qxl: fix modular builds with dtrace

Checking the enable/disable state of tracepoints via
trace_event_get_state_backends() does not work for modules.

qxl checks the state for a small optimization (avoid g_strndup
call in case log_buf will not be used anyway), so we can just
drop that check for modular builds.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-Id: <20200720100352.2477-2-kraxel@redhat.com>

hw/display/qxl.c

@@ -1762,7 +1762,16 @@ async_common:
         qxl_set_mode(d, val, 0);
         break;
     case QXL_IO_LOG:
+#ifdef CONFIG_MODULES
+        /*
+         * FIXME
+         * trace_event_get_state_backends() does not work for modules,
+         * it leads to "undefined symbol: qemu_qxl_io_log_semaphore"
+         */
+        if (true) {
+#else
         if (trace_event_get_state_backends(TRACE_QXL_IO_LOG) || d->guestdebug) {
+#endif
             /* We cannot trust the guest to NUL terminate d->ram->log_buf */
             char *log_buf = g_strndup((const char *)d->ram->log_buf,
                                       sizeof(d->ram->log_buf));