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 4D471FFA for ; Thu, 2 Feb 2017 17:48:00 +0100 (CET) Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (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 91F5B3D94D; Thu, 2 Feb 2017 16:48:00 +0000 (UTC) Received: from tlap.laine.org (ovpn-121-172.rdu2.redhat.com [10.10.121.172] (may be forged)) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id v12Glwct027378 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Thu, 2 Feb 2017 11:47:59 -0500 To: "Daniel P. Berrange" , Maxime Coquelin References: <20170201094304.GA3232@redhat.com> <20170201114119.GE3232@redhat.com> <20170202150621.GQ2915@redhat.com> Cc: "dev@openvswitch.org" , Yuanhan Liu , Flavio Leitner , "Michael S. Tsirkin" , "dev@dpdk.org" , Michal Privoznik , Ciara Loftus , Kevin Traynor , Daniele Di Proietto , "libvir-list@redhat.com" , mark.b.kavanagh@intel.com, Michal Privoznik From: Laine Stump Message-ID: Date: Thu, 2 Feb 2017 11:47:57 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <20170202150621.GQ2915@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.68 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Thu, 02 Feb 2017 16:48:00 +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 List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 02 Feb 2017 16:48:00 -0000 On 02/02/2017 10:06 AM, 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. (aside note: the code that exec's ovs-vsctl was written back when there was no standardized API for performing such operations. libvirt would prefer to not exec external programs though, and I've heard that OVS may now have an official API of some sort for doing things like this (maybe via netlink or dbus or something?) If that's the case, can someone point me in the right direction?) >>> 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. This brings up another tangentially related question I came up against last night - qemu now has an option to report the host's MTU to the guest for virtio and vhost-user interfaces, and Michal Privoznik recently pushed patches to set the MTU sent to the guest via an explicit in libvirt's interface config: https://bugzilla.redhat.com/1408701 But it would be much nicer if libvirt could learn the MTU of [that stuff at the other end of the unix socket] without requiring intervention in libvirt's config. For example, I'm just now testing patches for tap-based interfaces (connecting to Linux host bridges or OVS switches) that query the current MTU of the bridge and report that to qemu; this eliminates the burden of configuring each interface of each guest individually (and changing that config in all those places if someone ever wants to change the MTU of the bridge). As Dan says, though, libvirt's only interaction in the case of vhost-user is with the unix socket. Is there any way to learn what is the appropriate MTU from OVS in these cases? Or must Nova (or ovirt or some poor user) set that up in the libvirt config for every single interface?