Acked-by: Chengwen Feng <[email protected]>
On 3/20/2026 2:29 PM, Talluri Chaitanyababu wrote:
> Fix DCB forwarding failed when the number of TCs on ports is inconsistent.
>
> When ports have asymmetric TC configurations (e.g. 2 ports, port0 has
> 4 TCs and port1 has 8 TCs), the forwarding logic iterates based only
> on the Rx port TC count.
> This can lead to accessing invalid Tx TC entries and incorrect queue
> mapping, which will result in a SIGFPE exception.
>
> Additionally, the existing VMDq pool guard in dcb_fwd_config_setup()
> only checks RX queue counts and does not consider the case where the TX
> port has no queues for a given pool/TC combination.
>
> Fix this by:
> 1. Introducing an effective TC count using RTE_MIN() of Rx and Tx TC
> values, ensuring forwarding only operates on valid TCs supported by
> both ports.
> 2. Updating the loop condition to use the effective TC count instead of
> only the Rx TC count.
> 3. Extending the queue validation in dcb_fwd_config_setup() to ensure
> both Rx and Tx queues are valid for a given TC.
>
> Testpmd command to reproduce:
>
> x86_64-native-linuxapp-gcc/app/dpdk-testpmd -l 1-20 -n 4 \
> -a 0000:31:00.0 -a 0000:4b:00.0 \
> --file-prefix=testpmd1 -- -i --rxq=256 --txq=256 \
> --nb-cores=16 --total-num-mbufs=600000
>
> port stop all
> port config 0 dcb vt off 8 pfc on
> port config 1 dcb vt off 8 pfc on
> port start all
> port stop all
> port config 0 dcb vt off 4 pfc on
>
> This ensures correct queue mapping and avoids issues when switching
> between different DCB configurations across ports.
>
> Fixes: 1a572499beb6 ("app/testpmd: setup DCB forwarding based on traffic
> class")
> Cc: [email protected]
>
> Signed-off-by: Talluri Chaitanyababu <[email protected]>
> Signed-off-by: Shaiq Wani <[email protected]>
> ---
>
> v5:
> * Updated commit message as per review comments.
> * Added reproduction steps and SIGFPE explanation.
> * Updated Fixes tag.
>
> v4:
> * Removed runtime update of dcb_fwd_tc_mask as per review comments.
> * Used effective TC count (RTE_MIN of RX/TX) to handle asymmetric configs.
> * Moved queue validation to dcb_fwd_check_cores_per_tc().
>
> v3: Removed old email address.
>
> v2:
> * Used res->num_tcs to derive dcb_fwd_tc_mask.
> * Removed redundant rte_eth_dev_get_dcb_info().
> ---
> app/test-pmd/config.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/app/test-pmd/config.c b/app/test-pmd/config.c
> index f9f3c542a6..052e8b7c24 100644
> --- a/app/test-pmd/config.c
> +++ b/app/test-pmd/config.c
> @@ -5377,6 +5377,7 @@ dcb_fwd_config_setup(void)
> uint16_t nb_rx_queue, nb_tx_queue;
> uint16_t i, j, k, sm_id = 0;
> uint16_t sub_core_idx = 0;
> + uint8_t effective_nb_tcs;
> uint16_t total_tc_num;
> struct rte_port *port;
> uint8_t tc = 0;
> @@ -5442,6 +5443,7 @@ dcb_fwd_config_setup(void)
> dcb_fwd_tc_update_dcb_info(&rxp_dcb_info);
> (void)rte_eth_dev_get_dcb_info(fwd_ports_ids[txp], &txp_dcb_info);
> dcb_fwd_tc_update_dcb_info(&txp_dcb_info);
> + effective_nb_tcs = RTE_MIN(rxp_dcb_info.nb_tcs, txp_dcb_info.nb_tcs);
>
> for (lc_id = 0; lc_id < cur_fwd_config.nb_fwd_lcores; lc_id++) {
> fwd_lcores[lc_id]->stream_nb = 0;
> @@ -5450,7 +5452,8 @@ dcb_fwd_config_setup(void)
> /* if the nb_queue is zero, means this tc is
> * not enabled on the POOL
> */
> - if (rxp_dcb_info.tc_queue.tc_rxq[i][tc].nb_queue == 0)
> + if (rxp_dcb_info.tc_queue.tc_rxq[i][tc].nb_queue == 0 ||
> + txp_dcb_info.tc_queue.tc_txq[i][tc].nb_queue == 0)
> break;
> k = fwd_lcores[lc_id]->stream_nb +
> fwd_lcores[lc_id]->stream_idx;
> @@ -5480,7 +5483,7 @@ dcb_fwd_config_setup(void)
>
> sub_core_idx = 0;
> tc++;
> - if (tc < rxp_dcb_info.nb_tcs)
> + if (tc < effective_nb_tcs)
> continue;
> /* Restart from TC 0 on next RX port */
> tc = 0;
> @@ -5497,6 +5500,8 @@ dcb_fwd_config_setup(void)
> dcb_fwd_tc_update_dcb_info(&rxp_dcb_info);
> rte_eth_dev_get_dcb_info(fwd_ports_ids[txp], &txp_dcb_info);
> dcb_fwd_tc_update_dcb_info(&txp_dcb_info);
> +
> + effective_nb_tcs = RTE_MIN(rxp_dcb_info.nb_tcs,
> txp_dcb_info.nb_tcs);
> }
> }
>
