DDI 8 allows DMA access
to any part of memory, including that above 4GB.
Earlier DDI versions
prevented drivers from accessing memory above 4GB
because physical addresses were exposed
as the 32-bit unsigned
paddr_t data type.
In DDI 8, all references to physical addresses are eliminated except for the following two forms:
paddr32_ttype. 64-bit scatter/gather lists can represent 64-bit addresses from two