ASID_FIRST_AVAILABLE
for (i = 0; i < ASID_FIRST_AVAILABLE; i++)
set->asid_next = ASID_FIRST_AVAILABLE;
KASSERT(asid >= ASID_FIRST_AVAILABLE &&
bit_nclear(set->asid_set, ASID_FIRST_AVAILABLE,
bit_ffc_at(set->asid_set, ASID_FIRST_AVAILABLE,
bit_ffc_at(set->asid_set, ASID_FIRST_AVAILABLE,