Re: [PATCH net-next] tuntap: XDP_TX can use native XDP

On 2018年03月14日 11:37, Michael S. Tsirkin wrote:

quoted

  			return NULL;
  		case XDP_TX:
-			xdp_xmit = true;
-			/* fall through */
+			get_page(alloc_frag->page);
+			alloc_frag->offset += buflen;
+			if (tun_xdp_xmit(tun->dev, &xdp))
+				goto err_redirect;
+			tun_xdp_flush(tun->dev);

Why do we have to flush here though?
It might be a good idea to document the reason in a code comment.

ndo_xdp_xmit() does not touch doorbell, so we need a ndo_xdp_flush() here. It's the assumption of XDP API I think, so not sure it's worth to mention it here.

Thanks