virtio-blk: replace x-iothread with iothread link property

Up until now -device virtio-blk-pci,x-iothread=<id> was used to assign
an IOThread.  This was a temporary solution while we cleaned up QOM link
properties.

This patch switches over to a QOM link property since it is now possible
to restrict the setter to unrealized instances and automatically unref
the IOThread when the virtio-blk-pci device is freed.

Since the "iothread" property is a QOM property and not a qdev property,
we must alias it explicitly for virtio-blk-pci, as well as CCW and
s390-virtio.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

hw/block/virtio-blk.c

@@ -784,12 +784,21 @@ static void virtio_blk_device_unrealize(DeviceState *dev, Error **errp)
     virtio_cleanup(vdev);
 }
 
+static void virtio_blk_instance_init(Object *obj)
+{
+    VirtIOBlock *s = VIRTIO_BLK(obj);
+
+    object_property_add_link(obj, "iothread", TYPE_IOTHREAD,
+                             (Object **)&s->blk.iothread,
+                             qdev_prop_allow_set_link_before_realize,
+                             OBJ_PROP_LINK_UNREF_ON_RELEASE, NULL);
+}
+
 static Property virtio_blk_properties[] = {
     DEFINE_BLOCK_PROPERTIES(VirtIOBlock, blk.conf),
     DEFINE_BLOCK_CHS_PROPERTIES(VirtIOBlock, blk.conf),
     DEFINE_PROP_STRING("serial", VirtIOBlock, blk.serial),
     DEFINE_PROP_BIT("config-wce", VirtIOBlock, blk.config_wce, 0, true),
-    DEFINE_PROP_IOTHREAD("x-iothread", VirtIOBlock, blk.iothread),
 #ifdef __linux__
     DEFINE_PROP_BIT("scsi", VirtIOBlock, blk.scsi, 0, true),
 #endif
@@ -821,6 +830,7 @@ static const TypeInfo virtio_device_info = {
     .name = TYPE_VIRTIO_BLK,
     .parent = TYPE_VIRTIO_DEVICE,
     .instance_size = sizeof(VirtIOBlock),
+    .instance_init = virtio_blk_instance_init,
     .class_init = virtio_blk_class_init,
 };
 

hw/s390x/s390-virtio-bus.c

@@ -181,6 +181,8 @@ static void s390_virtio_blk_instance_init(Object *obj)
     object_property_add_child(obj, "virtio-backend", OBJECT(&dev->vdev), NULL);
     object_unref(OBJECT(&dev->vdev));
     qdev_alias_all_properties(DEVICE(&dev->vdev), obj);
+    object_property_add_alias(obj, "iothread", OBJECT(&dev->vdev),"iothread",
+                              &error_abort);
 }
 
 static int s390_virtio_serial_init(VirtIOS390Device *s390_dev)

hw/s390x/virtio-ccw.c

@@ -815,6 +815,8 @@ static void virtio_ccw_blk_instance_init(Object *obj)
     object_property_add_child(obj, "virtio-backend", OBJECT(&dev->vdev), NULL);
     object_unref(OBJECT(&dev->vdev));
     qdev_alias_all_properties(DEVICE(&dev->vdev), obj);
+    object_property_add_alias(obj, "iothread", OBJECT(&dev->vdev),"iothread",
+                              &error_abort);
 }
 
 static int virtio_ccw_serial_init(VirtioCcwDevice *ccw_dev)

hw/virtio/virtio-pci.c

@@ -1103,6 +1103,8 @@ static void virtio_blk_pci_instance_init(Object *obj)
     object_property_add_child(obj, "virtio-backend", OBJECT(&dev->vdev), NULL);
     object_unref(OBJECT(&dev->vdev));
     qdev_alias_all_properties(DEVICE(&dev->vdev), obj);
+    object_property_add_alias(obj, "iothread", OBJECT(&dev->vdev),"iothread",
+                              &error_abort);
 }
 
 static const TypeInfo virtio_blk_pci_info = {