On Tue, 10 Feb 2026, Zhao Liu wrote:
Introduce three new flags to `ObjectPropertyFlags` to better manage
property interactions with external users (CLI, QMP, HMP):
1. OBJ_PROP_FLAG_USER_SET:
Marks a property as having been modified by an external user.
This flag is designed to be "sticky": once set, it persists even if
the property value is subsequently overwritten by internal logic.
It allows the QEMU system to distinguish user intent.
The advantage of this design is that it is not needed to manually
clear the USER_SET flag on every internal write. This simplifies the
logic and decouples flag management from the current property setting
path (object_property_set()).
This is chosen over a strict "current origin" approach (where
internal writes would clear the flag) for a practical reason: QEMU
code often modifies underlying struct fields (which are defined as
properties) directly, bypassing the property API entirely. This makes
it impossible to "accurately" track whether the *current* value truly
comes from the user. Therefore, a sticky "user touched this" flag is
the only meaningful and robust solution.
2. OBJ_PROP_FLAG_DEPRECATED:
Marks a property as deprecated.
3. OBJ_PROP_FLAG_INTERNAL:
Marks a property as internal-only, disallowing external user access.
Additionally, update object_property_set_flags() to implement the
enforcement logic. When a property is flagged with
OBJ_PROP_FLAG_USER_SET:
- If the property is also marked OBJ_PROP_FLAG_DEPRECATED, report a
warning.
- If the property is also marked OBJ_PROP_FLAG_INTERNAL, raise an error
and stop the operation.
Suggested-by: Igor Mammedov <[email protected]>
Signed-off-by: Zhao Liu <[email protected]>
---
include/qom/object.h | 24 ++++++++++++++++++++++++
qom/object.c | 15 +++++++++++++++
2 files changed, 39 insertions(+)
diff --git a/include/qom/object.h b/include/qom/object.h
index 856b12e7289c..1b77429aa28b 100644
--- a/include/qom/object.h
+++ b/include/qom/object.h
@@ -109,6 +109,30 @@ typedef enum {
* will automatically add a getter and a setter to this property.
*/
OBJ_PROP_FLAG_READWRITE = (OBJ_PROP_FLAG_READ | OBJ_PROP_FLAG_WRITE),
+ /*
+ * The property was explicitly set by an external user.
+ *
+ * This flag is set whenever the property is modified via external
interfaces
+ * (CLI, QMP, HMP). It allows internal code to distinguish whether the
+ * property has been modified by the user.
+ *
+ * Once set, this flag persists even if the property value is subsequently
+ * overwritten by internal logic. It is NOT automatically cleared and must
+ * be explicitly cleared using object_property_clear_flags().
+ */
+ OBJ_PROP_FLAG_USER_SET = BIT(2),
As this isn't strictly for user set maybe jusr call it
OBJ_PROP_FLAG_EXTERNAL? (Can be set by external management application or
global compat prop in later patches so user set is not quite right name,)
