From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by dpdk.org (Postfix) with ESMTP id 5E247370 for ; Tue, 22 Dec 2015 09:21:04 +0100 (CET) Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga103.jf.intel.com with ESMTP; 22 Dec 2015 00:20:39 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.20,463,1444719600"; d="scan'208";a="876596478" Received: from yliu-dev.sh.intel.com (HELO yliu-dev) ([10.239.66.49]) by orsmga002.jf.intel.com with ESMTP; 22 Dec 2015 00:20:37 -0800 Date: Tue, 22 Dec 2015 16:21:52 +0800 From: Yuanhan Liu To: Peter Xu Message-ID: <20151222082152.GS18863@yliu-dev.sh.intel.com> References: <1449027793-30975-1-git-send-email-yuanhan.liu@linux.intel.com> <1450321921-27799-1-git-send-email-yuanhan.liu@linux.intel.com> <1450321921-27799-6-git-send-email-yuanhan.liu@linux.intel.com> <20151222081108.GF7532@pxdev.xzpeter.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151222081108.GF7532@pxdev.xzpeter.org> User-Agent: Mutt/1.5.23 (2014-03-12) Cc: "Michael S. Tsirkin" , dev@dpdk.org, Victor Kaplansky Subject: Re: [dpdk-dev] [PATCH v2 5/6] vhost: claim that we support GUEST_ANNOUNCE feature 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: Tue, 22 Dec 2015 08:21:04 -0000 On Tue, Dec 22, 2015 at 04:11:08PM +0800, Peter Xu wrote: > On Thu, Dec 17, 2015 at 11:12:00AM +0800, Yuanhan Liu wrote: > > It's actually a feature already enabled in Linux kernel. What we need to > > do is simply to claim that we support such feature, and nothing else. > > > > With that, the guest will send GARP messages after live migration. > > > > Signed-off-by: Yuanhan Liu > > --- > > lib/librte_vhost/virtio-net.c | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/lib/librte_vhost/virtio-net.c b/lib/librte_vhost/virtio-net.c > > index 03044f6..0ba5045 100644 > > --- a/lib/librte_vhost/virtio-net.c > > +++ b/lib/librte_vhost/virtio-net.c > > @@ -74,6 +74,7 @@ static struct virtio_net_config_ll *ll_root; > > #define VHOST_SUPPORTED_FEATURES ((1ULL << VIRTIO_NET_F_MRG_RXBUF) | \ > > (1ULL << VIRTIO_NET_F_CTRL_VQ) | \ > > (1ULL << VIRTIO_NET_F_CTRL_RX) | \ > > + (1ULL << VIRTIO_NET_F_GUEST_ANNOUNCE) | \ > > Do we really need this? I can understand when guest declare with > this VIRTIO_NET_F_GUEST_ANNOUNCE flag. With that, guest itself will > handle the announcement after migration. However, how could I > understand if it's declared by a vhost-user backend? What does it > mean? > > In vhost-user.txt (in QEMU repo docs/specs/), the only place that > mentioned this is SEND_RARP: > > * VHOST_USER_SEND_RARP > > Id: 19 > Equivalent ioctl: N/A > Master payload: u64 > > Ask vhost user backend to broadcast a fake RARP to notify the migration > is terminated for guest that does not support GUEST_ANNOUNCE. > ... > > Here, it mention the GUEST_ANNOUNCE since when guest support this, > we do not need to send SEND_RARP to vhost-user backend again. It > never explain what does it mean when vhost-user declaring to have > this flag... The actually work is done in QEMU and guest kernel. QEMU sends a config interrupt to guest kernel when such flag is enabled after live migration (see QEMU code virtio_net_load()). Guest kernel generates the GARP once it receives the interrupt (see the kernel code virtnet_config_changed_work()). Therefore, we could simply claim that we support VIRTIO_NET_F_GUEST_ANNOUNCE feature and do nothing here. --yliu