linux-kernel - Re: unify pagetable accessors patch causes double fault II

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Message-ID: <20080114165635.GK15542@elte.hu>
Date:	Mon, 14 Jan 2008 17:56:35 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Andi Kleen <andi@...stfloor.org>, tglx@...utronix.de,
	linux-kernel@...r.kernel.org
Subject: Re: unify pagetable accessors patch causes double fault II


* Jeremy Fitzhardinge <jeremy@...p.org> wrote:

>> This is with PAE and seems to only happen with enough RAM (6GB); a 
>> 2GB system boots. 64bit also works.
>
> Thanks, I'll have a close look at it.  Presumably a pfn is getting 
> truncated to 20/32-bits somewhere.

would be nice to have some debugging apparatus for bugs like this. 
Perhaps artificially add a large pfn, then convert/unconvert, then 
subtract it and expect the whole transformation to be an identity 
mapping? This way we could simulate most of the effects of >4GB RAM, 
right?

	Ingo
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