[PATCH for-6.2 v6 5/7] qapi/qdev.json: add DEVICE_UNPLUG_ERROR QAPI event

[Daniel Henrique Barboza <danielhb413@gmail.com>]

At this moment we only provide one event to report a hotunplug error,
MEM_UNPLUG_ERROR. As of Linux kernel 5.12 and QEMU 6.0.0, the pseries
machine is now able to report unplug errors for other device types, such
as CPUs.

Instead of creating a (device_type)_UNPLUG_ERROR for each new device,
create a generic DEVICE_UNPLUG_ERROR event that can be used by all
unplug errors in the future. This event has a similar API as the
existing DEVICE_DELETED event, with an extra optional 'msg' parameter
that can be used to explain the reason for the error.

With this new generic event, MEM_UNPLUG_ERROR is now marked as deprecated.

Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
---
 docs/about/deprecated.rst | 10 ++++++++++
 qapi/machine.json         |  6 +++++-
 qapi/qdev.json            | 30 +++++++++++++++++++++++++++++-
 stubs/qdev.c              |  7 +++++++
 4 files changed, 51 insertions(+), 2 deletions(-)

diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst
index 6d438f1c8d..c0c3431ada 100644
--- a/docs/about/deprecated.rst
+++ b/docs/about/deprecated.rst
@@ -204,6 +204,16 @@ The ``I7200`` guest CPU relies on the nanoMIPS ISA, which is deprecated
 (the ISA has never been upstreamed to a compiler toolchain). Therefore
 this CPU is also deprecated.
 
+
+QEMU API (QAPI) events
+----------------------
+
+``MEM_UNPLUG_ERROR`` (since 6.2)
+''''''''''''''''''''''''''''''''''''''''''''''''''''''''
+
+Use the more generic event ``DEVICE_UNPLUG_ERROR`` instead.
+
+
 System emulator machines
 ------------------------
 
diff --git a/qapi/machine.json b/qapi/machine.json
index c3210ee1fb..a595c753d2 100644
--- a/qapi/machine.json
+++ b/qapi/machine.json
@@ -1271,6 +1271,9 @@
 #
 # @msg: Informative message
 #
+# Features:
+# @deprecated: This event is deprecated. Use @DEVICE_UNPLUG_ERROR instead.
+#
 # Since: 2.4
 #
 # Example:
@@ -1283,7 +1286,8 @@
 #
 ##
 { 'event': 'MEM_UNPLUG_ERROR',
-  'data': { 'device': 'str', 'msg': 'str' } }
+  'data': { 'device': 'str', 'msg': 'str' },
+  'features': ['deprecated'] }
 
 ##
 # @SMPConfiguration:
diff --git a/qapi/qdev.json b/qapi/qdev.json
index d1d3681a50..52c36c7b9c 100644
--- a/qapi/qdev.json
+++ b/qapi/qdev.json
@@ -84,7 +84,9 @@
 #        This command merely requests that the guest begin the hot removal
 #        process.  Completion of the device removal process is signaled with a
 #        DEVICE_DELETED event. Guest reset will automatically complete removal
-#        for all devices.
+#        for all devices.  If an error in the hot removal process is detected,
+#        the device will not be removed and a DEVICE_UNPLUG_ERROR event is
+#        sent.  Some errors cannot be detected.
 #
 # Since: 0.14
 #
@@ -124,3 +126,29 @@
 ##
 { 'event': 'DEVICE_DELETED',
   'data': { '*device': 'str', 'path': 'str' } }
+
+##
+# @DEVICE_UNPLUG_ERROR:
+#
+# Emitted when a device hot unplug error occurs.
+#
+# @device: the device's ID if it has one
+#
+# @path: the device's path within the object model
+#
+# @msg: optional informative message
+#
+# Since: 6.2
+#
+# Example:
+#
+# <- { "event": "DEVICE_UNPLUG_ERROR"
+#      "data": { "device": "core1",
+#                "msg": "Device hotunplug rejected by the guest for device core1",
+#                "path": "/machine/peripheral/core1" },
+#      },
+#      "timestamp": { "seconds": 1615570772, "microseconds": 202844 } }
+#
+##
+{ 'event': 'DEVICE_UNPLUG_ERROR',
+  'data': { '*device': 'str', 'path': 'str' , '*msg': 'str' } }
diff --git a/stubs/qdev.c b/stubs/qdev.c
index 92e6143134..ffa8f7b59e 100644
--- a/stubs/qdev.c
+++ b/stubs/qdev.c
@@ -21,3 +21,10 @@ void qapi_event_send_device_deleted(bool has_device,
 {
     /* Nothing to do. */
 }
+
+void qapi_event_send_device_unplug_error(bool has_device, const char *device,
+                                         const char *path,
+                                         bool has_msg, const char *msg)
+{
+    /* Nothing to do. */
+}
-- 
2.31.1