Re: [PATCH v9 09/32] virtio_ring: split: extract the logic of vq init

[Jason Wang <jasowang@redhat.com>]

在 2022/4/6 上午11:43, Xuan Zhuo 写道:
> Separate the logic of initializing vq, and subsequent patches will call
> it separately.
>
> The feature of this part is that it does not depend on the information
> passed by the upper layer and can be called repeatedly.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> ---
>   drivers/virtio/virtio_ring.c | 68 ++++++++++++++++++++----------------
>   1 file changed, 38 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 083f2992ba0d..874f878087a3 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -916,6 +916,43 @@ static void *virtqueue_detach_unused_buf_split(struct virtqueue *_vq)
>   	return NULL;
>   }
>   
> +static void vring_virtqueue_init_split(struct vring_virtqueue *vq,
> +				       struct virtio_device *vdev,
> +				       bool own_ring)
> +{
> +	vq->packed_ring = false;
> +	vq->vq.num_free = vq->split.vring.num;
> +	vq->we_own_ring = own_ring;
> +	vq->broken = false;
> +	vq->last_used_idx = 0;
> +	vq->event_triggered = false;
> +	vq->num_added = 0;
> +	vq->use_dma_api = vring_use_dma_api(vdev);
> +#ifdef DEBUG
> +	vq->in_use = false;
> +	vq->last_add_time_valid = false;
> +#endif
> +
> +	vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
> +
> +	if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM))
> +		vq->weak_barriers = false;
> +
> +	vq->split.avail_flags_shadow = 0;
> +	vq->split.avail_idx_shadow = 0;
> +
> +	/* No callback?  Tell other side not to bother us. */
> +	if (!vq->vq.callback) {
> +		vq->split.avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
> +		if (!vq->event)
> +			vq->split.vring.avail->flags = cpu_to_virtio16(vdev,
> +					vq->split.avail_flags_shadow);
> +	}
> +
> +	/* Put everything in free lists. */
> +	vq->free_head = 0;


It's not clear what kind of initialization that we want to do here. E.g 
it mixes split specific setups with some general setups which is kind of 
duplication of vring_virtqueue_init_packed().

I wonder if it's better to only do split specific setups here and have a 
common helper to do the setup that is irrelevant to ring layout.

Thanks


> +}
> +
>   static void vring_virtqueue_attach_split(struct vring_virtqueue *vq,
>   					 struct vring vring,
>   					 struct vring_desc_state_split *desc_state,
> @@ -2249,42 +2286,15 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index,
>   	if (!vq)
>   		return NULL;
>   
> -	vq->packed_ring = false;
>   	vq->vq.callback = callback;
>   	vq->vq.vdev = vdev;
>   	vq->vq.name = name;
> -	vq->vq.num_free = vring.num;
>   	vq->vq.index = index;
> -	vq->we_own_ring = false;
>   	vq->notify = notify;
>   	vq->weak_barriers = weak_barriers;
> -	vq->broken = false;
> -	vq->last_used_idx = 0;
> -	vq->event_triggered = false;
> -	vq->num_added = 0;
> -	vq->use_dma_api = vring_use_dma_api(vdev);
> -#ifdef DEBUG
> -	vq->in_use = false;
> -	vq->last_add_time_valid = false;
> -#endif
>   
>   	vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) &&
>   		!context;
> -	vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
> -
> -	if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM))
> -		vq->weak_barriers = false;
> -
> -	vq->split.avail_flags_shadow = 0;
> -	vq->split.avail_idx_shadow = 0;
> -
> -	/* No callback?  Tell other side not to bother us. */
> -	if (!callback) {
> -		vq->split.avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
> -		if (!vq->event)
> -			vq->split.vring.avail->flags = cpu_to_virtio16(vdev,
> -					vq->split.avail_flags_shadow);
> -	}
>   
>   	err = vring_alloc_state_extra_split(vring.num, &state, &extra);
>   	if (err) {
> @@ -2293,9 +2303,7 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index,
>   	}
>   
>   	vring_virtqueue_attach_split(vq, vring, state, extra);
> -
> -	/* Put everything in free lists. */
> -	vq->free_head = 0;
> +	vring_virtqueue_init_split(vq, vdev, false);
>   
>   	spin_lock(&vdev->vqs_list_lock);
>   	list_add_tail(&vq->vq.list, &vdev->vqs);