Re: [dpdk-dev] [PATCH] net/ena: enable multi segment in Tx offload flags

[Olivier Matz <olivier.matz@6wind.com>]

Hi Michał,

On Wed, Jul 14, 2021 at 12:02:32PM +0200, Michał Krawczyk wrote:
> pon., 12 lip 2021 o 19:03 Ghalem Boudour <ghalem.boudour@6wind.com> napisał(a):
> >
> > The DPDK ENA driver does not provide multi-segment tx offload capability.
> > Let's add DEV_TX_OFFLOAD_MULTI_SEGS to ports offload capability by default.
> >
> 
> Hi Ghalem,
> 
> This patch enables announcement of the DEV_TX_OFFLOAD_MULTI_SEGS
> capability, but still the application may not request this offload.
> 
> As ENA PMD currently assumes all the mbufs may have multiple segments
> (and we don't have fast-path for the other cases), I suggest
> overwriting this flag in the ena_dev_configure(), similar to what
> we're doing with the DEV_RX_OFFLOAD_RSS_HASH flag.

To give some more context, our application currently checks if the
driver supports multi-segments by checking its capabilities, and asks
for the feature if it is advertised.

When dealing with drivers that do not advertise this capability, our app
linearizes the segmented mbufs before sending them to the driver.

I think this is the proper way to use the API: if the driver supports to
handle multisegmented mbufs, it should advertise the capability.

Regards,
Olivier


> Best regards,
> Michal
> 
> > This flag in not listed in doc/guides/nics/features/default.ini, so
> > ena.ini does not need to be updated.
> >
> > Signed-off-by: Ghalem Boudour <ghalem.boudour@6wind.com>
> > Reviewed-by: Olivier Matz <olivier.matz@6wind.com>
> > ---
> >  drivers/net/ena/ena_ethdev.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/net/ena/ena_ethdev.c b/drivers/net/ena/ena_ethdev.c
> > index dfe68279fa7b..a8422ee425ce 100644
> > --- a/drivers/net/ena/ena_ethdev.c
> > +++ b/drivers/net/ena/ena_ethdev.c
> > @@ -2055,6 +2055,7 @@ static int ena_infos_get(struct rte_eth_dev *dev,
> >                         DEV_RX_OFFLOAD_TCP_CKSUM;
> >
> >         rx_feat |= DEV_RX_OFFLOAD_JUMBO_FRAME;
> > +       tx_feat |= DEV_TX_OFFLOAD_MULTI_SEGS;
> >
> >         /* Inform framework about available features */
> >         dev_info->rx_offload_capa = rx_feat;
> > --
> > 2.28.0
> >