From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755382AbYINP7v (ORCPT ); Sun, 14 Sep 2008 11:59:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753131AbYINP7n (ORCPT ); Sun, 14 Sep 2008 11:59:43 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:3248 "EHLO spitz.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752738AbYINP7n (ORCPT ); Sun, 14 Sep 2008 11:59:43 -0400 Date: Sun, 14 Sep 2008 17:59:29 +0200 From: Pavel Machek To: Ingo Molnar 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: <20080914155928.GB4845@ucw.cz> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080914122618.GD16097@elte.hu> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html