spice: delay starting until display are initialized

QEMU used to run qemu_spice.display_init() before vm_start(), and
QXL/display interfaces where started then. Now, vm_start() happens
before QXL/display interfaces are added and Spice server doesn't
automatically start them in this case (fixed in spice git)

Fixes Spice regression introduced after 5.2, with refactoring commits
b4e1a34211 ("vl: remove separate preconfig main_loop") and
facf7c60ee ("vl: initialize displays _after_ exiting preconfiguration"),
probably others.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20210129152351.161971-1-marcandre.lureau@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

include/ui/qemu-spice.h

@@ -28,6 +28,7 @@
 
 void qemu_spice_input_init(void);
 void qemu_spice_display_init(void);
+void qemu_spice_display_init_done(void);
 bool qemu_spice_have_display_interface(QemuConsole *con);
 int qemu_spice_add_display_interface(QXLInstance *qxlin, QemuConsole *con);
 int qemu_spice_migrate_info(const char *hostname, int port, int tls_port,

ui/spice-core.c

@@ -625,6 +625,14 @@ static void vm_change_state_handler(void *opaque, int running,
     }
 }
 
+void qemu_spice_display_init_done(void)
+{
+    if (runstate_is_running()) {
+        qemu_spice_display_start();
+    }
+    qemu_add_vm_change_state_handler(vm_change_state_handler, NULL);
+}
+
 static void qemu_spice_init(void)
 {
     QemuOpts *opts = QTAILQ_FIRST(&qemu_spice_opts.head);
@@ -796,7 +804,6 @@ static void qemu_spice_init(void)
 
     qemu_spice_input_init();
 
-    qemu_add_vm_change_state_handler(vm_change_state_handler, NULL);
     qemu_spice_display_stop();
 
     g_free(x509_key_file);

ui/spice-display.c

@@ -1188,4 +1188,6 @@ void qemu_spice_display_init(void)
         }
         qemu_spice_display_init_one(con);
     }
+
+    qemu_spice_display_init_done();
 }