Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030500Ab2CABcG (ORCPT ); Wed, 29 Feb 2012 20:32:06 -0500 Received: from kirsty.vergenet.net ([202.4.237.240]:41153 "EHLO kirsty.vergenet.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965191Ab2CABcE (ORCPT ); Wed, 29 Feb 2012 20:32:04 -0500 Date: Thu, 1 Mar 2012 10:32:01 +0900 From: Simon Horman To: Eugene Surovegin Cc: linux-kernel@vger.kernel.org, kexec-list , Eric Biederman , Vivek Goyal Subject: Re: [PATCH] kdump: force page alignment for per-CPU crash notes. Message-ID: <20120301013200.GF16483@verge.net.au> References: <1330536083-13098-1-git-send-email-surovegin@google.com> <20120301011811.GC16483@verge.net.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organisation: Horms Solutions Ltd. 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 Content-Length: 1428 Lines: 31 On Wed, Feb 29, 2012 at 05:23:10PM -0800, Eugene Surovegin wrote: > On Wed, Feb 29, 2012 at 5:18 PM, Simon Horman wrote: > > > On Wed, Feb 29, 2012 at 09:21:23AM -0800, Eugene Surovegin wrote: > > > Per-CPU allocations are not guaranteed to be physically contiguous. > > > However, kdump kernel and user-space code assumes that per-CPU > > > memory, used for saving CPU registers on crash, is. > > > This can cause corrupted /proc/vmcore in some cases - the main > > > symptom being huge ELF note section. > > > > > > Force page alignment for note_buf_t to ensure that this assumption holds. > > > > Ouch. I'm surprised there is an allocation on crash, perhaps > > it could at least be done earlier? And am I right in thinking > > that this change increases the likely hood that the allocation > > could fail? > > > > I'm not following. This allocation is done on start-up, not on crash. > If you cannot allocate this much memory on system boot, I'm not sure what > else you can do on this system.... Sorry, my eyes deceived me. You are correct and I agree. Is it the case that note_buf_t is never larger than PAGE_SIZE? If so I your patch looks good to me. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/