1.) Handle maximum segment sizes which are smaller than the IOMMU page
size by splitting up pages across multiple segments if needed; this case
was previously unimplemented, and would cause panics.
2.) KASSERT that the physical address is in range; remove a KASSERT that
has become pointless.
3.) Add a comment describing what remains to be fixed in the IOMMU code;
I plan to address these issues soon.
Desired by: dwhite (1)
d462b4f058