Re: [PATCH 2/2] net/ice: fix TSO with big segments

[David Marchand <david.marchand@redhat.com>]

On Thu, Sep 21, 2023 at 7:48 AM Zhang, Qi Z <qi.z.zhang@intel.com> wrote:
>
>
>
> > -----Original Message-----
> > From: David Marchand <david.marchand@redhat.com>
> > Sent: Tuesday, September 19, 2023 10:05 PM
> > To: dev@dpdk.org
> > Cc: ktraynor@redhat.com; mkp@redhat.com; dexia.li@jaguarmicro.com;
> > stable@dpdk.org; Yang, Qiming <qiming.yang@intel.com>; Zhang, Qi Z
> > <qi.z.zhang@intel.com>; Kevin Liu <kevinx.liu@intel.com>
> > Subject: [PATCH 2/2] net/ice: fix TSO with big segments
> >
> > Packets to be segmented with TSO are usually larger than MTU.
> > Plus, a single segment for the whole packet may be used: in OVS case, an
> > external rte_malloc'd buffer is used for packets received from vhost-user
> > ports.
> >
> > Before this fix, TSO packets were dropped by net/ice with the following
> > message:
> > 2023-09-18T13:34:31.064Z|00020|dpdk(pmd-
> > c31/id:22)|ERR|ice_prep_pkts():
> >       INVALID mbuf: bad data_len=[2962]
> >
> > Remove the check on data_len.
> >
> > Besides, logging an error level message in a datapath function may slow
> > down the whole application. It is better not to log anything.
> >
> > Fixes: ccf33dccf7aa ("net/ice: check illegal packet sizes")
> > Cc: stable@dpdk.org
> >
> > Signed-off-by: David Marchand <david.marchand@redhat.com>
> > ---
> > Note: there may be some followup patch later, as some additional check has
> > been added in ice_prep_pkts.
> > For context, see:
> > http://inbox.dpdk.org/dev/CAJFAV8yOa3ShkVdEXHfnmOEmUTwV3e75Bu9U3
> > OqpNc5usTt3Rw@mail.gmail.com/T/#u
> >
> > ---
> >  drivers/net/ice/ice_rxtx.c | 8 +-------
> >  1 file changed, 1 insertion(+), 7 deletions(-)
> >
> > diff --git a/drivers/net/ice/ice_rxtx.c b/drivers/net/ice/ice_rxtx.c index
> > 64c4486b4b..80c4284200 100644
> > --- a/drivers/net/ice/ice_rxtx.c
> > +++ b/drivers/net/ice/ice_rxtx.c
> > @@ -3685,9 +3685,6 @@ ice_prep_pkts(__rte_unused void *tx_queue,
> > struct rte_mbuf **tx_pkts,
> >       int i, ret;
> >       uint64_t ol_flags;
> >       struct rte_mbuf *m;
> > -     struct ice_tx_queue *txq = tx_queue;
> > -     struct rte_eth_dev *dev = &rte_eth_devices[txq->port_id];
> > -     uint16_t max_frame_size = dev->data->mtu + ICE_ETH_OVERHEAD;
> >
> >       for (i = 0; i < nb_pkts; i++) {
> >               m = tx_pkts[i];
> > @@ -3704,11 +3701,8 @@ ice_prep_pkts(__rte_unused void *tx_queue,
> > struct rte_mbuf **tx_pkts,
> >                       return i;
> >               }
> >
> > -             /* check the data_len in mbuf */
> > -             if (m->data_len < ICE_TX_MIN_PKT_LEN ||
> > -                     m->data_len > max_frame_size) {
> > +             if (m->pkt_len < ICE_TX_MIN_PKT_LEN) {
>
> +1
>
> >                       rte_errno = EINVAL;
> > -                     PMD_DRV_LOG(ERR, "INVALID mbuf: bad
> > data_len=[%hu]", m->data_len);
>
> is it still worth to keep a debug level log here ? and it's better to unify the logging method in the same function.

Logging data_len is incorrect.

There are no log in other drivers.

If anything, the logging may happen in the application invoking
rte_eth_tx_prepare.

I am against keeping those logs.


-- 
David Marchand