MAX_POSSIBLE_PHYSMEM_BITS
#if !defined(MAX_POSSIBLE_PHYSMEM_BITS) && !defined(CONFIG_64BIT)
#if defined(MAX_POSSIBLE_PHYSMEM_BITS)
#define SWAP_CACHE_PFN_BITS (MAX_POSSIBLE_PHYSMEM_BITS - PAGE_SHIFT)
#ifndef MAX_POSSIBLE_PHYSMEM_BITS
#define _PFN_BITS (MAX_POSSIBLE_PHYSMEM_BITS - PAGE_SHIFT)