linux-kernel - Re: [PATCH 04/13] x86, mm: Revert back good

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Message-ID: <506F78A2.3050408@zytor.com>
Date:	Fri, 05 Oct 2012 17:17:38 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Yinghai Lu <yinghai@...nel.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Jacob Shin <jacob.shin@....com>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, Tejun Heo <tj@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 04/13] x86, mm: Revert back good_end setting for 64bit

On 10/05/2012 02:32 PM, Eric W. Biederman wrote:
> Yinghai Lu <yinghai@...nel.org> writes:
>
>> On Fri, Oct 5, 2012 at 2:04 PM, Eric W. Biederman <ebiederm@...ssion.com> wrote:
>>>>> Is there a git commit that explains what the 'big range' problem is?
>>>
>>> At least on x86_64 this was recently tested and anywhere below 4G is
>>> good, and there is a patch floating around somewhere to remove this
>>> issue.
>>
>> patch for kernel or kexec-tools?
>
> kernel.
>
> The sgi guys needed a kdump kernel with 1G of ram to dump their all of
> the memory on one of their crazy large machines and so investigated
> this.
>
> Basically they found that a kdump kernel loaded anywhere < 4G worked,
> the only change that was needed was to relaxy the 896M hard code.
>
> In one test they had a kdump kernel loaded above 2G.
>

Seriously, any case where we can't load anywhere in physical ram on 
x86-64 is a bug.  i386 is another matter.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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