[dpdk-dev] [PATCH v5 4/7] ethdev: copy fast-path API into separate structure

[Konstantin Ananyev]

Copy public function pointers (rx_pkt_burst(), etc.) and related
pointers to internal data from rte_eth_dev structure into a
separate flat array. That array will remain in a public header.
The intention here is to make rte_eth_dev and related structures internal.
That should allow future possible changes to core eth_dev structures
to be transparent to the user and help to avoid ABI/API breakages.
The plan is to keep minimal part of data from rte_eth_dev public,
so we still can use inline functions for fast-path calls
(like rte_eth_rx_burst(), etc.) to avoid/minimize slowdown.
The whole idea beyond this new schema:
1. PMDs keep to setup fast-path function pointers and related data
   inside rte_eth_dev struct in the same way they did it before.
2. Inside rte_eth_dev_start() and inside rte_eth_dev_probing_finish()
   (for secondary process) we call eth_dev_fp_ops_setup, which
   copies these function and data pointers into rte_eth_fp_ops[port_id].
3. Inside rte_eth_dev_stop() and inside rte_eth_dev_release_port()
   we call eth_dev_fp_ops_reset(), which resets rte_eth_fp_ops[port_id]
   into some dummy values.
4. fast-path ethdev API (rte_eth_rx_burst(), etc.) will use that new
   flat array to call PMD specific functions.
That approach should allow us to make rte_eth_devices[] private
without introducing regression and help to avoid changes in drivers code.

Signed-off-by: Konstantin Ananyev <konstantin.ananyev at intel.com>
---
 lib/ethdev/ethdev_private.c  | 52 ++++++++++++++++++++++++++++++++++
 lib/ethdev/ethdev_private.h  |  7 +++++
 lib/ethdev/rte_ethdev.c      | 27 ++++++++++++++++++
 lib/ethdev/rte_ethdev_core.h | 55 ++++++++++++++++++++++++++++++++++++
 4 files changed, 141 insertions(+)

diff --git a/lib/ethdev/ethdev_private.c b/lib/ethdev/ethdev_private.c
index 012cf73ca2..3eeda6e9f9 100644
--- a/lib/ethdev/ethdev_private.c
+++ b/lib/ethdev/ethdev_private.c
@@ -174,3 +174,55 @@ rte_eth_devargs_parse_representor_ports(char *str, void *data)
 		RTE_LOG(ERR, EAL, "wrong representor format: %s\n", str);
 	return str == NULL ? -1 : 0;
 }
+
+static uint16_t
+dummy_eth_rx_burst(__rte_unused void *rxq,
+		__rte_unused struct rte_mbuf **rx_pkts,
+		__rte_unused uint16_t nb_pkts)
+{
+	RTE_ETHDEV_LOG(ERR, "rx_pkt_burst for unconfigured port\n");
+	rte_errno = ENOTSUP;
+	return 0;
+}
+
+static uint16_t
+dummy_eth_tx_burst(__rte_unused void *txq,
+		__rte_unused struct rte_mbuf **tx_pkts,
+		__rte_unused uint16_t nb_pkts)
+{
+	RTE_ETHDEV_LOG(ERR, "tx_pkt_burst for unconfigured port\n");
+	rte_errno = ENOTSUP;
+	return 0;
+}
+
+void
+eth_dev_fp_ops_reset(struct rte_eth_fp_ops *fpo)
+{
+	static void *dummy_data[RTE_MAX_QUEUES_PER_PORT];
+	static const struct rte_eth_fp_ops dummy_ops = {
+		.rx_pkt_burst = dummy_eth_rx_burst,
+		.tx_pkt_burst = dummy_eth_tx_burst,
+		.rxq = {.data = dummy_data, .clbk = dummy_data,},
+		.txq = {.data = dummy_data, .clbk = dummy_data,},
+	};
+
+	*fpo = dummy_ops;
+}
+
+void
+eth_dev_fp_ops_setup(struct rte_eth_fp_ops *fpo,
+		const struct rte_eth_dev *dev)
+{
+	fpo->rx_pkt_burst = dev->rx_pkt_burst;
+	fpo->tx_pkt_burst = dev->tx_pkt_burst;
+	fpo->tx_pkt_prepare = dev->tx_pkt_prepare;
+	fpo->rx_queue_count = dev->rx_queue_count;
+	fpo->rx_descriptor_status = dev->rx_descriptor_status;
+	fpo->tx_descriptor_status = dev->tx_descriptor_status;
+
+	fpo->rxq.data = dev->data->rx_queues;
+	fpo->rxq.clbk = (void **)(uintptr_t)dev->post_rx_burst_cbs;
+
+	fpo->txq.data = dev->data->tx_queues;
+	fpo->txq.clbk = (void **)(uintptr_t)dev->pre_tx_burst_cbs;
+}
diff --git a/lib/ethdev/ethdev_private.h b/lib/ethdev/ethdev_private.h
index 3724429577..5721be7bdc 100644
--- a/lib/ethdev/ethdev_private.h
+++ b/lib/ethdev/ethdev_private.h
@@ -26,4 +26,11 @@ eth_find_device(const struct rte_eth_dev *_start, rte_eth_cmp_t cmp,
 /* Parse devargs value for representor parameter. */
 int rte_eth_devargs_parse_representor_ports(char *str, void *data);
 
+/* reset eth fast-path API to dummy values */
+void eth_dev_fp_ops_reset(struct rte_eth_fp_ops *fpo);
+
+/* setup eth fast-path API to ethdev values */
+void eth_dev_fp_ops_setup(struct rte_eth_fp_ops *fpo,
+		const struct rte_eth_dev *dev);
+
 #endif /* _ETH_PRIVATE_H_ */
diff --git a/lib/ethdev/rte_ethdev.c b/lib/ethdev/rte_ethdev.c
index c8abda6dd7..9f7a0cbb8c 100644
--- a/lib/ethdev/rte_ethdev.c
+++ b/lib/ethdev/rte_ethdev.c
@@ -44,6 +44,9 @@
 static const char *MZ_RTE_ETH_DEV_DATA = "rte_eth_dev_data";
 struct rte_eth_dev rte_eth_devices[RTE_MAX_ETHPORTS];
 
+/* public fast-path API */
+struct rte_eth_fp_ops rte_eth_fp_ops[RTE_MAX_ETHPORTS];
+
 /* spinlock for eth device callbacks */
 static rte_spinlock_t eth_dev_cb_lock = RTE_SPINLOCK_INITIALIZER;
 
@@ -578,6 +581,8 @@ rte_eth_dev_release_port(struct rte_eth_dev *eth_dev)
 		rte_eth_dev_callback_process(eth_dev,
 				RTE_ETH_EVENT_DESTROY, NULL);
 
+	eth_dev_fp_ops_reset(rte_eth_fp_ops + eth_dev->data->port_id);
+
 	rte_spinlock_lock(&eth_dev_shared_data->ownership_lock);
 
 	eth_dev->state = RTE_ETH_DEV_UNUSED;
@@ -1787,6 +1792,9 @@ rte_eth_dev_start(uint16_t port_id)
 		(*dev->dev_ops->link_update)(dev, 0);
 	}
 
+	/* expose selection of PMD fast-path functions */
+	eth_dev_fp_ops_setup(rte_eth_fp_ops + port_id, dev);
+
 	rte_ethdev_trace_start(port_id);
 	return 0;
 }
@@ -1809,6 +1817,9 @@ rte_eth_dev_stop(uint16_t port_id)
 		return 0;
 	}
 
+	/* point fast-path functions to dummy ones */
+	eth_dev_fp_ops_reset(rte_eth_fp_ops + port_id);
+
 	dev->data->dev_started = 0;
 	ret = (*dev->dev_ops->dev_stop)(dev);
 	rte_ethdev_trace_stop(port_id, ret);
@@ -4567,6 +4578,14 @@ rte_eth_mirror_rule_reset(uint16_t port_id, uint8_t rule_id)
 	return eth_err(port_id, (*dev->dev_ops->mirror_rule_reset)(dev, rule_id));
 }
 
+RTE_INIT(eth_dev_init_fp_ops)
+{
+	uint32_t i;
+
+	for (i = 0; i != RTE_DIM(rte_eth_fp_ops); i++)
+		eth_dev_fp_ops_reset(rte_eth_fp_ops + i);
+}
+
 RTE_INIT(eth_dev_init_cb_lists)
 {
 	uint16_t i;
@@ -4735,6 +4754,14 @@ rte_eth_dev_probing_finish(struct rte_eth_dev *dev)
 	if (dev == NULL)
 		return;
 
+	/*
+	 * for secondary process, at that point we expect device
+	 * to be already 'usable', so shared data and all function pointers
+	 * for fast-path devops have to be setup properly inside rte_eth_dev.
+	 */
+	if (rte_eal_process_type() == RTE_PROC_SECONDARY)
+		eth_dev_fp_ops_setup(rte_eth_fp_ops + dev->data->port_id, dev);
+
 	rte_eth_dev_callback_process(dev, RTE_ETH_EVENT_NEW, NULL);
 
 	dev->state = RTE_ETH_DEV_ATTACHED;
diff --git a/lib/ethdev/rte_ethdev_core.h b/lib/ethdev/rte_ethdev_core.h
index 51cd68de94..d5853dff86 100644
--- a/lib/ethdev/rte_ethdev_core.h
+++ b/lib/ethdev/rte_ethdev_core.h
@@ -50,6 +50,61 @@ typedef int (*eth_rx_descriptor_status_t)(void *rxq, uint16_t offset);
 typedef int (*eth_tx_descriptor_status_t)(void *txq, uint16_t offset);
 /**< @internal Check the status of a Tx descriptor */
 
+/**
+ * @internal
+ * Structure used to hold opaque pointers to internal ethdev Rx/Tx
+ * queues data.
+ * The main purpose to expose these pointers at all - allow compiler
+ * to fetch this data for fast-path ethdev inline functions in advance.
+ */
+struct rte_ethdev_qdata {
+	void **data;
+	/**< points to array of internal queue data pointers */
+	void **clbk;
+	/**< points to array of queue callback data pointers */
+};
+
+/**
+ * @internal
+ * fast-path ethdev functions and related data are hold in a flat array.
+ * One entry per ethdev.
+ * On 64-bit systems contents of this structure occupy exactly two 64B lines.
+ * On 32-bit systems contents of this structure fits into one 64B line.
+ */
+struct rte_eth_fp_ops {
+
+	/**
+	 * Rx fast-path functions and related data.
+	 * 64-bit systems: occupies first 64B line
+	 */
+	eth_rx_burst_t rx_pkt_burst;
+	/**< PMD receive function. */
+	eth_rx_queue_count_t rx_queue_count;
+	/**< Get the number of used RX descriptors. */
+	eth_rx_descriptor_status_t rx_descriptor_status;
+	/**< Check the status of a Rx descriptor. */
+	struct rte_ethdev_qdata rxq;
+	/**< Rx queues data. */
+	uintptr_t reserved1[3];
+
+	/**
+	 * Tx fast-path functions and related data.
+	 * 64-bit systems: occupies second 64B line
+	 */
+	eth_tx_burst_t tx_pkt_burst;
+	/**< PMD transmit function. */
+	eth_tx_prep_t tx_pkt_prepare;
+	/**< PMD transmit prepare function. */
+	eth_tx_descriptor_status_t tx_descriptor_status;
+	/**< Check the status of a Tx descriptor. */
+	struct rte_ethdev_qdata txq;
+	/**< Tx queues data. */
+	uintptr_t reserved2[3];
+
+} __rte_cache_aligned;
+
+extern struct rte_eth_fp_ops rte_eth_fp_ops[RTE_MAX_ETHPORTS];
+
 
 /**
  * @internal
-- 
2.26.3