vhost: support Rx queue count request

This patch implements the ops rx_queue_count for vhost PMD by adding
a helper function rte_vhost_rx_queue_count in vhost lib.

The ops rx_queue_count gets vhost RX queue avail count and helps to
understand the queue fill level.

Signed-off-by: Zhihong Wang <zhihong.wang@intel.com>
Acked-by: Ciara Loftus <ciara.loftus@intel.com>
Acked-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>

drivers/net/vhost/rte_eth_vhost.c

@@ -973,6 +973,18 @@ eth_link_update(struct rte_eth_dev *dev __rte_unused,
 	return 0;
 }
 
+static uint32_t
+eth_rx_queue_count(struct rte_eth_dev *dev, uint16_t rx_queue_id)
+{
+	struct vhost_queue *vq;
+
+	vq = dev->data->rx_queues[rx_queue_id];
+	if (vq == NULL)
+		return 0;
+
+	return rte_vhost_rx_queue_count(vq->vid, vq->virtqueue_id);
+}
+
 static const struct eth_dev_ops ops = {
 	.dev_start = eth_dev_start,
 	.dev_stop = eth_dev_stop,
@@ -984,6 +996,7 @@ static const struct eth_dev_ops ops = {
 	.rx_queue_release = eth_queue_release,
 	.tx_queue_release = eth_queue_release,
 	.tx_done_cleanup = eth_tx_done_cleanup,
+	.rx_queue_count = eth_rx_queue_count,
 	.link_update = eth_link_update,
 	.stats_get = eth_stats_get,
 	.stats_reset = eth_stats_reset,

lib/librte_vhost/rte_vhost.h

@@ -432,6 +432,18 @@ int rte_vhost_get_mem_table(int vid, struct rte_vhost_memory **mem);
 int rte_vhost_get_vhost_vring(int vid, uint16_t vring_idx,
 			      struct rte_vhost_vring *vring);
 
+/**
+ * Get vhost RX queue avail count.
+ *
+ * @param vid
+ *  vhost device ID
+ * @param qid
+ *  virtio queue index in mq case
+ * @return
+ *  num of desc available
+ */
+uint32_t rte_vhost_rx_queue_count(int vid, uint16_t qid);
+
 #ifdef __cplusplus
 }
 #endif

lib/librte_vhost/rte_vhost_version.map

@@ -45,3 +45,10 @@ DPDK_17.05 {
 	rte_vhost_log_write;
 
 } DPDK_16.07;
+
+DPDK_17.08 {
+	global:
+
+	rte_vhost_rx_queue_count;
+
+} DPDK_17.05;

lib/librte_vhost/vhost.c

@@ -475,3 +475,29 @@ rte_vhost_log_used_vring(int vid, uint16_t vring_idx,
 
 	vhost_log_used_vring(dev, vq, offset, len);
 }
+
+uint32_t
+rte_vhost_rx_queue_count(int vid, uint16_t qid)
+{
+	struct virtio_net *dev;
+	struct vhost_virtqueue *vq;
+
+	dev = get_device(vid);
+	if (dev == NULL)
+		return 0;
+
+	if (unlikely(qid >= dev->nr_vring || (qid & 1) == 0)) {
+		RTE_LOG(ERR, VHOST_DATA, "(%d) %s: invalid virtqueue idx %d.\n",
+			dev->vid, __func__, qid);
+		return 0;
+	}
+
+	vq = dev->virtqueue[qid];
+	if (vq == NULL)
+		return 0;
+
+	if (unlikely(vq->enabled == 0 || vq->avail == NULL))
+		return 0;
+
+	return *((volatile uint16_t *)&vq->avail->idx) - vq->last_avail_idx;
+}