From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Fedin Subject: Re: [PATCH v2 5/6] vhost: claim that we support GUEST_ANNOUNCE feature Date: Tue, 22 Dec 2015 11:24:25 +0300 Message-ID: <004401d13c92$2b9d35b0$82d7a110$@samsung.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=UTF-8 Content-Transfer-Encoding: quoted-printable Cc: dev@dpdk.org, 'Victor Kaplansky' , "'Michael S. Tsirkin'" To: 'Peter Xu' , 'Yuanhan Liu' Return-path: Received: from mailout3.w1.samsung.com (mailout3.w1.samsung.com [210.118.77.13]) by dpdk.org (Postfix) with ESMTP id 33468370 for ; Tue, 22 Dec 2015 09:24:28 +0100 (CET) Received: from eucpsbgm1.samsung.com (unknown [203.254.199.244]) by mailout3.w1.samsung.com (Oracle Communications Messaging Server 7.0.5.31.0 64bit (built May 5 2014)) with ESMTP id <0NZR000XF3CQIX80@mailout3.w1.samsung.com> for dev@dpdk.org; Tue, 22 Dec 2015 08:24:26 +0000 (GMT) In-reply-to: <20151222081108.GF7532@pxdev.xzpeter.org> Content-language: ru 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" Hello! > > 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) | \ >=20 > 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? I guess the documentation is unclear. This is due to way how qemu = works. It queries vhost-user backend for the features, then offers them = to the guest. The guest then responds with features FROM THE SUGGESTED = SET, which it supports. So, if the backend does not claim to support = this feature, qemu will not offer it to the guest, therefore the guest = will not try to activate it. I think this is done because this feature is only useful for migration. = If vhost-user backend does not support migration, it needs neither = VHOST_USER_SEND_RARP nor guest-side announce. Actually, i was thinking about patching qemu once, but... The changeset = seemed too complicated, and i imagined the situation described in the = above sentence, so decided to abandon it. Kind regards, Pavel Fedin Expert Engineer Samsung Electronics Research center Russia