[PATCH v2 1/3] net/tap: support Rx queue interrupt enable/disable

[Maxime Leroy <maxime@leroys.fr>]

The driver registers each queue file descriptor for Rx interrupts but
never provided the rx_queue_intr_enable/disable ops, so
rte_eth_dev_rx_intr_enable() returned -ENOTSUP. Applications that arm
queues before sleeping (l3fwd-power and similar) treat that as "no
interrupt support" and fall back to polling, even though the epoll wait
on the queue fd works. The advertised Rx interrupt feature is therefore
unusable through the generic API.

The queue fd is kept readable by the kernel whenever data is available
and is drained by the Rx burst itself, so there is no interrupt source to
arm or mask. Record whether the port was configured for Rx interrupts and
implement both ops to succeed in that mode and return -ENOTSUP otherwise,
so the generic Rx interrupt API works and applications can block on the
queue fd.

Fixes: 4870a8cdd968 ("net/tap: support Rx interrupt")
Cc: stable@dpdk.org

Signed-off-by: Maxime Leroy <maxime@leroys.fr>
---
 drivers/net/tap/rte_eth_tap.c |  5 ++++
 drivers/net/tap/rte_eth_tap.h |  3 +++
 drivers/net/tap/tap_intr.c    | 44 +++++++++++++++++++++++++++++++++++
 3 files changed, 52 insertions(+)

diff --git a/drivers/net/tap/rte_eth_tap.c b/drivers/net/tap/rte_eth_tap.c
index b93452f168..dc56c974da 100644
--- a/drivers/net/tap/rte_eth_tap.c
+++ b/drivers/net/tap/rte_eth_tap.c
@@ -935,6 +935,7 @@ static int
 tap_dev_configure(struct rte_eth_dev *dev)
 {
 	struct pmd_internals *pmd = dev->data->dev_private;
+	bool intr_mode = dev->data->dev_conf.intr_conf.rxq;
 
 	if (dev->data->nb_rx_queues != dev->data->nb_tx_queues) {
 		TAP_LOG(ERR,
@@ -945,6 +946,8 @@ tap_dev_configure(struct rte_eth_dev *dev)
 		return -1;
 	}
 
+	pmd->intr_mode = intr_mode;
+
 	TAP_LOG(INFO, "%s: %s: TX configured queues number: %u",
 		dev->device->name, pmd->name, dev->data->nb_tx_queues);
 
@@ -2098,6 +2101,8 @@ static const struct eth_dev_ops ops = {
 	.tx_queue_stop          = tap_tx_queue_stop,
 	.rx_queue_release       = tap_rx_queue_release,
 	.tx_queue_release       = tap_tx_queue_release,
+	.rx_queue_intr_enable   = tap_rx_queue_intr_enable,
+	.rx_queue_intr_disable  = tap_rx_queue_intr_disable,
 	.flow_ctrl_get          = tap_flow_ctrl_get,
 	.flow_ctrl_set          = tap_flow_ctrl_set,
 	.link_update            = tap_link_update,
diff --git a/drivers/net/tap/rte_eth_tap.h b/drivers/net/tap/rte_eth_tap.h
index f53a5ad077..51fd2339fc 100644
--- a/drivers/net/tap/rte_eth_tap.h
+++ b/drivers/net/tap/rte_eth_tap.h
@@ -93,6 +93,7 @@ struct pmd_internals {
 
 
 	struct rte_intr_handle *intr_handle;         /* LSC interrupt handle. */
+	bool intr_mode;                   /* Rx queue interrupt mode */
 	int ka_fd;                        /* keep-alive file descriptor */
 	struct rte_mempool *gso_ctx_mp;     /* Mempool for GSO packets */
 };
@@ -104,5 +105,7 @@ struct pmd_process_private {
 /* tap_intr.c */
 
 int tap_rx_intr_vec_set(struct rte_eth_dev *dev, int set);
+int tap_rx_queue_intr_enable(struct rte_eth_dev *dev, uint16_t queue_id);
+int tap_rx_queue_intr_disable(struct rte_eth_dev *dev, uint16_t queue_id);
 
 #endif /* _RTE_ETH_TAP_H_ */
diff --git a/drivers/net/tap/tap_intr.c b/drivers/net/tap/tap_intr.c
index 1908f71f97..7db22b69f5 100644
--- a/drivers/net/tap/tap_intr.c
+++ b/drivers/net/tap/tap_intr.c
@@ -112,3 +112,47 @@ tap_rx_intr_vec_set(struct rte_eth_dev *dev, int set)
 		return tap_rx_intr_vec_install(dev);
 	return 0;
 }
+
+/**
+ * Arm a queue for Rx interrupts.
+ *
+ * @param dev
+ *   Pointer to the tap rte_eth_dev device structure.
+ * @param queue_id
+ *   Rx queue index.
+ *
+ * @return
+ *   0 on success, -ENOTSUP if the port was not configured for Rx interrupts.
+ */
+int
+tap_rx_queue_intr_enable(struct rte_eth_dev *dev,
+			 uint16_t queue_id __rte_unused)
+{
+	struct pmd_internals *pmd = dev->data->dev_private;
+
+	if (!pmd->intr_mode)
+		return -ENOTSUP;
+	return 0;
+}
+
+/**
+ * Disarm a queue from Rx interrupts.
+ *
+ * @param dev
+ *   Pointer to the tap rte_eth_dev device structure.
+ * @param queue_id
+ *   Rx queue index.
+ *
+ * @return
+ *   0 on success, -ENOTSUP if the port was not configured for Rx interrupts.
+ */
+int
+tap_rx_queue_intr_disable(struct rte_eth_dev *dev,
+			  uint16_t queue_id __rte_unused)
+{
+	struct pmd_internals *pmd = dev->data->dev_private;
+
+	if (!pmd->intr_mode)
+		return -ENOTSUP;
+	return 0;
+}
-- 
2.43.0