From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by dpdk.org (Postfix) with ESMTP id 0A9138E79 for ; Mon, 19 Oct 2015 18:29:08 +0200 (CEST) Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga103.fm.intel.com with ESMTP; 19 Oct 2015 09:29:07 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.17,702,1437462000"; d="scan'208";a="814488763" Received: from fmsmsx107.amr.corp.intel.com ([10.18.124.205]) by fmsmga001.fm.intel.com with ESMTP; 19 Oct 2015 09:28:33 -0700 Received: from fmsmsx113.amr.corp.intel.com (10.18.116.7) by fmsmsx107.amr.corp.intel.com (10.18.124.205) with Microsoft SMTP Server (TLS) id 14.3.248.2; Mon, 19 Oct 2015 09:28:32 -0700 Received: from shsmsx103.ccr.corp.intel.com (10.239.4.69) by FMSMSX113.amr.corp.intel.com (10.18.116.7) with Microsoft SMTP Server (TLS) id 14.3.248.2; Mon, 19 Oct 2015 09:28:32 -0700 Received: from shsmsx101.ccr.corp.intel.com ([169.254.1.96]) by SHSMSX103.ccr.corp.intel.com ([169.254.4.204]) with mapi id 14.03.0248.002; Tue, 20 Oct 2015 00:28:31 +0800 From: "Xie, Huawei" To: Stephen Hemminger , "changchun.ouyang@intel.com" Thread-Topic: [PATCH 4/5] virtio: use any layout on transmit Thread-Index: AdEKizC3PWOT1QzQTPaVD07Lg4SGOw== Date: Mon, 19 Oct 2015 16:28:30 +0000 Message-ID: References: <1445231772-17467-1-git-send-email-stephen@networkplumber.org> <1445231772-17467-5-git-send-email-stephen@networkplumber.org> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.239.127.40] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Cc: "dev@dpdk.org" Subject: Re: [dpdk-dev] [PATCH 4/5] virtio: use any layout on transmit X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 19 Oct 2015 16:29:09 -0000 On 10/19/2015 1:16 PM, Stephen Hemminger wrote:=0A= > Virtio supports a feature that allows sender to put transmit=0A= > header prepended to data. It requires that the mbuf be writeable, correc= t=0A= > alignment, and the feature has been negotiatied. If all this works out,= =0A= > then it will be the optimum way to transmit a single segment packet.=0A= "When using legacy interfaces, transitional drivers which have not=0A= negotiated VIRTIO_F_ANY_LAYOUT=0A= MUST use a single descriptor for the struct virtio_net_hdr on both=0A= transmit and receive, with the=0A= network data in the following descriptors."=0A= =0A= I think we shouldn't assume that virtio header descriptor uses a=0A= separate descriptor. It could be with data. Virtio RX(and dpdk vhost)=0A= actually is implemented like this before, i.e, i thought this should be=0A= inherent but not a feature.=0A= Is the current RX implementation wrong?=0A= [...]=0A=