[RFC 1/2] vhost: add unsafe API to check inflight packets

[xuan.ding at intel.com]

From: Xuan Ding <xuan.ding at intel.com>

In async data path, when vring state changes or device is destroyed,
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 for a vhost queue without using any lock.

Signed-off-by: Xuan Ding <xuan.ding at intel.com>
---
 doc/guides/prog_guide/vhost_lib.rst    |  5 +++++
 doc/guides/rel_notes/release_22_03.rst |  4 ++++
 lib/vhost/rte_vhost_async.h            | 14 ++++++++++++++
 lib/vhost/version.map                  |  1 +
 lib/vhost/vhost.c                      | 26 ++++++++++++++++++++++++++
 5 files changed, 50 insertions(+)

diff --git a/doc/guides/prog_guide/vhost_lib.rst b/doc/guides/prog_guide/vhost_lib.rst
index 886f8f5e72..f95288d128 100644
--- a/doc/guides/prog_guide/vhost_lib.rst
+++ b/doc/guides/prog_guide/vhost_lib.rst
@@ -271,6 +271,11 @@ 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, dma_id, vchan_id)``
 
   Clear inflight packets which are submitted to DMA engine in vhost async data
diff --git a/doc/guides/rel_notes/release_22_03.rst b/doc/guides/rel_notes/release_22_03.rst
index ff3095d742..37ef37bb20 100644
--- a/doc/guides/rel_notes/release_22_03.rst
+++ b/doc/guides/rel_notes/release_22_03.rst
@@ -149,6 +149,10 @@ New Features
   * Called ``rte_ipv4/6_udptcp_cksum_mbuf()`` functions in testpmd csum mode
     to support software UDP/TCP checksum over multiple segments.
 
+* **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.
 
 Removed Items
 -------------
diff --git a/lib/vhost/rte_vhost_async.h b/lib/vhost/rte_vhost_async.h
index 838c4778cc..06b0b0a579 100644
--- a/lib/vhost/rte_vhost_async.h
+++ b/lib/vhost/rte_vhost_async.h
@@ -135,6 +135,20 @@ 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 1202ba9c1a..03b46cb10e 100644
--- a/lib/vhost/version.map
+++ b/lib/vhost/version.map
@@ -87,6 +87,7 @@ EXPERIMENTAL {
 
 	# added in 22.03
 	rte_vhost_async_dma_configure;
+	rte_vhost_async_get_inflight_thread_unsafe;
 };
 
 INTERNAL {
diff --git a/lib/vhost/vhost.c b/lib/vhost/vhost.c
index 6bcb716de0..33dca62c6c 100644
--- a/lib/vhost/vhost.c
+++ b/lib/vhost/vhost.c
@@ -1907,6 +1907,32 @@ 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)
+		return ret;
+
+	ret = vq->async->pkts_inflight_n;
+
+	return ret;
+}
+
 int
 rte_vhost_get_monitor_addr(int vid, uint16_t queue_id,
 		struct rte_vhost_power_monitor_cond *pmc)
-- 
2.17.1