func: static int64_t migration_set_rate_limit(void *opaque, int64_t new_rate)
  
  {
  
      MigrationState *s = opaque;
  
      if (qemu_file_get_error(s->file)) {
  
          goto out;
  
      }
  
  
  
      s->xfer_limit = new_rate;
  
  
  
  out:
  
      return s->xfer_limit;
  
  }
  