vl: Create (most) objects before creating chardev backends

Some types of object must be created before chardevs, other types of
object must be created after chardevs. As such there is no option but
to create objects in two phases.

This takes the decision to create as many object types as possible
right away before anyother backends are created, and only delay
creation of those few which have an explicit dependency on the
chardevs. Hopefully the set which need delaying will remain small
over time.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>

vl.c

@@ -2671,6 +2671,33 @@ static int machine_set_property(void *opaque,
     return 0;
 }
 
+
+/*
+ * Initial object creation happens before all other
+ * QEMU data types are created. The majority of objects
+ * can be created at this point. The rng-egd object
+ * cannot be created here, as it depends on the chardev
+ * already existing.
+ */
+static bool object_create_initial(const char *type)
+{
+    if (g_str_equal(type, "rng-egd")) {
+        return false;
+    }
+    return true;
+}
+
+
+/*
+ * The remainder of object creation happens after the
+ * creation of chardev, fsdev and device data types.
+ */
+static bool object_create_delayed(const char *type)
+{
+    return !object_create_initial(type);
+}
+
+
 static int object_create(void *opaque, QemuOpts *opts, Error **errp)
 {
     Error *err = NULL;
@@ -2679,6 +2706,7 @@ static int object_create(void *opaque, QemuOpts *opts, Error **errp)
     void *dummy = NULL;
     OptsVisitor *ov;
     QDict *pdict;
+    bool (*type_predicate)(const char *) = opaque;
 
     ov = opts_visitor_new(opts);
     pdict = qemu_opts_to_qdict(opts, NULL);
@@ -2693,6 +2721,9 @@ static int object_create(void *opaque, QemuOpts *opts, Error **errp)
     if (err) {
         goto out;
     }
+    if (!type_predicate(type)) {
+        goto out;
+    }
 
     qdict_del(pdict, "id");
     visit_type_str(opts_get_visitor(ov), &id, "id", &err);
@@ -4114,6 +4145,12 @@ int main(int argc, char **argv, char **envp)
 
     socket_init();
 
+    if (qemu_opts_foreach(qemu_find_opts("object"),
+                          object_create,
+                          object_create_initial, NULL)) {
+        exit(1);
+    }
+
     if (qemu_opts_foreach(qemu_find_opts("chardev"),
                           chardev_init_func, NULL, NULL)) {
         exit(1);
@@ -4137,7 +4174,8 @@ int main(int argc, char **argv, char **envp)
     }
 
     if (qemu_opts_foreach(qemu_find_opts("object"),
-                          object_create, NULL, NULL)) {
+                          object_create,
+                          object_create_delayed, NULL)) {
         exit(1);
     }