linux-kernel - Re: [PATCH 4/6] x86/mem-hotplug: Support initialize page tables bottom up

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Message-ID: <20130924140545.GA517@mtj.dyndns.org>
Date:	Tue, 24 Sep 2013 10:05:45 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Zhang Yanfei <zhangyanfei.yes@...il.com>
Cc:	Zhang Yanfei <zhangyanfei@...fujitsu.com>,
	"Rafael J . Wysocki" <rjw@...k.pl>, lenb@...nel.org,
	Thomas Gleixner <tglx@...utronix.de>, mingo@...e.hu,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Toshi Kani <toshi.kani@...com>,
	Wanpeng Li <liwanp@...ux.vnet.ibm.com>,
	Thomas Renninger <trenn@...e.de>,
	Yinghai Lu <yinghai@...nel.org>,
	Jiang Liu <jiang.liu@...wei.com>,
	Wen Congyang <wency@...fujitsu.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	isimatu.yasuaki@...fujitsu.com, izumi.taku@...fujitsu.com,
	Mel Gorman <mgorman@...e.de>, Minchan Kim <minchan@...nel.org>,
	mina86@...a86.com, gong.chen@...ux.intel.com,
	vasilis.liaskovitis@...fitbricks.com, lwoodman@...hat.com,
	Rik van Riel <riel@...hat.com>, jweiner@...hat.com,
	prarit@...hat.com, "x86@...nel.org" <x86@...nel.org>,
	linux-doc@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux MM <linux-mm@...ck.org>, linux-acpi@...r.kernel.org,
	imtangchen@...il.com
Subject: Re: [PATCH 4/6] x86/mem-hotplug: Support initialize page tables
 bottom up

On Tue, Sep 24, 2013 at 09:53:47PM +0800, Zhang Yanfei wrote:
> OK, this is just because we allocate pagtables just above the kernel.
> And if we use up the BRK space that is reserved for inital pagetables,
> we will use memblock to allocate memory for pagetables, and the memory
> allocated here should be mapped already. So we first map [kernel_end, end)
> to make memory above the kernel be mapped as soon as possible. And then
> use pagetables allocated above the kernel to map [ISA_END_ADDRESS, kernel_end).

I see.  The code seems fine to me then.  Can you please add comment
explaining why the split calls are necessary?

Thanks.

-- 
tejun
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