[dpdk-dev] [PATCH v3] vhost: add unsafe API to check inflight packets

[Xuan Ding]

In async data path, when vring state changes, it is necessary to
know the number of inflight packets in DMA engine. This patch
provides a thread unsafe API to return the number of inflight
packets without using any lock.

Signed-off-by: Xuan Ding <xuan.ding at intel.com>
---
v3:
* Fixed one typo.
* Revised the doc to be more accuracy.

v2:
* Fixed some format issues.
---
 doc/guides/prog_guide/vhost_lib.rst    |  5 +++++
 doc/guides/rel_notes/release_21_11.rst |  5 +++++
 lib/vhost/rte_vhost_async.h            | 14 ++++++++++++++
 lib/vhost/version.map                  |  3 +++
 lib/vhost/vhost.c                      | 26 ++++++++++++++++++++++++++
 5 files changed, 53 insertions(+)

diff --git a/doc/guides/prog_guide/vhost_lib.rst b/doc/guides/prog_guide/vhost_lib.rst
index 8874033165..0c4fb9ea91 100644
--- a/doc/guides/prog_guide/vhost_lib.rst
+++ b/doc/guides/prog_guide/vhost_lib.rst
@@ -305,6 +305,11 @@ The following is an overview of some key Vhost API functions:
   This function returns the amount of in-flight packets for the vhost
   queue using async acceleration.
 
+* ``rte_vhost_async_get_inflight_thread_unsafe(vid, queue_id)``
+
+  Get the number of inflight packets for a vhost queue without
+  performing any locking.
+
 * ``rte_vhost_clear_queue_thread_unsafe(vid, queue_id, **pkts, count)``
 
   Clear inflight packets which are submitted to DMA engine in vhost async data
diff --git a/doc/guides/rel_notes/release_21_11.rst b/doc/guides/rel_notes/release_21_11.rst
index 675b573834..c9814c68df 100644
--- a/doc/guides/rel_notes/release_21_11.rst
+++ b/doc/guides/rel_notes/release_21_11.rst
@@ -55,6 +55,11 @@ New Features
      Also, make sure to start the actual text at the margin.
      =======================================================
 
+* **Added vhost API to get the number of inflight packets.**
+
+  Added an API which can get the number of inflight packets in
+  vhost async data path without using lock.
+
 * **Enabled new devargs parser.**
 
   * Enabled devargs syntax
diff --git a/lib/vhost/rte_vhost_async.h b/lib/vhost/rte_vhost_async.h
index b25ff446f7..0af414bf78 100644
--- a/lib/vhost/rte_vhost_async.h
+++ b/lib/vhost/rte_vhost_async.h
@@ -246,6 +246,20 @@ uint16_t rte_vhost_poll_enqueue_completed(int vid, uint16_t queue_id,
 __rte_experimental
 int rte_vhost_async_get_inflight(int vid, uint16_t queue_id);
 
+/**
+ * This function is lock-free version to return the amount of in-flight
+ * packets for the vhost queue which uses async channel acceleration.
+ *
+ * @param vid
+ *  id of vhost device to enqueue data
+ * @param queue_id
+ *  queue id to enqueue data
+ * @return
+ *  the amount of in-flight packets on success; -1 on failure
+ */
+__rte_experimental
+int rte_vhost_async_get_inflight_thread_unsafe(int vid, uint16_t queue_id);
+
 /**
  * This function checks async completion status and clear packets for
  * a specific vhost device queue. Packets which are inflight will be
diff --git a/lib/vhost/version.map b/lib/vhost/version.map
index c92a9d4962..b150dc408d 100644
--- a/lib/vhost/version.map
+++ b/lib/vhost/version.map
@@ -85,4 +85,7 @@ EXPERIMENTAL {
 	rte_vhost_async_channel_register_thread_unsafe;
 	rte_vhost_async_channel_unregister_thread_unsafe;
 	rte_vhost_clear_queue_thread_unsafe;
+
+	#added in 21.11
+	rte_vhost_async_get_inflight_thread_unsafe;
 };
diff --git a/lib/vhost/vhost.c b/lib/vhost/vhost.c
index 355ff37651..24ae1025ea 100644
--- a/lib/vhost/vhost.c
+++ b/lib/vhost/vhost.c
@@ -1886,5 +1886,31 @@ int rte_vhost_async_get_inflight(int vid, uint16_t queue_id)
 	return ret;
 }
 
+int
+rte_vhost_async_get_inflight_thread_unsafe(int vid, uint16_t queue_id)
+{
+	struct vhost_virtqueue *vq;
+	struct virtio_net *dev = get_device(vid);
+	int ret = -1;
+
+	if (dev == NULL)
+		return ret;
+
+	if (queue_id >= VHOST_MAX_VRING)
+		return ret;
+
+	vq = dev->virtqueue[queue_id];
+
+	if (vq == NULL)
+		return ret;
+
+	if (!vq->async_registered)
+		return ret;
+
+	ret = vq->async_pkts_inflight_n;
+
+	return ret;
+}
+
 RTE_LOG_REGISTER_SUFFIX(vhost_config_log_level, config, INFO);
 RTE_LOG_REGISTER_SUFFIX(vhost_data_log_level, data, WARNING);
-- 
2.17.1