RE: [PATCH v3] net/iavf: revert fix VLAN insertion

["Zhou, YidingX" <yidingx.zhou@intel.com>]

> > Subject: [PATCH v3] net/iavf: revert fix VLAN insertion
> >
> > The vector Tx path does not support VLAN insertion via the L2TAG2
> > field, but the scalar path supports. The previous commit was to force
> > to select scalar path as soon as kernel driver requests to use L2TAG2.
> 
> In which situation, that kernel driver will request to use L2TAG2?

According to my tests, this happens when the kernel driver version is newer than 1.8.9

> >
> > That logic is incorrect. Because other case like VLAN offloading not
> > required but scalar path selected would have a significant performance drop .
> > Therefore the following commit needs to revert.
> 
> What will happen, if kernel driver request to use L2TAG2, but still vector path is
> selected?
> 
The VLAN tag will be inserted to wrong location (inner of QinQ),  and this behavior is inconsistent with PF (outer).

> >
> > commit 0d58caa7d6d1 ("net/iavf: fix VLAN insertion")
> >
> > After this commit reverted, the user can select scalar path with the
> > parameter '--force-max-simd-bitwidth' if necessary.
> >
> > Fixes: 0d58caa7d6d1 ("net/iavf: fix VLAN insertion")
> >
> > Signed-off-by: Yiding Zhou <yidingx.zhou@intel.com>
> > ---
> > v3: rebase and change commit log
> > ---
> >  drivers/net/iavf/iavf_rxtx_vec_common.h | 3 ---
> >  1 file changed, 3 deletions(-)
> >
> > diff --git a/drivers/net/iavf/iavf_rxtx_vec_common.h
> > b/drivers/net/iavf/iavf_rxtx_vec_common.h
> > index 4ab22c6b2b..a59cb2ceee 100644
> > --- a/drivers/net/iavf/iavf_rxtx_vec_common.h
> > +++ b/drivers/net/iavf/iavf_rxtx_vec_common.h
> > @@ -253,9 +253,6 @@ iavf_tx_vec_queue_default(struct iavf_tx_queue *txq)
> >  	if (txq->offloads & IAVF_TX_NO_VECTOR_FLAGS)
> >  		return -1;
> >
> > -	if (txq->vlan_flag == IAVF_TX_FLAGS_VLAN_TAG_LOC_L2TAG2)
> > -		return -1;
> > -
> >  	if (txq->offloads & IAVF_TX_VECTOR_OFFLOAD)
> >  		return IAVF_VECTOR_OFFLOAD_PATH;
> >
> > --
> > 2.34.1