[v5,6/6] hw/qdev: Check machine_hotplug_handler in hotplug_unplug_allowed_common

Commit Message

Philippe Mathieu-Daudé Jan. 10, 2025, 9:19 a.m. UTC

From: Akihiko Odaki <[e-mail]>

Commit 03fcbd9dc508 ("qdev: Check for the availability of a hotplug
controller before adding a device") says:

 > The qdev_unplug() function contains a g_assert(hotplug_ctrl)
 > statement, so QEMU crashes when the user tries to device_add +
 > device_del a device that does not have a corresponding hotplug
 > controller.

 > The code in qdev_device_add() already checks whether the bus has a
 > proper hotplug controller, but for devices that do not have a
 > corresponding bus, here is no appropriate check available yet. In that
 > case we should check whether the machine itself provides a suitable
 > hotplug controller and refuse to plug the device if none is available.

However, it forgot to add the corresponding check to qdev_unplug().

Check the machine hotplug handler once in the common
qdev_hotplug_unplug_allowed_common() helper so both hotplug
and hot-unplug path are covered.

Fixes: 7716b8ca74 ("qdev: HotplugHandler: Add support for unplugging BUS-less devices")
Signed-off-by: Akihiko Odaki <[e-mail]>
Signed-off-by: Philippe Mathieu-Daudé <[e-mail]>
---
 hw/core/qdev-hotplug.c |  7 +++++++
 system/qdev-monitor.c  | 14 +++-----------
 2 files changed, 10 insertions(+), 11 deletions(-)

Patch

diff --git a/hw/core/qdev-hotplug.c b/hw/core/qdev-hotplug.c
index f6422cd0e4e..e11597acd1f 100644
--- a/hw/core/qdev-hotplug.c
+++ b/hw/core/qdev-hotplug.c
@@ -48,6 +48,13 @@  static bool qdev_hotplug_unplug_allowed_common(DeviceState *dev, BusState *bus,
                        bus->name);
             return false;
         }
+    } else {
+        if (!qdev_get_machine_hotplug_handler(dev)) {
+            /* No bus, no machine hotplug handler --> device is not hotpluggable */
+            error_setg(errp, "Device '%s' can not be hotplugged on this machine",
+                       object_get_typename(OBJECT(dev)));
+            return false;
+        }
     }
 
     return true;
diff --git a/system/qdev-monitor.c b/system/qdev-monitor.c
index 99b638c0aca..30f28eb8e4a 100644
--- a/system/qdev-monitor.c
+++ b/system/qdev-monitor.c
@@ -683,17 +683,9 @@  DeviceState *qdev_device_add_from_qdict(const QDict *opts,
     dev = qdev_new(driver);
 
     /* Check whether the hotplug is allowed by the machine */
-    if (phase_check(PHASE_MACHINE_READY)) {
-        if (!qdev_hotplug_allowed(dev, bus, errp)) {
-            goto err_del_dev;
-        }
-
-        if (!bus && !qdev_get_machine_hotplug_handler(dev)) {
-            /* No bus, no machine hotplug handler --> device is not hotpluggable */
-            error_setg(errp, "Device '%s' can not be hotplugged on this machine",
-                       driver);
-            goto err_del_dev;
-        }
+    if (phase_check(PHASE_MACHINE_READY) &&
+        !qdev_hotplug_allowed(dev, bus, errp)) {
+        goto err_del_dev;
     }
 
     /*