vfio/ccw: Make vfio cdev pre-openable by passing a file handle

This gives management tools like libvirt a chance to open the vfio
cdev with privilege and pass FD to qemu. This way qemu never needs
to have privilege to open a VFIO or iommu cdev node.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>

hw/vfio/ccw.c

@@ -590,11 +590,12 @@ static void vfio_ccw_realize(DeviceState *dev, Error **errp)
         }
     }
 
+    if (vfio_device_get_name(vbasedev, errp) < 0) {
+        return;
+    }
+
     vbasedev->ops = &vfio_ccw_ops;
     vbasedev->type = VFIO_DEVICE_TYPE_CCW;
-    vbasedev->name = g_strdup_printf("%x.%x.%04x", vcdev->cdev.hostid.cssid,
-                           vcdev->cdev.hostid.ssid,
-                           vcdev->cdev.hostid.devid);
     vbasedev->dev = dev;
 
     /*
@@ -691,12 +692,29 @@ static const VMStateDescription vfio_ccw_vmstate = {
     .unmigratable = 1,
 };
 
+static void vfio_ccw_instance_init(Object *obj)
+{
+    VFIOCCWDevice *vcdev = VFIO_CCW(obj);
+
+    vcdev->vdev.fd = -1;
+}
+
+#ifdef CONFIG_IOMMUFD
+static void vfio_ccw_set_fd(Object *obj, const char *str, Error **errp)
+{
+    vfio_device_set_fd(&VFIO_CCW(obj)->vdev, str, errp);
+}
+#endif
+
 static void vfio_ccw_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
     S390CCWDeviceClass *cdc = S390_CCW_DEVICE_CLASS(klass);
 
     device_class_set_props(dc, vfio_ccw_properties);
+#ifdef CONFIG_IOMMUFD
+    object_class_property_add_str(klass, "fd", NULL, vfio_ccw_set_fd);
+#endif
     dc->vmsd = &vfio_ccw_vmstate;
     dc->desc = "VFIO-based subchannel assignment";
     set_bit(DEVICE_CATEGORY_MISC, dc->categories);
@@ -714,6 +732,7 @@ static const TypeInfo vfio_ccw_info = {
     .name = TYPE_VFIO_CCW,
     .parent = TYPE_S390_CCW,
     .instance_size = sizeof(VFIOCCWDevice),
+    .instance_init = vfio_ccw_instance_init,
     .class_init = vfio_ccw_class_init,
 };