From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Daniel P. Berrange" Subject: Re: [libvirt] [RFC] Vhost-user backends cross-version migration support Date: Thu, 2 Feb 2017 17:13:57 +0000 Message-ID: <20170202171357.GV2915@redhat.com> References:

<20170201094304.GA3232@redhat.com> <20170201114119.GE3232@redhat.com> <20170202150621.GQ2915@redhat.com> <20170202190811-mutt-send-email-mst@kernel.org> Reply-To: "Daniel P. Berrange" Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: "dev-yBygre7rU0TnMu66kgdUjQ@public.gmane.org" , Flavio Leitner , "dev-VfR2kkLFssw@public.gmane.org" , Michal Privoznik , Daniele Di Proietto , "libvir-list-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org" , Maxime Coquelin To: "Michael S. Tsirkin" Return-path: Content-Disposition: inline In-Reply-To: <20170202190811-mutt-send-email-mst-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: ovs-dev-bounces-yBygre7rU0TnMu66kgdUjQ@public.gmane.org Errors-To: ovs-dev-bounces-yBygre7rU0TnMu66kgdUjQ@public.gmane.org List-Id: dev.dpdk.org On Thu, Feb 02, 2017 at 07:09:24PM +0200, Michael S. Tsirkin wrote: > On Thu, Feb 02, 2017 at 11:47:57AM -0500, Laine Stump wrote: > > 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? > > We could add commands for all kind of queries to the vhost-user > protocol. libvirt would have to learn the vhost-user protocol though. > Interested? No, I really don't think libvirt should implement the vhost-user protocol 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/ :|