virtio: introduce virtio_get_num_queues()

This patch introduces virtio_get_num_queues() which iterates the vqs
array and return the number of virtqueues used by device.
Signed-off-by: NJason Wang <jasowang@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

hw/virtio/virtio.c

@@ -746,6 +746,19 @@ int virtio_queue_get_num(VirtIODevice *vdev, int n)
     return vdev->vq[n].vring.num;
 }
 
+int virtio_get_num_queues(VirtIODevice *vdev)
+{
+    int i;
+
+    for (i = 0; i < VIRTIO_PCI_QUEUE_MAX; i++) {
+        if (!virtio_queue_get_num(vdev, i)) {
+            break;
+        }
+    }
+
+    return i;
+}
+
 int virtio_queue_get_id(VirtQueue *vq)
 {
     VirtIODevice *vdev = vq->vdev;

include/hw/virtio/virtio.h

@@ -176,6 +176,7 @@ void virtio_queue_set_addr(VirtIODevice *vdev, int n, hwaddr addr);
 hwaddr virtio_queue_get_addr(VirtIODevice *vdev, int n);
 void virtio_queue_set_num(VirtIODevice *vdev, int n, int num);
 int virtio_queue_get_num(VirtIODevice *vdev, int n);
+int virtio_get_num_queues(VirtIODevice *vdev);
 void virtio_queue_set_align(VirtIODevice *vdev, int n, int align);
 void virtio_queue_notify(VirtIODevice *vdev, int n);
 uint16_t virtio_queue_vector(VirtIODevice *vdev, int n);