RE: [PATCH 1/1] net/i40e: unset vector flag when scalar path is chosen

["Loftus, Ciara" <ciara.loftus@intel.com>]

> Subject: Re: [PATCH 1/1] net/i40e: unset vector flag when scalar path is
> chosen
> 
> On Wed, Dec 17, 2025 at 02:54:36PM +0000, Ciara Loftus wrote:
> > The tx_vec_allowed flag should be set to false if a scalar Tx path is
> > chosen.
> >
> > Fixes: 1ff08bb7ad90 ("net/i40e: use common Tx path selection
> infrastructure")
> >
> > Signed-off-by: Ciara Loftus <ciara.loftus@intel.com>
> > ---
> >  drivers/net/intel/i40e/i40e_rxtx.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/net/intel/i40e/i40e_rxtx.c
> b/drivers/net/intel/i40e/i40e_rxtx.c
> > index 2db58c6b24..dd859bda4e 100644
> > --- a/drivers/net/intel/i40e/i40e_rxtx.c
> > +++ b/drivers/net/intel/i40e/i40e_rxtx.c
> > @@ -3631,6 +3631,9 @@ i40e_set_tx_function(struct rte_eth_dev *dev)
> >  			ad->tx_func_type == I40E_TX_ALTIVEC ||
> >  			ad->tx_func_type == I40E_TX_AVX2)
> >  		dev->recycle_tx_mbufs_reuse =
> i40e_recycle_tx_mbufs_reuse_vec;
> > +
> > +	if (i40e_tx_path_infos[ad->tx_func_type].features.simd_width <
> RTE_VECT_SIMD_128)
> > +		ad->tx_vec_allowed = false;
> >  }
> >
> Under what circumstances would this be a problem, or under what
> circumstances would we have this situaion?

The circumstances we would have this situation is when the driver
determines that tx vectorisation is allowed but we end up selecting
a scalar path. The result would be "vector_tx" being set for the txq
during tx_queue_start and later during tx_queue_stop, the wrong
path being taken in ci_txq_release_all_mbufs

> 
> /Bruce