Re: [PATCH net-next 6/8] devlink: introduce port's peer netdevs

[Jakub Kicinski <jakub.kicinski@netronome.com>]

On Thu, 28 Feb 2019 10:00:54 +0100, Jiri Pirko wrote:
> Wed, Feb 27, 2019 at 07:47:42PM CET, jakub.kicinski@netronome.com wrote:
> >On Wed, 27 Feb 2019 14:08:29 +0100, Jiri Pirko wrote:  
> >> Tue, Feb 26, 2019 at 07:24:34PM CET, jakub.kicinski@netronome.com wrote:  
> >> >Devlink ports represent ports of a switch device (or SR-IOV
> >> >NIC which has an embedded switch). In case of SR-IOV when
> >> >PCIe PFs are exposed the PFs which are directly connected
> >> >to the local machine may also spawn PF netdev (much like
> >> >VFs have a port/"repr" and an actual VF netdev).
> >> >
> >> >Allow devlink to expose such linking. There is currently no
> >> >way to find out which netdev corresponds to which PF.
> >> >
> >> >Example:
> >> >
> >> >$ devlink port
> >> >pci/0000:82:00.0/0: type eth netdev p4p1 flavour physical
> >> >pci/0000:82:00.0/10000: type eth netdev eth1 flavour pci_pf pf 0 peer_netdev enp130s0
> >> >pci/0000:82:00.0/10001: type eth netdev eth0 flavour pci_vf pf 0 vf 0
> >> >pci/0000:82:00.0/10002: type eth netdev eth2 flavour pci_vf pf 0 vf 1    
> >> 
> >> Peer as the other side of a "virtual cable". For PF, that is probably
> >> sufficient. But I think what a "peer of devlink port" should be "a
> >> devlink port".  
> >
> >Maybe I'm not clear on what devlink port is - to me its a port of the
> >ASIC.  The notion of devlink port connected to devlink port seems
> >to counter such definition :S    
> 
> "port of the ASIC" in a sence of "eswitch ports"?

Yes.

> >I do not think that every netdev should have a devlink port associated.
> >  
> >> Not sure about VF.
> >> 
> >> Consider a simple problem of setting up a VF mac address. In legacy, you
> >> do it like this:
> >> $ ip link set eth2 vf 1 mac 00:52:44:11:22:33
> >> However, in new model, you so far cannot do that.  
> >
> >Why?
> >
> >$ devlink port set pci/0000:82:00.0/10001 peer_eth_addr 00:52:44:11:22:33  
> 
> Yeah. That is not yet implemented. I agree it is most straightforward.
> The question is, is it fine to have set of:
> peer_eth_addr
> peer_mtu
> peer_something_else
> Or rather to have some object to pin this on. Something like:
> 
> $ devlink port peer set pci/0000:82:00.0/10001 eth_addr 00:52:44:11:22:33

I do like the object one better, would this mean I should restructure
the peer stuff somehow (netlink attribute structure)?

The MTU stuff is tricky, perhaps best left for its own series ;)

> >It's more of a neighbour info situation than a local port situation.
> >  
> >> What I was thinking about was some "dummy peer" which would be on the
> >> host. Not sure if only as a "dummy peer devlink port" or even as some
> >> sort of "dummy netdev".
> >> 
> >> One way or another, it would provide the user some info about which VF
> >> representor is connected to which VF in VM (mac mapping).  
> >
> >Ack, but isn't the MAC setting is the only thing we're missing from
> >"switchdev SR-IOV"?  Would the "dummy netdev" be used for anything
> >else?  I would rather not introduce new netdev just to do that   
> 
> Agreed. It was just a wild idea :)

:)

> >(that'd be a third for that port.)