linux-kernel - Re: [PATCH]Fix broken VMI in 2.6.27-rc..

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Date:	Fri, 08 Aug 2008 09:13:54 -0700
From:	"H. Peter Anvin" <hpa@...nel.org>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	Zachary Amsden <zach@...are.com>,
	Alok Kataria <akataria@...are.com>,
	"torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	the arch/x86 maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH]Fix broken VMI in 2.6.27-rc..

Jeremy Fitzhardinge wrote:
>>
>> No, but it's hardly vast effort, either.
> 
> Thinking about it, the fixmap really has to be as high as possible.  If 
> it were any lower, then it would either truncate the 1:1 mapping, or 
> shadow some physical memory.
> 

The proposal was to put it *before* the 1:1 mapping:

FIX_HOLE would start at TASK_SIZE
PAGE_OFFSET would shift to TASK_SIZE + PMD_PAGE_SIZE

All the remaining offsets remain as-is.

It's slightly less efficient than the current version, since we can't 
share the PDE page for the fixmap with the final vmalloc map, but not 
terribly so.

	-hpa
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