vmw_piter_start
extern void vmw_piter_start(struct vmw_piter *viter,
vmw_piter_start(&data_iter, vsgt, 0);
vmw_piter_start(&iter, vsgt, offset >> PAGE_SHIFT);
vmw_piter_start(&pt_iter, vsgt, 0);
vmw_piter_start(&data_iter, vsgt, 0);