On 9/11/2024 2:20 PM, Thomas Monjalon wrote: > 11/09/2024 14:17, Morten Brørup: >> From: Andrew Rybchenko [mailto:andrew.rybche...@oktetlabs.ru] >>> On 9/7/24 23:55, Morten Brørup wrote: >>>>> From: Morten Brørup [mailto:m...@smartsharesystems.com] >>>>> dev_info->rx_offload_capa |= RTE_ETH_RX_OFFLOAD_RSS_HASH; >>>> >>>> Or perhaps I'm misunderstanding this capability flag. >>>> >>>> I thought it indicated RSS ability, i.e. multi-queue, effectively shadowing >>> rte_eth_conf.rxmode.mq_mode RTE_ETH_MQ_RX_RSS_FLAG. >>>> But maybe it doesn't. Maybe it indicates the ability to store the RSS hash >>> value in the mbuf. >>>> >>>> The RTE_ETH_RX_OFFLOAD_RSS_HASH flag is completely undocumented. >>>> >>>> Can someone please clarify? >>>> >>> RTE_ETH_RX_OFFLOAD_RSS_HASH means that the driver can provide RSS hash >>> value in mbuf (it makes sense if HW can provide it to the driver). >> >> OK, thanks. >> >> Then what indicates this ethdev capability: Use RSS to distribute packets >> into multiple RX queues? >> I.e. what to check before setting >> rte_eth_conf.rxmode.mq_mode=RTE_ETH_MQ_RX_RSS_FLAG? > > It is supposed to be implemented by all DPDK drivers I think. > Is there any case where RSS is not supported? >
Hi Morten, There is no formal capability reporting support in ethdev [1]. `struct rte_eth_dev_info::[rt]x_[queue]_offload_capa` uses RTE_ETH_RX_OFFLOAD_* flags, and they are for limited scope, only to report the offloading capability of device. Also some capability reporting distributed to - struct rte_eth_dev_info::dev_capa (RTE_ETH_DEV_CAPA_*) - struct rte_eth_dev_info (various files like speed_capa) - struct rte_eth_dev_data::dev_flags (RTE_ETH_DEV_*) Programmatically there is no way for device to report RSS support. The .ini file has "RSS hash" feature, which covers RSS support, please check 'features.rst'. We mentioned formal capability reporting a few times in the past, but this is a big task to take, specially with all historical usages. Two things specially bothers me: 1. When we need a capability, since there is no dedicated place for it, it finds itself one of above locations, mostly in dev_info. 2. 'struct rte_eth_dev_info' has not defined role, it is combination of the status, configuration and capability reporting. With more capabilities hitting it, it is becoming a more mixed, central struct that many features depends on.
