[RFC 15/27] vhost: add API to set max queue pairs

[Xia, Chenbo]

Hi Maxime,

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin at redhat.com>
> Sent: Friday, March 31, 2023 11:43 PM
> To: dev at dpdk.org; david.marchand at redhat.com; Xia, Chenbo
> <chenbo.xia at intel.com>; mkp at redhat.com; fbl at redhat.com;
> jasowang at redhat.com; Liang, Cunming <cunming.liang at intel.com>; Xie, Yongji
> <xieyongji at bytedance.com>; echaudro at redhat.com; eperezma at redhat.com;
> amorenoz at redhat.com
> Cc: Maxime Coquelin <maxime.coquelin at redhat.com>
> Subject: [RFC 15/27] vhost: add API to set max queue pairs
> 
> This patch introduces a new rte_vhost_driver_set_max_queues
> API as preliminary work for multiqueue support with VDUSE.
> 
> Indeed, with VDUSE we need to pre-allocate the vrings at
> device creation time, so we need such API not to allocate
> the 128 queue pairs supported by the Vhost library.
> 
> Calling the API is optional, 128 queue pairs remaining the
> default.
> 
> Signed-off-by: Maxime Coquelin <maxime.coquelin at redhat.com>
> ---
>  doc/guides/prog_guide/vhost_lib.rst |  4 ++++
>  lib/vhost/rte_vhost.h               | 17 ++++++++++++++
>  lib/vhost/socket.c                  | 36 +++++++++++++++++++++++++++--
>  lib/vhost/version.map               |  3 +++
>  4 files changed, 58 insertions(+), 2 deletions(-)

Also add changes in release notes? Btw: somewhere we should also mention vduse
support is added in release notes.

Thanks,
Chenbo

> 
> diff --git a/doc/guides/prog_guide/vhost_lib.rst
> b/doc/guides/prog_guide/vhost_lib.rst
> index e8bb8c9b7b..cd4b109139 100644
> --- a/doc/guides/prog_guide/vhost_lib.rst
> +++ b/doc/guides/prog_guide/vhost_lib.rst
> @@ -334,6 +334,10 @@ The following is an overview of some key Vhost API
> functions:
>    Clean DMA vChannel finished to use. After this function is called,
>    the specified DMA vChannel should no longer be used by the Vhost
> library.
> 
> +* ``rte_vhost_driver_set_max_queue_num(path, max_queue_pairs)``
> +
> +  Set the maximum number of queue pairs supported by the device.
> +
>  Vhost-user Implementations
>  --------------------------
> 
> diff --git a/lib/vhost/rte_vhost.h b/lib/vhost/rte_vhost.h
> index 58a5d4be92..44cbfcb469 100644
> --- a/lib/vhost/rte_vhost.h
> +++ b/lib/vhost/rte_vhost.h
> @@ -588,6 +588,23 @@ rte_vhost_driver_get_protocol_features(const char
> *path,
>  int
>  rte_vhost_driver_get_queue_num(const char *path, uint32_t *queue_num);
> 
> +/**
> + * @warning
> + * @b EXPERIMENTAL: this API may change, or be removed, without prior
> notice.
> + *
> + * Set the maximum number of queue pairs supported by the device.
> + *
> + * @param path
> + *  The vhost-user socket file path
> + * @param max_queue_pairs
> + *  The maximum number of queue pairs
> + * @return
> + *  0 on success, -1 on failure
> + */
> +__rte_experimental
> +int
> +rte_vhost_driver_set_max_queue_num(const char *path, uint32_t
> max_queue_pairs);
> +
>  /**
>   * Get the feature bits after negotiation
>   *
> diff --git a/lib/vhost/socket.c b/lib/vhost/socket.c
> index ba54263824..e95c3ffeac 100644
> --- a/lib/vhost/socket.c
> +++ b/lib/vhost/socket.c
> @@ -56,6 +56,8 @@ struct vhost_user_socket {
> 
>  	uint64_t protocol_features;
> 
> +	uint32_t max_queue_pairs;
> +
>  	struct rte_vdpa_device *vdpa_dev;
> 
>  	struct rte_vhost_device_ops const *notify_ops;
> @@ -821,7 +823,7 @@ rte_vhost_driver_get_queue_num(const char *path,
> uint32_t *queue_num)
> 
>  	vdpa_dev = vsocket->vdpa_dev;
>  	if (!vdpa_dev) {
> -		*queue_num = VHOST_MAX_QUEUE_PAIRS;
> +		*queue_num = vsocket->max_queue_pairs;
>  		goto unlock_exit;
>  	}
> 
> @@ -831,7 +833,36 @@ rte_vhost_driver_get_queue_num(const char *path,
> uint32_t *queue_num)
>  		goto unlock_exit;
>  	}
> 
> -	*queue_num = RTE_MIN((uint32_t)VHOST_MAX_QUEUE_PAIRS,
> vdpa_queue_num);
> +	*queue_num = RTE_MIN(vsocket->max_queue_pairs, vdpa_queue_num);
> +
> +unlock_exit:
> +	pthread_mutex_unlock(&vhost_user.mutex);
> +	return ret;
> +}
> +
> +int
> +rte_vhost_driver_set_max_queue_num(const char *path, uint32_t
> max_queue_pairs)
> +{
> +	struct vhost_user_socket *vsocket;
> +	int ret = 0;
> +
> +	VHOST_LOG_CONFIG(path, INFO, "Setting max queue pairs to %u\n",
> max_queue_pairs);
> +
> +	if (max_queue_pairs > VHOST_MAX_QUEUE_PAIRS) {
> +		VHOST_LOG_CONFIG(path, ERR, "Library only supports up to %u
> queue pairs\n",
> +				VHOST_MAX_QUEUE_PAIRS);
> +		return -1;
> +	}
> +
> +	pthread_mutex_lock(&vhost_user.mutex);
> +	vsocket = find_vhost_user_socket(path);
> +	if (!vsocket) {
> +		VHOST_LOG_CONFIG(path, ERR, "socket file is not registered
> yet.\n");
> +		ret = -1;
> +		goto unlock_exit;
> +	}
> +
> +	vsocket->max_queue_pairs = max_queue_pairs;
> 
>  unlock_exit:
>  	pthread_mutex_unlock(&vhost_user.mutex);
> @@ -890,6 +921,7 @@ rte_vhost_driver_register(const char *path, uint64_t
> flags)
>  		goto out_free;
>  	}
>  	vsocket->vdpa_dev = NULL;
> +	vsocket->max_queue_pairs = VHOST_MAX_QUEUE_PAIRS;
>  	vsocket->extbuf = flags & RTE_VHOST_USER_EXTBUF_SUPPORT;
>  	vsocket->linearbuf = flags & RTE_VHOST_USER_LINEARBUF_SUPPORT;
>  	vsocket->async_copy = flags & RTE_VHOST_USER_ASYNC_COPY;
> diff --git a/lib/vhost/version.map b/lib/vhost/version.map
> index d322a4a888..dffb126aa8 100644
> --- a/lib/vhost/version.map
> +++ b/lib/vhost/version.map
> @@ -98,6 +98,9 @@ EXPERIMENTAL {
>  	# added in 22.11
>  	rte_vhost_async_dma_unconfigure;
>  	rte_vhost_vring_call_nonblock;
> +
> +	# added in 23.07
> +	rte_vhost_driver_set_max_queue_num;
>  };
> 
>  INTERNAL {
> --
> 2.39.2