From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753410AbbHDFwh (ORCPT ); Tue, 4 Aug 2015 01:52:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54317 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751132AbbHDFwg (ORCPT ); Tue, 4 Aug 2015 01:52:36 -0400 Date: Tue, 4 Aug 2015 07:52:29 +0200 From: Jiri Olsa To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, kexec@lists.infradead.org, Ingo Molnar , dong.su@ericsson.com, Vivek Goyal , Haren Myneni , Don Zickus Subject: Re: [RFC] perf: Clear MSRs on kexec Message-ID: <20150804055229.GD14481@krava.redhat.com> References: <20150803213228.GC14481@krava.redhat.com> <20150803215417.GG25159@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150803215417.GG25159@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 03, 2015 at 11:54:17PM +0200, Peter Zijlstra wrote: > On Mon, Aug 03, 2015 at 11:32:28PM +0200, Jiri Olsa wrote: > > hi, > > I'm getting following message on the kdump kernel start > > > > Broken BIOS detected, complain to your hardware vendor.\ > > [Firmware Bug]: the BIOS has corrupted hw-PMU resources (MSR 38d is b0) > > > > it seems to be caused by NMI watchdog being configured > > and fixed counter values stays in MSRs, which triggers > > warning in check_hw_exists and disables perf support > > in kdump kernel.. which probably does not hurt ;-) > > > > zeroing MSRs during kdump shutdown seems to work (attached) > > but I'm not sure thats correct place for kdump perf callback > > Right, but why bother? All that kernel needs to do is write a memory > dump to someplace and reboot, right? The less you do, the less can go > wrong. well, I was hunting that 'Broken BIOS..' message which is wrong I wouldn't think anyone wants to use perf under kdump kernel, but you never know ;-) jirka