Re: [PATCH 2/6] net/hns3: fix inconsistent enabled RSS behavior

["lihuisong (C)" <lihuisong@huawei.com>]

Hi, all,

在 2022/3/10 16:08, lihuisong (C) 写道:
>
> 在 2022/3/9 17:55, Ori Kam 写道:
>> Hi Lihusiong,
>>
>>> -----Original Message-----
>>> From: lihuisong (C) <lihuisong@huawei.com>
>>> Sent: Wednesday, March 9, 2022 10:03 AM
>>> Subject: Re: [PATCH 2/6] net/hns3: fix inconsistent enabled RSS 
>>> behavior
>>>
>>>
>>> 在 2022/3/3 10:47, lihuisong (C) 写道:
>>>> Hi, Ori,
>>>>
>>>> 在 2022/3/2 22:07, Ori Kam 写道:
>>>>> Hi Lihuisong,
>>>>>
>>>>>> -----Original Message-----
>>>>>> From: lihuisong (C) <lihuisong@huawei.com>
>>>>>> Sent: Wednesday, March 2, 2022 4:10 AM
>>>>>> Subject: Re: [PATCH 2/6] net/hns3: fix inconsistent enabled RSS
>>>>>> behavior
>>>>>>
>>>>>>
>>>>>> 在 2022/3/1 0:42, Ferruh Yigit 写道:
>>>>>>> On 2/28/2022 3:21 AM, Min Hu (Connor) wrote:
>>>>>>>> From: Huisong Li <lihuisong@huawei.com>
>>>>>>>>
>>>>>>>> RSS will not be enabled if the RTE_ETH_MQ_RX_RSS_FLAG isn't be 
>>>>>>>> set in
>>>>>>>> dev_configure phase. However, if this flag isn't set, RSS can be
>>>>>>>> enabled
>>>>>>>> through the ethdev ops and rte_flow API. This behavior is 
>>>>>>>> contrary to
>>>>>>>> each
>>>>>>>> other.
>>>>>>>>
>>>>>>>> Fixes: c37ca66f2b27 ("net/hns3: support RSS")
>>>>>>>> Cc: stable@dpdk.org
>>>>>>>>
>>>>>>>> Signed-off-by: Huisong Li <lihuisong@huawei.com>
>>>>>>> Hi Huisong, Connor,
>>>>>>>
>>>>>>> Let's get a little more feedback for this patch, cc'ed more people.
>>>>>>>
>>>>>>>
>>>>>>> To enable RSS, multi queue mode should be set to
>>>>>>> 'RTE_ETH_MQ_RX_RSS_FLAG'.
>>>>>>>
>>>>>>> But I wonder if it is required to configure RSS via flow API,
>>>>>> I do not know the original purpose of adding the RSS 
>>>>>> configuration in
>>>>>> flow API.
>>>>>>
>>>>> The purpose is simple, this allow to create RSS per rule and not a
>>>>> global one.
>>>>> For example create RSS that sends TCP to some queues while othe RSS
>>>>> will send
>>>>> UDP traffic to different queues.
>>>> I'm a little confused now. The "per rule" also seems to be a global
>>>> configuration.
>>>> Example:
>>>>   - start PMD with 0,1,2,3
>>>>   - create TCP packets to 2,3 queues. At this moment, only 2,3 queues
>>>> can be received for other types of packets.
>>>> Because this rule is implemented by modifying the entry of the
>>>> redirection table which is global for this device.
>>> Hi, Ori and Stephen.
>>> Can you help me clear up the confusion above? If some NICs behave like
>>> this, what should we do about it?
>> I'm not sure I understand the issue, maybe it is releated to some 
>> HW/PMD limitation.
>> In your example non TCP traffic will be routed to one of the 4 queues 
>> (0,1,2,3),
>> While TCP traffic will only be routed to queues 2,3.
>>
>> Now I can add new rule that matches on UDP packet and RSS to queue 0 
>> and 3 in this case:
>> TCP packets will be routed to queues 0,3.
>> UDP packets will be routed to queues 2,3.
>> All the rest of the traffic will be routed to queues 0,1,2,3
>>
>> And just to be clear if now I add a rule to match all packets in 
>> higher priority,
>> with RSS to queues 1,2. Then all traffic will be routed to queues 1,2.
>>
>> At least this is what is expected, from API point of view.
>>
>> Best,
>> Ori
> Thank you for your answer. I understand it.
> hns3 PMD cannot implement the above functions due to hardware limitation.
> we may need add a check that specified RSS queues cannot be supported 
> when specified packets types.
> And only the packet type is specified, which meets the requirements of 
> rte_flow API.
> The check for the RTE_ETH_MQ_RX_RSS_FLAG flag in rte_flow is not correct.
> Thanks, Ori and Stephen😁
>
> But, I think, it is necessary for the '.rss_hash_update' and 
> '.reta_update' APIs
> in eth_dev_ops to verify this flag. What do you think? @Thomas, 
> @Ferruh, @Ori and @Stephen.
What's your take on it? I am looking forward to your reply. Thanks!
>>
>>>>>> However, as far as I know, the hash algorithm can be configured via
>>>>>> this
>>>>>> API,
>>>>>>
>>>>>> but not via ethdev ops API.
>>>>>>
>>>>>>> and if other PMDs check this configuration for flow API?
>>>>>> Some PMDs already have similar check in RSS releated ops or rte_flow
>>>>>> API.
>>>>>>
>>>>>> For example, hinic, axbge, bnxt, cnxk, otx2, and ena.
>>>>>>
>>>>>>> .
>>>>>   From my view point those are two different settings.
>>>>> The RTE_ETH_MQ_RX_RSS_FLAG is global per port while
>>>>> rte_flow is per rule.
>>>>>
>>>>> I think, that if a PMD needs this flag, in order to enable it also
>>>>> for rte_flow then
>>>>> it should be documented in the release note of the PMD.
>>>>> It is a valid use case that the default traffic will not have RSS and
>>>>> only rules created by
>>>>> rte_flow will have the RSS, for matching traffc.
>>>>>
>>>>> Best,
>>>>> Ori
> .