On Fri, 26 Jan 2018 18:30:03 -0800 Jakub Kicinski <kubakici@xxxxx> wrote: > On Fri, 26 Jan 2018 15:30:35 -0800, Samudrala, Sridhar wrote: > > On 1/26/2018 2:47 PM, Jakub Kicinski wrote: > > > On Sat, 27 Jan 2018 00:14:20 +0200, Michael S. Tsirkin wrote: > > >> On Fri, Jan 26, 2018 at 01:46:42PM -0800, Siwei Liu wrote: > > >>>> and the VM is not expected to do any tuning/optimizations on the VF driver > > >>>> directly, > > >>>> i think the current patch that follows the netvsc model of 2 netdevs(virtio > > >>>> and vf) should > > >>>> work fine. > > >>> OK. For your use case that's fine. But that's too specific scenario > > >>> with lots of restrictions IMHO, perhaps very few users will benefit > > >>> from it, I'm not sure. If you're unwilling to move towards it, we'd > > >>> take this one and come back with a generic solution that is able to > > >>> address general use cases for VF/PT live migration . > > >> I think that's a fine approach. Scratch your own itch! I imagine a very > > >> generic virtio-switchdev providing host routing info to guests could > > >> address lots of usecases. A driver could bind to that one and enslave > > >> arbitrary other devices. Sounds reasonable. > > >> > > >> But given the fundamental idea of a failover was floated at least as > > >> early as 2013, and made 0 progress since precisely because it kept > > >> trying to address more and more features, and given netvsc is already > > >> using the basic solution with some success, I'm not inclined to block > > >> this specific effort waiting for the generic one. > > > I think there is an agreement that the extra netdev will be useful for > > > more advanced use cases, and is generally preferable. What is the > > > argument for not doing that from the start? If it was made I must have > > > missed it. Is it just unwillingness to write the extra 300 lines of > > > code? Sounds like a pretty weak argument when adding kernel ABI is at > > > stake... > > > > I am still not clear on the need for the extra netdev created by > > virtio_net. The only advantage i can see is that the stats can be > > broken between VF and virtio datapaths compared to the aggregrated > > stats on virtio netdev as seen with the 2 netdev approach. > > Maybe you're not convinced but multiple arguments were made. > > > With 2 netdev model, any VM image that has a working network > > configuration will transparently get VF based acceleration without > > any changes. > > Nothing happens transparently. Things may happen automatically. The > VF netdev doesn't disappear with netvsc. The PV netdev transforms into > something it did not use to be. And configures and reports some > information from the PV (e.g. speed) but PV doesn't pass traffic any > longer. > > > 3 netdev model breaks this configuration starting with the creation > > and naming of the 2 devices to udev needing to be aware of master and > > slave virtio-net devices. > > I don't understand this comment. There is one virtio-net device and > one "virtio-bond" netdev. And user space has to be aware of the special > automatic arrangement anyway, because it can't touch the VF. It > doesn't make any difference whether it ignores the VF or PV and VF. > It simply can't touch the slaves, no matter how many there are. > > > Also, from a user experience point of view, loading a virtio-net with > > BACKUP feature enabled will now show 2 virtio-net netdevs. > > One virtio-net and one virtio-bond, which represents what's happening. > > > For live migration with advanced usecases that Siwei is suggesting, i > > think we need a new driver with a new device type that can track the > > VF specific feature settings even when the VF driver is unloaded. I see no added value of the 3 netdev model, there is no need for a bond device. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
