ptbl_alloc
static pte_t *ptbl_alloc(pmap_t, unsigned int, bool);
ptbl = ptbl_alloc(pmap, pdir_idx, nosleep);
static pte_t *ptbl_alloc(pmap_t pmap, vm_offset_t va,
ptbl = ptbl_alloc(pmap, va, nosleep, &is_new);