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From: Vivek Goyal <vgoyal@redhat.com>
To: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Cc: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>,
	Jan Willeke <willeke@de.ibm.com>,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	linux-kernel@vger.kernel.org, kexec@lists.infradead.org,
	Andrew Morton <akpm@linux-foundation.org>,
	"Eric W. Biederman" <ebiederm@xmission.com>
Subject: Re: [PATCH 0/2] kdump/mmap: Fix mmap of /proc/vmcore for s390
Date: Fri, 24 May 2013 13:05:07 -0400	[thread overview]
Message-ID: <20130524170507.GG18218@redhat.com> (raw)
In-Reply-To: <20130524184653.52d75b5f@holzheu>

On Fri, May 24, 2013 at 06:46:53PM +0200, Michael Holzheu wrote:
> On Fri, 24 May 2013 11:28:49 -0400
> Vivek Goyal <vgoyal@redhat.com> 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

WARNING: multiple messages have this Message-ID (diff)
From: Vivek Goyal <vgoyal@redhat.com>
To: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>,
	kexec@lists.infradead.org, Jan Willeke <willeke@de.ibm.com>,
	linux-kernel@vger.kernel.org,
	HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 0/2] kdump/mmap: Fix mmap of /proc/vmcore for s390
Date: Fri, 24 May 2013 13:05:07 -0400	[thread overview]
Message-ID: <20130524170507.GG18218@redhat.com> (raw)
In-Reply-To: <20130524184653.52d75b5f@holzheu>

On Fri, May 24, 2013 at 06:46:53PM +0200, Michael Holzheu wrote:
> On Fri, 24 May 2013 11:28:49 -0400
> Vivek Goyal <vgoyal@redhat.com> 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

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kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec

  reply	other threads:[~2013-05-24 17:06 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-05-24 13:08 [PATCH 0/2] kdump/mmap: Fix mmap of /proc/vmcore for s390 Michael Holzheu
2013-05-24 13:08 ` Michael Holzheu
2013-05-24 13:08 ` [PATCH 1/2] kdump/mmap: Introduce arch_oldmem_remap_pfn_range() Michael Holzheu
2013-05-24 13:08   ` Michael Holzheu
2013-05-24 13:08 ` [PATCH 2/2] s390/kdump/mmap: Implement arch_oldmem_remap_pfn_range() for s390 Michael Holzheu
2013-05-24 13:08   ` Michael Holzheu
2013-05-24 14:36 ` [PATCH 0/2] kdump/mmap: Fix mmap of /proc/vmcore " Vivek Goyal
2013-05-24 14:36   ` Vivek Goyal
2013-05-24 15:06   ` Michael Holzheu
2013-05-24 15:06     ` Michael Holzheu
2013-05-24 15:28     ` Vivek Goyal
2013-05-24 15:28       ` Vivek Goyal
2013-05-24 16:46       ` Michael Holzheu
2013-05-24 16:46         ` Michael Holzheu
2013-05-24 17:05         ` Vivek Goyal [this message]
2013-05-24 17:05           ` Vivek Goyal
2013-05-25 13:13           ` Michael Holzheu
2013-05-25 13:13             ` Michael Holzheu
2013-05-24 22:44       ` Eric W. Biederman
2013-05-24 22:44         ` Eric W. Biederman
2013-05-25  0:33         ` Zhang Yanfei
2013-05-25  0:33           ` Zhang Yanfei
2013-05-25  3:01           ` Eric W. Biederman
2013-05-25  3:01             ` Eric W. Biederman
2013-05-25  8:31             ` Zhang Yanfei
2013-05-25  8:31               ` Zhang Yanfei
2013-05-25 12:52               ` Michael Holzheu
2013-05-25 12:52                 ` Michael Holzheu
2013-05-28 13:55                 ` Vivek Goyal
2013-05-28 13:55                   ` Vivek Goyal
2013-05-29 11:51                   ` Michael Holzheu
2013-05-29 11:51                     ` Michael Holzheu
2013-05-29 16:23                     ` Vivek Goyal
2013-05-29 16:23                       ` Vivek Goyal
2013-05-29 17:12                       ` Michael Holzheu
2013-05-29 17:12                         ` Michael Holzheu
2013-05-30 15:00                         ` Vivek Goyal
2013-05-30 15:00                           ` Vivek Goyal
2013-05-30 20:38                     ` Vivek Goyal
2013-05-30 20:38                       ` Vivek Goyal
2013-05-31 14:21                       ` Michael Holzheu
2013-05-31 14:21                         ` Michael Holzheu
2013-05-31 16:01                         ` Vivek Goyal
2013-05-31 16:01                           ` Vivek Goyal
2013-06-03 13:27                           ` Michael Holzheu
2013-06-03 13:27                             ` Michael Holzheu
2013-06-03 15:59                             ` Vivek Goyal
2013-06-03 15:59                               ` Vivek Goyal
2013-06-03 16:48                               ` Michael Holzheu
2013-06-03 16:48                                 ` Michael Holzheu
2013-05-28 14:44                 ` Vivek Goyal
2013-05-28 14:44                   ` Vivek Goyal
2013-05-25 20:36               ` Eric W. Biederman
2013-05-25 20:36                 ` Eric W. Biederman

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