Re: [PATCH v7 05/26] virtio_ring: split: extract the logic of init vq and attach vring

[Jason Wang <jasowang@redhat.com>]

在 2022/3/8 下午8:34, Xuan Zhuo 写道:
> Split the logic of split assignment vq into three parts.
>
> 1. The assignment passed from the function parameter
> 2. The part that attaches vring to vq. -- __vring_virtqueue_attach_split()
> 3. The part that initializes vq to a fixed value --
>     __vring_virtqueue_init_split()
>
> This feature is required for subsequent virtuqueue reset vring
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> ---
>   drivers/virtio/virtio_ring.c | 111 +++++++++++++++++++++--------------
>   1 file changed, 67 insertions(+), 44 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index d32793615451..dc6313b79305 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -2196,34 +2196,40 @@ irqreturn_t vring_interrupt(int irq, void *_vq)
>   }
>   EXPORT_SYMBOL_GPL(vring_interrupt);
>   
> -/* Only available for split ring */
> -struct virtqueue *__vring_new_virtqueue(unsigned int index,
> -					struct vring vring,
> -					struct virtio_device *vdev,
> -					bool weak_barriers,
> -					bool context,
> -					bool (*notify)(struct virtqueue *),
> -					void (*callback)(struct virtqueue *),
> -					const char *name)
> +static int __vring_virtqueue_attach_split(struct vring_virtqueue *vq,
> +					  struct virtio_device *vdev,
> +					  struct vring vring)
>   {
> -	struct vring_virtqueue *vq;
> +	vq->vq.num_free = vring.num;
>   
> -	if (virtio_has_feature(vdev, VIRTIO_F_RING_PACKED))
> -		return NULL;
> +	vq->split.vring = vring;
> +	vq->split.queue_dma_addr = 0;
> +	vq->split.queue_size_in_bytes = 0;
>   
> -	vq = kmalloc(sizeof(*vq), GFP_KERNEL);
> -	if (!vq)
> -		return NULL;
> +	vq->split.desc_state = kmalloc_array(vring.num,
> +					     sizeof(struct vring_desc_state_split), GFP_KERNEL);
> +	if (!vq->split.desc_state)
> +		goto err_state;
>   
> +	vq->split.desc_extra = vring_alloc_desc_extra(vq, vring.num);
> +	if (!vq->split.desc_extra)
> +		goto err_extra;


So this contains stuffs more than just attach. I wonder if it's better 
to split the allocation out to an dedicated helper (we have dedicated 
helper to allocate vring).

Thanks


> +
> +	memset(vq->split.desc_state, 0, vring.num *
> +	       sizeof(struct vring_desc_state_split));
> +	return 0;
> +
> +err_extra:
> +	kfree(vq->split.desc_state);
> +err_state:
> +	return -ENOMEM;
> +}
> +
> +static void __vring_virtqueue_init_split(struct vring_virtqueue *vq,
> +					 struct virtio_device *vdev)
> +{
>   	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;
> @@ -2234,50 +2240,67 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index,
>   	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.queue_dma_addr = 0;
> -	vq->split.queue_size_in_bytes = 0;
> -
> -	vq->split.vring = vring;
>   	vq->split.avail_flags_shadow = 0;
>   	vq->split.avail_idx_shadow = 0;
>   
>   	/* No callback?  Tell other side not to bother us. */
> -	if (!callback) {
> +	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);
>   	}
>   
> -	vq->split.desc_state = kmalloc_array(vring.num,
> -			sizeof(struct vring_desc_state_split), GFP_KERNEL);
> -	if (!vq->split.desc_state)
> -		goto err_state;
> -
> -	vq->split.desc_extra = vring_alloc_desc_extra(vq, vring.num);
> -	if (!vq->split.desc_extra)
> -		goto err_extra;
> -
>   	/* Put everything in free lists. */
>   	vq->free_head = 0;
> -	memset(vq->split.desc_state, 0, vring.num *
> -			sizeof(struct vring_desc_state_split));
> +}
> +
> +/* Only available for split ring */
> +struct virtqueue *__vring_new_virtqueue(unsigned int index,
> +					struct vring vring,
> +					struct virtio_device *vdev,
> +					bool weak_barriers,
> +					bool context,
> +					bool (*notify)(struct virtqueue *),
> +					void (*callback)(struct virtqueue *),
> +					const char *name)
> +{
> +	struct vring_virtqueue *vq;
> +	int err;
> +
> +	if (virtio_has_feature(vdev, VIRTIO_F_RING_PACKED))
> +		return NULL;
> +
> +	vq = kmalloc(sizeof(*vq), GFP_KERNEL);
> +	if (!vq)
> +		return NULL;
> +
> +	vq->vq.callback = callback;
> +	vq->vq.vdev = vdev;
> +	vq->vq.name = name;
> +	vq->vq.index = index;
> +	vq->notify = notify;
> +	vq->weak_barriers = weak_barriers;
> +	vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) &&
> +		!context;
> +
> +	err = __vring_virtqueue_attach_split(vq, vdev, vring);
> +	if (err)
> +		goto err;
> +
> +	__vring_virtqueue_init_split(vq, vdev);
>   
>   	spin_lock(&vdev->vqs_list_lock);
>   	list_add_tail(&vq->vq.list, &vdev->vqs);
>   	spin_unlock(&vdev->vqs_list_lock);
> -	return &vq->vq;
>   
> -err_extra:
> -	kfree(vq->split.desc_state);
> -err_state:
> +	return &vq->vq;
> +err:
>   	kfree(vq);
>   	return NULL;
>   }