From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id 7B1FE985FFA for ; Sun, 4 Sep 2022 20:32:09 +0000 (UTC) Date: Sun, 4 Sep 2022 16:31:59 -0400 From: "Michael S. Tsirkin" Message-ID: <20220904162809-mutt-send-email-mst@kernel.org> References: <1660642495-104002-1-git-send-email-hengqi@linux.alibaba.com> <20220902023546-mutt-send-email-mst@kernel.org> <94937aaa-e3c0-74fe-290c-59884c6eb9a4@linux.alibaba.com> MIME-Version: 1.0 In-Reply-To: <94937aaa-e3c0-74fe-290c-59884c6eb9a4@linux.alibaba.com> Subject: [virtio-dev] Re: [PATCH v7] virtio_net: support split header Content-Type: text/plain; charset=us-ascii Content-Disposition: inline To: Heng Qi Cc: virtio-dev@lists.oasis-open.org, Jason Wang , xuanzhuo@linux.alibaba.com, kangjie.xu@linux.alibaba.com List-ID: On Fri, Sep 02, 2022 at 04:58:16PM +0800, Heng Qi wrote: > When VIRTIO_NET_F_SPLIT_TRANSPORT_HEADER is negotiated, > the driver requires that the buffers submitted to receiveq > MUST be composed of at least two descriptors, > which means that each buffer the device gets is a descriptor chain, > even if the device does not split the header for some packets. > > To store packet in the descriptor chain without header splitting > by the device, the device MUST start with the first descriptor of > the descriptor chain to store the packet, and MUST NOT set the > VIRTIO_NET_HDR_F_SPLIT_TRANSPORT_HEADER bit in \field{flags}. > > Thanks. Descriptor chains will hurt performance badly. How about simply making this feature depend on mergeable buffers? Then we have a separate buffer for the header and this works cleanly. -- MST --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org