Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753241Ab1CYTXW (ORCPT ); Fri, 25 Mar 2011 15:23:22 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:57816 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752400Ab1CYTXV (ORCPT ); Fri, 25 Mar 2011 15:23:21 -0400 Date: Fri, 25 Mar 2011 20:23:03 +0100 From: Ingo Molnar To: Peter Zijlstra Cc: Linus Torvalds , mingo@redhat.com, hpa@zytor.com, acme@redhat.com, linux-kernel@vger.kernel.org, eric.dumazet@gmail.com, efault@gmx.de, fweisbec@gmail.com, rostedt@goodmis.org, tglx@linutronix.de, linux-tip-commits@vger.kernel.org Subject: Re: [tip:perf/urgent] perf, x86: Complain louder about BIOSen corrupting CPU/PMU state and continue Message-ID: <20110325192303.GB22960@elte.hu> References: <1301073100.2250.229.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1301073100.2250.229.camel@laptop> User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.3.1 -2.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Peter Zijlstra wrote: > > This might also be something we do want to give a kernel command line > > option for. As in "bios=allow-annoying-pmu-thing" or whatever. > > I had such a patch, Ingo argued against it and we decided not to do it, > but we could still. Basically for many kernel releases we ignored the BIOS corrupting the PMU - so one could fairly argue that this patch fixes a perf functionality regression for Eric. We'll still warn in the syslog about the BIOS so there's an indication that something is going on. Linus, which variant is the most efficient one in your opinion? I'm leaning slightly in favor of this patch in perf/urgent: it restores Eric's system to the before-BIOS-corruption-detection state, but also warns about the BIOS craziness. Ingo