Re: [PATCH net-next v2 4/7] devlink: allow subports on devlink PCI ports

Jakub Kicinski
2019-03-05T00:33:12Z

On Mon, 4 Mar 2019 08:56:09 +0100, Jiri Pirko wrote:
> Sat, Mar 02, 2019 at 08:48:47PM CET, jakub.kicinski@netronome.com wrote:
> >On Sat, 2 Mar 2019 10:41:16 +0100, Jiri Pirko wrote:
> >> Fri, Mar 01, 2019 at 07:04:50PM CET, jakub.kicinski@netronome.com wrote:
> >> >PCI endpoint corresponds to a PCI device, but such device
> >> >can have one more more logical device ports associated with it.
> >> >We need a way to distinguish those. Add a PCI subport in the
> >> >dumps and print the info in phys_port_name appropriately.
> >> >
> >> >This is not equivalent to port splitting, there is no split
> >> >group. It's just a way of representing multiple netdevs on
> >> >a single PCI function.
> >> >
> >> >Note that the quality of being multiport pertains only to
> >> >the PCI function itself. A PF having multiple netdevs does
> >> >not mean that its VFs will also have multiple, or that VFs
> >> >are associated with any particular port of a multiport VF.
> >> >
> >> >Example (bus 05 device has subports, bus 82 has only one port per
> >> >function):
> >> >
> >> >$ devlink port
> >> >pci/0000:05:00.0/0: type eth netdev enp5s0np0 flavour physical
> >> >pci/0000:05:00.0/10000: type eth netdev enp5s0npf0s0 flavour pci_pf pf 0 subport 0
> >> >pci/0000:05:00.0/4: type eth netdev enp5s0np1 flavour physical
> >> >pci/0000:05:00.0/11000: type eth netdev enp5s0npf0s1 flavour pci_pf pf 0 subport 1
> >>
> >> So these subport devlink ports are eswitch ports for subports, right?
> >>
> >> Please see the following drawing:
> >>
> >> +---+ +---+ +---+
> >> pfsub| 5 | vf| 6 | | 7 |pfsub
> >> +-+-+ +-+-+ +-+-+
> >> physical link <---------+ | | |
> >> | | | |
> >> | | | |
> >> | | | |
> >> +-+-+ +-+-+ +-+-+ +-+-+
> >> | 1 | | 2 | | 3 | | 4 |
> >> +--+---+------+---+------+---+------+---+--+
> >> | physical pfsub vf pfsub |
> >> | port port port port |
> >> | |
> >> | eswitch |
> >> | |
> >> | |
> >> +------------------------------------------+
> >>
> >> 1) pci/0000:05:00.0/0: type eth netdev enp5s0np0 flavour physical switch_id 00154d130d2f
> >> 2) pci/0000:05:00.0/10000: type eth netdev enp5s0npf0s0 flavour pci_pf pf 0 subport 0 switch_id 00154d130d2f
> >> 3) pci/0000:05:00.0/10001: type eth netdev enp5s0npf0vf0 flavour pci_vf pf 0 vf 0 switch_id 00154d130d2f
> >> 4) pci/0000:05:00.0/10001: type eth netdev enp5s0npf0s1 flavour pci_pf pf 0 subport 1 switch_id 00154d130d2f
> >>
> >> This is basically what you have and I think we are in sync with that.
> >> But what about 5,6,7? Should they have devlink port instances too?
> >>
> >> 5) pci/0000:05:00.0/1: type eth netdev enp5s0f0?? flavour ???? pf 0 subport 0
> >> 6) pci/0000:05:10.1/0: type eth netdev enp5s10f0 flavour ???? pf 0 vf 0
> >> 7) pci/0000:05:00.0/1: type eth netdev enp5s0f0?? flavour ???? pf 0 subport 1
> >>
> >> These are the "peers".
> >> I think that there could be flavours "pci_pf" and "pci_vf". Then the
> >> "representors" (switch ports) could have flavours "pci_pf_port" and
> >> "pci_vf_port" or something like that. User can see right away
> >> that is not "PF" of "VF" but rather something "on the other end".
> >> Note there is no "switch_id" for these devlink ports that tells the user
> >> these devlink ports are not part of any switch.
> >> What do you think?
> >
> >Hmmm.. Hm. Hm.
> >
> >To me its neat if the devlink instance matches an ASIC. I think it's
> >kind of clear for people to understand what it stands for then. So if
> >we wanted to do the above we'd have to make the switch_id the first
> >class identifier for devlink instances, rather than the bus? But then
>
> What do you mean by "first class identifier"? Like "a handle"?

Yes, a handle.

> >VF instances don't have a switch ID so that doesn't work...
>
> Wait a sec. VF-ports do have. VFs them selves don't.

Looking at your example this one:

6) pci/0000:05:10.1/0: type eth netdev enp5s10f0 flavour ???? pf 0 vf 0

that uses VF's DBDF in the devlink instance handle, so I presume this
is a VF's devlink instance that will get passed to the VM together with
the VF device?

> But that is the same for PF. PF would also not have switch id.

Yes :( You'd have to mark what constitutes a devlink instance on your
drawing. The semantics for devlink instances seem to be the focal point
of the discussion.

Right now it seems a little bit that folks on the NIC side see a devlink
instance as a PCI function and on switch side it's the whole ASIC.

> >I need to think about it.
> >
> >It's also kind of strange that we have to add the noun *port* to the
> >flavour of... a port... So I would prefer not to have those showing up
>
> Yeah.
>
> >as ports. Can we invent a new command (say "partition"?) that'd take
> >the bus info where the partition is to be spawned?
>
> Got it. But the question is how different this object would be from the
> existing "port" we have today.

They'd be where "the other side of a PCI link" is represented,
restricting ports to only ASIC's forwarding plane ports.

> >My next goal is to find a way of grouping multiple bus devices under one
> >"ASIC" (which is a devlink instance to me) so it can be understood
> >easily how things are laid out when there is more than one PF connected
> >to one host.
>
> These are the "aliases" you mentioned before right? Makes sense.

Yes.