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 X-Spam-Level: X-Spam-Status: No, score=-8.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 60D4EC31E5B for ; Tue, 18 Jun 2019 22:51:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 419F5214AF for ; Tue, 18 Jun 2019 22:51:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730965AbfFRWvO (ORCPT ); Tue, 18 Jun 2019 18:51:14 -0400 Received: from mga07.intel.com ([134.134.136.100]:48878 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730847AbfFRWvM (ORCPT ); Tue, 18 Jun 2019 18:51:12 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 18 Jun 2019 15:51:11 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.63,390,1557212400"; d="scan'208";a="358009345" Received: from romley-ivt3.sc.intel.com ([172.25.110.60]) by fmsmga005.fm.intel.com with ESMTP; 18 Jun 2019 15:51:10 -0700 From: Fenghua Yu To: "Thomas Gleixner" , "Ingo Molnar" , "Borislav Petkov" , "H Peter Anvin" , "Peter Zijlstra" , "Andrew Morton" , "Dave Hansen" , "Paolo Bonzini" , "Radim Krcmar" , "Christopherson Sean J" , "Ashok Raj" , "Tony Luck" , "Dan Williams" , "Xiaoyao Li " , "Sai Praneeth Prakhya" , "Ravi V Shankar" Cc: "linux-kernel" , "x86" , kvm@vger.kernel.org, Fenghua Yu Subject: [PATCH v9 03/17] x86/split_lock: Align x86_capability to unsigned long to avoid split locked access Date: Tue, 18 Jun 2019 15:41:05 -0700 Message-Id: <1560897679-228028-4-git-send-email-fenghua.yu@intel.com> X-Mailer: git-send-email 2.5.0 In-Reply-To: <1560897679-228028-1-git-send-email-fenghua.yu@intel.com> References: <1560897679-228028-1-git-send-email-fenghua.yu@intel.com> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org set_cpu_cap() calls locked BTS and clear_cpu_cap() calls locked BTR to operate on bitmap defined in x86_capability. Locked BTS/BTR accesses a single unsigned long location. In 64-bit mode, the location is at: base address of x86_capability + (bit offset in x86_capability / 64) * 8 Since base address of x86_capability may not be aligned to unsigned long, the single unsigned long location may cross two cache lines and accessing the location by locked BTS/BTR introductions will cause split lock. To fix the split lock issue, align x86_capability to size of unsigned long so that the location will be always within one cache line. Changing x86_capability's type to unsigned long may also fix the issue because x86_capability will be naturally aligned to size of unsigned long. But this needs additional code changes. So choose the simpler solution by setting the array's alignment to size of unsigned long. Signed-off-by: Fenghua Yu --- arch/x86/include/asm/processor.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index c34a35c78618..d3e017723634 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -93,7 +93,9 @@ struct cpuinfo_x86 { __u32 extended_cpuid_level; /* Maximum supported CPUID level, -1=no CPUID: */ int cpuid_level; - __u32 x86_capability[NCAPINTS + NBUGINTS]; + /* Aligned to size of unsigned long to avoid split lock in atomic ops */ + __u32 x86_capability[NCAPINTS + NBUGINTS] + __aligned(sizeof(unsigned long)); char x86_vendor_id[16]; char x86_model_id[64]; /* in KB - valid for CPUS which support this call: */ -- 2.19.1