From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757389Ab3E2QYs (ORCPT ); Wed, 29 May 2013 12:24:48 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56657 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754839Ab3E2QYj (ORCPT ); Wed, 29 May 2013 12:24:39 -0400 Date: Wed, 29 May 2013 12:23:26 -0400 From: Vivek Goyal To: Michael Holzheu Cc: Zhang Yanfei , "Eric W. Biederman" , HATAYAMA Daisuke , Jan Willeke , Martin Schwidefsky , Heiko Carstens , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, Andrew Morton Subject: Re: [PATCH 0/2] kdump/mmap: Fix mmap of /proc/vmcore for s390 Message-ID: <20130529162325.GD22146@redhat.com> References: <20130524143644.GD18218@redhat.com> <20130524170626.2ac06efe@holzheu> <20130524152849.GF18218@redhat.com> <87mwrkatgu.fsf@xmission.com> <51A006CF.90105@gmail.com> <87k3mnahkf.fsf@xmission.com> <51A076FE.3060604@gmail.com> <20130525145217.0549138a@holzheu> <20130528135500.GC7088@redhat.com> <20130529135144.7f95c4c0@holzheu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130529135144.7f95c4c0@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 Wed, May 29, 2013 at 01:51:44PM +0200, Michael Holzheu wrote: > On Tue, 28 May 2013 09:55:01 -0400 > Vivek Goyal wrote: > > > On Sat, May 25, 2013 at 02:52:17PM +0200, Michael Holzheu wrote: > > [snip] > > > > Besides of the newmem mechanism, for completeness, we also > > > implemented the oldmem ELF header mechansim in kexec. But this is > > > disabled by default. > > > > > > See: "#ifdef WITH_ELF_HEADER" in kexec/arch/s390/crashdump-s390.c > > > > > > Currently no distribution uses the oldmem mechanism. > > > > Hi Michael, > > > > Mechanism to read from newmem is not there yet (your patches are still > > being reviewed) and you mentioned that no distribution is building > > kexec-tools with WITH_ELF_HEADER on s390. So how things are currently > > working for kdump on s390? > > Hello Vivek, > > On s390, if we do not get the ELF header from the 1st kernel with > "elfcorehdr=", we build the ELF header in the 2nd kernel. This is > currently the default because WITH_ELF_HEADER is not defined for > kexec tools. > > >>> START QUOTE > > [PATCH v3 1/3] kdump: Introduce ELF header in new memory feature > > Currently for s390 we create the ELF core header in the 2nd kernel with > a small trick. We relocate the addresses in the ELF header in a way > that for the /proc/vmcore code it seems to be in the 1st kernel (old) > memory and the read_from_oldmem() returns the correct data. This allows > the /proc/vmcore code to use the ELF header in the 2nd kernel. > > >>> END QUOTE > > For our current zfcpdump project (see "[PATCH 3/3]s390/kdump: Use > vmcore for zfcpdump") we could no longer use this trick. Therefore we > sent you the patches to get a clean interface for ELF header creation > in the 2nd kernel. > > > > > > > Therefore, if necessary, IMHO we can switch to the ELF header memory > > > swap mechanism for s390 in the kernel. Of course we would then also > > > have to adjust the (disabled) kexec code. > > > > So are you saying that s390 is ready to switch to mechanism of > > creating ELF headers in first kernel by kexec-tools and new kernel > > does not have to preare ELF headers? > > No, I meant that currently nobody is using the kexec tools ELF header > creation in the 1st kernel on s390. We create the ELF header in the > 2nd kernel (mainly because of our cpuplugd issue). > > Therefore, I think, we can safely change the ELF header creation in 2nd > kernel to use your p_offset swap trick *and* we remove the swap code in > the copy_oldmem_page() implementation (same kernel). Ok. Got it. So s390 can fix it in kernel without creating any backward compatibility issues (given the fact that nobody sees to be using kexec-tools to build headers). So please go ahead and fix it and that should solve your mmap() issue too. Also please fix kexec-tools and that change will not be backward compatible. 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 1UhjAw-0002Ib-R6 for kexec@lists.infradead.org; Wed, 29 May 2013 16:24:35 +0000 Date: Wed, 29 May 2013 12:23:26 -0400 From: Vivek Goyal Subject: Re: [PATCH 0/2] kdump/mmap: Fix mmap of /proc/vmcore for s390 Message-ID: <20130529162325.GD22146@redhat.com> References: <20130524143644.GD18218@redhat.com> <20130524170626.2ac06efe@holzheu> <20130524152849.GF18218@redhat.com> <87mwrkatgu.fsf@xmission.com> <51A006CF.90105@gmail.com> <87k3mnahkf.fsf@xmission.com> <51A076FE.3060604@gmail.com> <20130525145217.0549138a@holzheu> <20130528135500.GC7088@redhat.com> <20130529135144.7f95c4c0@holzheu> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20130529135144.7f95c4c0@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: kexec@lists.infradead.org, Heiko Carstens , Jan Willeke , linux-kernel@vger.kernel.org, HATAYAMA Daisuke , "Eric W. Biederman" , Martin Schwidefsky , Andrew Morton , Zhang Yanfei On Wed, May 29, 2013 at 01:51:44PM +0200, Michael Holzheu wrote: > On Tue, 28 May 2013 09:55:01 -0400 > Vivek Goyal wrote: > > > On Sat, May 25, 2013 at 02:52:17PM +0200, Michael Holzheu wrote: > > [snip] > > > > Besides of the newmem mechanism, for completeness, we also > > > implemented the oldmem ELF header mechansim in kexec. But this is > > > disabled by default. > > > > > > See: "#ifdef WITH_ELF_HEADER" in kexec/arch/s390/crashdump-s390.c > > > > > > Currently no distribution uses the oldmem mechanism. > > > > Hi Michael, > > > > Mechanism to read from newmem is not there yet (your patches are still > > being reviewed) and you mentioned that no distribution is building > > kexec-tools with WITH_ELF_HEADER on s390. So how things are currently > > working for kdump on s390? > > Hello Vivek, > > On s390, if we do not get the ELF header from the 1st kernel with > "elfcorehdr=", we build the ELF header in the 2nd kernel. This is > currently the default because WITH_ELF_HEADER is not defined for > kexec tools. > > >>> START QUOTE > > [PATCH v3 1/3] kdump: Introduce ELF header in new memory feature > > Currently for s390 we create the ELF core header in the 2nd kernel with > a small trick. We relocate the addresses in the ELF header in a way > that for the /proc/vmcore code it seems to be in the 1st kernel (old) > memory and the read_from_oldmem() returns the correct data. This allows > the /proc/vmcore code to use the ELF header in the 2nd kernel. > > >>> END QUOTE > > For our current zfcpdump project (see "[PATCH 3/3]s390/kdump: Use > vmcore for zfcpdump") we could no longer use this trick. Therefore we > sent you the patches to get a clean interface for ELF header creation > in the 2nd kernel. > > > > > > > Therefore, if necessary, IMHO we can switch to the ELF header memory > > > swap mechanism for s390 in the kernel. Of course we would then also > > > have to adjust the (disabled) kexec code. > > > > So are you saying that s390 is ready to switch to mechanism of > > creating ELF headers in first kernel by kexec-tools and new kernel > > does not have to preare ELF headers? > > No, I meant that currently nobody is using the kexec tools ELF header > creation in the 1st kernel on s390. We create the ELF header in the > 2nd kernel (mainly because of our cpuplugd issue). > > Therefore, I think, we can safely change the ELF header creation in 2nd > kernel to use your p_offset swap trick *and* we remove the swap code in > the copy_oldmem_page() implementation (same kernel). Ok. Got it. So s390 can fix it in kernel without creating any backward compatibility issues (given the fact that nobody sees to be using kexec-tools to build headers). So please go ahead and fix it and that should solve your mmap() issue too. Also please fix kexec-tools and that change will not be backward compatible. Thanks Vivek _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec