[dpdk-dev] [PATCH] net/mlx5: fix calculating TSO inline size

[Yongseok Koh]

On Mon, Sep 04, 2017 at 04:01:08PM +0200, Nélio Laranjeiro wrote:
> Hi Yongseok,
> 
> Please see some comments below,
> 
> On Thu, Aug 31, 2017 at 09:27:06AM -0700, Yongseok Koh wrote:
> > Tx descriptor for TSO embeds packet header to be replicated. If Tx inline
> > is enabled, there could be additional packet data inlined with 4B inline
> > header ahead. And between the header and additional inlined packet data,
> > there may be padding to make the inline part aligned to
> > MLX5_WQE_DWORD_SIZE. In calculating the total size of inlined data, the
> > size of inline header and padding is missing.
> > 
> > Fixes: 3f13f8c23a7c ("net/mlx5: support hardware TSO")
> > Cc: stable at dpdk.org
> > 
> > Signed-off-by: Shahaf Shuler <shahafs at mellanox.com>
> > Signed-off-by: Yongseok Koh <yskoh at mellanox.com>
> > ---
> >  drivers/net/mlx5/mlx5_rxtx.c | 25 +++++++++----------------
> >  1 file changed, 9 insertions(+), 16 deletions(-)
> > 
> > diff --git a/drivers/net/mlx5/mlx5_rxtx.c b/drivers/net/mlx5/mlx5_rxtx.c
> > index fe9e7eac0..f89fa40b5 100644
> > --- a/drivers/net/mlx5/mlx5_rxtx.c
> > +++ b/drivers/net/mlx5/mlx5_rxtx.c
> > @@ -524,19 +521,20 @@ mlx5_tx_burst(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
> >  		}
> >  		/* Inline if enough room. */
> >  		if (inline_en || tso) {
> > +			uint32_t inl;
> >  			uintptr_t end = (uintptr_t)
> >  				(((uintptr_t)txq->wqes) +
> >  				 (1 << txq->wqe_n) * MLX5_WQE_SIZE);
> >  			unsigned int inline_room = max_inline *
> >  						   RTE_CACHE_LINE_SIZE -
> > -						   (pkt_inline_sz - 2);
> > +						   (pkt_inline_sz - 2) -
> > +						   !!tso * sizeof(inl);
> 
> Is not it dangerous to assume inl will always be 4 bytes long?  Why not
> writing the real value instead?
That was for readability of the code and uint32_t will be always 4bytes. But for
better readability, it should be 'inline_header' instead of 'inl' though. I'm
also okay with using "4" as well. Which way do you prefer?

Thanks,
Yongseok