From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753974Ab2DPNkm (ORCPT ); Mon, 16 Apr 2012 09:40:42 -0400 Received: from am1ehsobe002.messaging.microsoft.com ([213.199.154.205]:4418 "EHLO am1outboundpool.messaging.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753368Ab2DPNkl (ORCPT ); Mon, 16 Apr 2012 09:40:41 -0400 X-SpamScore: 0 X-BigFish: VPS0(zzzz1202hzz8275bhz2dh668h839h93fhd25h) X-Forefront-Antispam-Report: CIP:163.181.249.108;KIP:(null);UIP:(null);IPV:NLI;H:ausb3twp01.amd.com;RD:none;EFVD:NLI X-WSS-ID: 0M2KRBK-01-02J-02 X-M-MSG: Date: Mon, 16 Apr 2012 15:40:28 +0200 From: Andreas Herrmann To: Ingo Molnar CC: "H. Peter Anvin" , Thomas Gleixner , Subject: [PATCH v2] x86, amd: Re-enable CPU topology extensions in case BIOS has disabled it Message-ID: <20120416134028.GA25712@alberich.amd.com> References: <20120411152640.GC4794@alberich.amd.com> <20120416065249.GA5292@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Disposition: inline In-Reply-To: <20120416065249.GA5292@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-OriginatorOrg: amd.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>From 2da973d9e096cea39a3bd397c1449a821b76d816 Mon Sep 17 00:00:00 2001 From: Andreas Herrmann Date: Tue, 3 Apr 2012 12:13:07 +0200 Subject: [PATCH] x86, amd: Re-enable CPU topology extensions in case BIOS has disabled it BIOS will switch off the corresponding feature flag on family 15h models 10h-1fh non-desktop CPUs. The topology extension CPUID leafs are required to detect which cores belong to the same compute unit. (thread siblings mask is set accordingly and also correct information about L1i and L2 cache sharing depends on this). W/o this patch we wouldn't see which cores belong to the same compute unit and also cache sharing information for L1i and L2 would be incorrect on such systems. Signed-off-by: Andreas Herrmann --- arch/x86/kernel/cpu/amd.c | 18 ++++++++++++++++++ 1 files changed, 18 insertions(+), 0 deletions(-) Hi Ingo, Hope this new commit messages answers your questions. Of course this patch is more a workaround for "suboptimal BIOS settings" and thus not strictly stable material. (BTW, no there is no way to change the BIOS setting here.) But as a whole bunch of systems will be affected it might also be reasonable to add this patch to stable Linux versions. Regards, Andreas diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index 1248f9c..0ae388d 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -579,6 +579,24 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c) } } + /* re-enable TopologyExtensions if switched off by BIOS */ + if ((c->x86 == 0x15) && + (c->x86_model >= 0x10) && (c->x86_model <= 0x1f) && + !cpu_has(c, X86_FEATURE_TOPOEXT)) { + u64 val; + + if (!rdmsrl_amd_safe(0xc0011005, &val)) { + val |= 1ULL << 54; + wrmsrl_amd_safe(0xc0011005, val); + rdmsrl(0xc0011005, val); + if (val & (1ULL << 54)) { + set_cpu_cap(c, X86_FEATURE_TOPOEXT); + printk(KERN_INFO FW_INFO "CPU: Re-enabling " + "disabled Topology Extensions Support\n"); + } + } + } + cpu_detect_cache_sizes(c); /* Multi core CPU? */ -- 1.7.8.5