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Date: Tue, 3 Dec 2002 16:11:48 -0500 (EST)
From: "Richard B. Johnson" <root@chaos.analogic.com>
Reply-To: root@chaos.analogic.com
To: Duncan Sands <baldrick@wanadoo.fr>
cc: linux-kernel@vger.kernel.org
Subject: Re: Reserving physical memory at boot time
In-Reply-To: <200212031303.16487.baldrick@wanadoo.fr>
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On Tue, 3 Dec 2002, Duncan Sands wrote:

> I would like to reserve a particular page of physical memory when
> the kernel boots.  By reserving I mean that no one else gets to read
> from it or write to it: it is mine.  Any suggestions for the best way
> to go about this with a 2.5 kernel?
> 
> Thanks,
> 
> Duncan.

If you need a certain page reserved at boot-time you are out-of-luck.
You can tell the kernel (using mem=xxx on the boot command line) that
you have somewhat less memory than you do and then you can write a
module that accesses the other memory that the kernel doesn't use.

If you just want to make sure that your module owns a particular
page that nobody else uses, just use ioremap() in your module to
allocate a particular address. Those page(s) are now owned by
your module and will never be paged. You can access those pages
from user-space by providing some connectivity in your module
(like read()/write()/ioctl()). 

Cheers,
Dick Johnson
Penguin : Linux version 2.4.18 on an i686 machine (797.90 BogoMips).
   Bush : The Fourth Reich of America


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