Re: [dpdk-dev] [PATCH v5] app/testpmd: fix setting maximum packet length

[Lance Richardson <lance.richardson@broadcom.com>]

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On Mon, Jan 25, 2021 at 7:44 PM Ferruh Yigit <ferruh.yigit@intel.com> wrote:
>
> >> +       if (rx_offloads != port->dev_conf.rxmode.offloads) {
> >> +               uint16_t qid;
> >> +
> >> +               port->dev_conf.rxmode.offloads = rx_offloads;
> >> +
> >> +               /* Apply JUMBO_FRAME offload configuration to Rx queue(s) */
> >> +               for (qid = 0; qid < port->dev_info.nb_rx_queues; qid++) {
> >> +                       if (on)
> >> +                               port->rx_conf[qid].offloads |= DEV_RX_OFFLOAD_JUMBO_FRAME;
> >> +                       else
> >> +                               port->rx_conf[qid].offloads &= ~DEV_RX_OFFLOAD_JUMBO_FRAME;
> >> +               }
> >
> > Is it correct to set per-queue offloads that aren't advertised by the PMD
> > as supported in rx_queue_offload_capa?
> >
>
> 'port->rx_conf[]' is testpmd struct, and 'port->dev_conf.rxmode.offloads' values
> are reflected to 'port->rx_conf[].offloads' for all queues.
>
> We should set the offload in 'port->rx_conf[].offloads' if it is set in
> 'port->dev_conf.rxmode.offloads'.
>
> If a port has capability for 'JUMBO_FRAME', 'port->rx_conf[].offloads' can have
> it. And the port level capability is already checked above.
>

I'm still not 100% clear about the per-queue offload question.

With this patch, and jumbo max packet size configured (on the command
line in this case), I see:

testpmd> show port 0 rx_offload configuration
Rx Offloading Configuration of port 0 :
  Port : JUMBO_FRAME
  Queue[ 0] : JUMBO_FRAME

testpmd> show port 0 rx_offload capabilities
Rx Offloading Capabilities of port 0 :
  Per Queue :
  Per Port  : VLAN_STRIP IPV4_CKSUM UDP_CKSUM TCP_CKSUM TCP_LRO
OUTER_IPV4_CKSUM VLAN_FILTER VLAN_EXTEND JUMBO_FRAME SCATTER TIMESTAMP
KEEP_CRC OUTER_UDP_CKSUM RSS_HASH

Yet if I configure a jumbo MTU starting with standard max packet size,
jumbo is only enabled at the port level:
testpmd> port config mtu 0 9000
testpmd> port start all

testpmd> show port 0 rx_offload configuration
Rx Offloading Configuration of port 0 :
  Port : JUMBO_FRAME
  Queue[ 0] :

It still seems odd for a per-queue offload to be enabled on a PMD that
doesn't support per-queue receive offloads.