vgupta@synopsys.com> <1352720953-24321-15-git-send-email-vgupta@synopsys.com> <201211121400.13046.arnd@arndb.de> In-Reply-To: <201211121400.13046.arnd@arndb.de> Content-Type: text/plain; charset="ISO-8859-15" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.12.197.205] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday 12 November 2012 07:30 PM, Arnd Bergmann wrote: > On Monday 12 November 2012, Vineet.Gupta1@synopsys.com wrote: >> + >> +config ARC_MISALIGN_ACCESS >> + bool "Emulate unaligned memory access (userspace only)" >> + default N >> + help >> + This enables misaligned 16 & 32 bit memory access from user space. >> + Use ONLY-IF-ABS-NECESSARY as it will be very slow and also can hide >> + potential bugs in code > > parisc and ia64 both have the same feature, and they use sysctl to configure > it at run-time. Maybe you should pick one of the two sysctl implementations > and hook that up to your implementation as well. Spoke too soon ! The only caveat to removing the Kconfig option is that it will pull-in unaligned emulation code as well as the dependent in-kernel disassembler unconditionally into the build. Are you OK if we keep this support build time - provided that once it is build time enabled - we have the additional runtime sysctl based toggle-ability as you suggested. Only one of our customers need this feature and this gives people reasons to moan about the kernel .text size and such. Thanks, Vineet From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vineet Gupta Subject: Re: [RFC Patch v1 45/55] ARC: unaligned access emulation Date: Thu, 20 Dec 2012 13:38:43 +0530 Message-ID: <50D2C78B.4060109@synopsys.com> References: <1352720953-24321-1-git-send-email-vgupta@synopsys.com> <1352720953-24321-15-git-send-email-vgupta@synopsys.com> <201211121400.13046.arnd@arndb.de> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-15" Content-Transfer-Encoding: 7bit Return-path: Received: from us01smtp3.synopsys.com ([198.182.44.81]:35427 "EHLO hermes.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751069Ab2LTIM3 (ORCPT ); Thu, 20 Dec 2012 03:12:29 -0500 In-Reply-To: <201211121400.13046.arnd@arndb.de> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Arnd Bergmann Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de On Monday 12 November 2012 07:30 PM, Arnd Bergmann wrote: > On Monday 12 November 2012, Vineet.Gupta1@synopsys.com wrote: >> + >> +config ARC_MISALIGN_ACCESS >> + bool "Emulate unaligned memory access (userspace only)" >> + default N >> + help >> + This enables misaligned 16 & 32 bit memory access from user space. >> + Use ONLY-IF-ABS-NECESSARY as it will be very slow and also can hide >> + potential bugs in code > > parisc and ia64 both have the same feature, and they use sysctl to configure > it at run-time. Maybe you should pick one of the two sysctl implementations > and hook that up to your implementation as well. Spoke too soon ! The only caveat to removing the Kconfig option is that it will pull-in unaligned emulation code as well as the dependent in-kernel disassembler unconditionally into the build. Are you OK if we keep this support build time - provided that once it is build time enabled - we have the additional runtime sysctl based toggle-ability as you suggested. Only one of our customers need this feature and this gives people reasons to moan about the kernel .text size and such. Thanks, Vineet