From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [PATCH 4/5] virtio: use any layout on transmit Date: Mon, 19 Oct 2015 09:43:16 -0700 Message-ID: <20151019094316.1fffd775@xeon-e3> References: <1445231772-17467-1-git-send-email-stephen@networkplumber.org> <1445231772-17467-5-git-send-email-stephen@networkplumber.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: "dev@dpdk.org" , "changchun.ouyang@intel.com" To: "Xie, Huawei" Return-path: Received: from mail-pa0-f45.google.com (mail-pa0-f45.google.com [209.85.220.45]) by dpdk.org (Postfix) with ESMTP id E7E07234 for ; Mon, 19 Oct 2015 18:43:06 +0200 (CEST) Received: by pabrc13 with SMTP id rc13so195759128pab.0 for ; Mon, 19 Oct 2015 09:43:06 -0700 (PDT) In-Reply-To: List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On Mon, 19 Oct 2015 16:28:30 +0000 "Xie, Huawei" wrote: > On 10/19/2015 1:16 PM, Stephen Hemminger wrote: > > Virtio supports a feature that allows sender to put transmit > > header prepended to data. It requires that the mbuf be writeable, correct > > alignment, and the feature has been negotiatied. If all this works out, > > then it will be the optimum way to transmit a single segment packet. > "When using legacy interfaces, transitional drivers which have not > negotiated VIRTIO_F_ANY_LAYOUT > MUST use a single descriptor for the struct virtio_net_hdr on both > transmit and receive, with the > network data in the following descriptors." The code checks for the any layout feature, what is the problem?