IMMU_PGTABLE_LEVEL_STRIDE
offbits >>= IMMU_PGTABLE_LEVEL_STRIDE;
#define IMMU_PGTABLE_LEVEL_MASK ((1<<IMMU_PGTABLE_LEVEL_STRIDE) - 1)
#define IMMU_PGTABLE_OFFSHIFT (IMMU_PAGESHIFT - IMMU_PGTABLE_LEVEL_STRIDE)