linux-kernel - Re: [PATCH] kexec/powerpc: fix exporting memory limit

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Message-ID: <1394153258.21206.1.camel@concordia>
Date:	Fri, 07 Mar 2014 11:47:38 +1100
From:	Michael Ellerman <mpe@...erman.id.au>
To:	Nikita Yushchenko <nyushchenko@....rtsoft.ru>
Cc:	kexec@...ts.infradead.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Anton Blanchard <anton@...ba.org>,
	Hari Bathini <hbathini@...ux.vnet.ibm.com>,
	Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>,
	linuxppc-dev@...ts.ozlabs.org, yadviga@....rtsoft.ru,
	lugovskoy@....rtsoft.ru, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kexec/powerpc: fix exporting memory limit

On Thu, 2014-03-06 at 18:24 +0400, Nikita Yushchenko wrote:
> When preparing dump-capturing kernel, kexec userspace tool needs to know
> actual amount of memory used by the running kernel. This may differ from
> extire available DRAM for a couple of reasons. To address this issue,
> kdump kernel support code injects several attributes into device tree that
> are later captured by userspace kexec tool via /proc interface.
> 
> One such attrubute is 'chosen/linux,memory_limit' that is used to pass
> memory limit of the running kernel.
> 
> This was initialized using kernel's 'memory_limit' variable, that is set
> by early init code based on mem= kernel parameter and other reasons.
> 
> But there are cases when memory_limit variable does not contain proper
> information. One such case is when !CONFIG_HIGHMEM kernel runs on system
> with memory large enough not to fit into lowmem.

Why doesn't the !CONFIG_HIGHMEM code update memory_limit to reflect reality.

cheers


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