Re: [dpdk-stable] [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 1:15 PM Ferruh Yigit <ferruh.yigit@intel.com> wrote:
>
> From: Steve Yang <stevex.yang@intel.com>
>
> "port config all max-pkt-len" command fails because it doesn't set the
> 'DEV_RX_OFFLOAD_JUMBO_FRAME' offload flag properly.
>
> Commit in the fixes line moved the 'DEV_RX_OFFLOAD_JUMBO_FRAME' offload
> flag update from 'cmd_config_max_pkt_len_parsed()' to 'init_config()'.
> 'init_config()' function is only called during testpmd startup, but the
> flag status needs to be calculated whenever 'max_rx_pkt_len' changes.
>
> The issue can be reproduce as [1], where the 'max-pkt-len' reduced and
> 'DEV_RX_OFFLOAD_JUMBO_FRAME' offload flag should be cleared but it
> didn't.
>
> Adding the 'update_jumbo_frame_offload()' helper function to update
> 'DEV_RX_OFFLOAD_JUMBO_FRAME' offload flag and 'max_rx_pkt_len'. This
> function is called both by 'init_config()' and
> 'cmd_config_max_pkt_len_parsed()'.
>
> Default 'max-pkt-len' value set to zero, 'update_jumbo_frame_offload()'
> updates it to "RTE_ETHER_MTU + PMD specific Ethernet overhead" when it
> is zero.
> If '--max-pkt-len=N' argument provided, it will be used instead.
> And with each "port config all max-pkt-len" command, the
> 'DEV_RX_OFFLOAD_JUMBO_FRAME' offload flag, 'max-pkt-len' and MTU is
> updated.
>
> [1]

<snip>

> +/*
> + * Helper function to arrange max_rx_pktlen value and JUMBO_FRAME offload,
> + * MTU is also aligned if JUMBO_FRAME offload is not set.
> + *
> + * port->dev_info should be get before calling this function.

Should this be "port->dev_info should be set ..." instead?


<snip>

> +       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?

> +       }
> +
> +       /* If JUMBO_FRAME is set MTU conversion done by ethdev layer,
> +        * if unset do it here
> +        */
> +       if ((rx_offloads & DEV_RX_OFFLOAD_JUMBO_FRAME) == 0) {
> +               ret = rte_eth_dev_set_mtu(portid,
> +                               port->dev_conf.rxmode.max_rx_pkt_len - eth_overhead);
> +               if (ret)
> +                       printf("Failed to set MTU to %u for port %u\n",
> +                               port->dev_conf.rxmode.max_rx_pkt_len - eth_overhead,
> +                               portid);
> +       }
> +
> +       return 0;
> +}
> +

Applied and tested with a few iterations of configuring max packet size
back and forth between jumbo and non-jumbo sizes, also tried setting
max packet size using the command-line option, all seems good based
on rx offloads and packet forwarding.

Two minor questions above, otherwise LGTM.