mlx4: use dummy Rx queues when non-pow2 number requested

When using RSS, the number of rxqs has to be a power of two.
This is a problem because there is no API in DPDK that makes
the application aware of that.

A good compromise is to allow the application to request a
number of rxqs that is not a power of 2, but having inactive
queues that will never receive packets. In this configuration,
a warning will be issued to users to let them know that
this is not an optimal configuration.

Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Acked-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>

diff --git a/drivers/net/mlx4/mlx4.c b/drivers/net/mlx4/mlx4.c
index a5991ce..f946f08 100644 (file)
--- a/drivers/net/mlx4/mlx4.c
+++ b/drivers/net/mlx4/mlx4.c
@@ -698,7 +698,7 @@ txq_cleanup(struct txq *txq);
 
 static int
 rxq_setup(struct rte_eth_dev *dev, struct rxq *rxq, uint16_t desc,
-         unsigned int socket, const struct rte_eth_rxconf *conf,
+         unsigned int socket, int inactive, const struct rte_eth_rxconf *conf,
          struct rte_mempool *mp);
 
 static void
@@ -734,12 +734,15 @@ dev_configure(struct rte_eth_dev *dev)
        }
        if (rxqs_n == priv->rxqs_n)
                return 0;
-       if ((rxqs_n & (rxqs_n - 1)) != 0) {
-               ERROR("%p: invalid number of RX queues (%u),"
-                     " must be a power of 2",
-                     (void *)dev, rxqs_n);
-               return EINVAL;
+       if (!rte_is_power_of_2(rxqs_n)) {
+               unsigned n_active;
+
+               n_active = rte_align32pow2(rxqs_n + 1) >> 1;
+               WARN("%p: number of RX queues must be a power"
+                       " of 2: %u queues among %u will be active",
+                       (void *)dev, n_active, rxqs_n);
        }
+
        INFO("%p: RX queues number update: %u -> %u",
             (void *)dev, priv->rxqs_n, rxqs_n);
        /* If RSS is enabled, disable it first. */
@@ -775,7 +778,7 @@ dev_configure(struct rte_eth_dev *dev)
        priv->rss = 1;
        tmp = priv->rxqs_n;
        priv->rxqs_n = rxqs_n;
-       ret = rxq_setup(dev, &priv->rxq_parent, 0, 0, NULL, NULL);
+       ret = rxq_setup(dev, &priv->rxq_parent, 0, 0, 0, NULL, NULL);
        if (!ret)
                return 0;
        /* Failure, rollback. */
@@ -3468,7 +3471,8 @@ rxq_setup_qp_rss(struct priv *priv, struct ibv_cq *cq, uint16_t desc,
                attr.qpg.qpg_type = IBV_EXP_QPG_PARENT;
                /* TSS isn't necessary. */
                attr.qpg.parent_attrib.tss_child_count = 0;
-               attr.qpg.parent_attrib.rss_child_count = priv->rxqs_n;
+               attr.qpg.parent_attrib.rss_child_count =
+                       rte_align32pow2(priv->rxqs_n + 1) >> 1;
                DEBUG("initializing parent RSS queue");
        } else {
                attr.qpg.qpg_type = IBV_EXP_QPG_CHILD_RX;
@@ -3691,6 +3695,9 @@ skip_rtr:
  *   Number of descriptors to configure in queue.
  * @param socket
  *   NUMA socket on which memory must be allocated.
+ * @param inactive
+ *   If true, the queue is disabled because its index is higher or
+ *   equal to the real number of queues, which must be a power of 2.
  * @param[in] conf
  *   Thresholds parameters.
  * @param mp
@@ -3701,7 +3708,7 @@ skip_rtr:
  */
 static int
 rxq_setup(struct rte_eth_dev *dev, struct rxq *rxq, uint16_t desc,
-         unsigned int socket, const struct rte_eth_rxconf *conf,
+         unsigned int socket, int inactive, const struct rte_eth_rxconf *conf,
          struct rte_mempool *mp)
 {
        struct priv *priv = dev->data->dev_private;
@@ -3802,7 +3809,7 @@ skip_mr:
        DEBUG("priv->device_attr.max_sge is %d",
              priv->device_attr.max_sge);
 #ifdef RSS_SUPPORT
-       if (priv->rss)
+       if (priv->rss && !inactive)
                tmpl.qp = rxq_setup_qp_rss(priv, tmpl.cq, desc, parent,
                                           tmpl.rd);
        else
@@ -3938,6 +3945,7 @@ mlx4_rx_queue_setup(struct rte_eth_dev *dev, uint16_t idx, uint16_t desc,
 {
        struct priv *priv = dev->data->dev_private;
        struct rxq *rxq = (*priv->rxqs)[idx];
+       int inactive = 0;
        int ret;
 
        if (mlx4_is_secondary())
@@ -3969,7 +3977,9 @@ mlx4_rx_queue_setup(struct rte_eth_dev *dev, uint16_t idx, uint16_t desc,
                        return -ENOMEM;
                }
        }
-       ret = rxq_setup(dev, rxq, desc, socket, conf, mp);
+       if (idx >= rte_align32pow2(priv->rxqs_n + 1) >> 1)
+               inactive = 1;
+       ret = rxq_setup(dev, rxq, desc, socket, inactive, conf, mp);
        if (ret)
                rte_free(rxq);
        else {