[PATCH v2 2/2] qapi: Allow introspecting fix for savevm's cooperation with blockdev

[Peter Krempa <pkrempa@redhat.com>]

savevm was buggy as it considered all monitor owned block device nodes
for snapshot. With introduction of -blockdev the common usage made all
nodes including protocol nodes monitor owned and thus considered for
snapshot. This was fixed but clients need to be able to detect whether
this fix is present.

Since savevm does not have an QMP alternative add the feature for the
'human-monitor-command' backdoor which is used to call this command in
modern use.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
---
 qapi/misc.json | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/qapi/misc.json b/qapi/misc.json
index 6bd11f50e6..673445dfa9 100644
--- a/qapi/misc.json
+++ b/qapi/misc.json
@@ -1020,6 +1020,12 @@
 #
 # @cpu-index: The CPU to use for commands that require an implicit CPU
 #
+# Features:
+# @savevm-blockdev-monitor-nodes: If present, the savevm monitor command only
+#                                 snapshots monitor owned nodes if they have no
+#                                 parents. This allows to use 'savevm' with
+#                                 -blockdev. (since 4.2)
+#
 # Returns: the output of the command as a string
 #
 # Since: 0.14.0
@@ -1047,7 +1053,8 @@
 ##
 { 'command': 'human-monitor-command',
   'data': {'command-line': 'str', '*cpu-index': 'int'},
-  'returns': 'str' }
+  'returns': 'str',
+  'features' : [ { 'name': 'savevm-blockdev-monitor-nodes' } ] }

 ##
 # @change:
-- 
2.21.0