qapi/qdev.json: add DEVICE_UNPLUG_GUEST_ERROR QAPI event

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_GUEST_ERROR event that can be used by all
guest side unplug errors in the future. This event has a similar API as
the existing DEVICE_DELETED event, always providing the QOM path of the
device and dev->id if there's any.

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

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Message-Id: <20210907004755.424931-6-danielhb413@gmail.com>
[dwg: Correct missing ')' in stubs/qdev.c]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

docs/about/deprecated.rst

@@ -238,6 +238,16 @@ 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_GUEST_ERROR`` instead.
+
+
 System emulator machines
 ------------------------
 

qapi/machine.json

@@ -1305,6 +1305,10 @@
 #
 # @msg: Informative message
 #
+# Features:
+# @deprecated: This event is deprecated. Use @DEVICE_UNPLUG_GUEST_ERROR
+#              instead.
+#
 # Since: 2.4
 #
 # Example:
@@ -1317,7 +1321,8 @@
 #
 ##
 { 'event': 'MEM_UNPLUG_ERROR',
-  'data': { 'device': 'str', 'msg': 'str' } }
+  'data': { 'device': 'str', 'msg': 'str' },
+  'features': ['deprecated'] }
 
 ##
 # @SMPConfiguration:

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 a guest-side error in the hot removal process is
+#        detected, the device will not be removed and a DEVICE_UNPLUG_GUEST_ERROR
+#        event is sent.  Some errors cannot be detected.
 #
 # Since: 0.14
 #
@@ -124,3 +126,26 @@
 ##
 { 'event': 'DEVICE_DELETED',
   'data': { '*device': 'str', 'path': 'str' } }
+
+##
+# @DEVICE_UNPLUG_GUEST_ERROR:
+#
+# Emitted when a device hot unplug fails due to a guest reported error.
+#
+# @device: the device's ID if it has one
+#
+# @path: the device's QOM path
+#
+# Since: 6.2
+#
+# Example:
+#
+# <- { "event": "DEVICE_UNPLUG_GUEST_ERROR"
+#      "data": { "device": "core1",
+#                "path": "/machine/peripheral/core1" },
+#      },
+#      "timestamp": { "seconds": 1615570772, "microseconds": 202844 } }
+#
+##
+{ 'event': 'DEVICE_UNPLUG_GUEST_ERROR',
+  'data': { '*device': 'str', 'path': 'str' } }

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_guest_error(bool has_device,
+                                               const char *device,
+                                               const char *path)
+{
+    /* Nothing to do. */
+}