Re: Getting network port ID by ethdev port ID

[Ferruh Yigit <ferruh.yigit@amd.com>]

On 6/5/2023 9:30 PM, Ivan Malov wrote:
> Hi Stephen, Thomas,
> 
> Thanks for responding. PSB.
> 
> On Mon, 5 Jun 2023, Stephen Hemminger wrote:
> 
>> On Mon, 05 Jun 2023 18:03:14 +0200
>> Thomas Monjalon <thomas@monjalon.net> wrote:
>>
>>> 05/06/2023 16:29, Ivan Malov:
>>>> Sorry, I missed your question. See below.
>>>>
>>>> On Mon, 5 Jun 2023, Thomas Monjalon wrote:
>>>>
>>>>> 05/06/2023 16:03, Ivan Malov:
>>>>>> Hi Thomas,
>>>>>>
>>>>>> Thanks for responding. Please see below.
>>>>>>
>>>>>> On Mon, 5 Jun 2023, Thomas Monjalon wrote:
>>>>>>
>>>>>>> Hello,
>>>>>>>
>>>>>>> 05/06/2023 15:09, Ivan Malov:
>>>>>>>> Dear community,
>>>>>>>>
>>>>>>>> Is there any means in DPDK to discover relationship between
>>>>>>>> network/physical ports of the given adapter/board and
>>>>>>>> etdevs deployed in DPDK application on top of it?
>>>>>>>>
>>>>>>>> For example, in Linux, there are facilities like
>>>>>>>>
>>>>>>>>> /sys/class/net/<iface>/phys_port_name
>>>>>>>>> /sys/class/net/<iface>/dev_port
>>>>>>>>
>>>>>>>> and
>>>>>>>>
>>>>>>>>> devlink port show
>>>>>>>>
>>>>>>>> Do we have something similar in DPDK?
>>>>>>>
>>>>>>> We can get the device name of a port:
>>>>>>>     rte_eth_dev_get_name_by_port()
>>>>>>
>>>>>> I'm afraid this won't do. Consider the following example.
>>>>>> Say, there's a NIC with two network ports and two PFs,
>>>>>> 0000:01:00.0 and 0000:01:00.1. The user plugs these
>>>>>> PFs to DPDK application. The resulting ethdev IDs
>>>>>> are 0 and 1. If the user invokes the said API,
>>>>>> they will get 0000:01:00.0 and 0000:01:00.1.
>>>>>> But that's not what is really needed.
>>>>>>
>>>>>> We seek a means to get the network port ID by
>>>>>> ethdev ID. For example, something like this:
>>>>>> - get_netport_by_ethdev(0) => 0
>>>>>> - get_netport_by_ethdev(1) => 1
>>>>>>
>>>>>> If two different PCI functions are associated with the
>>>>>> same network port (0, for instance), this should be
>>>>>> - get_netport_by_ethdev(0) => 0
>>>>>> - get_netport_by_ethdev(1) => 0
>>>>>>
>>>>>> Do we have something like that in DPDK?
>>>>>
>>>>> No we don't have such underlying index.
>>>>> I don't understand why it is needed.
>>>>> To me the name is more informative than a number.
>>>>>
>>>>>
>>>>>>>> If no, would the feature be worthwhile implementing?
>>>>>>>
>>>>>>> We may have discrepancies in different device classes.
>>>>>>
>>>>>> I mean precisely "ethdev"s. I do realise, though, that
>>>>>> an ethdev may be backed by a vdev (af_xdp, etc.) = in
>>>>>> such cases the assumed "get_netport" method could
>>>>>> just return (-ENOTSUP). What do you think?
>>>>>
>>>>> Are you interested only in PCI devices? Looks limited.
>>>>
>>>> Theoretically, even a vdev may handle this request
>>>> appropriately. For example, a failsafe device may
>>>> ask its current underlying PCI device abot the
>>>> physical port ID in use. For af_xdp and the
>>>> likes, it's also possible. The PMD may
>>>> query sysfs to provide the value.
>>>>
>>>> Strictly speaking, it's not limited, but the primary
>>>> use case is querying the phys. port ID for PFs, yes.
>>>>
>>>> This information may be needed by some applications
>>>> that not only operate the higher-level ethdevs but
>>>> also take the real physical/wire interconnects
>>>> into account. It might be complex to explain
>>>> in a single email thread, though.
>>>>
>>>> Previously, DPDK even used to have a flow action PHY_PORT.
>>>> Yes, it has been deprecated, but that's not a problem.
>>>> The information can be useful anyway.
>>>
>>> In this case, this is something the driver should fill in
>>> rte_eth_dev_info.
>>> Note that we already have rte_eth_dev_info::if_index but it looks
>>> different.
>>>
>>> Who would be responsible of the numbering of the physical port?
>>> Should we report kernel numbering or do we need yet another numbering
>>> scheme?
>>
>> Very few DPDK hardware devices support multiple ports on same card.
>> And only a couple of devices (like Mellanox/Nvidia) use a kernel
>> driver component.
>>
> 
> So.. by the sound of it, it would be nice to introduce
> something like "int  phys_port_id" to rte_eth_dev_info,
> correct? That would indicate either -1 (for example,
> in the case of VFs connected with representors)
> or some sensible value, as per internal mapping.
> 

I am for having specific API for it (if we will have it), instead of
overloading the 'rte_eth_dev_info_get()', so purpose of new information
(and new API) can be more focused and clear.

> That would help certain applications to have
> physical port IDs mapped to ethdev IDs.
> Right now they have no way of knowing.
> 
> Thank you.