Re: [RFC] app/testpmd: use RSS conf from software when configuring DCB

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed, 12 Apr 2023 17:52:39 +0800
Min Zhou <zhoumin@loongson.cn> wrote:

> In the testpmd command, we have to stop the port firstly before configuring
> the DCB. However, some PMDs may execute a hardware reset during the port
> stop, such as ixgbe. Some kind of reset operations of PMD could clear the
> configurations of RSS in the hardware register. This would cause the loss
> of RSS configurations that were set during the testpmd initialization. As
> a result, I find that I cannot enable RSS and DCB at the same time in the
> testpmd command when using Intel 82599 NIC.
> 
> Although this patch can solve the problem I encountered, is there any risk
> of using rss conf from software instead of reading from the hardware
> register when configuring DCB?
> 
> Signed-off-by: Min Zhou <zhoumin@loongson.cn>
> ---
>  app/test-pmd/testpmd.c | 11 +----------
>  1 file changed, 1 insertion(+), 10 deletions(-)
> 
> diff --git a/app/test-pmd/testpmd.c b/app/test-pmd/testpmd.c
> index 5cb6f92523..3c382267b8 100644
> --- a/app/test-pmd/testpmd.c
> +++ b/app/test-pmd/testpmd.c
> @@ -4247,14 +4247,12 @@ const uint16_t vlan_tags[] = {
>  };
>  
>  static  int
> -get_eth_dcb_conf(portid_t pid, struct rte_eth_conf *eth_conf,
> +get_eth_dcb_conf(portid_t pid __rte_unused, struct rte_eth_conf *eth_conf,
>  		 enum dcb_mode_enable dcb_mode,
>  		 enum rte_eth_nb_tcs num_tcs,
>  		 uint8_t pfc_en)
>  {
>  	uint8_t i;
> -	int32_t rc;
> -	struct rte_eth_rss_conf rss_conf;
>  

Sorry for the late review, but almost uses DCB and fewer still with DPDK;
so not surprised that there would be issues like this.

If you change an internal function like get_eth_dcb_conf to remove parameters
then do not mark those parameters as unused, instead remove them from the function
and the caller. Plus the function now always returns 0 so it can be reset as void.
first place.


Suggest the following (untested):

diff --git a/app/test-pmd/testpmd.c b/app/test-pmd/testpmd.c
index b1401136e4..5eaac752c6 100644
--- a/app/test-pmd/testpmd.c
+++ b/app/test-pmd/testpmd.c
@@ -4291,15 +4291,11 @@ const uint16_t vlan_tags[] = {
 		24, 25, 26, 27, 28, 29, 30, 31
 };
 
-static  int
-get_eth_dcb_conf(portid_t pid, struct rte_eth_conf *eth_conf,
-		 enum dcb_mode_enable dcb_mode,
-		 enum rte_eth_nb_tcs num_tcs,
-		 uint8_t pfc_en)
+static void
+get_eth_dcb_conf(struct rte_eth_conf *eth_conf, enum dcb_mode_enable dcb_mode,
+		 enum rte_eth_nb_tcs num_tcs, uint8_t pfc_en)
 {
 	uint8_t i;
-	int32_t rc;
-	struct rte_eth_rss_conf rss_conf;
 
 	/*
 	 * Builds up the correct configuration for dcb+vt based on the vlan tags array
@@ -4341,12 +4337,6 @@ get_eth_dcb_conf(portid_t pid, struct rte_eth_conf *eth_conf,
 		struct rte_eth_dcb_tx_conf *tx_conf =
 				&eth_conf->tx_adv_conf.dcb_tx_conf;
 
-		memset(&rss_conf, 0, sizeof(struct rte_eth_rss_conf));
-
-		rc = rte_eth_dev_rss_hash_conf_get(pid, &rss_conf);
-		if (rc != 0)
-			return rc;
-
 		rx_conf->nb_tcs = num_tcs;
 		tx_conf->nb_tcs = num_tcs;
 
@@ -4358,7 +4348,6 @@ get_eth_dcb_conf(portid_t pid, struct rte_eth_conf *eth_conf,
 		eth_conf->rxmode.mq_mode =
 				(enum rte_eth_rx_mq_mode)
 					(rx_mq_mode & RTE_ETH_MQ_RX_DCB_RSS);
-		eth_conf->rx_adv_conf.rss_conf = rss_conf;
 		eth_conf->txmode.mq_mode = RTE_ETH_MQ_TX_DCB;
 	}
 
@@ -4367,8 +4356,6 @@ get_eth_dcb_conf(portid_t pid, struct rte_eth_conf *eth_conf,
 				RTE_ETH_DCB_PG_SUPPORT | RTE_ETH_DCB_PFC_SUPPORT;
 	else
 		eth_conf->dcb_capability_en = RTE_ETH_DCB_PG_SUPPORT;
-
-	return 0;
 }
 
 int
@@ -4391,10 +4378,9 @@ init_port_dcb_config(portid_t pid,
 	/* retain the original device configuration. */
 	memcpy(&port_conf, &rte_port->dev_conf, sizeof(struct rte_eth_conf));
 
-	/*set configuration of DCB in vt mode and DCB in non-vt mode*/
-	retval = get_eth_dcb_conf(pid, &port_conf, dcb_mode, num_tcs, pfc_en);
-	if (retval < 0)
-		return retval;
+	/* set configuration of DCB in vt mode and DCB in non-vt mode */
+	get_eth_dcb_conf(&port_conf, dcb_mode, num_tcs, pfc_en);
+
 	port_conf.rxmode.offloads |= RTE_ETH_RX_OFFLOAD_VLAN_FILTER;
 	/* remove RSS HASH offload for DCB in vt mode */
 	if (port_conf.rxmode.mq_mode == RTE_ETH_MQ_RX_VMDQ_DCB) {