From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755562AbYINQEf (ORCPT ); Sun, 14 Sep 2008 12:04:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752838AbYINQEY (ORCPT ); Sun, 14 Sep 2008 12:04:24 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:43203 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751474AbYINQEX (ORCPT ); Sun, 14 Sep 2008 12:04:23 -0400 Date: Sun, 14 Sep 2008 18:04:03 +0200 From: Ingo Molnar To: Pavel Machek Cc: Thomas Gleixner , Andi Kleen , Yinghai Lu , Andrew Morton , hpa@zytor.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] apci: dump slit Message-ID: <20080914160403.GA20082@elte.hu> References: <1221243468-8016-1-git-send-email-yhlu.kernel@gmail.com> <20080912122031.eca8723e.akpm@linux-foundation.org> <86802c440809121229i14727af4nd1416044b06ebb94@mail.gmail.com> <878wtxrrwh.fsf@basil.nowhere.org> <20080914112222.GA3956@ucw.cz> <20080914122618.GD16097@elte.hu> <20080914155928.GB4845@ucw.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080914155928.GB4845@ucw.cz> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian 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 * Pavel Machek wrote: > On Sun 2008-09-14 14:26:18, Ingo Molnar wrote: > > > > * Pavel Machek wrote: > > > > > On Fri 2008-09-12 23:19:21, Thomas Gleixner wrote: > > > > On Fri, 12 Sep 2008, Andi Kleen wrote: > > > > > "Yinghai Lu" writes: > > > > > > > > > > > > to see how wrong could be set by BIOS. > > > > > > > > > > Just dump it from user space then. There are plenty of tools > > > > > to access ACPI tables. > > > > > > > > 1.) what guarantees that we reach user space ? > > > > > > We can dump in *any* kernel. > > > > > > > 2) If it is _valuable_ information which we can gather via kernel > > > > output, then it is much more conveniant than asking the user to type > > > > whatevercryptictoolcommandline and provide the output. > > > > > > Ooh, 'lets dump more junk at everyone, typing commands is hard' :-(. > > > > no, the principle is, information like the boot-time CPUID information > > (and even the BIOS environment) can be indicative of _kernel bugs_. It > > is often essential to dump what the booting (and failing) kernel thinks > > is its environment. > > > > Often that environment is corrupted (by the kernel) and that leads to > > problems. This 'environment' can also be affected by things like hard > > boot vs cold boot differences, whether it's in a kexec environment, > > whether it's booted as a virtual guest, etc., etc. > > > > For a long time we had the kernel's x86 bootup pretty much as a mostly > > silent black box and when it broke we tried to figure things out > > afterwards which was difficult and error-prone. Now we've got various > > quite effective debug mechanisms (which includes printouts as well) and > > figuring out x86 problems is visibly easier. We definitely wont go back > > to the 'black box code, can only be debugged by a few experts' method. > > > > So extending on that is a good and obvious idea in general - and i agree > > with Peter that this should be command-line dependent, i.e. not printed > > by default. Only printing it when 'debug' is specified on the command > > line is a good solution. > > Dumping when user requested it on commandline seems like good > compromise to me. great! Yinghai, mind reworking the patch in that direction please? I'd suggest to enable the optional dumping of all things BIOS environment related, not just the ACPI/SLIT. there's also CONFIG_X86_VERBOSE_BOOTUP=y [default disabled] - which could be coupled with an x86=verbose boot parameter or so. Ingo