linux-kernel - Re: [PATCH 10/28] i386: map enough initial memory to create lowmem mappings

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Message-ID: <462CD877.8000302@zytor.com>
Date:	Mon, 23 Apr 2007 09:01:59 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Chuck Ebbert <cebbert@...hat.com>, Andi Kleen <ak@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	virtualization@...ts.osdl.org, lkml <linux-kernel@...r.kernel.org>,
	Zachary Amsden <zach@...are.com>,
	Chris Wright <chrisw@...s-sol.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 10/28] i386: map enough initial memory to create lowmem
 mappings

Eric W. Biederman wrote:
> 
> I happened to be looking at this stretch of code and I have realized
> that this is quite simply the wrong fix.
> 
> The problem is that it depends intimately on the details of
> alloc_bootmem_pages_low.  Essentially the problem is that when
> we are setting up the identity mappings in paging_init we assume
> the identity mappings already exist.
> 
> If there are holes in the memory map or someone changes the way
> pages are returned from alloc_bootmem_pages_low() this code
> will break again.
> 

How would holes in the memory map affect it?

	-hpa
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