[PATCH v11 02/40] virtio: struct virtio_config_ops add callbacks for queue_reset

[Michael S. Tsirkin]

On Wed, Jun 29, 2022 at 02:56:18PM +0800, Xuan Zhuo wrote:
> reset can be divided into the following four steps (example):
>  1. transport: notify the device to reset the queue
>  2. vring:     recycle the buffer submitted
>  3. vring:     reset/resize the vring (may re-alloc)
>  4. transport: mmap vring to device, and enable the queue
> 
> In order to support queue reset, add two callbacks(reset_vq,
> enable_reset_vq) in struct virtio_config_ops to implement steps 1 and 4.
> 
> Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com>
> ---
>  include/linux/virtio_config.h | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
> index b47c2e7ed0ee..ded51b0d4823 100644
> --- a/include/linux/virtio_config.h
> +++ b/include/linux/virtio_config.h
> @@ -78,6 +78,16 @@ struct virtio_shm_region {
>   * @set_vq_affinity: set the affinity for a virtqueue (optional).
>   * @get_vq_affinity: get the affinity for a virtqueue (optional).
>   * @get_shm_region: get a shared memory region based on the index.
> + * @reset_vq: reset a queue individually (optional).
> + *	vq: the virtqueue
> + *	Returns 0 on success or error status
> + *	reset_vq will guarantee that the callbacks are disabled and synchronized.
> + *	Except for the callback, the caller should guarantee that the vring is
> + *	not accessed by any functions of virtqueue.
> + * @enable_reset_vq: enable a reset queue
> + *	vq: the virtqueue
> + *	Returns 0 on success or error status
> + *	If reset_vq is set, then enable_reset_vq must also be set.
>   */
>  typedef void vq_callback_t(struct virtqueue *);
>  struct virtio_config_ops {
> @@ -104,6 +114,8 @@ struct virtio_config_ops {
>  			int index);
>  	bool (*get_shm_region)(struct virtio_device *vdev,
>  			       struct virtio_shm_region *region, u8 id);
> +	int (*reset_vq)(struct virtqueue *vq);
> +	int (*enable_reset_vq)(struct virtqueue *vq);
>  };

The names need some tweaking.
I came up with
 	int (*disable_vq_and_reset)(struct virtqueue *vq);
 	int (*enable_vq_after_reset)(struct virtqueue *vq);


>  /* If driver didn't advertise the feature, it will never appear. */
> -- 
> 2.31.0