From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Monjalon Subject: Re: [PATCH] vhost: reserve some spaces for virtio_net and vhost_virtqueue struct Date: Tue, 08 Dec 2015 00:54:15 +0100 Message-ID: <2034837.2nzjXYH9Th@xps13> References: <1449109622-11675-1-git-send-email-yuanhan.liu@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: dev@dpdk.org, Victor Kaplansky , "Michael S. Tsirkin" To: Yuanhan Liu Return-path: Received: from mail-wm0-f48.google.com (mail-wm0-f48.google.com [74.125.82.48]) by dpdk.org (Postfix) with ESMTP id 746222A5E for ; Tue, 8 Dec 2015 00:55:27 +0100 (CET) Received: by wmec201 with SMTP id c201so189509003wme.0 for ; Mon, 07 Dec 2015 15:55:27 -0800 (PST) In-Reply-To: <1449109622-11675-1-git-send-email-yuanhan.liu@linux.intel.com> 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" 2015-12-03 10:27, Yuanhan Liu: > So that we will not break ABI in future extension by adding few more > fields. > > Struct vhost_virtqueue is reserved with 16 qwords (the later vhost-live > migration support would at least consume 3 of them), and struct virtio_net > is reserved with a bit more, 64 qwords, as there is only one instance for > a virtio nic instance. > > Note that both reservation are not placed at the end of the struct, but > instead before the last field, since both the last field at the two struct > take a lot spaces. Putting the reservation after it would divide those > reserved fields to another cacheline. (we might need fix them in future, btw) > > CC: Panu Matilainen > CC: Thomas Monjalon > CC: Michael S. Tsirkin > CC: Victor Kaplansky > Suggested-by: Panu Matilainen > Signed-off-by: Yuanhan Liu > --- > > Is the reservation a bit too large? :) You are maintainer in this area. Applied, thanks