linux-kernel - Re: [patch v2 01/10] kdump: Add KEXEC_CRASH_CONTROL_MEMORY

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Date:	Tue, 02 Aug 2011 11:51:04 +0200
From:	Michael Holzheu <holzheu@...ux.vnet.ibm.com>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	ebiederm@...ssion.com, mahesh@...ux.vnet.ibm.com, hbabu@...ibm.com,
	oomichi@....nes.nec.co.jp, horms@...ge.net.au,
	schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-s390@...r.kernel.org
Subject: Re: [patch v2 01/10] kdump: Add KEXEC_CRASH_CONTROL_MEMORY_LIMIT

Hello Vivek,

On Mon, 2011-08-01 at 16:16 -0400, Vivek Goyal wrote:
> On Wed, Jul 27, 2011 at 02:55:05PM +0200, Michael Holzheu wrote:
> > From: Michael Holzheu <holzheu@...ux.vnet.ibm.com>
> > 
> > On s390 there is a different KEXEC_CONTROL_MEMORY_LIMIT for the normal and
> > the kdump kexec case. Therefore this patch introduces a new macro
> > KEXEC_CRASH_CONTROL_MEMORY_LIMIT. This is set to
> > KEXEC_CONTROL_MEMORY_LIMIT for all architectures that do not define
> > KEXEC_CRASH_CONTROL_MEMORY_LIMIT.
> 
> Hi Michael,
> 
> Curious that why limit is different for kexec and kdump cases on s390
> only.

The standard kexec relocate_kernel code calls a machine instruction that
must run below 2 GiB. For kdump we currently do not use the control page
at all because no segments have to be moved in that case. Perhaps I am
still missing something here?

Michael

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