Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754464AbaAULNB (ORCPT ); Tue, 21 Jan 2014 06:13:01 -0500 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:54419 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754204AbaAULM7 (ORCPT ); Tue, 21 Jan 2014 06:12:59 -0500 Date: Tue, 21 Jan 2014 11:08:26 +0000 From: Will Deacon To: Stefano Stabellini Cc: Arnd Bergmann , "linux-arm-kernel@lists.infradead.org" , "linux@arm.linux.org.uk" , Catalin Marinas , "gang.chen@asianux.com" , "linux-kernel@vger.kernel.org" , "jaccon.bastiaansen@gmail.com" Subject: Re: [PATCH v3] arm: remove !CPU_V6 and !GENERIC_ATOMIC64 build dependencies for XEN Message-ID: <20140121110826.GG30706@mudshark.cambridge.arm.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> <20140116193123.GB22105@mudshark.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 20, 2014 at 03:32:48PM +0000, Stefano Stabellini wrote: > On Thu, 16 Jan 2014, Will Deacon wrote: > > For the xchg part, yes, that looks a lot better. I don't like the #undef > > CONFIG_CPU_V6 though, can that be rewritten to use __LINUX_ARM_ARCH__? > > The problem is that the 1 and 2 byte parameter size cases in __cmpxchg > are ifdef'ed CONFIG_CPU_V6 but drivers/xen/grant-table.c needs them. > > So we can either undef CONFIG_CPU_V6 in grant-table.c or call a > different function. > > If I switch from ifdef CONFIG_CPU_V6 to if __LINUX_ARM_ARCH__ > 6 in > __cmpxchg, we still have the problem that if __LINUX_ARM_ARCH__ == 6, > grant-table.c doesn't compile. > > Maybe the approach taken by the other patch for cmpxchg is better, see > below. Yes, I prefer this approach. Minor comment below. > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > index c1f1a7e..ae54ae0 100644 > --- a/arch/arm/Kconfig > +++ b/arch/arm/Kconfig > @@ -1881,8 +1881,7 @@ config XEN_DOM0 > config XEN > bool "Xen guest support on ARM (EXPERIMENTAL)" > depends on ARM && AEABI && OF > - depends on CPU_V7 && !CPU_V6 > - depends on !GENERIC_ATOMIC64 > + depends on CPU_V7 > select ARM_PSCI > select SWIOTLB_XEN > help > diff --git a/arch/arm/include/asm/cmpxchg.h b/arch/arm/include/asm/cmpxchg.h > index df2fbba..cc8a4a2 100644 > --- a/arch/arm/include/asm/cmpxchg.h > +++ b/arch/arm/include/asm/cmpxchg.h > @@ -133,6 +133,44 @@ extern void __bad_cmpxchg(volatile void *ptr, int size); > * cmpxchg only support 32-bits operands on ARMv6. > */ > > +static inline unsigned long __cmpxchg8(volatile void *ptr, unsigned long old, > + unsigned long new) > +{ > + unsigned long oldval, res; > + > + do { > + asm volatile("@ __cmpxchg1\n" > + " ldrexb %1, [%2]\n" > + " mov %0, #0\n" > + " teq %1, %3\n" > + " strexbeq %0, %4, [%2]\n" > + : "=&r" (res), "=&r" (oldval) > + : "r" (ptr), "Ir" (old), "r" (new) > + : "memory", "cc"); > + } while (res); > + > + return oldval; > +} > + > +static inline unsigned long __cmpxchg16(volatile void *ptr, unsigned long old, > + unsigned long new) > +{ > + unsigned long oldval, res; > + > + do { > + asm volatile("@ __cmpxchg1\n" Can you fix this comment while you're here please? Will -- 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/