monitor: add object-add (QMP) and object_add (HMP) command

Add two commands that are the monitor counterparts of -object.  The commands
have the same Visitor-based implementation, but use different kinds of
visitors so that the HMP command has a DWIM string-based syntax, while
the QMP variant accepts a stricter JSON-based properties dictionary.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NIgor Mammedov <imammedo@redhat.com>
Tested-by: NIgor Mammedov <imammedo@redhat.com>
Signed-off-by: NLuiz Capitulino <lcapitulino@redhat.com>

hmp-commands.hx

@@ -1241,6 +1241,20 @@ STEXI
 @item netdev_del
 @findex netdev_del
 Remove host network device.
+ETEXI
+
+    {
+        .name       = "object_add",
+        .args_type  = "object:O",
+        .params     = "[qom-type=]type,id=str[,prop=value][,...]",
+        .help       = "create QOM object",
+        .mhandler.cmd = hmp_object_add,
+    },
+
+STEXI
+@item object_add
+@findex object_add
+Create QOM object.
 ETEXI
 
     {

hmp.c

@@ -21,6 +21,7 @@
 #include "qmp-commands.h"
 #include "qemu/sockets.h"
 #include "monitor/monitor.h"
+#include "qapi/opts-visitor.h"
 #include "ui/console.h"
 #include "block/qapi.h"
 #include "qemu-io.h"
@@ -1354,6 +1355,63 @@ void hmp_netdev_del(Monitor *mon, const QDict *qdict)
     hmp_handle_error(mon, &err);
 }
 
+void hmp_object_add(Monitor *mon, const QDict *qdict)
+{
+    Error *err = NULL;
+    QemuOpts *opts;
+    char *type = NULL;
+    char *id = NULL;
+    void *dummy = NULL;
+    OptsVisitor *ov;
+    QDict *pdict;
+
+    opts = qemu_opts_from_qdict(qemu_find_opts("object"), qdict, &err);
+    if (err) {
+        goto out;
+    }
+
+    ov = opts_visitor_new(opts);
+    pdict = qdict_clone_shallow(qdict);
+
+    visit_start_struct(opts_get_visitor(ov), &dummy, NULL, NULL, 0, &err);
+    if (err) {
+        goto out_clean;
+    }
+
+    qdict_del(pdict, "qom-type");
+    visit_type_str(opts_get_visitor(ov), &type, "qom-type", &err);
+    if (err) {
+        goto out_clean;
+    }
+
+    qdict_del(pdict, "id");
+    visit_type_str(opts_get_visitor(ov), &id, "id", &err);
+    if (err) {
+        goto out_clean;
+    }
+
+    object_add(type, id, pdict, opts_get_visitor(ov), &err);
+    if (err) {
+        goto out_clean;
+    }
+    visit_end_struct(opts_get_visitor(ov), &err);
+    if (err) {
+        qmp_object_del(id, NULL);
+    }
+
+out_clean:
+    opts_visitor_cleanup(ov);
+
+    QDECREF(pdict);
+    qemu_opts_del(opts);
+    g_free(id);
+    g_free(type);
+    g_free(dummy);
+
+out:
+    hmp_handle_error(mon, &err);
+}
+
 void hmp_getfd(Monitor *mon, const QDict *qdict)
 {
     const char *fdname = qdict_get_str(qdict, "fdname");

hmp.h

@@ -90,6 +90,7 @@ void hmp_chardev_add(Monitor *mon, const QDict *qdict);
 void hmp_chardev_remove(Monitor *mon, const QDict *qdict);
 void hmp_qemu_io(Monitor *mon, const QDict *qdict);
 void hmp_cpu_add(Monitor *mon, const QDict *qdict);
+void hmp_object_add(Monitor *mon, const QDict *qdict);
 void hmp_object_del(Monitor *mon, const QDict *qdict);
 
 #endif

include/monitor/monitor.h

@@ -93,6 +93,9 @@ int monitor_read_password(Monitor *mon, ReadLineFunc *readline_func,
 int qmp_qom_set(Monitor *mon, const QDict *qdict, QObject **ret);
 
 int qmp_qom_get(Monitor *mon, const QDict *qdict, QObject **ret);
+int qmp_object_add(Monitor *mon, const QDict *qdict, QObject **ret);
+void object_add(const char *type, const char *id, const QDict *qdict,
+                Visitor *v, Error **errp);
 
 AddfdInfo *monitor_fdset_add_fd(int fd, bool has_fdset_id, int64_t fdset_id,
                                 bool has_opaque, const char *opaque,

include/qapi/visitor.h

@@ -13,6 +13,7 @@
 #ifndef QAPI_VISITOR_CORE_H
 #define QAPI_VISITOR_CORE_H
 
+#include "qemu/typedefs.h"
 #include "qapi/qmp/qobject.h"
 #include "qapi/error.h"
 #include <stdlib.h>
@@ -26,8 +27,6 @@ typedef struct GenericList
     struct GenericList *next;
 } GenericList;
 
-typedef struct Visitor Visitor;
-
 void visit_start_handle(Visitor *v, void **obj, const char *kind,
                         const char *name, Error **errp);
 void visit_end_handle(Visitor *v, Error **errp);

include/qemu/typedefs.h

@@ -10,6 +10,8 @@ typedef struct QEMUBH QEMUBH;
 
 typedef struct AioContext AioContext;
 
+typedef struct Visitor Visitor;
+
 struct Monitor;
 typedef struct Monitor Monitor;
 typedef struct MigrationParams MigrationParams;

qapi-schema.json

@@ -2758,6 +2758,26 @@
 ##
 { 'command': 'netdev_del', 'data': {'id': 'str'} }
 
+##
+# @object-add:
+#
+# Create a QOM object.
+#
+# @qom-type: the class name for the object to be created
+#
+# @id: the name of the new object
+#
+# @props: #optional a dictionary of properties to be passed to the backend
+#
+# Returns: Nothing on success
+#          Error if @qom-type is not a valid class name
+#
+# Since: 2.0
+##
+{ 'command': 'object-add',
+  'data': {'qom-type': 'str', 'id': 'str', '*props': 'dict'},
+  'gen': 'no' }
+
 ##
 # @object-del:
 #

qmp-commands.hx

@@ -876,6 +876,32 @@ Example:
 <- { "return": {} }
 
 
+EQMP
+
+    {
+        .name       = "object-add",
+        .args_type  = "qom-type:s,id:s,props:q?",
+        .mhandler.cmd_new = qmp_object_add,
+    },
+
+SQMP
+object-add
+----------
+
+Create QOM object.
+
+Arguments:
+
+- "qom-type": the object's QOM type, i.e. the class name (json-string)
+- "id": the object's ID, must be unique (json-string)
+- "props": a dictionary of object property values (optional, json-dict)
+
+Example:
+
+-> { "execute": "object-add", "arguments": { "qom-type": "rng-random", "id": "rng1",
+     "props": { "filename": "/dev/hwrng" } } }
+<- { "return": {} }
+
 EQMP
 
     {

qmp.c

@@ -24,6 +24,8 @@
 #include "hw/qdev.h"
 #include "sysemu/blockdev.h"
 #include "qom/qom-qobject.h"
+#include "qapi/qmp/qobject.h"
+#include "qapi/qmp-input-visitor.h"
 #include "hw/boards.h"
 
 NameInfo *qmp_query_name(Error **errp)
@@ -530,6 +532,66 @@ void qmp_add_client(const char *protocol, const char *fdname,
     close(fd);
 }
 
+void object_add(const char *type, const char *id, const QDict *qdict,
+                Visitor *v, Error **errp)
+{
+    Object *obj;
+    const QDictEntry *e;
+    Error *local_err = NULL;
+
+    if (!object_class_by_name(type)) {
+        error_setg(errp, "invalid class name");
+        return;
+    }
+
+    obj = object_new(type);
+    if (qdict) {
+        for (e = qdict_first(qdict); e; e = qdict_next(qdict, e)) {
+            object_property_set(obj, v, e->key, &local_err);
+            if (local_err) {
+                error_propagate(errp, local_err);
+                object_unref(obj);
+                return;
+            }
+        }
+    }
+
+    object_property_add_child(container_get(object_get_root(), "/objects"),
+                              id, obj, errp);
+    object_unref(obj);
+}
+
+int qmp_object_add(Monitor *mon, const QDict *qdict, QObject **ret)
+{
+    const char *type = qdict_get_str(qdict, "qom-type");
+    const char *id = qdict_get_str(qdict, "id");
+    QObject *props = qdict_get(qdict, "props");
+    const QDict *pdict = NULL;
+    Error *local_err = NULL;
+    QmpInputVisitor *qiv;
+
+    if (props) {
+        pdict = qobject_to_qdict(props);
+        if (!pdict) {
+            error_set(&local_err, QERR_INVALID_PARAMETER_TYPE, "props", "dict");
+            goto out;
+        }
+    }
+
+    qiv = qmp_input_visitor_new(props);
+    object_add(type, id, pdict, qmp_input_get_visitor(qiv), &local_err);
+    qmp_input_visitor_cleanup(qiv);
+
+out:
+    if (local_err) {
+        qerror_report_err(local_err);
+        error_free(local_err);
+        return -1;
+    }
+
+    return 0;
+}
+
 void qmp_object_del(const char *id, Error **errp)
 {
     Object *container;