Re: alpha iommu fixes

[Alan Cox]

> I can be really wrong on this because I didn't checked anything about
> the GART yet but I suspect you cannot use the GART for this stuff on
> ia32 in 2.4 because I think I recall it provides not an huge marging of
> mapping entries that so would far too easily trigger the bugs in the
> device drivers not checking for pci_map_* faliures also in a common
> desktop/webserver/fileserver kind of usage of an high end machine.

Not all chipsets support reading through GART address space from PCI either,
it is meant for AGP to use.