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

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Date:   Fri, 1 Mar 2019 08:37:00 +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

Thu, Feb 28, 2019 at 05:36:44PM CET, jakub.kicinski@...ronome.com wrote:
>On Thu, 28 Feb 2019 10:00:54 +0100, Jiri Pirko wrote:
>> 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"?
>
>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)?

Well we can introduce separate commands:
DEVLINK_CMD_PORT_PEER_GET
DEVLINK_CMD_PORT_PEER_SET

For "set" part, this would work nice. However for the "get" part, we
would have to call both DEVLINK_CMD_PORT_GET and
DEVLINK_CMD_PORT_PEER_GET. So probably better to add a nest attr:
DEVLINK_ATTR_PORT_PEER
and have attrs like:
DEVLINK_ATTR_PORT_PEER_HW_ADDR  (does not have to be always eth, right?)
DEVLINK_ATTR_PORT_PEER_TYPE (DEVLINK_PORT_TYPE_NOTSET/DEVLINK_PORT_TYPE_ETH/DEVLINK_PORT_TYPE_IB)
DEVLINK_ATTR_PORT_PEER_NETDEV_IFINDEX
DEVLINK_ATTR_PORT_PEER_NETDEV_NAME
DEVLINK_ATTR_PORT_PEER_NETDEV_IBDEV_NAME
in the nest.

The userspace part can stay as I described previously:
$ devlink port peer set pci/0000:82:00.0/10001 hw_addr 00:52:44:11:22:33

Not sure about "port show" output. In json, the "peer" things should be
under "peer" dictionary.



>
>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.)