linux-kernel - Re: [patch v2 03/10] kdump: Add size to elfcorehdr kernel parameter

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Date:	Tue, 2 Aug 2011 14:55:01 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Michael Holzheu <holzheu@...ux.vnet.ibm.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 03/10] kdump: Add size to elfcorehdr kernel parameter

On Tue, Aug 02, 2011 at 11:08:07AM +0200, Michael Holzheu wrote:
> Hello Vivek,
> 
> #On Mon, 2011-08-01 at 16:36 -0400, Vivek Goyal wrote: 
> > On Wed, Jul 27, 2011 at 02:55:07PM +0200, Michael Holzheu wrote:
> > > From: Michael Holzheu <holzheu@...ux.vnet.ibm.com>
> > > 
> > > Currently only the address of the pre-allocated ELF header is passed with
> > > the elfcorehdr= kernel parameter. In order to reserve memory for the header
> > > in the 2nd kernel also the size is required. To pass the size with this
> > > patch the syntax of the kernel parameter is extended as follows:
> > > 
> > > elfcorehdr=[size[KMG]@]offset[KMG]
> > > 
> > > This change is backward compatible because elfcorehdr=size is still allowed.
> > 
> > Generally vmcore parses elfcorehdr to figure out the sizes. kexec-tools
> > knows about it and relevant memory is excluded from second kernel's map
> > with the help of memmap= command line option.
> > 
> > Can you please mention that this is only s390 specific requirement as
> > there are no memmap= equivalent options and somehow dump tools wants
> > to know how big the elf header size is?
> 
> I updated the description: 
> 
> Currently only the address of the pre-allocated ELF header is passed with
> the elfcorehdr= kernel parameter. In order to reserve memory for the header
> in the 2nd kernel also the size is required. Current kdump architecture
> backends use different methods to do that, e.g. x86 uses the memmap= kernel
> parameter. On s390 there is no easy way to transfer this information.
> Therefore the elfcorehdr kernel parameter is extended to also pass the size.
> This now can also be used as standard mechanism by all future kdump
> architecture backends.
> 
> The syntax of the kernel parameter is extended as follows:
> 
> elfcorehdr=[size[KMG]@]offset[KMG]
> 
> This change is backward compatible because elfcorehdr=size is still allowed.
> 
> Ok?

Yes, this one looks ok.

Thanks
Vivek
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