Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754221Ab0AEA41 (ORCPT ); Mon, 4 Jan 2010 19:56:27 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754002Ab0AEA4S (ORCPT ); Mon, 4 Jan 2010 19:56:18 -0500 Received: from kroah.org ([198.145.64.141]:34094 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753095Ab0AEAek (ORCPT ); Mon, 4 Jan 2010 19:34:40 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@kernel.org, stable-review@kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Suresh Siddha , "H. Peter Anvin" , Greg Kroah-Hartman Subject: [PATCH 06/97] x86, cpuid: Add "volatile" to asm in native_cpuid() Date: Mon, 4 Jan 2010 16:32:19 -0800 Message-Id: <1262651630-7354-6-git-send-email-gregkh@suse.de> X-Mailer: git-send-email 1.6.6 In-Reply-To: <20100105003133.GA7199@kroah.com> References: <20100105003133.GA7199@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1871 Lines: 52 From: Suresh Siddha commit 45a94d7cd45ed991914011919e7d40eb6d2546d1 upstream. 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> Signed-off-by: H. Peter Anvin Signed-off-by: Greg Kroah-Hartman --- 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 c978648..13b1885 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -180,7 +180,7 @@ 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), -- 1.6.6 -- 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/