From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754199AbZHJW4u (ORCPT ); Mon, 10 Aug 2009 18:56:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754154AbZHJW4s (ORCPT ); Mon, 10 Aug 2009 18:56:48 -0400 Received: from mail-qy0-f196.google.com ([209.85.221.196]:45505 "EHLO mail-qy0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752127AbZHJW4s (ORCPT ); Mon, 10 Aug 2009 18:56:48 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:x-enigmail-version:content-type :content-transfer-encoding; b=iXzH+2v1/ePfynSsK95lBelI+IR9xydGZkD1ms7cYAPa7XAaa5CXr+Iokdb4KwFtJ6 dPBG1ZVUOyCfBt2JIDVBIeiWks+stAUomUoLGk41t6E/gPcyeyKQFMLdVTlU4p15cepp 7eWvu3Sa0ZR7gHKewXPbN3ov8BBKIhB0HnVU8= Message-ID: <4A80A5AD.2000209@gmail.com> Date: Mon, 10 Aug 2009 19:56:45 -0300 From: Kevin Winchester User-Agent: Thunderbird 2.0.0.22 (X11/20090725) MIME-Version: 1.0 To: Borislav Petkov CC: Borislav Petkov , Ingo Molnar , LKML Subject: [PATCH v3] x86: clear incorrectly forced X86_FEATURE_LAHF_LM flag References: <4A7D673A.1090401@gmail.com> <20090808152016.GB25374@liondog.tnic> <4A7E0797.7060504@gmail.com> <20090810131219.GD21879@aftab> In-Reply-To: <20090810131219.GD21879@aftab> X-Enigmail-Version: 0.95.7 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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); -- 1.6.4