Re: [PATCH virtio v2 04/19] virtio: introduce virtio_queue_info struct and find_vqs_info() config op

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Jul 04, 2024 at 08:43:35AM +0200, Jiri Pirko wrote:
> From: Jiri Pirko <jiri@nvidia.com>
> 
> Introduce a structure virtio_queue_info to carry name, callback and ctx
> together. In order to allow config implementations to accept config op
> with array of virtio_queue_info structures, introduce a new
> find_vqs_info() op. Do the needed conversion in virtio_find_vqs_ctx().
> Note that whole virtio_find_vqs_ctx() is going to be eventually removed
> at the and of this patchset.
> 
> Signed-off-by: Jiri Pirko <jiri@nvidia.com>
> ---
> v1->v2:
> - fixed comments for struct virtqueue_info
> - s/virtio_queue_info/virtqueue_info/
> ---
>  include/linux/virtio_config.h | 51 ++++++++++++++++++++++++++++++++---
>  1 file changed, 48 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
> index 82a1d798b2f1..9b975c2830f6 100644
> --- a/include/linux/virtio_config.h
> +++ b/include/linux/virtio_config.h
> @@ -18,6 +18,16 @@ struct virtio_shm_region {
>  
>  typedef void vq_callback_t(struct virtqueue *);
>  
> +struct virtqueue_info {
> +	const char *name; /* Mainly for debugging, may be NULL for a virtqueue
> +			   * unused by driver.
> +			   */
> +	vq_callback_t *callback; /* May be NULL for vq that does
> +				  * not need a callback.
> +				  */
> +	bool ctx;


	/*
	 * Always
	 * like this
	 * outside of netdev code
	 * and it comes before the code being documented
	 */

	/* Never
	 * like this
	 */


Also "may be null" is a bit confusing - it has to be null
for such a vq.

Thus:

	/*
	 * name: mainly for debugging, NULL for a virtqueue
         * unused by the driver.
	 */
	const char *name;

and similarly for the callback.



> +};
> +
>  /**
>   * struct virtio_config_ops - operations for configuring a virtio device
>   * Note: Do not assume that a transport implements all of the operations
> @@ -58,6 +68,12 @@ typedef void vq_callback_t(struct virtqueue *);
>   *	names: array of virtqueue names (mainly for debugging)
>   *		include a NULL entry for vqs unused by driver
>   *	Returns 0 on success or error status
> + * @find_vqs_info: find virtqueues and instantiate them.
> + *	vdev: the virtio_device
> + *	nvqs: the number of virtqueues to find
> + *	vqs: on success, includes new virtqueues
> + *	vqs_info: array of virtqueue info structures
> + *	Returns 0 on success or error status
>   * @del_vqs: free virtqueues found by find_vqs().
>   * @synchronize_cbs: synchronize with the virtqueue callbacks (optional)
>   *      The function guarantees that all memory operations on the
> @@ -109,6 +125,10 @@ struct virtio_config_ops {
>  			struct virtqueue *vqs[], vq_callback_t *callbacks[],
>  			const char * const names[], const bool *ctx,
>  			struct irq_affinity *desc);
> +	int (*find_vqs_info)(struct virtio_device *vdev, unsigned int nvqs,
> +			     struct virtqueue *vqs[],
> +			     struct virtqueue_info vqs_info[],
> +			     struct irq_affinity *desc);
>  	void (*del_vqs)(struct virtio_device *);
>  	void (*synchronize_cbs)(struct virtio_device *);
>  	u64 (*get_features)(struct virtio_device *vdev);
> @@ -117,7 +137,7 @@ struct virtio_config_ops {
>  	int (*set_vq_affinity)(struct virtqueue *vq,
>  			       const struct cpumask *cpu_mask);
>  	const struct cpumask *(*get_vq_affinity)(struct virtio_device *vdev,
> -			int index);
> +						 int index);
>  	bool (*get_shm_region)(struct virtio_device *vdev,
>  			       struct virtio_shm_region *region, u8 id);
>  	int (*disable_vq_and_reset)(struct virtqueue *vq);
> @@ -210,14 +230,39 @@ static inline bool virtio_has_dma_quirk(const struct virtio_device *vdev)
>  	return !virtio_has_feature(vdev, VIRTIO_F_ACCESS_PLATFORM);
>  }
>  
> +static inline
> +int virtio_find_vqs_info(struct virtio_device *vdev, unsigned int nvqs,
> +			 struct virtqueue *vqs[],
> +			 struct virtqueue_info vqs_info[],
> +			 struct irq_affinity *desc)
> +{
> +	return vdev->config->find_vqs_info(vdev, nvqs, vqs, vqs_info, desc);
> +}
> +
>  static inline
>  int virtio_find_vqs_ctx(struct virtio_device *vdev, unsigned nvqs,
>  			struct virtqueue *vqs[], vq_callback_t *callbacks[],
>  			const char * const names[], const bool *ctx,
>  			struct irq_affinity *desc)
>  {
> -	return vdev->config->find_vqs(vdev, nvqs, vqs, callbacks, names, ctx,
> -				      desc);
> +	struct virtqueue_info *vqs_info;
> +	int err, i;
> +
> +	if (!vdev->config->find_vqs_info)
> +		return vdev->config->find_vqs(vdev, nvqs, vqs, callbacks,
> +					      names, ctx, desc);
> +
> +	vqs_info = kmalloc_array(nvqs, sizeof(*vqs_info), GFP_KERNEL);
> +	if (!vqs_info)
> +		return -ENOMEM;
> +	for (i = 0; i < nvqs; i++) {
> +		vqs_info[i].name = names[i];
> +		vqs_info[i].callback = callbacks[i];
> +		vqs_info[i].ctx = ctx ? ctx[i] : false;
> +	}
> +	err = virtio_find_vqs_info(vdev, nvqs, vqs, vqs_info, desc);
> +	kfree(vqs_info);
> +	return err;
>  }
>  
>  static inline
> -- 
> 2.45.2