On Mon, Apr 29, 2024 at 08:13:59PM +1000, Gavin Shan wrote:
> Improve vhost_get_avail_head() so that the head or errno is returned.
> With it, the relevant sanity checks are squeezed to vhost_get_avail_head()
> and vhost_get_vq_desc() is further simplified.
>
> No functional change intended.
>
> Signed-off-by: Gavin Shan <gs...@redhat.com>
I don't see what does this moving code around achieve.
> ---
> drivers/vhost/vhost.c | 50 ++++++++++++++++++++++---------------------
> 1 file changed, 26 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index b278c0333a66..4ddb9ec2fe46 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -1322,11 +1322,27 @@ static inline int vhost_get_avail_idx(struct
> vhost_virtqueue *vq)
> return 1;
> }
>
> -static inline int vhost_get_avail_head(struct vhost_virtqueue *vq,
> - __virtio16 *head, int idx)
> +static inline int vhost_get_avail_head(struct vhost_virtqueue *vq)
> {
> - return vhost_get_avail(vq, *head,
> - &vq->avail->ring[idx & (vq->num - 1)]);
> + __virtio16 head;
> + int r;
> +
> + r = vhost_get_avail(vq, head,
> + &vq->avail->ring[vq->last_avail_idx & (vq->num -
> 1)]);
> + if (unlikely(r)) {
> + vq_err(vq, "Failed to read head: index %u address %p\n",
> + vq->last_avail_idx,
> + &vq->avail->ring[vq->last_avail_idx & (vq->num - 1)]);
> + return r;
> + }
> +
> + r = vhost16_to_cpu(vq, head);
> + if (unlikely(r >= vq->num)) {
> + vq_err(vq, "Invalid head %d (%u)\n", r, vq->num);
> + return -EINVAL;
> + }
> +
> + return r;
> }
>
> static inline int vhost_get_avail_flags(struct vhost_virtqueue *vq,
> @@ -2523,9 +2539,8 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
> struct vhost_log *log, unsigned int *log_num)
> {
> struct vring_desc desc;
> - unsigned int i, head, found = 0;
> - __virtio16 ring_head;
> - int ret, access;
> + unsigned int i, found = 0;
> + int head, ret, access;
>
> if (vq->avail_idx == vq->last_avail_idx) {
> ret = vhost_get_avail_idx(vq);
> @@ -2536,23 +2551,10 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
> return vq->num;
> }
>
> - /* Grab the next descriptor number they're advertising, and increment
> - * the index we've seen. */
> - if (unlikely(vhost_get_avail_head(vq, &ring_head, vq->last_avail_idx)))
> {
> - vq_err(vq, "Failed to read head: idx %d address %p\n",
> - vq->last_avail_idx,
> - &vq->avail->ring[vq->last_avail_idx % vq->num]);
> - return -EFAULT;
> - }
> -
> - head = vhost16_to_cpu(vq, ring_head);
> -
> - /* If their number is silly, that's an error. */
> - if (unlikely(head >= vq->num)) {
> - vq_err(vq, "Guest says index %u > %u is available",
> - head, vq->num);
> - return -EINVAL;
> - }
> + /* Grab the next descriptor number they're advertising */
> + head = vhost_get_avail_head(vq);
> + if (unlikely(head < 0))
> + return head;
>
> /* When we start there are none of either input nor output. */
> *out_num = *in_num = 0;
> --
> 2.44.0
