Re: [dpdk-dev] [PATCH v5 2/3] vhost: rework async configuration structure

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 7/16/21 9:51 PM, Jiayu Hu wrote:
> This patch reworks the async configuration structure to improve code
> readability. In addition, add preserved padding fields on the structure
> for future usage.
> 
> Signed-off-by: Jiayu Hu <jiayu.hu@intel.com>
> ---
>  doc/guides/prog_guide/vhost_lib.rst | 21 +++++++++--------
>  examples/vhost/main.c               |  8 +++----
>  lib/vhost/rte_vhost_async.h         | 45 ++++++++++++++++++-------------------
>  lib/vhost/vhost.c                   | 19 +++++++---------
>  lib/vhost/vhost.h                   |  3 +--
>  5 files changed, 47 insertions(+), 49 deletions(-)
> 
> diff --git a/doc/guides/prog_guide/vhost_lib.rst b/doc/guides/prog_guide/vhost_lib.rst
> index d18fb98..2a61b85 100644
> --- a/doc/guides/prog_guide/vhost_lib.rst
> +++ b/doc/guides/prog_guide/vhost_lib.rst
> @@ -218,26 +218,29 @@ The following is an overview of some key Vhost API functions:
>  
>    Enable or disable zero copy feature of the vhost crypto backend.
>  
> -* ``rte_vhost_async_channel_register(vid, queue_id, features, ops)``
> +* ``rte_vhost_async_channel_register(vid, queue_id, config, ops)``
>  
> -  Register a vhost queue with async copy device channel after vring
> -  is enabled. Following device ``features`` must be specified together
> +  Register an async copy device channel for a vhost queue after vring
> +  is enabled. Following device ``config`` must be specified together
>    with the registration:
>  
> -  * ``async_inorder``
> +  * ``features``
>  
> -    Async copy device can guarantee the ordering of copy completion
> -    sequence. Copies are completed in the same order with that at
> -    the submission time.
> +    This field is used to specify async copy device features.
>  
> -    Currently, only ``async_inorder`` capable device is supported by vhost.
> +    ``RTE_VHOST_ASYNC_INORDER`` represents the async copy device can
> +    guarantee the order of copy completion is the same as the order
> +    of copy submission.
> +
> +    Currently, only ``RTE_VHOST_ASYNC_INORDER`` capable device is
> +    supported by vhost.
>  
>    * ``async_threshold``
>  
>      The copy length (in bytes) below which CPU copy will be used even if
>      applications call async vhost APIs to enqueue/dequeue data.
>  
> -    Typical value is 512~1024 depending on the async device capability.
> +    Typical value is 256~1024 depending on the async device capability.
>  
>    Applications must provide following ``ops`` callbacks for vhost lib to
>    work with the async copy devices:
> diff --git a/examples/vhost/main.c b/examples/vhost/main.c
> index d2179ea..9cd855a 100644
> --- a/examples/vhost/main.c
> +++ b/examples/vhost/main.c
> @@ -1468,7 +1468,7 @@ new_device(int vid)
>  		vid, vdev->coreid);
>  
>  	if (async_vhost_driver) {
> -		struct rte_vhost_async_features f;
> +		struct rte_vhost_async_config config = {0};
>  		struct rte_vhost_async_channel_ops channel_ops;
>  
>  		if (dma_type != NULL && strncmp(dma_type, "ioat", 4) == 0) {
> @@ -1476,11 +1476,11 @@ new_device(int vid)
>  			channel_ops.check_completed_copies =
>  				ioat_check_completed_copies_cb;
>  
> -			f.async_inorder = 1;
> -			f.async_threshold = 256;
> +			config.features = RTE_VHOST_ASYNC_INORDER;
> +			config.async_threshold = 256;
>  
>  			return rte_vhost_async_channel_register(vid, VIRTIO_RXQ,
> -				f.intval, &channel_ops);
> +				config, &channel_ops);
>  		}
>  	}
>  
> diff --git a/lib/vhost/rte_vhost_async.h b/lib/vhost/rte_vhost_async.h
> index 6faa31f..52b1727 100644
> --- a/lib/vhost/rte_vhost_async.h
> +++ b/lib/vhost/rte_vhost_async.h
> @@ -93,49 +93,48 @@ struct async_inflight_info {
>  };
>  
>  /**
> - *  dma channel feature bit definition
> + *  async channel features
>   */
> -struct rte_vhost_async_features {
> -	union {
> -		uint32_t intval;
> -		struct {
> -			uint32_t async_inorder:1;
> -			uint32_t resvd_0:15;
> -			uint32_t async_threshold:12;
> -			uint32_t resvd_1:4;
> -		};
> -	};
> +enum {
> +	RTE_VHOST_ASYNC_FEATURE_UNKNOWN = 0U,
Please remove this entry, it has no meaning.

> +	RTE_VHOST_ASYNC_INORDER = 1U << 0,
>  };
>  
>  /**
> - * register an async channel for vhost
> + *  async channel configuration
> + */
> +struct rte_vhost_async_config {
> +	uint32_t async_threshold;
> +	uint32_t features;
> +	uint32_t rsvd[2];
> +};
> +
> +/**
> + * Register an async channel for a vhost queue
>   *
>   * @param vid
>   *  vhost device id async channel to be attached to
>   * @param queue_id
>   *  vhost queue id async channel to be attached to
> - * @param features
> - *  DMA channel feature bit
> - *    b0       : DMA supports inorder data transfer
> - *    b1  - b15: reserved
> - *    b16 - b27: Packet length threshold for DMA transfer
> - *    b28 - b31: reserved
> + * @param config
> + *  Async channel configuration structure
>   * @param ops
> - *  DMA operation callbacks
> + *  Async channel operation callbacks
>   * @return
>   *  0 on success, -1 on failures
>   */
>  __rte_experimental
>  int rte_vhost_async_channel_register(int vid, uint16_t queue_id,
> -	uint32_t features, struct rte_vhost_async_channel_ops *ops);
> +	struct rte_vhost_async_config config,
> +	struct rte_vhost_async_channel_ops *ops);
>  
>  /**
> - * unregister a dma channel for vhost
> + * Unregister an async channel for a vhost queue
>   *
>   * @param vid
> - *  vhost device id DMA channel to be detached
> + *  vhost device id async channel to be detached from
>   * @param queue_id
> - *  vhost queue id DMA channel to be detached
> + *  vhost queue id async channel to be detached from
>   * @return
>   *  0 on success, -1 on failures
>   */
> diff --git a/lib/vhost/vhost.c b/lib/vhost/vhost.c
> index 53a470f..908758e 100644
> --- a/lib/vhost/vhost.c
> +++ b/lib/vhost/vhost.c
> @@ -1619,19 +1619,17 @@ int rte_vhost_extern_callback_register(int vid,
>  	return 0;
>  }
>  
> -int rte_vhost_async_channel_register(int vid, uint16_t queue_id,
> -					uint32_t features,
> -					struct rte_vhost_async_channel_ops *ops)
> +int
> +rte_vhost_async_channel_register(int vid, uint16_t queue_id,
> +		struct rte_vhost_async_config config,
> +		struct rte_vhost_async_channel_ops *ops)
>  {
>  	struct vhost_virtqueue *vq;
>  	struct virtio_net *dev = get_device(vid);
> -	struct rte_vhost_async_features f;
>  
>  	if (dev == NULL || ops == NULL)
>  		return -1;
>  
> -	f.intval = features;
> -
>  	if (queue_id >= VHOST_MAX_VRING)
>  		return -1;
>  
> @@ -1640,7 +1638,7 @@ int rte_vhost_async_channel_register(int vid, uint16_t queue_id,
>  	if (unlikely(vq == NULL || !dev->async_copy))
>  		return -1;
>  
> -	if (unlikely(!f.async_inorder)) {
> +	if (unlikely(!(config.features & RTE_VHOST_ASYNC_INORDER))) {
>  		VHOST_LOG_CONFIG(ERR,
>  			"async copy is not supported on non-inorder mode "
>  			"(vid %d, qid: %d)\n", vid, queue_id);
> @@ -1719,9 +1717,7 @@ int rte_vhost_async_channel_register(int vid, uint16_t queue_id,
>  
>  	vq->async_ops.check_completed_copies = ops->check_completed_copies;
>  	vq->async_ops.transfer_data = ops->transfer_data;
> -
> -	vq->async_inorder = f.async_inorder;
> -	vq->async_threshold = f.async_threshold;
> +	vq->async_threshold = config.async_threshold;
>  
>  	vq->async_registered = true;
>  
> @@ -1731,7 +1727,8 @@ int rte_vhost_async_channel_register(int vid, uint16_t queue_id,
>  	return 0;
>  }
>  
> -int rte_vhost_async_channel_unregister(int vid, uint16_t queue_id)
> +int
> +rte_vhost_async_channel_unregister(int vid, uint16_t queue_id)
>  {
>  	struct vhost_virtqueue *vq;
>  	struct virtio_net *dev = get_device(vid);
> diff --git a/lib/vhost/vhost.h b/lib/vhost/vhost.h
> index 8ffe387..d98ca8a 100644
> --- a/lib/vhost/vhost.h
> +++ b/lib/vhost/vhost.h
> @@ -218,9 +218,8 @@ struct vhost_virtqueue {
>  	};
>  
>  	/* vq async features */
> -	bool		async_inorder;
>  	bool		async_registered;
> -	uint16_t	async_threshold;
> +	uint32_t	async_threshold;
>  
>  	int			notif_enable;
>  #define VIRTIO_UNINITIALIZED_NOTIF	(-1)
>