From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 87013C32774 for ; Tue, 16 Aug 2022 07:57:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229929AbiHPH53 (ORCPT ); Tue, 16 Aug 2022 03:57:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42700 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229772AbiHPH4p (ORCPT ); Tue, 16 Aug 2022 03:56:45 -0400 Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B025D119862; Mon, 15 Aug 2022 22:13:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1660626787; x=1692162787; h=from:to:cc:subject:date:message-id:in-reply-to: references; bh=7nu5UaOkh101GWA0xrXJbyB81JiIDTjN5u61jUDVgko=; b=RsZKqWgtieYyYOtOzyMpyVudol/bWznAcPdwBPW3A52zlE4kWRkdEh6B +SnKCkDEudk0NkK87+dcdZ7NtOwwG9T1jUop3/7/sSpNRWlBMA1xrgOLD neJ84kt8XQ+AjvWsc5c9Wiu2UXiBAg1rS7Ku9d4nb/m4mvIDVeXTBqBF7 vre+Bk06yUSZDx7WNbGMgYJcpa6wC87Q986nuzxH+wshi4/bRATZ99slu cPwVaIOVBxEpovqdw9+NW/RBVc7z+ykgAyv9G40OOSHpccfAOqJsQh7gw qHrwOTCJRENg5Mur6ASOfnKxCG8mQriB7Wi0Ev1butF9KsEPrgUDPBpki A==; X-IronPort-AV: E=McAfee;i="6400,9594,10440"; a="356130175" X-IronPort-AV: E=Sophos;i="5.93,240,1654585200"; d="scan'208";a="356130175" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Aug 2022 22:13:07 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.93,240,1654585200"; d="scan'208";a="666953503" Received: from power-sh.sh.intel.com ([10.239.183.122]) by fmsmga008.fm.intel.com with ESMTP; 15 Aug 2022 22:13:03 -0700 From: Zhang Rui To: linux-kernel@vger.kernel.org, x86@kernel.org, linux-hwmon@vger.kernel.org Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, corbet@lwn.net, fenghua.yu@intel.com, jdelvare@suse.com, linux@roeck-us.net, len.brown@intel.com, rui.zhang@intel.com Subject: [PATCH V2 6/8] x86/topology: Fix max_siblings calculation Date: Tue, 16 Aug 2022 13:16:31 +0800 Message-Id: <20220816051633.17775-7-rui.zhang@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20220816051633.17775-1-rui.zhang@intel.com> References: <20220816051633.17775-1-rui.zhang@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-hwmon@vger.kernel.org The max siblings value returned by CPUID.1F SMT level EBX differs among CPUs on Intel Hybrid platforms like ADL-S/P. It returns 2 for Pcore CPUs which have HT sibling and 1 for Ecore CPUs which do not. Today, CPUID SMT level EBX sets the global variable smp_num_siblings. Thus, smp_num_siblings is overridden to different values based on the CPU Pcore/Ecore enumeration order. For example, [ 0.201005] detect_extended_topology: CPU APICID 0x0, smp_num_siblings 2, x86_max_cores 10 [ 0.201117] start_kernel->check_bugs->cpu_smt_check_topology: smp_num_siblings 2 ... [ 0.010146] detect_extended_topology: CPU APICID 0x8, smp_num_siblings 2, x86_max_cores 10 ... [ 0.010146] detect_extended_topology: CPU APICID 0x39, smp_num_siblings 2, x86_max_cores 10 [ 0.010146] detect_extended_topology: CPU APICID 0x48, smp_num_siblings 1, x86_max_cores 20 ... [ 0.010146] detect_extended_topology: CPU APICID 0x4e, smp_num_siblings 1, x86_max_cores 20 [ 2.583800] sched_set_itmt_core_prio: smp_num_siblings 1 This inconsistency brings several potential issues: 1. some kernel configuration like cpu_smt_control, as set in start_kernel()->check_bugs()->cpu_smt_check_topology(), depends on smp_num_siblings set by cpu0. It is pure luck that all the current hybrid platforms use Pcore as cpu0 and hide this problem. 2. some per CPU data like cpuinfo_x86.x86_max_cores that depends on smp_num_siblings becomes inconsistent and bogus. 3. the final smp_num_siblings value after boot depends on the last CPU enumerated, which could either be Pcore or Ecore CPU. The solution is to use CPUID EAX bits_shift to get the maximum number of addressable logical processors, and use this to determin max siblings. Because: 1. the CPUID EAX bits_shift values are consistent among CPUs as far as observed. 2. some code already uses smp_num_siblings value to isolate the SMT ID bits in APIC-ID, like apic_id_is_primary_thread(). Suggested-and-reviewed-by: Len Brown Signed-off-by: Zhang Rui --- arch/x86/kernel/cpu/topology.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/arch/x86/kernel/cpu/topology.c b/arch/x86/kernel/cpu/topology.c index 5e868b62a7c4..2a88f2fa5756 100644 --- a/arch/x86/kernel/cpu/topology.c +++ b/arch/x86/kernel/cpu/topology.c @@ -23,7 +23,12 @@ #define LEAFB_SUBTYPE(ecx) (((ecx) >> 8) & 0xff) #define BITS_SHIFT_NEXT_LEVEL(eax) ((eax) & 0x1f) -#define LEVEL_MAX_SIBLINGS(ebx) ((ebx) & 0xffff) + +/* + * Use EAX bit_shift to calculate the maximum number of addressable logical + * processors sharing the current level. + */ +#define LEVEL_MAX_SIBLINGS(eax) (1 << BITS_SHIFT_NEXT_LEVEL(eax)) unsigned int __max_die_per_package __read_mostly = 1; EXPORT_SYMBOL(__max_die_per_package); @@ -79,7 +84,7 @@ int detect_extended_topology_early(struct cpuinfo_x86 *c) * initial apic id, which also represents 32-bit extended x2apic id. */ c->initial_apicid = edx; - smp_num_siblings = LEVEL_MAX_SIBLINGS(ebx); + smp_num_siblings = LEVEL_MAX_SIBLINGS(eax); #endif return 0; } @@ -109,9 +114,9 @@ int detect_extended_topology(struct cpuinfo_x86 *c) */ cpuid_count(leaf, SMT_LEVEL, &eax, &ebx, &ecx, &edx); c->initial_apicid = edx; - core_level_siblings = smp_num_siblings = LEVEL_MAX_SIBLINGS(ebx); + core_level_siblings = smp_num_siblings = LEVEL_MAX_SIBLINGS(eax); core_plus_mask_width = ht_mask_width = BITS_SHIFT_NEXT_LEVEL(eax); - die_level_siblings = LEVEL_MAX_SIBLINGS(ebx); + die_level_siblings = LEVEL_MAX_SIBLINGS(eax); pkg_mask_width = die_plus_mask_width = BITS_SHIFT_NEXT_LEVEL(eax); sub_index = 1; @@ -122,14 +127,14 @@ int detect_extended_topology(struct cpuinfo_x86 *c) * Check for the Core type in the implemented sub leaves. */ if (LEAFB_SUBTYPE(ecx) == CORE_TYPE) { - core_level_siblings = LEVEL_MAX_SIBLINGS(ebx); + core_level_siblings = LEVEL_MAX_SIBLINGS(eax); core_plus_mask_width = BITS_SHIFT_NEXT_LEVEL(eax); die_level_siblings = core_level_siblings; die_plus_mask_width = BITS_SHIFT_NEXT_LEVEL(eax); } if (LEAFB_SUBTYPE(ecx) == DIE_TYPE) { die_level_present = true; - die_level_siblings = LEVEL_MAX_SIBLINGS(ebx); + die_level_siblings = LEVEL_MAX_SIBLINGS(eax); die_plus_mask_width = BITS_SHIFT_NEXT_LEVEL(eax); } -- 2.25.1