@@ -295,8 +295,9 @@ void virtqueue_push(VirtQueue *vq, const VirtQueueElement *elem,
virtqueue_flush(vq, 1);
}
-static int virtqueue_num_heads(VirtQueue *vq, unsigned int idx)
+static int virtqueue_get_head(VirtQueue *vq, unsigned int idx)
{
+ unsigned int head;
uint16_t num_heads = vring_avail_idx(vq) - idx;
/* Check it isn't doing very strange things with descriptor numbers. */
@@ -305,18 +306,13 @@ static int virtqueue_num_heads(VirtQueue *vq, unsigned int idx)
idx, vring_avail_idx(vq));
exit(1);
}
- /* On success, callers read a descriptor at vq->last_avail_idx.
- * Make sure descriptor read does not bypass avail index read. */
- if (num_heads) {
- smp_rmb();
- }
- return num_heads;
-}
+ if (!num_heads) {
+ return -EAGAIN;
+ }
-static unsigned int virtqueue_get_head(VirtQueue *vq, unsigned int idx)
-{
- unsigned int head;
+ /* Make sure head read below does not bypass avail index read. */
+ smp_rmb();
/* Grab the next descriptor number they're advertising, and increment
* the index we've seen. */
@@ -360,19 +356,19 @@ void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes,
{
unsigned int idx;
unsigned int total_bufs, in_total, out_total;
+ int i;
idx = vq->last_avail_idx;
total_bufs = in_total = out_total = 0;
- while (virtqueue_num_heads(vq, idx)) {
+ while ((i = virtqueue_get_head(vq, idx)) >= 0) {
VirtIODevice *vdev = vq->vdev;
unsigned int max, num_bufs, indirect = 0;
hwaddr desc_pa;
- int i;
max = vq->vring.num;
num_bufs = total_bufs;
- i = virtqueue_get_head(vq, idx++);
+ idx++;
desc_pa = vq->vring.desc;
if (vring_desc_flags(vdev, desc_pa, i) & VRING_DESC_F_INDIRECT) {
@@ -462,15 +458,17 @@ int virtqueue_pop(VirtQueue *vq, VirtQueueElement *elem)
hwaddr desc_pa = vq->vring.desc;
VirtIODevice *vdev = vq->vdev;
- if (!virtqueue_num_heads(vq, vq->last_avail_idx))
+ if ((i = virtqueue_get_head(vq, vq->last_avail_idx)) < 0) {
return 0;
+ }
/* When we start there are none of either input nor output. */
elem->out_num = elem->in_num = 0;
max = vq->vring.num;
- i = head = virtqueue_get_head(vq, vq->last_avail_idx++);
+ head = i;
+ vq->last_avail_idx++;
if (virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX)) {
vring_set_avail_event(vq, vq->last_avail_idx);
}