PTmap
vm_offset_t PTmap __read_mostly = (vm_offset_t)P4Tmap;
return ((pt_entry_t *)(PTmap + ((va >> (PAGE_SHIFT - 3)) & vtoptem)));
PTmap = (vm_offset_t)P5Tmap;
#define vtopte(va) (PTmap + i386_btop(va))
trm_pte = PTmap + atop(prev_addr);
extern pt_entry_t PTmap[];