softmmu: fix device deletion events with -device JSON syntax

The -device JSON syntax impl leaks a reference on the created
DeviceState instance. As a result when you hot-unplug the
device, the device_finalize method won't be called and thus
it will fail to emit the required DEVICE_DELETED event.

A 'json-cli' feature was previously added against the
'device_add' QMP command QAPI schema to indicated to mgmt
apps that -device supported JSON syntax. Given the hotplug
bug that feature flag is not usable for its purpose, so
we add a new 'json-cli-hotplug' feature to indicate the
-device supports JSON without breaking hotplug.

Fixes: 5dacda5167560b3af8eadbce5814f60ba44b467e
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/802
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20220105123847.4047954-2-berrange@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Tested-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/softmmu/vl.c b/softmmu/vl.c
index 207a9eb..5e1b35b 100644
--- a/softmmu/vl.c
+++ b/softmmu/vl.c
@@ -2684,6 +2684,7 @@ static void qemu_create_cli_devices(void)
     qemu_opts_foreach(qemu_find_opts("device"),
                       device_init_func, NULL, &error_fatal);
     QTAILQ_FOREACH(opt, &device_opts, next) {
+        DeviceState *dev;
         loc_push_restore(&opt->loc);
         /*
          * TODO Eventually we should call qmp_device_add() here to make sure it
@@ -2692,7 +2693,8 @@ static void qemu_create_cli_devices(void)
          * from the start, so call qdev_device_add_from_qdict() directly for
          * now.
          */
-        qdev_device_add_from_qdict(opt->opts, true, &error_fatal);
+        dev = qdev_device_add_from_qdict(opt->opts, true, &error_fatal);
+        object_unref(OBJECT(dev));
         loc_pop(&opt->loc);
     }
     rom_reset_order_override();