virtio: RSS support capa

[Morten Brørup]

> From: Morten Brørup [mailto:mb at smartsharesystems.com]
> Sent: Friday, 6 September 2024 21.38
> 
> Maxime, Chenbo,
> 
> If the virtio PMD supports RSS, it should be announced in its
> capabilities.
> 
> I think this should be added to virtio_dev_info_get():
> 
> 	if (host_features & (1ULL << VIRTIO_NET_F_RSS))
> 		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?