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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 AAA56C43381 for ; Tue, 12 Mar 2019 23:10:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 75181217D9 for ; Tue, 12 Mar 2019 23:10:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727844AbfCLXKX (ORCPT ); Tue, 12 Mar 2019 19:10:23 -0400 Received: from mga11.intel.com ([192.55.52.93]:27631 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727263AbfCLXIQ (ORCPT ); Tue, 12 Mar 2019 19:08:16 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 12 Mar 2019 16:08:13 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,472,1544515200"; d="scan'208";a="326744224" Received: from romley-ivt3.sc.intel.com ([172.25.110.60]) by fmsmga006.fm.intel.com with ESMTP; 12 Mar 2019 16:08:13 -0700 From: Fenghua Yu To: "Thomas Gleixner" , "Ingo Molnar" , "H Peter Anvin" , "Dave Hansen" , "Paolo Bonzini" , "Ashok Raj" , "Peter Zijlstra" , "Xiaoyao Li " , "Michael Chan" , "Ravi V Shankar" Cc: "linux-kernel" , "x86" , linux-wireless@vger.kernel.org, netdev@vger.kernel.org, kvm@vger.kernel.org, Fenghua Yu Subject: [PATCH v5 04/18] x86/split_lock: Align x86_capability to unsigned long to avoid split locked access Date: Tue, 12 Mar 2019 16:00:22 -0700 Message-Id: <1552431636-31511-5-git-send-email-fenghua.yu@intel.com> X-Mailer: git-send-email 2.5.0 In-Reply-To: <1552431636-31511-1-git-send-email-fenghua.yu@intel.com> References: <1552431636-31511-1-git-send-email-fenghua.yu@intel.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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 aligned to unsigned long, the single unsigned long location may cross two cache lines and accessing the location by locked BTS/BTR introductions will trigger #AC. To fix the split lock issue, align x86_capability to 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 unsigned long. But this needs additional code changes. So we choose the simpler solution by enforcing alignment using __aligned(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 2bb3a648fc12..b92296595fbe 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]; + /* Unsigned long alignment to avoid split lock in atomic bitmap 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