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

Xuan Zhuo
2022-04-13T07:05:01Z

On Tue, 12 Apr 2022 11:42:25 +0800, Jason Wang <jasowang@redhat.com> wrote:
>
> 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.

Yes, you are right, I didn't notice this situation before.

Thanks.

>
> 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);
>