Re: [dpdk-dev] [dpdk-stable] [PATCH v4] app/testpmd: fix testpmd doesn't show RSS hash offload

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

On 7/19/2021 10:55 AM, Wang, Jie1X wrote:
> 
> 
>> -----Original Message-----
>> From: Yigit, Ferruh <ferruh.yigit@intel.com>
>> Sent: Friday, July 16, 2021 4:52 PM
>> To: Li, Xiaoyun <xiaoyun.li@intel.com>; Wang, Jie1X <jie1x.wang@intel.com>;
>> dev@dpdk.org
>> Cc: andrew.rybchenko@oktetlabs.ru; stable@dpdk.org
>> Subject: Re: [dpdk-stable] [PATCH v4] app/testpmd: fix testpmd doesn't show
>> RSS hash offload
>>
>> On 7/16/2021 9:30 AM, Li, Xiaoyun wrote:
>>>> -----Original Message-----
>>>> From: stable <stable-bounces@dpdk.org> On Behalf Of Li, Xiaoyun
>>>> Sent: Thursday, July 15, 2021 12:54
>>>> To: Wang, Jie1X <jie1x.wang@intel.com>; dev@dpdk.org
>>>> Cc: andrew.rybchenko@oktetlabs.ru; stable@dpdk.org
>>>> Subject: Re: [dpdk-stable] [PATCH v4] app/testpmd: fix testpmd
>>>> doesn't show RSS hash offload
>>>>
>>>>> -----Original Message-----
>>>>> From: Wang, Jie1X <jie1x.wang@intel.com>
>>>>> Sent: Thursday, July 15, 2021 19:57
>>>>> To: dev@dpdk.org
>>>>> Cc: Li, Xiaoyun <xiaoyun.li@intel.com>;
>>>>> andrew.rybchenko@oktetlabs.ru; Wang, Jie1X <jie1x.wang@intel.com>;
>>>>> stable@dpdk.org
>>>>> Subject: [PATCH v4] app/testpmd: fix testpmd doesn't show RSS hash
>>>>> offload
>>>>>
>>>>> The driver may change offloads info into dev->data->dev_conf in
>>>>> dev_configure which may cause port->dev_conf and port->rx_conf
>>>>> contain
>>>> outdated values.
>>>>>
>>>>> This patch updates the offloads info if it changes to fix this issue.
>>>>>
>>>>> Fixes: ce8d561418d4 ("app/testpmd: add port configuration settings")
>>>>> Cc: stable@dpdk.org
>>>>>
>>>>> Signed-off-by: Jie Wang <jie1x.wang@intel.com>
>>>>> ---
>>>>> v4: delete the whitespace at the end of the line.
>>>>> v3:
>>>>>  - check and update the "offloads" of "port->dev_conf.rx/txmode".
>>>>>  - update the commit log.
>>>>> v2: copy "rx/txmode.offloads", instead of copying the entire struct
>>>>> "dev->data-
>>>>>> dev_conf.rx/txmode".
>>>>> ---
>>>>>  app/test-pmd/testpmd.c | 27 +++++++++++++++++++++++++++
>>>>>  1 file changed, 27 insertions(+)
>>>>
>>>> Acked-by: Xiaoyun Li <xiaoyun.li@intel.com>
>>>
>>> Although I gave my ack, app shouldn't touch rte_eth_devices which this patch
>> does. Usually, testpmd should only call function like
>> eth_dev_info_get_print_err().
>>> But dev_info doesn't contain the info dev->data->dev_conf which the driver
>> modifies.
>>>
>>> Probably we need a better fix.
>>>
>>
>> Agree, an application accessing directly to 'rte_eth_devices' is sign of something
>> missing/wrong.
>>
>> In this case there is no way for application to know what is the configured
>> offload settings per port and queue. Which is missing part I think.
>>
>> As you said normally we get data from PMD mainly via 'rte_eth_dev_info_get()',
>> which is an overloaded function, it provides many different things, like driver
>> default values, limitations, current config/status, capabilities etc...
>>
>> So I think we can do a few things:
>> 1) Add current offload configuration to 'rte_eth_dev_info_get()', so application
>> can get it and use it.
>> The advantage is this API already called many places, many times, so there is a
>> big chance that application already have this information when it needs.
>> Disadvantage is, as mentioned above the API already big and messy, making it
>> bigger makes more error prone and makes easier to break ABI.
>>
> I prefer to choose the 1st suggestion. 
> 
> Normally PMD gets data via 'rte_eth_dev_info_get()'. When we add offloads configuration 
> to it, we can get offloads as same as getting other info.
> 

Most probably it is easier to implement 1), I see your point but as said before
I think 'rte_eth_dev_info_get()' is already messy and I am worried to make it
even bigger.

I prefer option 2).

@Thomas, @Andrew, what do you think?


>> 2) Add a new API to get configured offload information, so a specific API for it.
>>
>> 3) Get a more generic API to get configured config (dev_conf) which will cover
>> offloads too.
>> Disadvantage can be leaking out too many internal config to user unintentionally.