diff options
Diffstat (limited to 'drivers/vhost/vhost.c')
| -rw-r--r-- | drivers/vhost/vhost.c | 39 |
1 files changed, 23 insertions, 16 deletions
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 8f99fe08de02..1f7e4e4e6f8e 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -1930,25 +1930,32 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq, /* Check it isn't doing very strange things with descriptor numbers. */ last_avail_idx = vq->last_avail_idx; - if (unlikely(vhost_get_user(vq, avail_idx, &vq->avail->idx))) { - vq_err(vq, "Failed to access avail idx at %p\n", - &vq->avail->idx); - return -EFAULT; - } - vq->avail_idx = vhost16_to_cpu(vq, avail_idx); - if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) { - vq_err(vq, "Guest moved used index from %u to %u", - last_avail_idx, vq->avail_idx); - return -EFAULT; - } + if (vq->avail_idx == vq->last_avail_idx) { + if (unlikely(vhost_get_user(vq, avail_idx, &vq->avail->idx))) { + vq_err(vq, "Failed to access avail idx at %p\n", + &vq->avail->idx); + return -EFAULT; + } + vq->avail_idx = vhost16_to_cpu(vq, avail_idx); - /* If there's nothing new since last we looked, return invalid. */ - if (vq->avail_idx == last_avail_idx) - return vq->num; + if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) { + vq_err(vq, "Guest moved used index from %u to %u", + last_avail_idx, vq->avail_idx); + return -EFAULT; + } + + /* If there's nothing new since last we looked, return + * invalid. + */ + if (vq->avail_idx == last_avail_idx) + return vq->num; - /* Only get avail ring entries after they have been exposed by guest. */ - smp_rmb(); + /* Only get avail ring entries after they have been + * exposed by guest. + */ + smp_rmb(); + } /* Grab the next descriptor number they're advertising, and increment * the index we've seen. */ |