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[PATCH v8 07/11] hw/core/qdev: update hotplug reset regarding resettable

From: Damien Hedde
Subject: [PATCH v8 07/11] hw/core/qdev: update hotplug reset regarding resettable
Date: Thu, 23 Jan 2020 14:28:19 +0100

This commit make use of the resettable API to reset the device being
hotplugged when it is realized. Also it ensures it is put in a reset
state coherent with the parent it is plugged into.

Note that there is a difference in the reset. Instead of resetting
only the hotplugged device, we reset also its subtree (switch to
resettable API). This is not expected to be a problem because
sub-buses are just realized too. If a hotplugged device has any
sub-buses it is logical to reset them too at this point.

The recently added should_be_hidden and PCI's partially_hotplugged
mechanisms do not interfere with realize operation:
+ In the should_be_hidden use case, device creation is
+ The partially_hotplugged mechanism prevents a device to be
unplugged and unrealized from qdev POV and unrealized.

Signed-off-by: Damien Hedde <address@hidden>
Reviewed-by: Richard Henderson <address@hidden>
Reviewed-by: Philippe Mathieu-Daudé <address@hidden>
Tested-by: Philippe Mathieu-Daudé <address@hidden>

v7 update: inline resettable_state_clear()

v6 update: clear the reset state before doing any reset. Although it
is apparently highly improbable that a device be realized again after
being unrealized. See here for a discussion about this point and the
partially_hotplugged/shoud_be_hidden cases.
 include/hw/resettable.h | 11 +++++++++++
 hw/core/qdev.c          | 15 ++++++++++++++-
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/include/hw/resettable.h b/include/hw/resettable.h
index 96073354fd..5e215d94e4 100644
--- a/include/hw/resettable.h
+++ b/include/hw/resettable.h
@@ -153,6 +153,17 @@ struct ResettableState {
     bool exit_phase_in_progress;
+ * resettable_state_clear:
+ * Clear the state. It puts the state to the initial (zeroed) state required
+ * to reuse an object. Typically used in realize step of base classes
+ * implementing the interface.
+ */
+static inline void resettable_state_clear(ResettableState *state)
+    memset(state, 0, sizeof(ResettableState));
  * resettable_reset:
  * Trigger a reset on an object @obj of type @type. @obj must implement
diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index ce23b35383..36bfcbc697 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -938,6 +938,12 @@ static void device_set_realized(Object *obj, bool value, 
Error **errp)
+        /*
+         * Clear the reset state, in case the object was previously unrealized
+         * with a dirty state.
+         */
+        resettable_state_clear(&dev->reset);
         QLIST_FOREACH(bus, &dev->child_bus, sibling) {
             object_property_set_bool(OBJECT(bus), true, "realized",
@@ -946,7 +952,14 @@ static void device_set_realized(Object *obj, bool value, 
Error **errp)
         if (dev->hotplugged) {
-            device_legacy_reset(dev);
+            /*
+             * Reset the device, as well as its subtree which, at this point,
+             * should be realized too.
+             */
+            resettable_assert_reset(OBJECT(dev), RESET_TYPE_COLD);
+            resettable_change_parent(OBJECT(dev), OBJECT(dev->parent_bus),
+                                     NULL);
+            resettable_release_reset(OBJECT(dev), RESET_TYPE_COLD);
         dev->pending_deleted_event = false;

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