Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752003AbcJJSzs (ORCPT ); Mon, 10 Oct 2016 14:55:48 -0400 Received: from mga03.intel.com ([134.134.136.65]:55173 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751015AbcJJSzq (ORCPT ); Mon, 10 Oct 2016 14:55:46 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.31,325,1473145200"; d="scan'208";a="770994342" Date: Mon, 10 Oct 2016 11:55:45 -0700 From: "Luck, Tony" To: Borislav Petkov Cc: Fenghua Yu , Thomas Gleixner , "H. Peter Anvin" , Ingo Molnar , Peter Zijlstra , Stephane Eranian , Dave Hansen , Nilay Vaish , Shaohua Li , David Carrillo-Cisneros , Ravi V Shankar , Sai Prakhya , Vikas Shivappa , linux-kernel , x86 Subject: Re: [PATCH v3 07/18] x86/intel_rdt: Add Haswell feature discovery Message-ID: <20161010185545.GA8429@intel.com> References: <1475894763-64683-1-git-send-email-fenghua.yu@intel.com> <1475894763-64683-8-git-send-email-fenghua.yu@intel.com> <20161009114116.js3cevxzbuucjeni@pd.tnic> <20161009170936.GC7672@linux.intel.com> <20161009162822.dpi3foa2eqcnw635@pd.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161009162822.dpi3foa2eqcnw635@pd.tnic> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3068 Lines: 86 On Sun, Oct 09, 2016 at 06:28:23PM +0200, Borislav Petkov wrote: > On Sun, Oct 09, 2016 at 10:09:37AM -0700, Fenghua Yu wrote: > > The MSR is not guaranteed on every stepping of the family and model machine > > because some parts may have the MSR fused off. And some bits in the MSR > > may not be implemented on some parts. And in KVM or guest, the MSR may not > > implemented. Those are reasons why we use wrmsr_safe/rdmsr_safe in Haswell > > probe. > > Please add that info in a comment somewhere there as we'll all forget > about it otherwise. How about this (this diff on top of current series, but obviously we'll fold it into part 07. commit cdb05159fb91ed1f85c950c0f2c6de25f143961d Author: Tony Luck Date: Mon Oct 10 11:48:42 2016 -0700 Update the HSW probe code - better comments, and use IA32_L3_CBM_BASE as the probe MSR instead of PQR_ASSOC at suggestion of h/w architect). diff --git a/arch/x86/kernel/cpu/intel_rdt.c b/arch/x86/kernel/cpu/intel_rdt.c index 4903e21d660d..e3c397306f1a 100644 --- a/arch/x86/kernel/cpu/intel_rdt.c +++ b/arch/x86/kernel/cpu/intel_rdt.c @@ -56,39 +56,39 @@ struct rdt_resource rdt_resources_all[] = { /* * cache_alloc_hsw_probe() - Have to probe for Intel haswell server CPUs - * as it does not have CPUID enumeration support for Cache allocation. + * as they do not have CPUID enumeration support for Cache allocation. + * The check for Vendor/Family/Model is not enough to guarantee that + * the MSRs won't #GP fault because only the following SKUs support + * CAT: + * Intel(R) Xeon(R) CPU E5-2658 v3 @ 2.20GHz + * Intel(R) Xeon(R) CPU E5-2648L v3 @ 1.80GHz + * Intel(R) Xeon(R) CPU E5-2628L v3 @ 2.00GHz + * Intel(R) Xeon(R) CPU E5-2618L v3 @ 2.30GHz + * Intel(R) Xeon(R) CPU E5-2608L v3 @ 2.00GHz * - * Probes by writing to the high 32 bits(CLOSid) of the IA32_PQR_MSR and - * testing if the bits stick. Max CLOSids is always 4 and max cbm length + * Probe by trying to write the first of the L3 cach mask registers + * and checking that the bits stick. Max CLOSids is always 4 and max cbm length * is always 20 on hsw server parts. The minimum cache bitmask length * allowed for HSW server is always 2 bits. Hardcode all of them. */ static inline bool cache_alloc_hsw_probe(void) { - u32 l, h_old, h_new, h_tmp; + u32 l, h; struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3]; - if (rdmsr_safe(MSR_IA32_PQR_ASSOC, &l, &h_old)) - return false; - - /* - * Default value is always 0 if feature is present. - */ - h_tmp = h_old ^ 0x1U; - if (wrmsr_safe(MSR_IA32_PQR_ASSOC, l, h_tmp)) - return false; - rdmsr(MSR_IA32_PQR_ASSOC, l, h_new); - - if (h_tmp != h_new) - return false; - - wrmsr(MSR_IA32_PQR_ASSOC, l, h_old); - r->max_closid = 4; r->num_closid = r->max_closid; r->cbm_len = 20; r->max_cbm = BIT_MASK(20) - 1; r->min_cbm_bits = 2; + + if (wrmsr_safe(IA32_L3_CBM_BASE, r->max_cbm, 0)) + return false; + rdmsr(IA32_L3_CBM_BASE, l, h); + + if (l != r->max_cbm) + return false; + r->enabled = true; return true;