Re: virtio: RSS support capa

[Thomas Monjalon <thomas@monjalon.net>]

11/09/2024 14:17, Morten Brørup:
> From: Andrew Rybchenko [mailto:andrew.rybchenko@oktetlabs.ru]
> > On 9/7/24 23:55, Morten Brørup wrote:
> > >> From: Morten Brørup [mailto:mb@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?