Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751414AbaAMIMK (ORCPT ); Mon, 13 Jan 2014 03:12:10 -0500 Received: from mail-qc0-f180.google.com ([209.85.216.180]:53599 "EHLO mail-qc0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751250AbaAMIMI (ORCPT ); Mon, 13 Jan 2014 03:12:08 -0500 MIME-Version: 1.0 In-Reply-To: <52D02470.6050303@gmail.com> References: <1389204023-26912-1-git-send-email-stefano.stabellini@eu.citrix.com> <20140109103004.GB11089@mudshark.cambridge.arm.com> <201401091204.17932.arnd@arndb.de> <20140109184251.GL17838@mudshark.cambridge.arm.com> <52D02470.6050303@gmail.com> Date: Mon, 13 Jan 2014 09:12:07 +0100 Message-ID: Subject: Re: [PATCH v3] arm: remove !CPU_V6 and !GENERIC_ATOMIC64 build dependencies for XEN From: Jaccon Bastiaansen To: Chen Gang F T Cc: Will Deacon , Stefano Stabellini , Arnd Bergmann , "linux-arm-kernel@lists.infradead.org" , "linux@arm.linux.org.uk" , Catalin Marinas , "gang.chen@asianux.com" , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2014/1/10 Chen Gang F T : > On 01/10/2014 02:42 AM, Will Deacon wrote: >> On Thu, Jan 09, 2014 at 12:47:24PM +0000, Stefano Stabellini wrote: >>> On Thu, 9 Jan 2014, Arnd Bergmann wrote: >>>> On Thursday 09 January 2014, Will Deacon wrote: >>>>> On Wed, Jan 08, 2014 at 06:00:23PM +0000, Stefano Stabellini wrote: >>>>>> Remove !GENERIC_ATOMIC64 build dependency: >>>>>> - rename atomic64_xchg to armv7_atomic64_xchg and define it even ifdef >>>>>> GENERIC_ATOMIC64; >>>>>> - call armv7_atomic64_xchg directly from xen/events.h. >>>>>> >>>>>> Remove !CPU_V6 build dependency: >>>>>> - introduce __cmpxchg8 and __cmpxchg16, compiled even ifdef >>>>>> CONFIG_CPU_V6; >>>>>> - implement sync_cmpxchg using __cmpxchg8 and __cmpxchg16. >>>>>> >>>>>> Signed-off-by: Stefano Stabellini >>>>>> CC: arnd@arndb.de >>>>>> CC: linux@arm.linux.org.uk >>>>>> CC: will.deacon@arm.com >>>>>> CC: gang.chen@asianux.com >>>>>> CC: catalin.marinas@arm.com >>>>>> CC: jaccon.bastiaansen@gmail.com >>>>>> CC: linux-arm-kernel@lists.infradead.org >>>>>> CC: linux-kernel@vger.kernel.org >>>>>> >>>>> >>>>> I'm confused here. It looks like you want to call armv7 code in a v6 kernel. >>>>> What am I missing? >>>> >>>> This is about being able to build a kernel that runs on ARMv6 and ARMv7 >>>> and also includes Xen. Because of obvious hardware limitations, Xen >>>> will only run on v7, but currently you cannot even build it once you >>>> enable (pre-v6K) ARMv6 support, since the combined v6+v7 kernel can't >>>> do atomic accesses in a generic way on non-32bit variables. >>> >>> Yep, that's right. >> >> Ok, thanks for the explanation. Looking at the patch, I wonder whether it's >> not cleaner just to implement xchg code separately for Xen? The Linux code >> isn't always sufficient (due to the GENERIC_ATOMIC64 stuff) and most of the >> churn coming out of this patch is an attempt to provide some small code >> reuse at the cost of code readability. >> >> What do others think? >> > > What Will said sounds reasonable to me. > > > Thanks. > -- > Chen Gang I agree with Will, Regards, Jaccon -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/