From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756562Ab3GDLjI (ORCPT ); Thu, 4 Jul 2013 07:39:08 -0400 Received: from mga09.intel.com ([134.134.136.24]:49007 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752996Ab3GDLjG (ORCPT ); Thu, 4 Jul 2013 07:39:06 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.87,994,1363158000"; d="scan'208";a="364742178" Message-ID: <51D55ED4.5030405@intel.com> Date: Thu, 04 Jul 2013 19:39:00 +0800 From: "Yan, Zheng" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130514 Thunderbird/17.0.6 MIME-Version: 1.0 To: Peter Zijlstra CC: linux-kernel@vger.kernel.org, mingo@kernel.org, eranian@google.com, andi@firstfloor.org Subject: Re: [PATCH v2 4/7] perf, x86: Save/resotre LBR stack during context switch References: <1372663387-11754-1-git-send-email-zheng.z.yan@intel.com> <1372663387-11754-5-git-send-email-zheng.z.yan@intel.com> <20130704095735.GL18898@dyad.programming.kicks-ass.net> In-Reply-To: <20130704095735.GL18898@dyad.programming.kicks-ass.net> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/04/2013 05:57 PM, Peter Zijlstra wrote: > On Mon, Jul 01, 2013 at 03:23:04PM +0800, Yan, Zheng wrote: >> +++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c >> @@ -185,6 +185,13 @@ void intel_pmu_lbr_reset(void) >> intel_pmu_lbr_reset_32(); >> else >> intel_pmu_lbr_reset_64(); >> + >> + wrmsrl(x86_pmu.lbr_tos, 0); >> +} > > I double checked; my SDM Jun 2013, Vol 3C 35-93 very explicitly states that > MSR_LASTBRANCH_TOS is a read-only MSR. And afaicr all previous times I checked > this it did say this too. > thank you for point out this. I will update the patch Yan, Zheng