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

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Date:   Thu, 28 Feb 2019 10:00:54 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     davem@...emloft.net, oss-drivers@...ronome.com,
        netdev@...r.kernel.org
Subject: Re: [PATCH net-next 6/8] devlink: introduce port's peer netdevs

Wed, Feb 27, 2019 at 07:47:42PM CET, jakub.kicinski@...ronome.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@...ronome.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"?


>
>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


>
>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.)