IMMU_PAGESHIFT
offbits = dvma >> IMMU_PAGESHIFT;
dvma += (npages << IMMU_PAGESHIFT);
#define IMMU_BTOP(b) (((uint64_t)b) >> IMMU_PAGESHIFT)
#define IMMU_PTOB(p) (((uint64_t)p) << IMMU_PAGESHIFT)
#define IMMU_BTOPR(x) ((((x) + IMMU_PAGEOFFSET) >> IMMU_PAGESHIFT))
#define IMMU_PGTABLE_OFFSHIFT (IMMU_PAGESHIFT - IMMU_PGTABLE_LEVEL_STRIDE)