linux-kernel - Re: mm: BUG in do_huge_pmd_wp

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Date:	Thu, 25 Apr 2013 19:28:34 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Simon Jeons <simon.jeons@...il.com>
CC:	Minchan Kim <minchan@...nel.org>,
	Sasha Levin <sasha.levin@...cle.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Mel Gorman <mgorman@...e.de>, Dave Jones <davej@...hat.com>,
	linux-mm <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: mm: BUG in do_huge_pmd_wp_page

On 04/24/2013 04:40 PM, Simon Jeons wrote:
> 
> I see in memblock_trim_memory(): start = round_up(orig_start, align);
> here align is PAGE_SIZE, so the dump of zone ranges in my machine is [ 
>   0.000000]  DMA      [mem 0x00001000-0x00ffffff]. Why PFN 0 is not
> used? just for align?
> 

PFN 0 contains the real-mode interrupt vector table and BIOS data area,
so we just reserve it.  Avoids issues with zero being special, too.

	-hpa


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