From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763561AbZLQBBk (ORCPT ); Wed, 16 Dec 2009 20:01:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1763530AbZLQBBb (ORCPT ); Wed, 16 Dec 2009 20:01:31 -0500 Received: from hera.kernel.org ([140.211.167.34]:35279 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1763556AbZLQBBZ (ORCPT ); Wed, 16 Dec 2009 20:01:25 -0500 Date: Thu, 17 Dec 2009 01:01:12 GMT From: tip-bot for Suresh Siddha Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, suresh.b.siddha@intel.com, tglx@linutronix.de Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, suresh.b.siddha@intel.com, tglx@linutronix.de In-Reply-To: <1261009542.2745.55.camel@sbs-t61.sc.intel.com> References: <1261009542.2745.55.camel@sbs-t61.sc.intel.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/urgent] x86, cpuid: Add "volatile" to asm in native_cpuid() Message-ID: Git-Commit-ID: 45a94d7cd45ed991914011919e7d40eb6d2546d1 X-Mailer: tip-git-log-daemon MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 45a94d7cd45ed991914011919e7d40eb6d2546d1 Gitweb: http://git.kernel.org/tip/45a94d7cd45ed991914011919e7d40eb6d2546d1 Author: Suresh Siddha AuthorDate: Wed, 16 Dec 2009 16:25:42 -0800 Committer: H. Peter Anvin CommitDate: Wed, 16 Dec 2009 16:30:57 -0800 x86, cpuid: Add "volatile" to asm in native_cpuid() xsave_cntxt_init() does something like: cpuid(0xd, ..); // find out what features FP/SSE/.. etc are supported xsetbv(); // enable the features known to OS cpuid(0xd, ..); // find out the size of the context for features enabled Depending on what features get enabled in xsetbv(), value of the cpuid.eax=0xd.ecx=0.ebx changes correspondingly (representing the size of the context that is enabled). As we don't have volatile keyword for native_cpuid(), gcc 4.1.2 optimizes away the second cpuid and the kernel continues to use the cpuid information obtained before xsetbv(), ultimately leading to kernel crash on processors supporting more state than the legacy FP/SSE. Add "volatile" for native_cpuid(). Signed-off-by: Suresh Siddha LKML-Reference: <1261009542.2745.55.camel@sbs-t61.sc.intel.com> Cc: stable@kernel.org Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/processor.h | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 6f8ec1c..fc801ba 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -181,7 +181,7 @@ static inline void native_cpuid(unsigned int *eax, unsigned int *ebx, unsigned int *ecx, unsigned int *edx) { /* ecx is often an input as well as an output. */ - asm("cpuid" + asm volatile("cpuid" : "=a" (*eax), "=b" (*ebx), "=c" (*ecx),