Re: [dpdk-dev] [PATCH 2/3] app/testpmd: fix RSS hash type update

[Maxime Coquelin <maxime.coquelin@redhat.com>]

Hi Nélio,

On 9/10/21 4:16 PM, Nélio Laranjeiro wrote:
> On Fri, Sep 10, 2021 at 01:06:53PM +0300, Andrew Rybchenko wrote:
>> On 9/10/21 12:57 PM, Maxime Coquelin wrote:
>>>
>>>
>>> On 9/10/21 11:51 AM, Andrew Rybchenko wrote:
>>>> On 9/10/21 12:17 PM, Maxime Coquelin wrote:
>>>>> port_rss_hash_key_update() initializes rss_conf with the
>>>>> RSS hash type and key provided by the user, but it calls
>>>>> rte_eth_dev_rss_hash_conf_get() before calling
>>>>> rte_eth_dev_rss_hash_update(), which overides the parsed
>>>>> config with current NIC's config.
>>>>>
>>>>> While the RSS key value is set again after, this is not
>>>>> the case of the key length and the type of hash.
>>>>>
>>>>> There is no need to read the RSS config from the NIC, let's
>>>>> just try to set the user defined one.
>>>>>
>>>>> Fixes: 8205e241b2b0 ("app/testpmd: add missing type to RSS hash commands")
>>>>> Cc: stable@dpdk.org
>>>>> Cc: nelio.laranjeiro@6wind.com
>>>>>
>>>>> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
>>>>> ---
>>>>>  app/test-pmd/config.c | 8 ++------
>>>>>  1 file changed, 2 insertions(+), 6 deletions(-)
>>>>>
>>>>> diff --git a/app/test-pmd/config.c b/app/test-pmd/config.c
>>>>> index 31d8ba1b91..451bda53b1 100644
>>>>> --- a/app/test-pmd/config.c
>>>>> +++ b/app/test-pmd/config.c
>>>>> @@ -2853,18 +2853,14 @@ port_rss_hash_key_update(portid_t port_id, char rss_type[], uint8_t *hash_key,
>>>>>  	int diag;
>>>>>  	unsigned int i;
>>>>>  
>>>>> -	rss_conf.rss_key = NULL;
>>>>> +	rss_conf.rss_key = hash_key;
>>>>>  	rss_conf.rss_key_len = hash_key_len;
>>>>>  	rss_conf.rss_hf = 0;
>>>>>  	for (i = 0; rss_type_table[i].str; i++) {
>>>>>  		if (!strcmp(rss_type_table[i].str, rss_type))
>>>>>  			rss_conf.rss_hf = rss_type_table[i].rss_type;
>>>>>  	}
>>>>> -	diag = rte_eth_dev_rss_hash_conf_get(port_id, &rss_conf);
>>>>> -	if (diag == 0) {
>>>>> -		rss_conf.rss_key = hash_key;
>>>>> -		diag = rte_eth_dev_rss_hash_update(port_id, &rss_conf);
>>>>> -	}
>>>>> +	diag = rte_eth_dev_rss_hash_update(port_id, &rss_conf);
>>>>
>>>> I'm not 100% sure, but I'd say the intent above could be
>>>> to update key only as the function name says. I.e. keep
>>>> rss_hf as is. That could be the reason to get first.
> 
> True,
> 
>>> I think that was the intial purpose of the command, but patch
>>> 8205e241b2b0 added setting the hash type as mandatory. There are
>>> no other command to configure the hash type from testpmd AFAICT.
> 
> Also for the same initial purpose, some NIC have an hash key per
> protocol, by default it uses the same key for all of them but it can be
> configured individually making for example key0 for all protocols expect
> IPv4 which uses key1.

Thanks for the info, I have looked at most drivers but didn't found one
that support this feature, could you give some pointer?

Given how the drivers implément the callback, do you agree with the fix,
or do you have something else in mind?

Thanks,
Maxime

>>> Also, even without 8205e241b2b0, the function was broken because the
>>> key length was overiden.
>>
>> I see, many thanks for explanations.
>