From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758039Ab1JEP0B (ORCPT ); Wed, 5 Oct 2011 11:26:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:17350 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757963Ab1JEP0A (ORCPT ); Wed, 5 Oct 2011 11:26:00 -0400 Date: Wed, 5 Oct 2011 11:25:37 -0400 From: Vivek Goyal To: "K.Prasad" Cc: linux-kernel@vger.kernel.org, crash-utility@redhat.com, kexec@lists.infradead.org, Andi Kleen , "Luck, Tony" , "Eric W. Biederman" , anderson@redhat.com, tachibana@mxm.nes.nec.co.jp, oomichi@mxs.nes.nec.co.jp, Borislav Petkov Subject: Re: [Patch 1/4][kernel][slimdump] Add new elf-note of type NT_NOCOREDUMP to capture slimdump Message-ID: <20111005152537.GB30146@redhat.com> References: <20111003070735.GJ2223@in.ibm.com> <20111003073203.GA22694@in.ibm.com> <20111004140437.GA28306@redhat.com> <20111005071844.GB2235@in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20111005071844.GB2235@in.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 05, 2011 at 12:48:44PM +0530, K.Prasad wrote: > On Tue, Oct 04, 2011 at 10:04:37AM -0400, Vivek Goyal wrote: > > On Mon, Oct 03, 2011 at 01:02:03PM +0530, K.Prasad wrote: > > > There are certain types of crashes induced by faulty hardware in which > > > capturing crashing kernel's memory (through kdump) makes no sense (or sometimes > > > dangerous). > > > > > > A case in point, is unrecoverable memory errors (resulting in fatal machine > > > check exceptions) in which reading from the faulty memory location from the > > > kexec'ed kernel will cause double fault and system reset (leaving no > > > information for the user). > > > > Prasad, > > > > I am just trying to remember what was wrong with Andi's approach of > > disable MCE while copying the dump? > > > > Hi Vivek, > The behaviour upon a read operation on an UC memory location is > undefined and so we want to avoid it (previously discussed here: > http://article.gmane.org/gmane.linux.kernel/1146799). > When we disable MCE and copy the dump, we will invariably read the faulty > memory location. And how that is worse then not capturing a dump at all? Anyway, you said that in case of MCE vmcore is of no use and we don't want to capture it. Thanks Vivek