qmp: Include "share" property of memory backends

Let's include the property, which can be helpful when debugging,
for example, to spot misuse of MAP_PRIVATE which can result in some ugly
corner cases (e.g., double-memory consumption on shmem).

Use the same description we also use for describing the property.

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Acked-by: Eduardo Habkost <ehabkost@redhat.com> for memory backend and machine core
Cc: Eric Blake <eblake@redhat.com>
Cc: Markus Armbruster <armbru@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20210510114328.21835-13-david@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

hw/core/machine-qmp-cmds.c

@@ -172,6 +172,7 @@ static int query_memdev(Object *obj, void *opaque)
         m->merge = object_property_get_bool(obj, "merge", &error_abort);
         m->dump = object_property_get_bool(obj, "dump", &error_abort);
         m->prealloc = object_property_get_bool(obj, "prealloc", &error_abort);
+        m->share = object_property_get_bool(obj, "share", &error_abort);
         m->policy = object_property_get_enum(obj, "policy", "HostMemPolicy",
                                              &error_abort);
         host_nodes = object_property_get_qobject(obj,

qapi/machine.json

@@ -796,6 +796,8 @@
 #
 # @prealloc: whether memory was preallocated
 #
+# @share: whether memory is private to QEMU or shared (since 6.1)
+#
 # @host-nodes: host nodes for its memory policy
 #
 # @policy: memory policy of memory backend
@@ -809,6 +811,7 @@
     'merge':      'bool',
     'dump':       'bool',
     'prealloc':   'bool',
+    'share':      'bool',
     'host-nodes': ['uint16'],
     'policy':     'HostMemPolicy' }}