virtio: add a queue_index to VirtQueue

Add a queue_index to VirtQueue and a helper to fetch it, this could be used by
multiqueue supported device.
Signed-off-by: NJason Wang <jasowang@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

hw/virtio.c

@@ -73,6 +73,8 @@ struct VirtQueue
     /* Notification enabled? */
     bool notification;
 
+    uint16_t queue_index;
+
     int inuse;
 
     uint16_t vector;
@@ -931,6 +933,7 @@ void virtio_init(VirtIODevice *vdev, const char *name,
     for (i = 0; i < VIRTIO_PCI_QUEUE_MAX; i++) {
         vdev->vq[i].vector = VIRTIO_NO_VECTOR;
         vdev->vq[i].vdev = vdev;
+        vdev->vq[i].queue_index = i;
     }
 
     vdev->name = name;
@@ -1018,6 +1021,11 @@ VirtQueue *virtio_get_queue(VirtIODevice *vdev, int n)
     return vdev->vq + n;
 }
 
+uint16_t virtio_get_queue_index(VirtQueue *vq)
+{
+    return vq->queue_index;
+}
+
 static void virtio_queue_guest_notifier_read(EventNotifier *n)
 {
     VirtQueue *vq = container_of(n, VirtQueue, guest_notifier);

hw/virtio.h

@@ -280,6 +280,7 @@ hwaddr virtio_queue_get_ring_size(VirtIODevice *vdev, int n);
 uint16_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n);
 void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint16_t idx);
 VirtQueue *virtio_get_queue(VirtIODevice *vdev, int n);
+uint16_t virtio_get_queue_index(VirtQueue *vq);
 int virtio_queue_get_id(VirtQueue *vq);
 EventNotifier *virtio_queue_get_guest_notifier(VirtQueue *vq);
 void virtio_queue_set_guest_notifier_fd_handler(VirtQueue *vq, bool assign,