Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756834Ab1CNSNZ (ORCPT ); Mon, 14 Mar 2011 14:13:25 -0400 Received: from e28smtp04.in.ibm.com ([122.248.162.4]:42255 "EHLO e28smtp04.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752465Ab1CNSNY (ORCPT ); Mon, 14 Mar 2011 14:13:24 -0400 Date: Mon, 14 Mar 2011 23:43:15 +0530 From: Mahesh J Salgaonkar To: =?iso-8859-1?Q?Am=E9rico?= Wang Cc: Anton Blanchard , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, "Eric W. Biederman" , akpm@linux-foundation.org Subject: Re: [PATCH 1/2] kdump: Allow shrinking of kdump region to be overridden Message-ID: <20110314181315.GA16075@in.ibm.com> Reply-To: mahesh@linux.vnet.ibm.com References: <20100825002258.GD28360@kryten> <4D771EE6.5050404@linux.vnet.ibm.com> <20110309122046.GC16951@cr0.redhat.com> <20110309234657.264d3080@kryten> <20110309142108.GD16951@cr0.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20110309142108.GD16951@cr0.redhat.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2269 Lines: 54 On Wed, Mar 09, 2011 at 10:21:08PM +0800, Am?rico Wang wrote: > On Wed, Mar 09, 2011 at 11:46:57PM +1100, Anton Blanchard wrote: > > > >Hi, > > > >> The crashkernel region is specified via kernel cmdline, so why > >> not just drop a failure when it overlaps with RMO region? > >> Am I missing something? > > > >Unfortunately a ppc64 kernel requires a chunk of RMO memory. We would > >need the ability to specify multiple crashkernel regions - about 32MB > >in the RMO and the rest can be anywhere. That sounds pretty fragile for > >a user to configure successfully on the cmdline. > > > >Thats why the ppc64 crashkernel region begins mid way through the RMO > >region. It means both kernels get a chunk of RMO and we only have to > >deal with one crashkernel reservation in all the tools and > >documentation. > > > > So, when I specify 128M in cmdline, 32M of them are RMO, and the > rest 96M are normal memory? And when I want to free all of them, > actually the 32M RMO will never be freed? In ppc64 implementation the crashkernel region begins mid way through the RMO and spans across into the normal memory. For e.g. on power system with 128M RMO size, when user specifies 128M in cmdline, the crashkernel starts from default offset 64M through 192M. Which means 64M in RMO region and rest beyond RMO. <-------------------RMO---------------> <---rtas--> 0 64M 128M End |=====================|=================|===========|============| Crash_start|<------------128M----------->| Crash End During free we do free all of them including RMO region. But since the rtas region is always on top of RMO, crashkernel memory overlaps rtas region and we endup freeing that even, which is causing the crash. > > > _______________________________________________ > kexec mailing list > kexec@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kexec -- Signed-off-by: Mahesh Salgaonkar -- 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/