bus_to_virt()

["Jan Beulich" <jbeulich@novell.com>]

Isn't it inappropriate for bus_to_virt() to use, through machine_to_phys(),
mfn_to_pfn() rather than mfn_to_local_pfn()? If a foreign domain's address
gets uses here, the virtual address returned might be anything. I'm
specifically asking because I finally want to make an attempt to (a) merge
our swiotlb.c up with native's lib/swiotlb.c and then (b) move ours to
lib/swiotlb-xen.c. Native, however, uses a virtual address range check, and
hence the bus_to_virt() return value must reliable. If changing the macro
globally isn't appropriate (I can't see what valid uses there might be for this
macro with non-local addresses, hence a change like this would be benign to
all other users), I'd have to hand-craft a mechanism local to swiotlb.c to that
I can keep the delta to native down.

Thanks, Jan