linux-kernel - Re: [PATCH] x86: Find offset for crashkernel reservation automatically

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Message-ID: <m1od50ztoa.fsf@frodo.ebiederm.org>
Date:	Mon, 14 Jul 2008 02:44:37 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Bernhard Walle <bwalle@...e.de>
Cc:	"Yinghai Lu" <yhlu.kernel@...il.com>,
	"Vivek Goyal" <vgoyal@...hat.com>, kexec@...ts.infradead.org,
	x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: Find offset for crashkernel reservation automatically

Bernhard Walle <bwalle@...e.de> writes:

> * Yinghai Lu [2008-07-14 00:11]:
>>
>> should use min_t(u64, 1ULL<<32, max_low_pfn<<PAGE_SHIFT) replace ULONG_MAX
>
> Shouldn't we use  min_t(u64, ULLONG_MAX, max_low_pfn<<PAGE_SHIFT), i.e.
> should we really limit the crashkernel to a 32 bit address on a 64 bit
> system?

We should use the lowest physical address that meets our size and
alignment constraints.  However there is no reason to make this be <
4G or even < 1G.  The worst case is that we reserve an area the kdump
kernel can't run out of.  However /sbin/kexec should check for that as
the kexec on panic code is not necessarily a linux kernel.

Eric
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