Re: [dpdk-dev] [PATCH] ethdev: fix representor port ID search by name

[Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>]

On 7/19/21 2:54 PM, Xueming(Steven) Li wrote:
> 
> 
>> -----Original Message-----
>> From: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
>> Sent: Monday, July 19, 2021 4:46 PM
>> To: Xueming(Steven) Li <xuemingl@nvidia.com>; Ajit Khaparde <ajit.khaparde@broadcom.com>; Somnath Kotur
>> <somnath.kotur@broadcom.com>; John Daley <johndale@cisco.com>; Hyong Youb Kim <hyonkim@cisco.com>; Beilei Xing
>> <beilei.xing@intel.com>; Qiming Yang <qiming.yang@intel.com>; Qi Zhang <qi.z.zhang@intel.com>; Haiyue Wang
>> <haiyue.wang@intel.com>; Matan Azrad <matan@nvidia.com>; Shahaf Shuler <shahafs@nvidia.com>; Slava Ovsiienko
>> <viacheslavo@nvidia.com>; NBU-Contact-Thomas Monjalon <thomas@monjalon.net>; Ferruh Yigit <ferruh.yigit@intel.com>
>> Cc: dev@dpdk.org; Viacheslav Galaktionov <viacheslav.galaktionov@oktetlabs.ru>; stable@dpdk.org
>> Subject: Re: [PATCH] ethdev: fix representor port ID search by name
>>
>> On 7/19/21 9:58 AM, Xueming(Steven) Li wrote:
>>>
>>>
>>>> -----Original Message-----
>>>> From: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
>>>> Sent: Tuesday, July 13, 2021 12:18 AM
>>>> To: Ajit Khaparde <ajit.khaparde@broadcom.com>; Somnath Kotur
>>>> <somnath.kotur@broadcom.com>; John Daley <johndale@cisco.com>; Hyong
>>>> Youb Kim <hyonkim@cisco.com>; Beilei Xing <beilei.xing@intel.com>;
>>>> Qiming Yang <qiming.yang@intel.com>; Qi Zhang <qi.z.zhang@intel.com>;
>>>> Haiyue Wang <haiyue.wang@intel.com>; Matan Azrad <matan@nvidia.com>;
>>>> Shahaf Shuler <shahafs@nvidia.com>; Slava Ovsiienko
>>>> <viacheslavo@nvidia.com>; NBU-Contact-Thomas Monjalon
>>>> <thomas@monjalon.net>; Ferruh Yigit <ferruh.yigit@intel.com>;
>>>> Xueming(Steven) Li <xuemingl@nvidia.com>
>>>> Cc: dev@dpdk.org; Viacheslav Galaktionov
>>>> <viacheslav.galaktionov@oktetlabs.ru>; stable@dpdk.org
>>>> Subject: [PATCH] ethdev: fix representor port ID search by name
>>>>
>>>> From: Viacheslav Galaktionov <viacheslav.galaktionov@oktetlabs.ru>
>>>>
>>>> Fix representor port ID search by name if the representor itself does
>>>> not provide representors info. Getting a list of representors from a representor does not make sense. Instead, a parent device
>> should be used.
>>>>
>>>> To this end, extend the rte_eth_dev_data structure to include the port ID of the parent device for representors.
>>>>
>>>> Fixes: df7547a6a2cc ("ethdev: add helper function to get representor
>>>> ID")
>>>> Cc: stable@dpdk.org
>>>>
>>>> Signed-off-by: Viacheslav Galaktionov
>>>> <viacheslav.galaktionov@oktetlabs.ru>
>>>> Signed-off-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
>>>> ---
>>>> The new field is added into the hole in rte_eth_dev_data structure.
>>>> The patch does not change ABI, but extra care is required since ABI check is disabled for the structure because of the libabigail bug
>> [1].
>>>>
>>>> Potentially it is bad for out-of-tree drivers which implement
>>>> representors but do not fill in a new parert_port_id field in rte_eth_dev_data structure. Do we care?
>>>>
>>>> May be the patch should add lines to release notes, but I'd like to get initial feedback first.
>>>>
>>>> mlx5 changes should be reviwed by maintainers very carefully, since we are not sure if we patch it correctly.
>>>>
>>>> [1] https://sourceware.org/bugzilla/show_bug.cgi?id=28060
>>
>> [snip]
>>
>>>> --- a/lib/ethdev/ethdev_driver.h
>>>> +++ b/lib/ethdev/ethdev_driver.h
>>>> @@ -1248,8 +1248,8 @@ struct rte_eth_devargs {
>>>>     * For backward compatibility, if no representor info, direct
>>>>     * map legacy VF (no controller and pf).
>>>>     *
>>>> - * @param ethdev
>>>> - *  Handle of ethdev port.
>>>> + * @param parent_port_id
>>>> + *  Port ID of the backing device.
>>>>     * @param type
>>>>     *  Representor type.
>>>>     * @param controller
>>>> @@ -1266,7 +1266,7 @@ struct rte_eth_devargs {
>>>>     */
>>>>    __rte_internal
>>>>    int
>>>> -rte_eth_representor_id_get(const struct rte_eth_dev *ethdev,
>>>> +rte_eth_representor_id_get(uint16_t parent_port_id,
>>>
>>> It make more sense to get representor info from parent port.
>>> Representor is a member of switch domain, PMD owns the information of
>>> the representor owner port and info of representors. This change looks better, but not sure whether it valuable to introduce a new
>> member to the EAL data structure.
>>
>> IMHO, it is simply incorrect to return representors info on a representor itself. Representor info is an information which representors
>> may be populated using the device.
>>
>> If above statement is correct, we need a way to get parent device by representor to do name to representor ID mapping. I see two
>> options to do it:
>>    A. Dedicated field in rte_eth_dev_data as the patch does.
>>    B. Dedicated ethdev op (since representor knows parent port ID anyway).
>> We have chosen (A) because of simplicity.
> 
> Just recalled that representor port could be probed w/o owner PF, is a force for parent port?

I thought that it is impossible and parent port is absolutely required
for a representor. Could you provide an example and explain how will it
work?