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

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Message-ID: <479922D0.3010708@zytor.com>
Date:	Thu, 24 Jan 2008 15:44:16 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	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.

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.
> 

Yes.  We'd use it during initialization and at other times when we need 
trampolining, but give the swapper something which only has the kernel map.

	-hpa
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