Re: [dpdk-dev] [PATCH 1/2] app/testpmd: update Rx RSS HASH offload when setting MQ RSS

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

On 9/8/2020 3:16 AM, Wei Hu (Xavier) wrote:
> From: Huisong Li <lihuisong@huawei.com>
> 
> Currently, when starting testpmd application without '--disable-rss' and
> the number of Rx queue configured is greater than 1, ETH_MQ_RX_RSS flag
> is set in port->dev_conf.rxmode.mq_mode in testpmd application, and
> DEV_RX_OFFLOAD_RSS_HASH flag is set in rx_offloads
> (dev->data->dev_conf.rxmode.offloads) according to the ETH_MQ_RX_RSS
> flag of rxmode.mq_mode in PMD drivers.
> 
> However, DEV_RX_OFFLOAD_RSS_HASH is not set to rx_offloads maintained
> in testpmd application, this will cause the inconsistent problem that
> rx_offloads is different for testpmd and PMD drivers.

Yes for DEV_RX_OFFLOAD_RSS_HASH, application rx_offload config and PMD 
one diverges, for *some* PMDs.

This is done to have the backward compatibility of the PMD behavior.

The PMDs that would like to write the provide the calculated hash value 
back, overwrites the offload config to enable 'DEV_RX_OFFLOAD_RSS_HASH'. 
And does more work than user requested, this shouldn't have any side affect.
Some doesn't provide the hash unless user explicitly requests it.

Applications shouldn't set it blindly, at least first check if PMD 
supports it but even that case, unless it is needed I think HASH offload 
shouldn't be requested by default.

> 
> Signed-off-by: Huisong Li <lihuisong@huawei.com>
> Signed-off-by: Wei Hu (Xavier) <xavier.huwei@huawei.com>
> ---
>   app/test-pmd/testpmd.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/app/test-pmd/testpmd.c b/app/test-pmd/testpmd.c
> index 7842c3b..73543bb 100644
> --- a/app/test-pmd/testpmd.c
> +++ b/app/test-pmd/testpmd.c
> @@ -3356,11 +3356,13 @@ init_port_config(void)
>   		}
>   
>   		if (port->dcb_flag == 0) {
> -			if( port->dev_conf.rx_adv_conf.rss_conf.rss_hf != 0)
> +			if (port->dev_conf.rx_adv_conf.rss_conf.rss_hf != 0) {
>   				port->dev_conf.rxmode.mq_mode =
>   					(enum rte_eth_rx_mq_mode)
>   						(rx_mq_mode & ETH_MQ_RX_RSS);
> -			else
> +				port->dev_conf.rxmode.offloads |=
> +							DEV_RX_OFFLOAD_RSS_HASH;
> +			} else
>   				port->dev_conf.rxmode.mq_mode = ETH_MQ_RX_NONE;
>   		}
>   
>