--- xen-4.3.0.orig/tools/Makefile
+++ xen-4.3.0/tools/Makefile
@@ -204,6 +204,7 @@
 		--sysconfdir=/etc/qemu \
 		--disable-kvm \
 		--enable-vnc-ws \
+		--with-coroutine=gthread \
 		--disable-docs \
 		--python=$(PYTHON) \
 		$(IOEMU_CONFIGURE_CROSS); \