From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757041Ab3EXRGC (ORCPT ); Fri, 24 May 2013 13:06:02 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51106 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756996Ab3EXRGA (ORCPT ); Fri, 24 May 2013 13:06:00 -0400 Date: Fri, 24 May 2013 13:05:07 -0400 From: Vivek Goyal To: Michael Holzheu Cc: HATAYAMA Daisuke , Jan Willeke , Martin Schwidefsky , Heiko Carstens , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, Andrew Morton , "Eric W. Biederman" Subject: Re: [PATCH 0/2] kdump/mmap: Fix mmap of /proc/vmcore for s390 Message-ID: <20130524170507.GG18218@redhat.com> References: <1369400889-11064-1-git-send-email-holzheu@linux.vnet.ibm.com> <20130524143644.GD18218@redhat.com> <20130524170626.2ac06efe@holzheu> <20130524152849.GF18218@redhat.com> <20130524184653.52d75b5f@holzheu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130524184653.52d75b5f@holzheu> 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 Fri, May 24, 2013 at 06:46:53PM +0200, Michael Holzheu wrote: > On Fri, 24 May 2013 11:28:49 -0400 > Vivek Goyal wrote: > > > On Fri, May 24, 2013 at 05:06:26PM +0200, Michael Holzheu wrote: > > [snip] > > > As /proc/vmcore is the most used and useful interface, I prefer that > > we swap memory and put that info in elf headers. For /dev/oldme, I > > don't mind if we leave it as it is. If somebody really cares, then > > I guess we need to write a new command line option which /dev/mem > > can parse and which tells it about swaps so that /dev/oldmem can > > map things correctly. (This is better than hardcoding things). > > Besides of the potential /dev/oldmem issue, I still do not understand > the option of doing the swap in the elf header. Looks like I missed > here a fundamental design point of kdump :( > > Is that done by specifying different virtual and physical addresses in > the ELF header? Nope. We keep the virtual to physical address mapping same. We just modify the p_offset in PT_LOAD elf header to represent where actually the memory is present physically. And when /proc/vmcore reads the data, it reads it from p_offset. IOW, p_offset and p_paddr will be different for swapped memory but should be same for memory which has not been swapped. Thanks Vivek From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx1.redhat.com ([209.132.183.28]) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1UfvRG-0003ty-RX for kexec@lists.infradead.org; Fri, 24 May 2013 17:06:00 +0000 Date: Fri, 24 May 2013 13:05:07 -0400 From: Vivek Goyal Subject: Re: [PATCH 0/2] kdump/mmap: Fix mmap of /proc/vmcore for s390 Message-ID: <20130524170507.GG18218@redhat.com> References: <1369400889-11064-1-git-send-email-holzheu@linux.vnet.ibm.com> <20130524143644.GD18218@redhat.com> <20130524170626.2ac06efe@holzheu> <20130524152849.GF18218@redhat.com> <20130524184653.52d75b5f@holzheu> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20130524184653.52d75b5f@holzheu> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=twosheds.infradead.org@lists.infradead.org To: Michael Holzheu Cc: Heiko Carstens , kexec@lists.infradead.org, Jan Willeke , linux-kernel@vger.kernel.org, HATAYAMA Daisuke , "Eric W. Biederman" , Martin Schwidefsky , Andrew Morton On Fri, May 24, 2013 at 06:46:53PM +0200, Michael Holzheu wrote: > On Fri, 24 May 2013 11:28:49 -0400 > Vivek Goyal wrote: > > > On Fri, May 24, 2013 at 05:06:26PM +0200, Michael Holzheu wrote: > > [snip] > > > As /proc/vmcore is the most used and useful interface, I prefer that > > we swap memory and put that info in elf headers. For /dev/oldme, I > > don't mind if we leave it as it is. If somebody really cares, then > > I guess we need to write a new command line option which /dev/mem > > can parse and which tells it about swaps so that /dev/oldmem can > > map things correctly. (This is better than hardcoding things). > > Besides of the potential /dev/oldmem issue, I still do not understand > the option of doing the swap in the elf header. Looks like I missed > here a fundamental design point of kdump :( > > Is that done by specifying different virtual and physical addresses in > the ELF header? Nope. We keep the virtual to physical address mapping same. We just modify the p_offset in PT_LOAD elf header to represent where actually the memory is present physically. And when /proc/vmcore reads the data, it reads it from p_offset. IOW, p_offset and p_paddr will be different for swapped memory but should be same for memory which has not been swapped. Thanks Vivek _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec