linux-kernel - Re: [PATCH 3/4] x86, kdump: Retore crashkernel= to allocate low

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Date:	Tue, 2 Apr 2013 13:00:46 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Vivek Goyal <vgoyal@...hat.com>
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 Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/4] x86, kdump: Retore crashkernel= to allocate low

On Tue, Apr 2, 2013 at 12:11 PM, Vivek Goyal <vgoyal@...hat.com> wrote:
> On Tue, Apr 02, 2013 at 11:49:13AM -0700, Yinghai Lu wrote:
>> On Tue, Apr 2, 2013 at 11:42 AM, Yinghai Lu <yinghai@...nel.org> wrote:
>> > aka:
>> > old kexec-tools stay with "crashkernel=X"
>> > new kexec-tools stay with
>> > 1. like old kexec tools
>> > 2. or "crashkernel=X,high" or "crashkernel=X,high crashkernel=Y,low",
>> > Y could be 100M or 0 etc.
>>
>> I keep the old logic like:
>> if there are several "crashkernel=X,high", only last one is honored.
>> if there are several "crashkernel=Y,low", only last one is honored.
>
> Yes but if different types of crashkernel= options are mixes then
> behavior is not defined.

dmesg or /proc/iomem will show them what is finally reserved.

>
> crashkernel=X,high crashkernel=X

==> crashkernel=X is tossed away.

> crashkernel=X,high crashkernel=Y;low

normal case. if user want more or disable low range.

> crashkernel=Y;low crashkernel=X

crashkernel=X will be used.

>
> And possibilities go on. So I think it makes life simpler if we always
> parse last crashkernel= option and act upon that. And use
> crashkernel_no_auto_low to opt out of auto reserved low memory area.

No, that is not just disable. User could want more like 128M instead of 72M.

Thanks

Yinghai
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