[PATCH v5 02/40] ethdev: support setting and querying RSS algorithm

[Stephen Hemminger]

On Wed, 11 Oct 2023 17:27:27 +0800
Jie Hai <haijie1 at huawei.com> wrote:

> Currently, rte_eth_rss_conf supports configuring and querying
> RSS hash functions, rss key and it's length, but not RSS hash
> algorithm.
> 
> The structure ``rte_eth_rss_conf`` is extended by adding a new
> field "algorithm". This represents the RSS algorithms to apply.
> The following API will be affected:
> 	- rte_eth_dev_configure
> 	- rte_eth_dev_rss_hash_update
> 	- rte_eth_dev_rss_hash_conf_get
> 
> If the value of "algorithm" used for configuration is a gibberish
> value, report the error and return. Do the same for
> rte_eth_dev_rss_hash_update and rte_eth_dev_configure.
> 
> To check whether the drivers report valid "algorithm", it is set
> to default value before querying.
> 
> Signed-off-by: Jie Hai <haijie1 at huawei.com>
> Signed-off-by: Dongdong Liu <liudongdong3 at huawei.com>
> ---
>  doc/guides/rel_notes/release_23_11.rst |  2 ++
>  lib/ethdev/rte_ethdev.c                | 17 ++++++++++++++++
>  lib/ethdev/rte_ethdev.h                | 27 +++++++++++++++++++++++++
>  lib/ethdev/rte_flow.c                  |  1 -
>  lib/ethdev/rte_flow.h                  | 28 ++------------------------
>  5 files changed, 48 insertions(+), 27 deletions(-)
> 
> diff --git a/doc/guides/rel_notes/release_23_11.rst b/doc/guides/rel_notes/release_23_11.rst
> index e13d57728071..92a445ab2ed3 100644
> --- a/doc/guides/rel_notes/release_23_11.rst
> +++ b/doc/guides/rel_notes/release_23_11.rst
> @@ -197,6 +197,8 @@ ABI Changes
>    fields, to move ``rxq`` and ``txq`` fields, to change the size of
>    ``reserved1`` and ``reserved2`` fields.
>  
> +* ethdev: Added "algorithm" field to ``rte_eth_rss_conf`` structure for RSS
> +  hash algorithm.
>  
>  Known Issues
>  ------------
> diff --git a/lib/ethdev/rte_ethdev.c b/lib/ethdev/rte_ethdev.c
> index 18a4b950b184..2eda1b8072e5 100644
> --- a/lib/ethdev/rte_ethdev.c
> +++ b/lib/ethdev/rte_ethdev.c
> @@ -1464,6 +1464,14 @@ rte_eth_dev_configure(uint16_t port_id, uint16_t nb_rx_q, uint16_t nb_tx_q,
>  		goto rollback;
>  	}
>  
> +	if (dev_conf->rx_adv_conf.rss_conf.algorithm >= RTE_ETH_HASH_FUNCTION_MAX) {
> +		RTE_ETHDEV_LOG(ERR,
> +			"Ethdev port_id=%u invalid RSS algorithm: 0x%"PRIx64"\n",
> +			port_id, dev_conf->rx_adv_conf.rss_conf.algorithm);
> +		ret = -EINVAL;
> +		goto rollback;
> +	}
> +

Rather than having every driver check the algorithm, why not handle this like
other features in DPDK (which may mean API/ABI changes). 

Add a field rss_algo_capa which is bit field of available RSS functions.
Then the check for algorithm can be done in generic code. There a couple
of reserved fields that could be used.

It would mean updating all the drivers once with the capa field but
would provide way for application to know what fields are possible.

It has proved to be a problem in later ABI changes if a maximum value
is exposed. I.e don't expose RTE_ETH_HASH_FUNCTION_MAX.