The mergeable receive buffer scheme will introduce a new function
which peeks at how much buffer space is available in the queue.
Split out some helper functions from virtqueue_pop() for that purpose.
Signed-off-by: Mark McLoughlin <[EMAIL PROTECTED]>
---
qemu/hw/virtio.c | 45 +++++++++++++++++++++++++++++----------------
1 files changed, 29 insertions(+), 16 deletions(-)
diff --git a/qemu/hw/virtio.c b/qemu/hw/virtio.c
index 18ad3ed..42022d4 100644
--- a/qemu/hw/virtio.c
+++ b/qemu/hw/virtio.c
@@ -135,6 +135,33 @@ void virtqueue_push(VirtQueue *vq, const VirtQueueElement
*elem,
virtqueue_flush(vq, 1);
}
+static int virtqueue_num_heads(VirtQueue *vq, unsigned int idx)
+{
+ uint16_t num_heads = vq->vring.avail->idx - idx;
+
+ /* Check it isn't doing very strange things with descriptor numbers. */
+ if (num_heads > vq->vring.num)
+ errx(1, "Guest moved used index from %u to %u",
+ idx, vq->vring.avail->idx);
+
+ return num_heads;
+}
+
+static unsigned int virtqueue_get_head(VirtQueue *vq, unsigned int idx)
+{
+ unsigned int head;
+
+ /* Grab the next descriptor number they're advertising, and increment
+ * the index we've seen. */
+ head = vq->vring.avail->ring[idx % vq->vring.num];
+
+ /* If their number is silly, that's a fatal mistake. */
+ if (head >= vq->vring.num)
+ errx(1, "Guest says index %u is available", head);
+
+ return head;
+}
+
static unsigned virtqueue_next_desc(VirtQueue *vq, unsigned int i)
{
unsigned int next;
@@ -158,27 +185,13 @@ int virtqueue_pop(VirtQueue *vq, VirtQueueElement *elem)
{
unsigned int i, head;
- /* Check it isn't doing very strange things with descriptor numbers. */
- if ((uint16_t)(vq->vring.avail->idx - vq->last_avail_idx) > vq->vring.num)
- errx(1, "Guest moved used index from %u to %u",
- vq->last_avail_idx, vq->vring.avail->idx);
-
- /* If there's nothing new since last we looked, return invalid. */
- if (vq->vring.avail->idx == vq->last_avail_idx)
+ if (!virtqueue_num_heads(vq, vq->last_avail_idx))
return 0;
- /* Grab the next descriptor number they're advertising, and increment
- * the index we've seen. */
- head = vq->vring.avail->ring[vq->last_avail_idx++ % vq->vring.num];
-
- /* If their number is silly, that's a fatal mistake. */
- if (head >= vq->vring.num)
- errx(1, "Guest says index %u is available", head);
-
/* When we start there are none of either input nor output. */
elem->out_num = elem->in_num = 0;
- i = head;
+ i = head = virtqueue_get_head(vq, vq->last_avail_idx++);
do {
struct iovec *sg;
--
1.5.4.3
--
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