Re: [dpdk-dev] [PATCH v5] app/testpmd: fix the default RSS key configuration

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

On 10/15/2020 3:04 PM, oulijun wrote:
> 
> 
> 在 2020/10/15 21:52, Ferruh Yigit 写道:
>> On 10/15/2020 1:41 PM, Lijun Ou wrote:
>>> When start the testpmd, the pmd driver initializes the RSS
>>> configuration. Generally, the recommended RSS hash key is
>>> used as the default key in the driver. In addition, the
>>> default key is different from the default RSS flow in testpmd
>>> without specifying RSS hash key. So. if you do not specify
>>> the RSS key when creating an RSS rule, the testpmd uses the
>>> default key as the default RSS key of the RSS rule. As a result,
>>> you may mistakenly consider that the RSS key in use is the valid
>>> default key of the NIC, actually, the key and the valid default
>>> key of the NIC are two values.
>>>
>>> Consider the follow usage with testpmd:
>>> 1. first, startup testpmd:
>>> testpmd> show port 0 rss-hash key
>>> RSS functions:
>>>    all ipv4-frag ipv4-other ipv6-frag ipv6-other ip
>>> RSS key:
>>> -6D5A56DA255B0EC24167253D43A38FB0D0CA2BCBAE7B30B477CB2DA38030F
>>> -20C6A42B73BBEAC01FA
>>> 2. create a rss rule
>>> testpmd> flow create 0 ingress pattern eth / ipv4 / udp / end actions rss \
>>> types ipv4-udp end queues end / end
>>>
>>> 3. show rss-hash key
>>> testpmd> show port 0 rss-hash key
>>> RSS functions:
>>>    all ipv4-udp udp
>>> RSS key:
>>> -74657374706D6427732064656661756C74205253532068617368206B65792C206F
>>> -76657272696465
>>>
>>> In order to solve the above problems, it use the NIC valid default
>>> RSS key instead of the testpmd dummy RSS key in the flow configuration
>>> when the RSS key is not specified in the flow rule. If the NIC RSS key
>>> is invalid, it will use testpmd dummy RSS key as the default key.
>>>
>>> Fixes: ac8d22de2394 ("ethdev: flatten RSS configuration in flow API")
>>> Cc: stable@dpdk.org
>>>
>>> Signed-off-by: Lijun Ou <oulijun@huawei.com>
>>> Reviewed-by: Phil Yang <phil.yang@arm.com>
>>> ---
>>> V4->V5:
>>> -rewrite the commit log
>>> -add reviewed-by
>>
>> Hi Lijun,
>>
>> There were multiple other comments, it seems they are not addressed but only 
>> updated the commit log, can you please check comments to prev versions.
>>
>> Before going into the details, my question was what happens if default key not 
>> provided at all?
>> It seems this has been already tried by Ophir [1], later reverted back [2] 
>> bringing the initial issue back.
>>
>> According commit, the reason of revert is to support following command:
>> "flow create 0 <pattern> actions rss queues 0 1 end key_len 40 / end"
>>
>> @Ophir, @Lijun,
>> Can we ignore the 'key_len' if the 'key' is not supported and solve current 
>> issue as initially intended ([1])?
>>
> Hi, Ferruh
>    I have discussed with Phil Yang about the problem in [1]. I think there may 
> be other problems with the idea and there is no better solution. and we need to 
> remove key_len definition from rte_rss_conf structure. They don't have a plan. 
> And [1] was eventually reverted.
> 

Why ignoring 'key_len' (set it to zero) when there is no 'key' provided doesn't 
work?

> Thanks
> Lijun Ou
>>
>> [1] https://git.dpdk.org/dpdk/commit/?id=a4391f8bae8
>>
>> [2] https://git.dpdk.org/dpdk/commit/?id=f3698c3d09a
>> .
>>