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

Jason Wang
2022-03-09T07:37:28Z

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;
> }