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

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

在 2022/3/23 1:13, Thomas Monjalon 写道:
> 21/03/2022 08:14, lihuisong (C):
>> 2022/3/10 16:08, lihuisong (C):
>>> 2022/3/9 17:55, Ori Kam:
>>>> From: lihuisong (C) <lihuisong@huawei.com>
>>>>> 2022/3/3 10:47, lihuisong (C):
>>>>>> 2022/3/2 22:07, Ori Kam:
>>>>>>> From: lihuisong (C) <lihuisong@huawei.com>
>>>>>>>> 2022/3/1 0:42, Ferruh Yigit:
>>>>>>>>> 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!
> I am not sure why you want to check this flag.
I want to make sure that the behavior that PMD configured RSS is
consistent across different interfaces. The RTE_ETH_MQ_RX_RSS_FLAG
flag is a switch to enable RSS hash. If the switch isn't open, some
PMD do not configure RSS function. I think the consistency is necessary.
If not set RSS muti-queue mode, it is unnecessary to configure RSS.
> I can imagine we configure the hash and the table before enabling RSS
> with the RTE_ETH_MQ_RX_RSS_FLAG flag.
The flag is derived from dev_configure() which also configures
hash and key. I don't think it makes sense to configure hash and
reta before calling dev_configure. Because they'll be updated.
This is similar to configuring mtu.
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