linux-kernel - Re: [PATCH v5] x86, kdump: Set crashkernel

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Message-ID: <20130320160327.GD2273@redhat.com>
Date:	Wed, 20 Mar 2013 12:03:27 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>, WANG Chao <chaowang@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5] x86, kdump: Set crashkernel_low automatically

On Wed, Mar 20, 2013 at 08:53:29AM -0700, Yinghai Lu wrote:
> On Wed, Mar 20, 2013 at 6:08 AM, Vivek Goyal <vgoyal@...hat.com> wrote:
> 
> > Have a general question about crashkernel_low. Why does it need to
> > show up as "Crash kernel low" in /proc/iomem. Will it not be better
> > that all memory reserved for crashkernel (whether high or low), shows
> > as "Crash Kernel" and let kexec-tools decide whether to load kernel
> > high or low etc.
> >
> > IOW, there should not be any need to differentiate between "Crash kernel"
> > and "Crash kernel low". There are address ranges associated and looking
> > at addresses it is obivious that certain memory is below 4G.
> 
> yes. it is doable.
> but
> 1. will need to add more code to expand parse_iomem_single to handle
> multiple "Crash kernel" in kexec-tools.
> 2. also we already have "crashkernel_low=" in command line, so it is
> good to keep them consistent in /proc/iomem.

I think command line and /proc/iomem output are very different.
crashkernel_low is just enforcing that reserve it below 4G and memory
type still remains "Crash Kernel".

So to me, /proc/iomem is showing ranges and memory type and both the
memory types should be "Crash Kernel".

IMHO, we should add code in kexec-tools to deal with it (multiple
entries for memory type "Crash Kernel"), instead of especial casing
"Crash Kernel Low". Who knows down the line we end up reserving more
crash kernel memory which is not contiguous. Keeping all reserved
memory of same type will help then.

Thanks
Vivek
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