ui/vnc: clean up VNC displays on exit

Previously, VNC displays were never torn down on QEMU exit, leaking
resources and leaving connected clients with unclean disconnects.

Add vnc_cleanup() to free all VNC displays during qemu_cleanup().
Make vnc_display_close() initiate disconnection of active clients,
and have vnc_display_free() drain the main loop until all clients
have completed their teardown, instead of asserting the client list
is empty.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>

include/ui/console.h

@@ -445,6 +445,7 @@ void vnc_parse(const char *str);
 int vnc_init_func(void *opaque, QemuOpts *opts, Error **errp);
 bool vnc_display_reload_certs(const char *id,  Error **errp);
 bool vnc_display_update(DisplayUpdateOptionsVNC *arg, Error **errp);
+void vnc_cleanup(void);
 
 /* input.c */
 int index_from_key(const char *key, size_t key_length);

system/runstate.c

@@ -61,6 +61,8 @@
 #include "system/confidential-guest-support.h"
 #include "system/system.h"
 #include "system/tpm.h"
+#include "ui/console.h"
+
 #include "trace.h"
 
 static NotifierList exit_notifiers =
@@ -1044,5 +1046,8 @@ void qemu_cleanup(int status)
     monitor_cleanup();
     qemu_chr_cleanup();
     user_creatable_cleanup();
+#ifdef CONFIG_VNC
+    vnc_cleanup();
+#endif
     /* TODO: unref root container, check all devices are ok */
 }

ui/vnc.c

@@ -3473,8 +3473,13 @@ VncDisplay *vnc_display_new(const char *id, Error **errp)
 
 static void vnc_display_close(VncDisplay *vd)
 {
+    VncState *vs;
+
     assert(vd);
 
+    QTAILQ_FOREACH(vs, &vd->clients, next) {
+        vnc_disconnect_start(vs);
+    }
     if (vd->listener) {
         qio_net_listener_disconnect(vd->listener);
         object_unref(OBJECT(vd->listener));
@@ -3515,10 +3520,12 @@ void vnc_display_free(VncDisplay *vd)
         return;
     }
 
-    assert(QTAILQ_EMPTY(&vd->clients));
+    vnc_display_close(vd);
+    while (!QTAILQ_EMPTY(&vd->clients)) {
+        main_loop_wait(false);
+    }
 
     vnc_stop_worker_thread(vd);
-    vnc_display_close(vd);
     unregister_displaychangelistener(&vd->dcl);
     qkbd_state_free(vd->kbd);
     qemu_del_vm_change_state_handler(vd->vmstate_handler_entry);
@@ -4348,6 +4355,15 @@ int vnc_init_func(void *opaque, QemuOpts *opts, Error **errp)
     return vnc_display_new(id, errp) != NULL ? 0 : -1;
 }
 
+void vnc_cleanup(void)
+{
+    VncDisplay *vd, *vd_next;
+
+    QTAILQ_FOREACH_SAFE(vd, &vnc_displays, next, vd_next) {
+        vnc_display_free(vd);
+    }
+}
+
 static void vnc_register_config(void)
 {
     qemu_add_opts(&qemu_vnc_opts);