linux-kernel - Re: [PATCH] x86: Construct 32 bit boot time page tables in native format.

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Message-ID: <20080125002054.GA2059@elf.ucw.cz>
Date:	Fri, 25 Jan 2008 01:20:54 +0100
From:	Pavel Machek <pavel@....cz>
To:	"H. Peter Anvin" <hpa@...or.com>, "Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Ian Campbell <ijc@...lion.org.uk>, Ingo Molnar <mingo@...e.hu>,
	Mika Penttilä <mika.penttila@...umbus.fi>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH] x86: Construct 32 bit boot time page tables in native
	format.

On Thu 2008-01-24 15:51:24, H. Peter Anvin wrote:
> Jeremy Fitzhardinge wrote:
>> H. Peter Anvin wrote:
>>> While we're mucking around in this area, there is another thing which we 
>>> should eventually get around to fixing:
>>>
>>> we need a set of page tables with an identity mapping as well as the 
>>> kernel mapping, for trampolining (during startup, but also during things 
>>> like ACPI suspend/resume.)  Right now, we let those be the swapper page 
>>> tables, but that's probably not really a good idea, since it can hide 
>>> bugs.
>>
>> So you're suggesting a second system pagetable which has a P=V alias as 
>> well as the normal kernel mapping, used only when we actually need that 
>> alias?  Sounds simple enough to arrange.
>>
>
> I just looked at the ACPI suspend code, and it looks like it hacks its own 
> identity map at runtime.  Pavel, am I reading that code right?

Yes, I think so, I believe we do it on both 32 and 64 bit now.

(It is early here. And I almost got the .c wakeup code to work... it
already sets the mode).
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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