[Linux-ia64] heads up: i/o mmu related changes

[David Mosberger <davidm@napali.hpl.hp.com>]

I justed checked in a changeset
(davidm@tiger.hpl.hp.com|ChangeSet|20030610070955|57077) to make the
kernel work better for machines with I/O MMU.  This should fix the
long-standing bug where IDE disks on machines with memory above 4GB
would MCA if the machine has an I/O MMU.

The trick was to make PCI_DMA_BUS_IS_PHYS a variable which is set at
runtime.  Machines with I/O MMUs or machines with PCI buses which live
in separate address spaces MUST clear this variable.  I updated the
code for the zx1 I/O MMU.  I didn't touch the SGI I/O MMU code,
though, as I wouldn't be able to test it.  Also, it would be good if
someone could test whether IDE disks work fine on machines with
Intel-chipsets and memory above 4GB.

	--david