On Thu, 7 Jun 2018 07:17:51 -0700 Alexander Duyck <alexander.du...@gmail.com> wrote:
> On Wed, Jun 6, 2018 at 3:25 PM, Stephen Hemminger > <step...@networkplumber.org> wrote: > > On Wed, 6 Jun 2018 14:54:04 -0700 > > "Samudrala, Sridhar" <sridhar.samudr...@intel.com> wrote: > > > >> On 6/6/2018 2:24 PM, 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. > >> > 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 think it should be possible for netvsc to work with 3 dev model if the > >> only > >> requirement is that eth0 will always be present. With net_failover, you > >> will > >> see eth0 and eth0nsby OR with older distros eth0 and eth1. It may be an > >> issue > >> if somehow there is userspace requirement that there can be only 2 > >> netdevs, not 3 > >> when VF is plugged. > >> > >> eth0 will be the net_failover device and eth0nsby/eth1 will be the netvsc > >> device > >> and the IP address gets configured on eth0. Will this be an issue? > > > > DPDK drivers in 18.05 depend on 2 device model. Yes it is a bit of mess > > but that is the way it is. > > Why would DPDK care what we do in the kernel? Isn't it just slapping > vfio-pci on the netdevs it sees? Alex, you are correct for Intel devices; but DPDK on Azure is not Intel based.,. The DPDK support uses: * Mellanox MLX5 which uses the Infinband hooks to do DMA directly to userspace. This means VF netdev device must exist and be visible. * Slow path using kernel netvsc device, TAP and BPF to get exception path packets to userspace. * A autodiscovery mechanism that to set all this up that relies on 2 device model and sysfs. In this version, there is no VFIO-PCI. And also Hyper-V does not have virtual IOMMU so VFIO will not work there at all.
