Re: [PATCH 2/2] virtio_ring: fix complaint by sparse

From: Michael S. Tsirkin
Date: Tue Nov 22 2016 - 10:04:43 EST


On Tue, Nov 22, 2016 at 01:51:50PM +0800, Gonglei wrote:
> # make C=2 CF="-D__CHECK_ENDIAN__" ./drivers/virtio/
>
> drivers/virtio/virtio_ring.c:423:19: warning: incorrect type in assignment (different base types)
> drivers/virtio/virtio_ring.c:423:19: expected unsigned int [unsigned] [assigned] i
> drivers/virtio/virtio_ring.c:423:19: got restricted __virtio16 [usertype] next
> drivers/virtio/virtio_ring.c:423:19: warning: incorrect type in assignment (different base types)
> drivers/virtio/virtio_ring.c:423:19: expected unsigned int [unsigned] [assigned] i
> drivers/virtio/virtio_ring.c:423:19: got restricted __virtio16 [usertype] next
> drivers/virtio/virtio_ring.c:423:19: warning: incorrect type in assignment (different base types)
> drivers/virtio/virtio_ring.c:423:19: expected unsigned int [unsigned] [assigned] i
> drivers/virtio/virtio_ring.c:423:19: got restricted __virtio16 [usertype] next
> drivers/virtio/virtio_ring.c:604:39: warning: incorrect type in initializer (different base types)
> drivers/virtio/virtio_ring.c:604:39: expected unsigned short [unsigned] [usertype] nextflag
> drivers/virtio/virtio_ring.c:604:39: got restricted __virtio16
> drivers/virtio/virtio_ring.c:612:33: warning: restricted __virtio16 degrades to integer
>
> Signed-off-by: Gonglei <arei.gonglei@xxxxxxxxxx>
> ---
> drivers/virtio/virtio_ring.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 489bfc6..d2863c3 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -420,7 +420,7 @@ static inline int virtqueue_add(struct virtqueue *_vq,
> if (i == err_idx)
> break;
> vring_unmap_one(vq, &desc[i]);
> - i = vq->vring.desc[i].next;
> + i = virtio16_to_cpu(_vq->vdev, vq->vring.desc[i].next);
> }
>
> vq->vq.num_free += total_sg;
> @@ -601,7 +601,7 @@ bool virtqueue_kick(struct virtqueue *vq)
> static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
> {
> unsigned int i, j;
> - u16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
> + __virtio16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
>
> /* Clear data ptr. */
> vq->desc_state[head].data = NULL;
> --
> 1.8.3.1
>

Wow are you saying endian-ness is all wrong for the next field?
How do things ever work then?

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MST