From patchwork Tue Jul 30 11:32:06 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paul Walmsley X-Patchwork-Id: 2835561 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id B64729F9CE for ; Tue, 30 Jul 2013 11:32:38 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 97EA920371 for ; Tue, 30 Jul 2013 11:32:37 +0000 (UTC) Received: from casper.infradead.org (casper.infradead.org [85.118.1.10]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3CCD520349 for ; Tue, 30 Jul 2013 11:32:36 +0000 (UTC) Received: from merlin.infradead.org ([2001:4978:20e::2]) by casper.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1V48AL-0003t7-V9; Tue, 30 Jul 2013 11:32:34 +0000 Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1V48AJ-0003QW-Sk; Tue, 30 Jul 2013 11:32:31 +0000 Received: from utopia.booyaka.com ([74.50.51.50]) by merlin.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1V48AG-0003PM-GV for linux-arm-kernel@lists.infradead.org; Tue, 30 Jul 2013 11:32:29 +0000 Received: (qmail 6516 invoked by uid 1019); 30 Jul 2013 11:32:06 -0000 Date: Tue, 30 Jul 2013 11:32:06 +0000 (UTC) From: Paul Walmsley To: Russell King - ARM Linux , Will Deacon Subject: [PATCH v2] ARM: v6: prevent gcc 4.5 from reordering extended CP15 reads above is_smp() test In-Reply-To: Message-ID: References: <20130722184325.GA21614@n2100.arm.linux.org.uk> <51EE2AA7.5060503@ti.com> <51EE474D.5070804@ti.com> <20130724135617.GI11072@mudshark.cambridge.arm.com> <51EFE1DD.8070801@ti.com> <20130724142059.GJ11072@mudshark.cambridge.arm.com> <20130727122221.GB6618@mudshark.cambridge.arm.com> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20130730_073228_644716_9D89B721 X-CRM114-Status: GOOD ( 11.83 ) X-Spam-Score: -1.9 (-) Cc: "linux-omap@vger.kernel.org" , Rajendra Nayak , Santosh Shilimkar , "linux-arm-kernel@lists.infradead.org" X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-5.7 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Commit 621a0147d5c921f4cc33636ccd0602ad5d7cbfbc ("ARM: 7757/1: mm: don't flush icache in switch_mm with hardware broadcasting") breaks the boot on OMAP2430SDP with omap2plus_defconfig. Tracked to an undefined instruction abort from the CP15 read in cache_ops_need_broadcast(). It turns out that gcc 4.5 reorders the extended CP15 read above the is_smp() test. This breaks ARM1136 r0 cores, since they don't support several CP15 registers that later ARM cores do. ARM1136JF-S TRM section 3.2.1 "Register allocation" has the details. So mark the extended CP15 read as clobbering memory, which prevents the compiler from reordering it before the is_smp() test. Russell states that the code generated from this approach is preferable to marking the inline asm as volatile. Remove the existing condition code clobber as it's obsolete, per Nico's post: http://www.spinics.net/lists/arm-kernel/msg261208.html This patch is a collaboration with Will Deacon and Russell King. Signed-off-by: Paul Walmsley Cc: Will Deacon Cc: Russell King Cc: Nicolas Pitre Cc: Tony Lindgren Acked-by: Will Deacon --- Intended for v3.11-rc. Basic test logs available here: http://www.pwsan.com/omap/testlogs/bisect_2430sdp_hang_v3.11-rc/20130730045715/ N.B., several boards have problems on v3.11-rc that are unrelated to this patch. arch/arm/include/asm/cputype.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/arm/include/asm/cputype.h b/arch/arm/include/asm/cputype.h index 8c25dc4..9672e97 100644 --- a/arch/arm/include/asm/cputype.h +++ b/arch/arm/include/asm/cputype.h @@ -89,13 +89,18 @@ extern unsigned int processor_id; __val; \ }) +/* + * The memory clobber prevents gcc 4.5 from reordering the mrc before + * any is_smp() tests, which can cause undefined instruction aborts on + * ARM1136 r0 due to the missing extended CP15 registers. + */ #define read_cpuid_ext(ext_reg) \ ({ \ unsigned int __val; \ asm("mrc p15, 0, %0, c0, " ext_reg \ : "=r" (__val) \ : \ - : "cc"); \ + : "memory"); \ __val; \ })