[dpdk-dev] [PATCH v4 2/3] vhost: rework async configuration struct

Xia, Chenbo chenbo.xia at intel.com
Fri Jul 16 08:03:16 CEST 2021


Hi Jiayu,

> -----Original Message-----
> From: Hu, Jiayu <jiayu.hu at intel.com>
> Sent: Tuesday, July 13, 2021 3:46 PM
> To: dev at dpdk.org
> Cc: maxime.coquelin at redhat.com; Xia, Chenbo <chenbo.xia at intel.com>; Hu, Jiayu
> <jiayu.hu at intel.com>
> Subject: [PATCH v4 2/3] vhost: rework async configuration struct

Struct -> structure 

> 
> 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 at intel.com>
> ---
>  doc/guides/prog_guide/vhost_lib.rst | 19 +++++++++++--------
>  examples/vhost/main.c               |  8 ++++----
>  lib/vhost/rte_vhost_async.h         | 35 +++++++++++++++++------------------
>  lib/vhost/vhost.c                   | 13 +++++--------
>  4 files changed, 37 insertions(+), 38 deletions(-)
> 
> diff --git a/doc/guides/prog_guide/vhost_lib.rst
> b/doc/guides/prog_guide/vhost_lib.rst
> index d18fb98..affdc57 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

Not related to this patch. But maybe 'Register an async copy device channel
for a vhost queue' is better?

> -  is enabled. Following device ``features`` must be specified together
> +  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;

This is ok as for now we are using ioat API. But I guess there should be
a more user-friendly way to know the value. I mean, no users want to do
complicated tests for his platform to know the value. Maybe there could be
some auto-test in specific driver to show the value to user?

It's off-topic for this patch. But thinking about it should be good.

> 
>  			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..c93490d 100644
> --- a/lib/vhost/rte_vhost_async.h
> +++ b/lib/vhost/rte_vhost_async.h
> @@ -93,18 +93,20 @@ struct async_inflight_info {
>  };
> 
>  /**
> - *  dma channel feature bit definition
> + *  dma channel features

Let's use 'async channel' which is also the name for API.
It's always good to use one term for one thing.

>   */
> -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,
> +	RTE_VHOST_ASYNC_INORDER = 1U << 0,
> +};
> +
> +/**
> + *  dma channel configuration

Ditto

> + */
> +struct rte_vhost_async_config {
> +	uint32_t async_threshold;
> +	uint32_t features;
> +	uint32_t resvd[2];

Generally we use 'rsvd' for the word 'reserved'.

>  };
> 
>  /**
> @@ -114,12 +116,8 @@ struct rte_vhost_async_features {
>   *  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
> + *  DMA channel configuration structure

DMA -> async

>   * @param ops
>   *  DMA operation callbacks
>   * @return
> @@ -127,7 +125,8 @@ struct rte_vhost_async_features {
>   */
>  __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
> diff --git a/lib/vhost/vhost.c b/lib/vhost/vhost.c
> index 53a470f..a20f05a 100644
> --- a/lib/vhost/vhost.c
> +++ b/lib/vhost/vhost.c
> @@ -1620,18 +1620,15 @@ int rte_vhost_extern_callback_register(int vid,
>  }
> 
>  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)
>  {
>  	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 +1637,7 @@ 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);
> @@ -1720,8 +1717,8 @@ 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_inorder = true;

Do we still need this? It's never used.

> +	vq->async_threshold = config.async_threshold;

vq->async_threshold is uint16_t and config.async_threshold is uint32_t.
They should be the same.

Thanks,
Chenbo

> 
>  	vq->async_registered = true;
> 
> --
> 2.7.4



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