From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752254AbeCONcJ (ORCPT ); Thu, 15 Mar 2018 09:32:09 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:48964 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752169AbeCONcH (ORCPT ); Thu, 15 Mar 2018 09:32:07 -0400 Date: Thu, 15 Mar 2018 15:32:06 +0200 From: "Michael S. Tsirkin" To: Jason Wang Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next] tuntap: XDP_TX can use native XDP Message-ID: <20180315153150-mutt-send-email-mst@kernel.org> References: <1520997820-8289-1-git-send-email-jasowang@redhat.com> <20180314053424-mutt-send-email-mst@kernel.org> <21e53c2b-6677-fc9a-0771-e895da1c257f@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <21e53c2b-6677-fc9a-0771-e895da1c257f@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 15, 2018 at 04:39:25PM +0800, Jason Wang wrote: > > > On 2018年03月14日 11:37, Michael S. Tsirkin wrote: > > > 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 Can't one flush we called after multiple xmit calls?