[Qemu-devel] [PATCH v4 3/9] dataplane: bail out on unsupported transport

[Stefan Hajnoczi <stefanha@redhat.com>]

From: Cornelia Huck <cornelia.huck@de.ibm.com>

If the virtio transport does not support notifiers (like s390-virtio),
we can't use dataplane. Bail out early and let the user know what is
wrong.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 hw/block/dataplane/virtio-blk.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index c10b7b7..92ebb44 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -331,6 +331,8 @@ void virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *blk,
 {
     VirtIOBlockDataPlane *s;
     Error *local_err = NULL;
+    BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
+    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
 
     *dataplane = NULL;
 
@@ -338,6 +340,14 @@ void virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *blk,
         return;
     }
 
+    /* Don't try if transport does not support notifiers. */
+    if (!k->set_guest_notifiers || !k->set_host_notifier) {
+        error_setg(errp,
+                   "device is incompatible with x-data-plane "
+                   "(transport does not support notifiers)");
+        return;
+    }
+
     /* If dataplane is (re-)enabled while the guest is running there could be
      * block jobs that can conflict.
      */
-- 
1.9.3