linux-kernel - Re: Query about set_pages

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Message-ID: <20080209155707.787ddc47@laptopd505.fenrus.org>
Date:	Sat, 9 Feb 2008 15:57:07 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Larry Finger <Larry.Finger@...inger.net>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Query about set_pages_* API

On Sat, 09 Feb 2008 15:40:12 -0700
Larry Finger <Larry.Finger@...inger.net> wrote:

> I'm trying to modify the VirtualBox kernel module to work with
> 2.6.24-git (and 2.6.25) on x86_64 architecture. The current code has
> a value of the third argument of the call (prot) with 3 variants. All
> variations have the following bits set: _PAGE_PRESENT, _PAGE_RW,
> _PAGE_DIRTY, and _PAGE_ACCESSED. Number 2 adds _PAGE_NX to the above,
> and number 3 adds _PAGE_GLOBAL to the bits in variation 1.
> 
>  From the code in arch/x86/mm/pageattr.c, I figured I need to call
> set_pages_wb() unconditionally, and set_pages_nx() if _PAGE_NX is
> set. Will these calls be sufficient? I thought about calling
> set_pages_rw(), but that entry is not exported.

it depends on what the code is trying to achieve.
(this makes it not a trivial 1:1 scripted replacement ;-)

Which attribute is the code trying to change? Is it trying to make
a piece of code (non) cachable? or executable? You need to figure out what
the intent is..

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