Re: [dpdk-dev] [PATCH v3 2/2] vhost: add thread-safe API for clearing in-flight packets in async vhost

["Ding, Xuan" <xuan.ding@intel.com>]

Hi Yuan,

> -----Original Message-----
> From: Wang, YuanX <yuanx.wang@intel.com>
> Sent: Wednesday, September 22, 2021 4:56 PM
> To: dev@dpdk.org
> Cc: maxime.coquelin@redhat.com; Xia, Chenbo <chenbo.xia@intel.com>; Hu,
> Jiayu <jiayu.hu@intel.com>; Ding, Xuan <xuan.ding@intel.com>; Jiang,
> Cheng1 <cheng1.jiang@intel.com>; Ma, WenwuX <wenwux.ma@intel.com>;
> Yang, YvonneX <yvonnex.yang@intel.com>; Pai G, Sunil
> <sunil.pai.g@intel.com>
> Subject: [PATCH v3 2/2] vhost: add thread-safe API for clearing in-flight
> packets in async vhost
> 
> This patch adds thread safe version for
> clearing in-flight packets function.

Maybe the commit log can refined to be more accurate, like when will clear in-flight packets needed?
What is the difference between thread safe and unsafe version(whether use lock I think).

> 
> Signed-off-by: Yuan Wang <yuanx.wang@intel.com>
> ---
>  doc/guides/prog_guide/vhost_lib.rst |  8 ++++-
>  lib/vhost/rte_vhost_async.h         | 21 +++++++++++++
>  lib/vhost/version.map               |  1 +
>  lib/vhost/virtio_net.c              | 49 +++++++++++++++++++++++++++++
>  4 files changed, 78 insertions(+), 1 deletion(-)

Remember to add the new API explanation in 21.11 rel_note.

Thanks,
Xuan

> 
> diff --git a/doc/guides/prog_guide/vhost_lib.rst
> b/doc/guides/prog_guide/vhost_lib.rst
> index 9ed544db7a..bc21c879f3 100644
> --- a/doc/guides/prog_guide/vhost_lib.rst
> +++ b/doc/guides/prog_guide/vhost_lib.rst
> @@ -300,7 +300,13 @@ The following is an overview of some key Vhost API
> functions:
> 
>  * ``rte_vhost_clear_queue_thread_unsafe(vid, queue_id, **pkts, count)``
> 
> -  Clear inflight packets which are submitted to DMA engine in vhost async
> data
> +  Clear in-flight packets which are submitted to async channel in vhost
> +  async data path without performing any locking. Completed packets are
> +  returned to applications through ``pkts``.
> +
> +* ``rte_vhost_clear_queue(vid, queue_id, **pkts, count)``
> +
> +  Clear in-flight packets which are submitted to async channel in vhost async
> data
>    path. Completed packets are returned to applications through ``pkts``.
> 
>  * ``rte_vhost_async_try_dequeue_burst(vid, queue_id, mbuf_pool, pkts,
> count, nr_inflight)``
> diff --git a/lib/vhost/rte_vhost_async.h b/lib/vhost/rte_vhost_async.h
> index 5e2429ab70..a418e0a03d 100644
> --- a/lib/vhost/rte_vhost_async.h
> +++ b/lib/vhost/rte_vhost_async.h
> @@ -261,6 +261,27 @@ int rte_vhost_async_get_inflight(int vid, uint16_t
> queue_id);
>  __rte_experimental
>  uint16_t rte_vhost_clear_queue_thread_unsafe(int vid, uint16_t queue_id,
>  		struct rte_mbuf **pkts, uint16_t count);
> +
> +/**
> + * This function checks async completion status and clear packets for
> + * a specific vhost device queue. Packets which are inflight will be
> + * returned in an array.
> + *
> + * @param vid
> + *  ID of vhost device to clear data
> + * @param queue_id
> + *  Queue id to clear data
> + * @param pkts
> + *  Blank array to get return packet pointer
> + * @param count
> + *  Size of the packet array
> + * @return
> + *  Number of packets returned
> + */
> +__rte_experimental
> +uint16_t rte_vhost_clear_queue(int vid, uint16_t queue_id,
> +		struct rte_mbuf **pkts, uint16_t count);
> +
>  /**
>   * This function tries to receive packets from the guest with offloading
>   * copies to the async channel. The packets that are transfer completed
> diff --git a/lib/vhost/version.map b/lib/vhost/version.map
> index 8eb7e92c32..b87d5906b8 100644
> --- a/lib/vhost/version.map
> +++ b/lib/vhost/version.map
> @@ -88,4 +88,5 @@ EXPERIMENTAL {
> 
>  	# added in 21.11
>  	rte_vhost_async_try_dequeue_burst;
> +	rte_vhost_clear_queue;
>  };
> diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c
> index 21afcd1854..2bf8a511d5 100644
> --- a/lib/vhost/virtio_net.c
> +++ b/lib/vhost/virtio_net.c
> @@ -2154,6 +2154,55 @@ rte_vhost_clear_queue_thread_unsafe(int vid,
> uint16_t queue_id,
>  	return n_pkts_cpl;
>  }
> 
> +uint16_t
> +rte_vhost_clear_queue(int vid, uint16_t queue_id, struct rte_mbuf **pkts,
> uint16_t count)
> +{
> +	struct virtio_net *dev = get_device(vid);
> +	struct vhost_virtqueue *vq;
> +	uint16_t n_pkts_cpl = 0;
> +
> +	if (!dev)
> +		return 0;
> +
> +	VHOST_LOG_DATA(DEBUG, "(%d) %s\n", dev->vid, __func__);
> +	if (unlikely(queue_id >= dev->nr_vring)) {
> +		VHOST_LOG_DATA(ERR, "(%d) %s: invalid virtqueue
> idx %d.\n",
> +			dev->vid, __func__, queue_id);
> +		return 0;
> +	}
> +
> +	vq = dev->virtqueue[queue_id];
> +
> +	if (unlikely(!vq->async_registered)) {
> +		VHOST_LOG_DATA(ERR, "(%d) %s: async not registered for
> queue id %d.\n",
> +			dev->vid, __func__, queue_id);
> +		return 0;
> +	}
> +
> +	if (!rte_spinlock_trylock(&vq->access_lock)) {
> +		VHOST_LOG_DATA(ERR,
> +			"(%d) %s: failed to clear async queue id %d,
> virtqueue busy.\n",
> +			dev->vid, __func__, queue_id);
> +		return 0;
> +	}
> +
> +	if (queue_id % 2 == 0)
> +		n_pkts_cpl = vhost_poll_enqueue_completed(dev,
> queue_id, pkts, count);
> +	else {
> +		if (unlikely(vq_is_packed(dev)))
> +			VHOST_LOG_DATA(ERR,
> +				"(%d) %s: async dequeue does not support
> packed ring.\n",
> +				dev->vid, __func__);
> +		else
> +			n_pkts_cpl =
> async_poll_dequeue_completed_split(dev, vq, queue_id, pkts,
> +						count, dev->flags &
> VIRTIO_DEV_LEGACY_OL_FLAGS);
> +	}
> +
> +	rte_spinlock_unlock(&vq->access_lock);
> +
> +	return n_pkts_cpl;
> +}
> +
>  static __rte_always_inline uint32_t
>  virtio_dev_rx_async_submit(struct virtio_net *dev, uint16_t queue_id,
>  	struct rte_mbuf **pkts, uint32_t count)
> --
> 2.25.1