ttm_io_prot
extern vm_memattr_t ttm_io_prot(uint32_t caching_flags);
vm_memattr_t prot = ttm_io_prot(old_mem->placement);
vm_memattr_t prot = ttm_io_prot(new_mem->placement);
VM_MEMATTR_DEFAULT : ttm_io_prot(mem->placement);
pmap_page_set_memattr(m, ttm_io_prot(bo->mem.placement));
VM_MEMATTR_WRITE_BACK : ttm_io_prot(bo->mem.placement));