On Wed, Jun 06, 2018 at 03:24:08PM -0700, Stephen Hemminger wrote: > On Thu, 7 Jun 2018 00:47:52 +0300 > "Michael S. Tsirkin" <m...@redhat.com> wrote: > > > On Wed, Jun 06, 2018 at 02:24:47PM -0700, Stephen Hemminger wrote: > > > On Wed, 6 Jun 2018 15:30:27 +0300 > > > "Michael S. Tsirkin" <m...@redhat.com> wrote: > > > > > > > On Wed, Jun 06, 2018 at 09:25:12AM +0200, Jiri Pirko wrote: > > > > > Tue, Jun 05, 2018 at 05:42:31AM CEST, step...@networkplumber.org > > > > > wrote: > > > > > >The net failover should be a simple library, not a virtual > > > > > >object with function callbacks (see callback hell). > > > > > > > > > > Why just a library? It should do a common things. I think it should > > > > > be a > > > > > virtual object. Looks like your patch again splits the common > > > > > functionality into multiple drivers. That is kind of backwards > > > > > attitude. > > > > > I don't get it. We should rather focus on fixing the mess the > > > > > introduction of netvsc-bonding caused and switch netvsc to 3-netdev > > > > > model. > > > > > > > > So it seems that at least one benefit for netvsc would be better > > > > handling of renames. > > > > > > > > Question is how can this change to 3-netdev happen? Stephen is > > > > concerned about risk of breaking some userspace. > > > > > > > > Stephen, this seems to be the usecase that IFF_HIDDEN was trying to > > > > address, and you said then "why not use existing network namespaces > > > > rather than inventing a new abstraction". So how about it then? Do you > > > > want to find a way to use namespaces to hide the PV device for netvsc > > > > compatibility? > > > > > > > > > > Netvsc can't work with 3 dev model. MS has worked with enough distro's and > > > startups that all demand eth0 always be present. And VF may come and go. > > > > Well failover seems to maintain this invariant with the 3 dev model. > > > > > After this history, there is a strong motivation not to change how kernel > > > behaves. Switching to 3 device model would be perceived as breaking > > > existing userspace. > > > > I feel I'm misunderstood. I was asking whether a 3-rd device can be > > hidden so that userspace does not know that you switched to a 3 device > > model. It will think there are 2 devices and will keep working. > > > > If you do that, then there won't be anything that > > would be perceived as breaking existing userspace, will there? > > DPDK now knows about the netvsc 2 device model and drivers in userspace > depend on it.
Interesting but I'm not sure how this answers the question. How would DPDK care that there's a hidden device? If you can point out the code in question, maybe a way can be found to make changes while keeping it working. > > > > > > > With virtio you can work it out with the distro's yourself. > > > There is no pre-existing semantics to deal with. > > > > > > For the virtio, I don't see the need for IFF_HIDDEN. > > > With 3-dev model as long as you mark the PV and VF devices > > > as slaves, then userspace knows to leave them alone. Assuming userspace > > > is already able to deal with team and bond devices. > > > > That's clear enough. > > > > > Any time you introduce new UAPI behavior something breaks. > > > > Not if we do it right. > > > > > On the rename front, I really don't care if VF can be renamed. > > > > OK that's nice. > > > > > And for > > > netvsc want to allow the PV device to be renamed. > > > > That's because of the 2 device model, right? So that explains why even > > if the delayed hack is good for the goose it might not be good for the > > gander :) > > You are bringing up the VF right away. How does the 3-device initialization > state machine work? Do you give a window for udev to possibly rename the > VF? Do you rely on that? > > > > > > Udev developers want that > > > but have not found a stable/persistent value to expose to userspace > > > to allow it.
