[dpdk-dev] [PATCH] net/enic: update enic guide and add warning for invalid conf

[John Daley <johndale@cisco.com>]

From: Nelson Escobar <neescoba@cisco.com>

Update the enic guide to better explain how to setup vNIC parameters
on the Cisco VIC since the introduction of rx scatter and print an
error message for the case of having 1 RQ configured in the vNIC.

Signed-off-by: Nelson Escobar <neescoba@cisco.com>
---
 doc/guides/nics/enic.rst     | 53 +++++++++++++++++++++++++++++++++++++++-----
 drivers/net/enic/enic_main.c | 14 +++++++-----
 2 files changed, 57 insertions(+), 10 deletions(-)

diff --git a/doc/guides/nics/enic.rst b/doc/guides/nics/enic.rst
index 8170286..bff5c77 100644
--- a/doc/guides/nics/enic.rst
+++ b/doc/guides/nics/enic.rst
@@ -59,11 +59,31 @@ Configuration information
 
   - **Number of Queues**
 
-    The maximum number of receive and transmit queues are configurable on a per
-    vNIC basis through the Cisco UCS Manager (CIMC or UCSM). These values
-    should be configured to be greater than or equal to the nb_rx_q and nb_tx_q
-    parameters expected to  used in the call to the rte_eth_dev_configure()
-    function.
+    The maximum number of receive queues (RQs), work queues (WQs) and
+    completion queues (CQs) are configurable on a per vNIC basis
+    through the Cisco UCS Manager (CIMC or UCSM).
+
+    These values should be configured as follows:
+
+    - The number of WQs should be greater or equal to the value of the
+      expected nb_tx_q parameter in the call to the
+      rte_eth_dev_configure()
+
+    - The number of RQs configured in the vNIC should be greater or
+      equal to *twice* the value of the expected nb_rx_q parameter in
+      the call to rte_eth_dev_configure().  With the addition of rx
+      scatter, a pair of RQs on the vnic is needed for each receive
+      queue used by DPDK, even if rx scatter is not being used.
+      Having a vNIC with only 1 RQ is not a valid configuration, and
+      will fail with an error message.
+
+    - The number of CQs should set so that there is one CQ for each
+      WQ, and one CQ for each pair of RQs.
+
+    For example: If the application requires 3 Rx queues, and 3 Tx
+    queues, the vNIC should be configured to have at least 3 WQs, 6
+    RQs (3 pairs), and 6 CQs (3 for use by WQs + 3 for use by the 3
+    pairs of RQs).
 
   - **Size of Queues**
 
@@ -71,6 +91,29 @@ Configuration information
     a per vNIC bases via the UCS Manager and should be greater than or equal to
     the nb_rx_desc and   nb_tx_desc parameters expected to be used in the calls
     to rte_eth_rx_queue_setup() and rte_eth_tx_queue_setup() respectively.
+    An application requesting more than the set size will be limited to that
+    size.
+
+    Unless there is a lack of resources due to creating many vNICs, it
+    is recommended that the WQ and RQ sizes be set to the maximum.  This
+    gives the application the greatest amount of flexibility in its
+    queue configuration.
+
+    - *Note*: Since the introduction of rx scatter, for performance
+      reasons, this PMD uses two RQs on the vNIC per receive queue in
+      DPDK.  One RQ holds descriptors for the start of a packet the
+      second RQ holds the descriptors for the rest of the fragments of
+      a packet.  This means that the nb_rx_desc parameter to
+      rte_eth_rx_queue_setup() can be a greater than 4096.  The exact
+      amount will depend on the size of the mbufs being used for
+      receives, and the MTU size.
+
+      For example: If the mbuf size is 2048, and the MTU is 9000, then
+      receiving a full size packet will take 5 descriptors, 1 from the
+      start of packet queue, and 4 from the second queue.  Assuming
+      that the RQ size was set to the maximum of 4096, then the
+      application can specify up to 1024 + 4096 as the nb_rx_desc
+      parameter to rte_eth_rx_queue_setup().
 
   - **Interrupts**
 
diff --git a/drivers/net/enic/enic_main.c b/drivers/net/enic/enic_main.c
index 15a05b4..e3e58fb 100644
--- a/drivers/net/enic/enic_main.c
+++ b/drivers/net/enic/enic_main.c
@@ -1284,6 +1284,15 @@ static int enic_dev_init(struct enic *enic)
 		return err;
 	}
 
+	/* Get available resource counts */
+	enic_get_res_counts(enic);
+	if (enic->conf_rq_count == 1) {
+		dev_err(enic, "Running with only 1 RQ configured in the vNIC is not supported.\n");
+		dev_err(enic, "Please configure 2 RQs in the vNIC for each Rx queue used by DPDK.\n");
+		dev_err(enic, "See the ENIC PMD guide for more information.\n");
+		return -EINVAL;
+	}
+
 	eth_dev->data->mac_addrs = rte_zmalloc("enic_mac_addr", ETH_ALEN, 0);
 	if (!eth_dev->data->mac_addrs) {
 		dev_err(enic, "mac addr storage alloc failed, aborting.\n");
@@ -1292,11 +1301,6 @@ static int enic_dev_init(struct enic *enic)
 	ether_addr_copy((struct ether_addr *) enic->mac_addr,
 		&eth_dev->data->mac_addrs[0]);
 
-
-	/* Get available resource counts
-	*/
-	enic_get_res_counts(enic);
-
 	vnic_dev_set_reset_flag(enic->vdev, 0);
 
 	/* set up link status checking */
-- 
2.10.0