linux-kernel - Re: [PATCH] i386/PAE: avoid temporarily inconsistent pte-s

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Message-Id: <46F16779.76E4.0078.0@novell.com>
Date:	Wed, 19 Sep 2007 17:16:25 +0100
From:	"Jan Beulich" <jbeulich@...ell.com>
To:	"Andi Kleen" <ak@...e.de>
Cc:	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] i386/PAE: avoid temporarily inconsistent pte-s

>>> Andi Kleen <ak@...e.de> 19.09.07 18:09 >>>
>On Wednesday 19 September 2007 16:39:39 Jan Beulich wrote:
>> One more of these issues (which were considered fixed a few releases
>> back): Other than on x86-64, i386 allows set_fixmap() to replace
>> already present mappings. Consequently, on PAE, care must be taken to
>> not update the high half of a pte while the low half is still holding
>> the old value.
>
>Hmm perhaps it would be better to just forbid it on i386 too.
>Do you know who uses it?

PCI's mmconfig accessor. One could of course make it call clear_fixmap() prior
to establishing a new mapping, but I thought that was not intended and is the
reason for allowing this.

Jan

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