From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by dpdk.org (Postfix) with ESMTP id E54222C37 for ; Thu, 2 Feb 2017 18:29:15 +0100 (CET) Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 4FB2861E73; Thu, 2 Feb 2017 17:29:16 +0000 (UTC) Received: from redhat.com (ovpn-117-166.ams2.redhat.com [10.36.117.166]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id v12HT9EH013834 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Thu, 2 Feb 2017 12:29:12 -0500 Date: Thu, 2 Feb 2017 17:29:08 +0000 From: "Daniel P. Berrange" To: "Michael S. Tsirkin" Cc: Maxime Coquelin , Michal Privoznik , Kevin Traynor , Ciara Loftus , mark.b.kavanagh@intel.com, Flavio Leitner , Yuanhan Liu , Daniele Di Proietto , "dev@openvswitch.org" , "dev@dpdk.org" , "libvir-list@redhat.com" Message-ID: <20170202172908.GW2915@redhat.com> References: <20170201094304.GA3232@redhat.com> <20170201114119.GE3232@redhat.com> <20170202150621.GQ2915@redhat.com> <20170202181827-mutt-send-email-mst@kernel.org> <20170202171028.GT2915@redhat.com> <20170202191248-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20170202191248-mutt-send-email-mst@kernel.org> User-Agent: Mutt/1.7.1 (2016-10-04) X-Scanned-By: MIMEDefang 2.68 on 10.5.11.24 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Thu, 02 Feb 2017 17:29:16 +0000 (UTC) Subject: Re: [dpdk-dev] [libvirt] [RFC] Vhost-user backends cross-version migration support X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list Reply-To: "Daniel P. Berrange" List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 02 Feb 2017 17:29:16 -0000 On Thu, Feb 02, 2017 at 07:20:35PM +0200, Michael S. Tsirkin wrote: > On Thu, Feb 02, 2017 at 05:10:28PM +0000, Daniel P. Berrange wrote: > > On Thu, Feb 02, 2017 at 06:21:55PM +0200, Michael S. Tsirkin wrote: > > > On Thu, Feb 02, 2017 at 03:06:21PM +0000, Daniel P. Berrange wrote: > > > > On Thu, Feb 02, 2017 at 03:14:01PM +0100, Maxime Coquelin wrote: > > > > > > > > > > > > > > > On 02/01/2017 12:41 PM, Daniel P. Berrange wrote: > > > > > > > > > > > > It depends where / how in OVS it needs to be set. The only stuff libvirt > > > > > > does with OVS is to run 'add-port' and 'del-port' commands via the ovs > > > > > > cli tool. We pass through arguments from the port profile stored in the > > > > > > XML config. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > eg those things in get passed as cli args to the 'add-port' > > > > > > command. Soo if add-port needs this new version string, then we'd need > > > > > > to add the version to the openvswitch virtualport XML. > > > > > > > > > > > > If the version is provided to OVS in a different command, then it would > > > > > > probably be outside scope of libvirt. > > > > > > > > > > I think it would make sense to be a parameter of the add-port command. > > > > > But it would be for vhost-user related add-port command, I didn't find > > > > > where/if this is managed in libvirt XML. > > > > > > > > For vhost-user, libvirt does not have any interaction with OVS at > > > > all. If the thing that's using the vhost-user UNIX socket, in turn > > > > connects to OVS, that's outside scope of libvirt. IOW, for vhost-user > > > > OVS it seems like that job is for Nova / os-vif to solve. > > > > > > I don't think they currently understand the issues involved in > > > cross-version migration though. This is a complex subject and easy to > > > get wrong. It would be significantly better to figure it out at libvirt > > > level since it already deals with cross-version migration issues. > > > > Libvirt considers vhost-user to be a blackbox though - it just exposes > > a UNIX socket, and whatever is on the other end is completely opaque. > > The fact that the other end might plumb the data stream into openvswitch > > is not something libvirt should know, as we don't want to end up having > > to add custom code to libvirt for every different vhost-user server > > impl. > > > > IOW, if the version str can be passed to QEMU, and then onto vhost-user > > backend in QEMU, then libvirt can be involved. If the version str has > > to be given to openvswitch that's not for libvirt to deall with. > > > > Regards, > > Daniel > > It's not just about passing it to QEMU. The following is needed: > - need to query version when creating VM/device > - need to query supported versions when migrating VM Those are both things that nova can do, since it knows what the vhost-user device in question is connected to, and so can query the versions, and check versions before triggering migration with libvirt Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://entangle-photo.org -o- http://search.cpan.org/~danberr/ :|