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

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Date:	Mon, 11 Mar 2013 15:20:21 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	WANG Chao <chaowang@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86, kdump: Set crashkernel_low automatically

On Mon, Mar 11, 2013 at 12:06:06PM -0700, Yinghai Lu wrote:

[..]
> > I actually disagree with trying low memory at all.  Push kdump as high
> > into the memory range as we can go, if there is a performance penalty it
> > is much better to take it in the kdump kernel.
> 
> Agreed, It's better let 64 bit all use one code path.
> And we can find more bugs while load them all high.
> otherwise it would be hard to fix them if the bugs only happens on systems
> that have bunch of dimms.

I find it odd that if a user wants to load a 32bit kernel or use 32bit
entry point then he needs to first reboot the kernel and re-reserve
the memory.

At installation time, one does not necessarily know what kind of kernel
will be used for crashdump. So reserving as high as possible limits
the choices.

I would rather prefer that user opt in for higher addresses instead of
these being reserved by default.

Thanks
Vivek
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