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

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

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
VF instances don't have a switch ID so that doesn't work...

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
as ports.  Can we invent a new command (say "partition"?) that'd take
the bus info where the partition is to be spawned?

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.