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Subject: Re: [PATCH v8 01/10] ethdev: overwrite some comment related to RSS
To: Ferruh Yigit <ferruh.yigit@amd.com>, <dev@dpdk.org>, Thomas Monjalon
<thomas@monjalon.net>, Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>, Ori
Kam <orika@nvidia.com>
CC: <lihuisong@huawei.com>, <fengchengwen@huawei.com>,
<liudongdong3@huawei.com>
References: <20230315110033.30143-1-liudongdong3@huawei.com>
<20231101074039.3088716-1-haijie1@huawei.com>
<20231101074039.3088716-2-haijie1@huawei.com>
<53497412-9211-47c1-a57a-27ee19ada312@amd.com>
From: Jie Hai <haijie1@huawei.com>
In-Reply-To: <53497412-9211-47c1-a57a-27ee19ada312@amd.com>
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On 2023/11/1 21:13, Ferruh Yigit wrote:
> On 11/1/2023 7:40 AM, Jie Hai wrote:
>> 1. overwrite the comments of fields of 'rte_eth_rss_conf'.
>> 2. Add comments for RTE_ETH_HASH_FUNCTION_DEFAULT.
>>
>> Signed-off-by: Jie Hai <haijie1@huawei.com>
>> ---
>> lib/ethdev/rte_ethdev.h | 34 +++++++++++++++++++---------------
>> lib/ethdev/rte_flow.h | 1 +
>> 2 files changed, 20 insertions(+), 15 deletions(-)
>>
>> diff --git a/lib/ethdev/rte_ethdev.h b/lib/ethdev/rte_ethdev.h
>> index a53dd5a1efec..343a134fdd12 100644
>> --- a/lib/ethdev/rte_ethdev.h
>> +++ b/lib/ethdev/rte_ethdev.h
>> @@ -448,24 +448,28 @@ struct rte_vlan_filter_conf {
>> /**
>> * A structure used to configure the Receive Side Scaling (RSS) feature
>> * of an Ethernet port.
>> - * If not NULL, the *rss_key* pointer of the *rss_conf* structure points
>> - * to an array holding the RSS key to use for hashing specific header
>> - * fields of received packets. The length of this array should be indicated
>> - * by *rss_key_len* below. Otherwise, a default random hash key is used by
>> - * the device driver.
>> - *
>> - * The *rss_key_len* field of the *rss_conf* structure indicates the length
>> - * in bytes of the array pointed by *rss_key*. To be compatible, this length
>> - * will be checked in i40e only. Others assume 40 bytes to be used as before.
>> - *
>> - * The *rss_hf* field of the *rss_conf* structure indicates the different
>> - * types of IPv4/IPv6 packets to which the RSS hashing must be applied.
>> - * Supplying an *rss_hf* equal to zero disables the RSS feature.
>> */
>> struct rte_eth_rss_conf {
>> - uint8_t *rss_key; /**< If not NULL, 40-byte hash key. */
>> + /**
>> + * In rte_eth_dev_rss_hash_conf_get(), the *rss_key_len* should be
>> + * greater than or equal to the *hash_key_size* which get from
>> + * rte_eth_dev_info_get() API. And the *rss_key* should contain at least
>> + * *hash_key_size* bytes. If not meet these requirements, the query
>> + * result is unreliable even if the operation returns success.
>> + *
>> + * In rte_eth_dev_rss_hash_update() or rte_eth_dev_configure(), if
>> + * *rss_key* is not NULL, the *rss_key_len* indicates the length of the
>> + * *rss_key* in bytes of the array pointed by *rss_key*,
>>
>
> I think it is sufficient to say "length of the *rss_key* in bytes".
>
>
>> and it should
>> + * be equal to *hash_key_size*.
>>
>
> I don't know if we missed something here, first driver reports key size
> via 'rte_eth_dev_info_get()::hash_key_size', later other APIs require
> 'rss_key_len' parameter that should be same as 'hash_key_size', as
> driver already know this parameter why we are requesting it back from
> the application?
>
To unify user behavior and verify user behavior at the ethdev level.
>
>>> Otherwise, drivers are free to use a
>> + * random or a default key or to ignore this configuration.
>> + */
>>
>
>
> I guess above clause describes when 'rss_key' is null, can you please
> clarify it as following, perhaps with a line break:
> "If *rss_key* is NULL, drivers are free to use a random or a default key."
>
>
> For the "Drivers are free to ignore the *rss_key_len* and assume key
> length is 40 bytes." part, as checks in ethdev layer now forces
> application to provide 'rss_key_len' as 'hash_key_size', I think we can
> remove above, as application will provide 40 bytes when it is the case.
>
> My concern is this check now can break some applications, because
> 'rss_key_len' wasn't mandatory previously, but it became now.
>
The testpmd already use 'rte_eth_dev_info_get()::hash_key_size' to
correct the rss_key_len.
If hash_key_size is zero or too big for user's rss_key, it report errors.
Otherwise, it use hash_key_size as rss_key_len.
If all drivers use this app to test rss configuration, the check has no
problem.
The test_link_bonding_rssconf use 40 Bytes rss_key, we know that is
valid for now.
>
> Overall it becomes:
> "
> In rte_eth_dev_rss_hash_update() or rte_eth_dev_configure(), if
> *rss_key* is not NULL, the *rss_key_len* indicates the length of the
> *rss_key* in bytes and it should be equal to *hash_key_size*.
> If *rss_key* is NULL, drivers are free to use a random or a default key.
> "
>
ok, thanks.
>
>
>> + uint8_t *rss_key;
>> uint8_t rss_key_len; /**< hash key length in bytes. */
>> - uint64_t rss_hf; /**< Hash functions to apply - see below. */
>> + /**
>> + * Indicates the type of packets or the specific part of packets to
>> + * which RSS hashing is to be applied.
>> + */
>> + uint64_t rss_hf;
>> };
>>
>> /*
>> diff --git a/lib/ethdev/rte_flow.h b/lib/ethdev/rte_flow.h
>> index c16fe8c21f2f..751c29a0f3f3 100644
>> --- a/lib/ethdev/rte_flow.h
>> +++ b/lib/ethdev/rte_flow.h
>> @@ -3226,6 +3226,7 @@ struct rte_flow_query_count {
>> * Hash function types.
>> */
>> enum rte_eth_hash_function {
>> + /** DEFAULT means driver decides which hash algorithm to pick. */
>> RTE_ETH_HASH_FUNCTION_DEFAULT = 0,
>> RTE_ETH_HASH_FUNCTION_TOEPLITZ, /**< Toeplitz */
>> RTE_ETH_HASH_FUNCTION_SIMPLE_XOR, /**< Simple XOR */
>
> .