Re: [dpdk-stable] [dpdk-dev] [PATCH 1/2] app/testpmd: fix scatter offload configuration

[Matan Azrad <matan@mellanox.com>]

Hi Ferruh

From: Yigit, Ferruh <ferruh.yigit@linux.intel.com>
> On 7/31/2019 7:11 AM, Matan Azrad wrote:
> > Hi Ferruh
> >
> > From: Ferruh Yigit
> >> On 7/30/2019 7:34 PM, Matan Azrad wrote:
> >>>
> >>>
> >>> From: Ferruh Yigit
> >>>> On 7/30/2019 4:56 PM, Matan Azrad wrote:
> >>>>> Hi Ferruh
> >>>>>
> >>>>>  From: Ferruh Yigit
> >>>>>> Sent: Tuesday, July 30, 2019 6:22 PM
> >>>>>> To: Matan Azrad <matan@mellanox.com>; Wenzhuo Lu
> >>>>>> <wenzhuo.lu@intel.com>; Jingjing Wu <jingjing.wu@intel.com>
> >>>>>> Cc: dev@dpdk.org; stable@dpdk.org
> >>>>>> Subject: Re: [dpdk-dev] [PATCH 1/2] app/testpmd: fix scatter
> >>>>>> offload configuration
> >>>>>>
> >>>>>> On 7/30/2019 2:17 PM, Matan Azrad wrote:
> >>>>>>> Hi Ferruh
> >>>>>>>
> >>>>>>> From: Ferruh Yigit
> >>>>>>>> Sent: Tuesday, July 30, 2019 4:09 PM
> >>>>>>>> To: Matan Azrad <matan@mellanox.com>; Wenzhuo Lu
> >>>>>>>> <wenzhuo.lu@intel.com>; Jingjing Wu <jingjing.wu@intel.com>
> >>>>>>>> Cc: dev@dpdk.org; stable@dpdk.org
> >>>>>>>> Subject: Re: [dpdk-dev] [PATCH 1/2] app/testpmd: fix scatter
> >>>>>>>> offload configuration
> >>>>>>>>
> >>>>>>>> On 7/29/2019 1:36 PM, Matan Azrad wrote:
> >>>>>>>>> When the mbuf data size cannot contain the maximum Rx
> packet
> >>>>>>>>> length with the mbuf headroom, a packet should be scattered in
> >>>>>>>>> more than one
> >>>>>>>> mbuf.
> >>>>>>>>>
> >>>>>>>>> The application did not configure scatter offload in the above
> case.
> >>>>>>>>>
> >>>>>>>>> Enable the Rx scatter offload in the above case.
> >>>>>>>>>
> >>>>>>>>> Fixes: 33f9630fc23d ("app/testpmd: create mbuf based on max
> >>>>>>>>> supported
> >>>>>>>>> segments")
> >>>>>>>>> Cc: stable@dpdk.org
> >>>>>>>>>
> >>>>>>>>> Signed-off-by: Matan Azrad <matan@mellanox.com>
> >>>>>>>>
> >>>>>>>> Deferring the patchset to next release, they were late anyway
> >>>>>>>> and not actually fixing a defect, safer to defer than getting them in
> rc3.
> >>>>>>>
> >>>>>>> Yes this patch came late for RC3 but it is a fix.
> >>>>>>>
> >>>>>>> What are you concerns here?
> >>>>>>> Why don't you think defect found?
> >>>>>>
> >>>>>> First patch changes the behavior, when mbuf size is larger than
> >>>>>> configured size and user didn't provided the scatter offload,
> >>>>>> should test application automatically enable it?
> >>>>>
> >>>>> No, only when the mbuf size is smaller than the max_rx_pkt_len
> >>>>> with
> >>>> headroom.
> >>>>> If scatter is not enabled in the above case, how can the PMD
> >>>>> provide a
> >>>> packet with max_rx_pkt_len size?
> >>>>>
> >>>
> >>> Answer here?
> >>
> >> Is it because drivers also "automatically" enable scattered Rx based
> >> on other values?
> >
> > Scatter is a defined RX offload.
> > Like other offloads I think it always should be explicitly set by the user if he
> wants it, and vice versa.
> > If the user doesn't configure it, the PMD should not scatter packets
> because the user doesn't expect multi-mbuf packets in datapath and maybe
> even doesn't handle it.
> 
> +1
> 
> So what about having the log message but not implicitly update the offload
> config?
> 

Yes, we need this massage at least.

Will work on it.

Thanks.