I recently learnt that limiting RAM with by using only "mem=xxxM" is no
good on machines equipped with PCI.  In my case (vanilla 2.6.9) the cardbus
bridge on my laptop got mapped to the unused RAM area which resulted in
wierd errors due to the collision.

The right solution is to use "mem=" together with "memmap=" to mark the
unused RAM area reserved.

Henceforth I force the kernel to use 2016MiB by passing "mem=2016M
memmap=32M#2016M" instead of just "mem=2016M".
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>