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Date: Sat, 26 Jun 2004 20:26:48 -0700
From: Matt Porter <mporter@kernel.crashing.org>
To: Matt Sexton <sexton@mc.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: DRAM and PCI devices at same physical address
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On Fri, Jun 25, 2004 at 05:23:00PM -0400, Matt Sexton wrote:
> I have a dual Xeon system with the Lindenhurst (E7710) chip set and 1 GB
> of memory.  In order to reserve a very large block of memory for a
> (user-space) device driver I am writing, I pass "mem=XX" to the kernel
> at boot time.  Unfortunately, /proc/pci shows two devices now appearing
> in the reserved upper memory range.  

<snip>
 
> The devices always appear right after the limit I specify on the kernel
> boot line.  If I specify "mem=512M", then the first device appears at
> 0x20000000.  If I specify nothing, then it appears at 0x40000000.  All
> other PCI devices show up at addresses of 0xDD000000 and above.
> 
> Is there any way to prevent these devices from showing up in the
> physical address range of my reserved memory?

You could try using reserve_bootmem() to reserve your driver memory.

> Should they be appearing there at all?  Does Linux make any guarantees
> when there is more physical memory than specified by "mem=" ?

Depends on the arch, I don't know what ia32 does.
 
-Matt
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