From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752369AbZHKL7g (ORCPT ); Tue, 11 Aug 2009 07:59:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752388AbZHKL7c (ORCPT ); Tue, 11 Aug 2009 07:59:32 -0400 Received: from hera.kernel.org ([140.211.167.34]:35438 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752303AbZHKL73 (ORCPT ); Tue, 11 Aug 2009 07:59:29 -0400 Date: Tue, 11 Aug 2009 11:36:39 GMT From: tip-bot for Kevin Winchester To: linux-tip-commits@vger.kernel.org Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, petkovbb@googlemail.com, kjwinchester@gmail.com, tglx@linutronix.de, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, petkovbb@googlemail.com, kjwinchester@gmail.com, tglx@linutronix.de, mingo@elte.hu In-Reply-To: <4A80A5AD.2000209@gmail.com> References: <4A80A5AD.2000209@gmail.com> Subject: [tip:x86/urgent] x86: Clear incorrectly forced X86_FEATURE_LAHF_LM flag Message-ID: Git-Commit-ID: fbd8b1819e80ac5a176d085fdddc3a34d1499318 X-Mailer: tip-git-log-daemon MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.0 (hera.kernel.org [127.0.0.1]); Tue, 11 Aug 2009 11:36:40 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: fbd8b1819e80ac5a176d085fdddc3a34d1499318 Gitweb: http://git.kernel.org/tip/fbd8b1819e80ac5a176d085fdddc3a34d1499318 Author: Kevin Winchester AuthorDate: Mon, 10 Aug 2009 19:56:45 -0300 Committer: Ingo Molnar CommitDate: Tue, 11 Aug 2009 13:34:54 +0200 x86: Clear incorrectly forced X86_FEATURE_LAHF_LM flag Due to an erratum with certain AMD Athlon 64 processors, the BIOS may need to force enable the LAHF_LM capability. Unfortunately, in at least one case, the BIOS does this even for processors that do not support the functionality. Add a specific check that will clear the feature bit for processors known not to support the LAHF/SAHF instructions. Signed-off-by: Kevin Winchester Acked-by: Borislav Petkov LKML-Reference: <4A80A5AD.2000209@gmail.com> Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/amd.c | 7 +++++++ 1 files changed, 7 insertions(+), 0 deletions(-) diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index e2485b0..63fddcd 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -400,6 +400,13 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c) level = cpuid_eax(1); if((level >= 0x0f48 && level < 0x0f50) || level >= 0x0f58) set_cpu_cap(c, X86_FEATURE_REP_GOOD); + + /* + * Some BIOSes incorrectly force this feature, but only K8 + * revision D (model = 0x14) and later actually support it. + */ + if (c->x86_model < 0x14) + clear_cpu_cap(c, X86_FEATURE_LAHF_LM); } if (c->x86 == 0x10 || c->x86 == 0x11) set_cpu_cap(c, X86_FEATURE_REP_GOOD);