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

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Date:   Mon, 4 Mar 2019 08:56:09 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        oss-drivers@...ronome.com
Subject: Re: [PATCH net-next v2 4/7] devlink: allow subports on devlink PCI
 ports

Sat, Mar 02, 2019 at 08:48:47PM CET, jakub.kicinski@...ronome.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@...ronome.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"?


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


>
>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.


>
>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.