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 10:19:34 -0700 Message-ID: <20151019101934.6f3b92f9@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-f52.google.com (mail-pa0-f52.google.com [209.85.220.52]) by dpdk.org (Postfix) with ESMTP id B15038E76 for ; Mon, 19 Oct 2015 19:19:24 +0200 (CEST) Received: by pabrc13 with SMTP id rc13so196549640pab.0 for ; Mon, 19 Oct 2015 10:19:24 -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: > "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." > > I think we shouldn't assume that virtio header descriptor uses a > separate descriptor. It could be with data. Virtio RX(and dpdk vhost) > actually is implemented like this before, i.e, i thought this should be > inherent but not a feature. > Is the current RX implementation wrong? I believe current RX is ok, the any layout refers more to what is handed to the host on transmit. Rusty said something like "any sane implementation would work with contiguous buffer" but the standard couldn't assume sanity!