@@ -233,21 +233,29 @@ static void vhost_svq_kick(VhostShadowVirtqueue *svq)
* Add an element to a SVQ.
*
* The caller must check that there is enough slots for the new element. It
- * takes ownership of the element: In case of failure, it is free and the SVQ
- * is considered broken.
+ * takes ownership of the element: In case of failure not ENOSPC, it is free.
+ *
+ * Return -EINVAL if element is invalid, -ENOSPC if dev queue is full
*/
-static bool vhost_svq_add(VhostShadowVirtqueue *svq, VirtQueueElement *elem)
+static int vhost_svq_add(VhostShadowVirtqueue *svq, VirtQueueElement *elem)
{
unsigned qemu_head;
- bool ok = vhost_svq_add_split(svq, elem, &qemu_head);
+ unsigned ndescs = elem->in_num + elem->out_num;
+ bool ok;
+
+ if (unlikely(ndescs > vhost_svq_available_slots(svq))) {
+ return -ENOSPC;
+ }
+
+ ok = vhost_svq_add_split(svq, elem, &qemu_head);
if (unlikely(!ok)) {
g_free(elem);
- return false;
+ return -EINVAL;
}
svq->ring_id_maps[qemu_head] = elem;
vhost_svq_kick(svq);
- return true;
+ return 0;
}
/**
@@ -274,7 +282,7 @@ static void vhost_handle_guest_kick(VhostShadowVirtqueue *svq)
while (true) {
VirtQueueElement *elem;
- bool ok;
+ int r;
if (svq->next_guest_avail_elem) {
elem = g_steal_pointer(&svq->next_guest_avail_elem);
@@ -286,25 +294,24 @@ static void vhost_handle_guest_kick(VhostShadowVirtqueue *svq)
break;
}
- if (elem->out_num + elem->in_num > vhost_svq_available_slots(svq)) {
- /*
- * This condition is possible since a contiguous buffer in GPA
- * does not imply a contiguous buffer in qemu's VA
- * scatter-gather segments. If that happens, the buffer exposed
- * to the device needs to be a chain of descriptors at this
- * moment.
- *
- * SVQ cannot hold more available buffers if we are here:
- * queue the current guest descriptor and ignore further kicks
- * until some elements are used.
- */
- svq->next_guest_avail_elem = elem;
- return;
- }
-
- ok = vhost_svq_add(svq, elem);
- if (unlikely(!ok)) {
- /* VQ is broken, just return and ignore any other kicks */
+ r = vhost_svq_add(svq, elem);
+ if (unlikely(r != 0)) {
+ if (r == -ENOSPC) {
+ /*
+ * This condition is possible since a contiguous buffer in
+ * GPA does not imply a contiguous buffer in qemu's VA
+ * scatter-gather segments. If that happens, the buffer
+ * exposed to the device needs to be a chain of descriptors
+ * at this moment.
+ *
+ * SVQ cannot hold more available buffers if we are here:
+ * queue the current guest descriptor and ignore kicks
+ * until some elements are used.
+ */
+ svq->next_guest_avail_elem = elem;
+ }
+
+ /* VQ is full or broken, just return and ignore kicks */
return;
}
}