pmd_deref
return __pa(pmd_deref(pmd)) >> PAGE_SHIFT;
return (unsigned long) pmd_deref(pmd);
vmem_pte_free((unsigned long *)pmd_deref(pmdp_get(pmd)));
vmem_free_pages(pmd_deref(entry), get_order(PMD_SIZE), altmap);
vmem_free_pages(pmd_deref(entry), get_order(PMD_SIZE), altmap);