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

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Date:	Thu, 07 Aug 2008 15:17:20 -0700
From:	"H. Peter Anvin" <hpa@...nel.org>
To:	Zachary Amsden <zach@...are.com>
CC:	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..

Zachary Amsden wrote:
> 
>> Realistically speaking, any (virtual) machine which does *not* have a
>> full complement of lowmem (i.e. less than 896 MB in the common case)
>> will not suffer significatly from losing a few megabytes of address space.
> 
> Yes, the reason to make the fixmap moveable is to allow as much address
> space as possible for big memory (physical) machines.
> 

That being said, the fixmap area being movable more than kind of defeats 
a major point of the fixmap area; the addresses in it are no longer fixed.

The only way I can see around that, though, is to move the 1:1 mapping 
base up by 2/4 MB (for PAE/no PAE, respectively) and put the fixmap area 
there.  Kind of sucks, but would be doable.

	-hpa
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