Re: [dpdk-dev] [PATCH v2 1/2] net/fm10k: convert to new Rx offloads API

["Zhang, Qi Z" <qi.z.zhang@intel.com>]

> -----Original Message-----
> From: Ananyev, Konstantin
> Sent: Thursday, March 29, 2018 6:21 PM
> To: Zhang, Qi Z <qi.z.zhang@intel.com>; Dai, Wei <wei.dai@intel.com>; Wang,
> Xiao W <xiao.w.wang@intel.com>
> Cc: 'dev@dpdk.org' <dev@dpdk.org>
> Subject: RE: [dpdk-dev] [PATCH v2 1/2] net/fm10k: convert to new Rx
> offloads API
> 
> Hi Qi,
> 
> > -----Original Message-----
> > From: Zhang, Qi Z
> > Sent: Thursday, March 29, 2018 10:51 AM
> > To: Ananyev, Konstantin <konstantin.ananyev@intel.com>; Dai, Wei
> > <wei.dai@intel.com>; Wang, Xiao W <xiao.w.wang@intel.com>
> > Cc: 'dev@dpdk.org' <dev@dpdk.org>
> > Subject: RE: [dpdk-dev] [PATCH v2 1/2] net/fm10k: convert to new Rx
> > offloads API
> >
> > Hi Konstantin:
> >
> > > -----Original Message-----
> > > From: Ananyev, Konstantin
> > > Sent: Thursday, March 29, 2018 5:29 PM
> > > To: Zhang, Qi Z <qi.z.zhang@intel.com>; Dai, Wei
> > > <wei.dai@intel.com>; Wang, Xiao W <xiao.w.wang@intel.com>
> > > Cc: 'dev@dpdk.org' <dev@dpdk.org>
> > > Subject: RE: [dpdk-dev] [PATCH v2 1/2] net/fm10k: convert to new Rx
> > > offloads API
> > >
> > >
> > >
> > > > -----Original Message-----
> > > > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Zhang, Qi Z
> > > > Sent: Thursday, March 29, 2018 7:09 AM
> > > > To: Dai, Wei <wei.dai@intel.com>; Wang, Xiao W
> > > > <xiao.w.wang@intel.com>
> > > > Cc: 'dev@dpdk.org' <dev@dpdk.org>
> > > > Subject: Re: [dpdk-dev] [PATCH v2 1/2] net/fm10k: convert to new
> > > > Rx offloads API
> > > >
> > > >
> > > >
> > > > > -----Original Message-----
> > > > > From: Zhang, Qi Z
> > > > > Sent: Wednesday, March 28, 2018 6:08 PM
> > > > > To: Dai, Wei <wei.dai@intel.com>; Wang, Xiao W
> > > > > <xiao.w.wang@intel.com>
> > > > > Cc: dev@dpdk.org
> > > > > Subject: RE: [PATCH v2 1/2] net/fm10k: convert to new Rx
> > > > > offloads API
> > > > >
> > > > > Hi Daiwei:
> > > > >
> > > > > > +static uint64_t fm10k_get_rx_queue_offloads_capa(struct
> > > > > > +rte_eth_dev
> > > > > > +*dev) {
> > > > > > +	RTE_SET_USED(dev);
> > > > > > +
> > > > > > +	return (uint64_t)(DEV_RX_OFFLOAD_SCATTER);
> > > > > > +}
> > > > >
> > > > > why per queue rx scattered feature here?
> > > > > My understanding is either we use scattered rx function that
> > > > > enable this feature for all queues or we use non-scattered rx
> > > > > function that disable this feature for all queues, right?
> > > >
> > > > Checked with Dai Wei offline, fm10k have per queue register that
> > > > can be configured to support rx scattered, So it is per queue offload.
> > >
> > > Ok, but these days we have one RX function per device.
> > > Looking at fm10k - it clearly has different RX function for
> > > scattered and non-scattered case.
> > > Yes, HW does support scatter/non-scatter selection per queue, but
> > > our SW - doesn't (same for ixgbe and i40e) So how it could be per queue
> offload?
> >
> > We saw the implementation of fm10k is a little bit different with i40e.
> > It set per queue register "FM10K_SRRCTL_BUFFER_CHAINING_EN" to turn
> on multi-seg feature when offload is required.
> >
> > That means two queues can have different behavior when process a
> > packet that exceed the buffer size base on the register setting, though we
> use the same rx scattered function, so we think this is per queue feature, is
> that make sense?
> 
> Ok, suppose we have 2 functions configured.
> One with DEV_RX_OFFLOAD_SCATTER is on, second with
> DEV_RX_OFFLOAD_SCATTER is off.
> So scatter RX function will be selected, but for second queue  HW support
> will not be enabled, so packets bigger then RX buffer will be silently dropped
> by HW, right?

Yes according to datasheet

Bit FM10K_SRRCTL_BUFFER_CHAINING_EN:

0b = Any packet longer than the data buffer size is terminated with a
TOO_BIG error status in Rx descriptor write-back. The remainder of the
frame is not posted to host, it is silently dropped.
1b = A packet can be spread over more than one single receive data buffer

> Konstantin
> 
> >
> > Regards
> > Qi
> >
> >
> > > Konstantin
> >
> >
> > >
> > > > >
> > > > > Regards
> > > > > Qi