RE: virtio: RSS support capa

["Morten Brørup" <mb@smartsharesystems.com>]

> From: Andrew Rybchenko [mailto:andrew.rybchenko@oktetlabs.ru]
> Sent: Sunday, 8 September 2024 10.33
> 
> On 9/7/24 23:55, Morten Brørup wrote:
> >> From: Morten Brørup [mailto:mb@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?
> >
> 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?