linux-kernel - Re: [PATCH 0/2] kdump/mmap: Fix mmap of /proc/vmcore for s390

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Date:	Fri, 24 May 2013 17:06:26 +0200
From:	Michael Holzheu <holzheu@...ux.vnet.ibm.com>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>,
	Jan Willeke <willeke@...ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	linux-kernel@...r.kernel.org, kexec@...ts.infradead.org
Subject: Re: [PATCH 0/2] kdump/mmap: Fix mmap of /proc/vmcore for s390

Hello Vivek,

On Fri, 24 May 2013 10:36:44 -0400
Vivek Goyal <vgoyal@...hat.com> wrote:

[snip]

> Sorry, I don't understand the problem. If we swapped low memory and
> crash reserved memory, that should have been taken care by prepared
> ELF headers so that we map the right pfns. In x86 we swap 640K of low
> memory with 640K of memory in reserved and we take care of this by
> preparing elf headers accordingly.
> 
> So why s390 can't do the same thing?

I am not sure if I understand this. Currently we create the ELF
header in a way that we have virtual=real. In the copy_oldmem_page() we
do the swap so that for the /proc/vmcore code it looks like contiguous
non-swapped memory.

One reason why I thought this was necessary was that /dev/oldmem
also uses the function and it should provide linear memory access like
it is on the live system with /dev/mem.

Is that implementation incorrect?

Best Regards,
Michael


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