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 1AC41C00140 for ; Tue, 2 Aug 2022 11:29:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236438AbiHBL3k (ORCPT ); Tue, 2 Aug 2022 07:29:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60748 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236278AbiHBL3f (ORCPT ); Tue, 2 Aug 2022 07:29:35 -0400 Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AA445313AD for ; Tue, 2 Aug 2022 04:29:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1659439774; x=1690975774; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=2W0p4AOerrYk2hF7PCF4DyJlk0QZ7/ldfaGLcxCA7fM=; b=cJpO2O0BBFs6JKzanEO+k1TaTH2EYIUinhe1dyLbTRhzQZwQu2tA27kX j1A2h5ti+th1Xl6WkibbMzD7sgmPDgpVEHxSJqiPoh65vheP6obwCXPdH YsN1DPQlFGiyzwFGb0GcEsB1rzFXiyF26b7v3vhI/9V/9EsSln+26walw /bpRKlgqnC9IPWd7Po8JNvcV18E8X63NFXQ3h4foPVPSXo8x7zsZJQHCP UuzCVV6x+nkcOOFcOq9HML+bi7JR12+Ar+DjvP56dbbtuopSbdTXz2qfb ik9YQnwi+BJaR0rkb2zePWARtV1YAXRowGZ/DTHbE4PLYxunOYqClu0yP g==; X-IronPort-AV: E=McAfee;i="6400,9594,10426"; a="315226398" X-IronPort-AV: E=Sophos;i="5.93,210,1654585200"; d="scan'208";a="315226398" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Aug 2022 04:29:34 -0700 X-IronPort-AV: E=Sophos;i="5.93,210,1654585200"; d="scan'208";a="661585782" Received: from cqiang-mobl.ccr.corp.intel.com (HELO [10.249.174.172]) ([10.249.174.172]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Aug 2022 04:29:32 -0700 Message-ID: <897aa91c-9d45-e16a-9b09-849fab588cd7@intel.com> Date: Tue, 2 Aug 2022 19:29:30 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Firefox/91.0 Thunderbird/91.11.0 Subject: Re: [RESEND] x86/bus_lock: Don't assume the init value of DEBUGCTLMSR.BUS_LOCK_DETECT to be zero Content-Language: en-US To: Ingo Molnar Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , Tony Luck , Fenghua Yu , linux-kernel@vger.kernel.org, x86@kernel.org References: <20220802033206.21333-1-chenyi.qiang@intel.com> From: Chenyi Qiang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/2/2022 6:51 PM, Ingo Molnar wrote: > > * Chenyi Qiang wrote: > >> It's possible that BIOS/firmware has set DEBUGCTLMSR_BUS_LOCK_DETECT, or >> this kernel has been kexec'd from a kernel that enabled bus lock >> detection. >> >> Disable bus lock detection explicitly if not wanted. > > Makes sense. > > Just curious: in what circumstances does the BIOS/firmware set > DEBUGCTLMSR_BUS_LOCK_DETECT? Does it use it, or does it enable it for some > spurious reason, without really using the feature? (Assuming you are aware > of instances where this happened - or was this simply a hypothetical?) Yes, It's just a hypothetical for BIOS/firmware. Kexec is the real case I met with this problem. > > Thanks, > > Ingo