qemu-config: load modules when instantiating option groups

Right now the SPICE module is special cased to be loaded when processing
of the -spice command line option.  However, the spice option group
can also be brought in via -readconfig, in which case the module is
not loaded.

Add a generic hook to load modules that provide a QemuOpts group,
and use it for the "spice" and "iscsi" groups.

Fixes: #194
Fixes: https://bugs.launchpad.net/qemu/+bug/1910696
Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/qemu/config-file.h

@@ -1,7 +1,7 @@
 #ifndef QEMU_CONFIG_FILE_H
 #define QEMU_CONFIG_FILE_H
 
-
+void qemu_load_module_for_opts(const char *group);
 QemuOptsList *qemu_find_opts(const char *group);
 QemuOptsList *qemu_find_opts_err(const char *group, Error **errp);
 QemuOpts *qemu_find_opts_singleton(const char *group);

softmmu/vl.c

@@ -2627,6 +2627,23 @@ void qmp_x_exit_preconfig(Error **errp)
     }
 }
 
+#ifdef CONFIG_MODULES
+void qemu_load_module_for_opts(const char *group)
+{
+    static bool spice_tried;
+    if (g_str_equal(group, "spice") && !spice_tried) {
+        ui_module_load_one("spice-core");
+        spice_tried = true;
+    }
+
+    static bool iscsi_tried;
+    if (g_str_equal(group, "iscsi") && !iscsi_tried) {
+        block_module_load_one("iscsi");
+        iscsi_tried = true;
+    }
+}
+#endif
+
 void qemu_init(int argc, char **argv, char **envp)
 {
     QemuOpts *opts;
@@ -3386,10 +3403,6 @@ void qemu_init(int argc, char **argv, char **envp)
                 break;
             case QEMU_OPTION_spice:
                 olist = qemu_find_opts_err("spice", NULL);
-                if (!olist) {
-                    ui_module_load_one("spice-core");
-                    olist = qemu_find_opts("spice");
-                }
                 if (!olist) {
                     error_report("spice support is disabled");
                     exit(1);

stubs/meson.build

@@ -22,6 +22,7 @@ stub_ss.add(files('isa-bus.c'))
 stub_ss.add(files('is-daemonized.c'))
 stub_ss.add(when: 'CONFIG_LINUX_AIO', if_true: files('linux-aio.c'))
 stub_ss.add(files('migr-blocker.c'))
+stub_ss.add(files('module-opts.c'))
 stub_ss.add(files('monitor.c'))
 stub_ss.add(files('monitor-core.c'))
 stub_ss.add(files('pci-bus.c'))

stubs/module-opts.c

@@ -0,0 +1,6 @@
+#include "qemu/osdep.h"
+#include "qemu/config-file.h"
+
+void qemu_load_module_for_opts(const char *group)
+{
+}

util/qemu-config.c

@@ -16,6 +16,7 @@ static QemuOptsList *find_list(QemuOptsList **lists, const char *group,
 {
     int i;
 
+    qemu_load_module_for_opts(group);
     for (i = 0; lists[i] != NULL; i++) {
         if (strcmp(lists[i]->name, group) == 0)
             break;