virtio: add virtio_queue_get_id

Serializing virtio-scsi requests needs a simple way to get from a
VirtQueue to the number of the queue.  The virtio_queue_get_id
provides this.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

2 files changed, 8 insertions, 0 deletions

diff --git a/hw/virtio.c b/hw/virtio.c
index 064aecf..314abf8 100644
--- a/hw/virtio.c
+++ b/hw/virtio.c
@@ -624,6 +624,13 @@ int virtio_queue_get_num(VirtIODevice *vdev, int n)
     return vdev->vq[n].vring.num;
 }
 
+int virtio_queue_get_id(VirtQueue *vq)
+{
+    VirtIODevice *vdev = vq->vdev;
+    assert(vq >= &vdev->vq[0] && vq < &vdev->vq[VIRTIO_PCI_QUEUE_MAX]);
+    return vq - &vdev->vq[0];
+}
+
 void virtio_queue_notify_vq(VirtQueue *vq)
 {
     if (vq->vring.desc) {
diff --git a/hw/virtio.h b/hw/virtio.h
index 400c092..0aef7d1 100644
--- a/hw/virtio.h
+++ b/hw/virtio.h
@@ -229,6 +229,7 @@ target_phys_addr_t 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);
+int virtio_queue_get_id(VirtQueue *vq);
 EventNotifier *virtio_queue_get_guest_notifier(VirtQueue *vq);
 EventNotifier *virtio_queue_get_host_notifier(VirtQueue *vq);
 void virtio_queue_notify_vq(VirtQueue *vq);