char: allow specifying a GMainContext at opening time

This will be needed by vhost-user-test, when each test switches to
its own GMainLoop and GMainContext.  Otherwise, for a reconnecting
socket the initial connection will happen on the default GMainContext,
and no one will be listening on it.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20190202110834.24880-1-pbonzini@redhat.com>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
diff --git a/chardev/char.c b/chardev/char.c
index b99f369..f6d61fa 100644
--- a/chardev/char.c
+++ b/chardev/char.c
@@ -636,7 +636,8 @@
     return backend;
 }
 
-Chardev *qemu_chr_new_from_opts(QemuOpts *opts, Error **errp)
+Chardev *qemu_chr_new_from_opts(QemuOpts *opts, GMainContext *context,
+                                Error **errp)
 {
     const ChardevClass *cc;
     Chardev *chr = NULL;
@@ -676,7 +677,7 @@
 
     chr = qemu_chardev_new(bid ? bid : id,
                            object_class_get_name(OBJECT_CLASS(cc)),
-                           backend, errp);
+                           backend, context, errp);
 
     if (chr == NULL) {
         goto out;
@@ -689,7 +690,7 @@
         backend->type = CHARDEV_BACKEND_KIND_MUX;
         backend->u.mux.data = g_new0(ChardevMux, 1);
         backend->u.mux.data->chardev = g_strdup(bid);
-        mux = qemu_chardev_new(id, TYPE_CHARDEV_MUX, backend, errp);
+        mux = qemu_chardev_new(id, TYPE_CHARDEV_MUX, backend, context, errp);
         if (mux == NULL) {
             object_unparent(OBJECT(chr));
             chr = NULL;
@@ -705,7 +706,7 @@
 }
 
 Chardev *qemu_chr_new_noreplay(const char *label, const char *filename,
-                               bool permit_mux_mon)
+                               bool permit_mux_mon, GMainContext *context)
 {
     const char *p;
     Chardev *chr;
@@ -720,7 +721,7 @@
     if (!opts)
         return NULL;
 
-    chr = qemu_chr_new_from_opts(opts, &err);
+    chr = qemu_chr_new_from_opts(opts, context, &err);
     if (!chr) {
         error_report_err(err);
         goto out;
@@ -738,10 +739,11 @@
 
 static Chardev *qemu_chr_new_permit_mux_mon(const char *label,
                                           const char *filename,
-                                          bool permit_mux_mon)
+                                          bool permit_mux_mon,
+                                          GMainContext *context)
 {
     Chardev *chr;
-    chr = qemu_chr_new_noreplay(label, filename, permit_mux_mon);
+    chr = qemu_chr_new_noreplay(label, filename, permit_mux_mon, context);
     if (chr) {
         if (replay_mode != REPLAY_MODE_NONE) {
             qemu_chr_set_feature(chr, QEMU_CHAR_FEATURE_REPLAY);
@@ -755,14 +757,16 @@
     return chr;
 }
 
-Chardev *qemu_chr_new(const char *label, const char *filename)
+Chardev *qemu_chr_new(const char *label, const char *filename,
+                      GMainContext *context)
 {
-    return qemu_chr_new_permit_mux_mon(label, filename, false);
+    return qemu_chr_new_permit_mux_mon(label, filename, false, context);
 }
 
-Chardev *qemu_chr_new_mux_mon(const char *label, const char *filename)
+Chardev *qemu_chr_new_mux_mon(const char *label, const char *filename,
+                              GMainContext *context)
 {
-    return qemu_chr_new_permit_mux_mon(label, filename, true);
+    return qemu_chr_new_permit_mux_mon(label, filename, true, context);
 }
 
 static int qmp_query_chardev_foreach(Object *obj, void *data)
@@ -937,6 +941,7 @@
 
 Chardev *qemu_chardev_new(const char *id, const char *typename,
                           ChardevBackend *backend,
+                          GMainContext *gcontext,
                           Error **errp)
 {
     Object *obj;
@@ -949,6 +954,7 @@
     obj = object_new(typename);
     chr = CHARDEV(obj);
     chr->label = g_strdup(id);
+    chr->gcontext = gcontext;
 
     qemu_char_open(chr, backend, &be_opened, &local_err);
     if (local_err) {
@@ -993,7 +999,7 @@
     }
 
     chr = qemu_chardev_new(id, object_class_get_name(OBJECT_CLASS(cc)),
-                           backend, errp);
+                           backend, NULL, errp);
     if (!chr) {
         return NULL;
     }
@@ -1051,7 +1057,7 @@
     }
 
     chr_new = qemu_chardev_new(NULL, object_class_get_name(OBJECT_CLASS(cc)),
-                               backend, errp);
+                               backend, chr->gcontext, errp);
     if (!chr_new) {
         return NULL;
     }
diff --git a/gdbstub.c b/gdbstub.c
index a4be63f..ff19579 100644
--- a/gdbstub.c
+++ b/gdbstub.c
@@ -2531,7 +2531,7 @@
          * FIXME: it's a bit weird to allow using a mux chardev here
          * and implicitly setup a monitor. We may want to break this.
          */
-        chr = qemu_chr_new_noreplay("gdb", device, true);
+        chr = qemu_chr_new_noreplay("gdb", device, true, NULL);
         if (!chr)
             return -1;
     }
@@ -2545,7 +2545,7 @@
 
         /* Initialize a monitor terminal for gdb */
         mon_chr = qemu_chardev_new(NULL, TYPE_CHARDEV_GDB,
-                                   NULL, &error_abort);
+                                   NULL, NULL, &error_abort);
         monitor_init(mon_chr, 0);
     } else {
         qemu_chr_fe_deinit(&s->chr, true);
diff --git a/hmp.c b/hmp.c
index b2a2b1f..c18caac 100644
--- a/hmp.c
+++ b/hmp.c
@@ -2395,7 +2395,7 @@
     if (opts == NULL) {
         error_setg(&err, "Parsing chardev args failed");
     } else {
-        qemu_chr_new_from_opts(opts, &err);
+        qemu_chr_new_from_opts(opts, NULL, &err);
         qemu_opts_del(opts);
     }
     hmp_handle_error(mon, &err);
diff --git a/hw/arm/omap2.c b/hw/arm/omap2.c
index 3c7d136..94dffb2 100644
--- a/hw/arm/omap2.c
+++ b/hw/arm/omap2.c
@@ -799,7 +799,7 @@
     s->irq = irq;
     omap_sti_reset(s);
 
-    qemu_chr_fe_init(&s->chr, chr ?: qemu_chr_new("null", "null"),
+    qemu_chr_fe_init(&s->chr, chr ?: qemu_chr_new("null", "null", NULL),
                      &error_abort);
 
     memory_region_init_io(&s->iomem, NULL, &omap_sti_ops, s, "omap.sti",
diff --git a/hw/bt/hci-csr.c b/hw/bt/hci-csr.c
index 0341ded..fa6660a 100644
--- a/hw/bt/hci-csr.c
+++ b/hw/bt/hci-csr.c
@@ -501,7 +501,7 @@
 Chardev *uart_hci_init(void)
 {
     return qemu_chardev_new(NULL, TYPE_CHARDEV_HCI,
-                            NULL, &error_abort);
+                            NULL, NULL, &error_abort);
 }
 
 static void register_types(void)
diff --git a/hw/char/omap_uart.c b/hw/char/omap_uart.c
index 6fd1b9c..b3bb1cf 100644
--- a/hw/char/omap_uart.c
+++ b/hw/char/omap_uart.c
@@ -63,7 +63,7 @@
     s->irq = irq;
     s->serial = serial_mm_init(get_system_memory(), base, 2, irq,
                                omap_clk_getrate(fclk)/16,
-                               chr ?: qemu_chr_new(label, "null"),
+                               chr ?: qemu_chr_new(label, "null", NULL),
                                DEVICE_NATIVE_ENDIAN);
     return s;
 }
@@ -183,6 +183,6 @@
     /* TODO: Should reuse or destroy current s->serial */
     s->serial = serial_mm_init(get_system_memory(), s->base, 2, s->irq,
                                omap_clk_getrate(s->fclk) / 16,
-                               chr ?: qemu_chr_new("null", "null"),
+                               chr ?: qemu_chr_new("null", "null", NULL),
                                DEVICE_NATIVE_ENDIAN);
 }
diff --git a/hw/char/xen_console.c b/hw/char/xen_console.c
index dc6ff0e..91f34ef 100644
--- a/hw/char/xen_console.c
+++ b/hw/char/xen_console.c
@@ -211,7 +211,8 @@
                           * FIXME: sure we want to support implicit
                           * muxed monitors here?
                           */
-                         qemu_chr_new_mux_mon(label, output), &error_abort);
+                         qemu_chr_new_mux_mon(label, output, NULL),
+                         &error_abort);
     }
 
     xenstore_store_pv_console_info(con->xendev.dev,
diff --git a/hw/isa/isa-superio.c b/hw/isa/isa-superio.c
index 8bc2f69..d54463b 100644
--- a/hw/isa/isa-superio.c
+++ b/hw/isa/isa-superio.c
@@ -44,7 +44,7 @@
             chr = parallel_hds[i];
             if (chr == NULL) {
                 name = g_strdup_printf("discarding-parallel%d", i);
-                chr = qemu_chr_new(name, "null");
+                chr = qemu_chr_new(name, "null", NULL);
             } else {
                 name = g_strdup_printf("parallel%d", i);
             }
@@ -84,7 +84,7 @@
             chr = serial_hd(i);
             if (chr == NULL) {
                 name = g_strdup_printf("discarding-serial%d", i);
-                chr = qemu_chr_new(name, "null");
+                chr = qemu_chr_new(name, "null", NULL);
             } else {
                 name = g_strdup_printf("serial%d", i);
             }
diff --git a/hw/mips/boston.c b/hw/mips/boston.c
index 6c9c20a..e5bab3c 100644
--- a/hw/mips/boston.c
+++ b/hw/mips/boston.c
@@ -512,7 +512,7 @@
     memory_region_init_io(lcd, NULL, &boston_lcd_ops, s, "boston-lcd", 0x8);
     memory_region_add_subregion_overlap(sys_mem, 0x17fff000, lcd, 0);
 
-    chr = qemu_chr_new("lcd", "vc:320x240");
+    chr = qemu_chr_new("lcd", "vc:320x240", NULL);
     qemu_chr_fe_init(&s->lcd_display, chr, NULL);
     qemu_chr_fe_set_handlers(&s->lcd_display, NULL, NULL,
                              boston_lcd_event, NULL, s, NULL, true);
diff --git a/hw/mips/mips_malta.c b/hw/mips/mips_malta.c
index 7466776..7a403ef 100644
--- a/hw/mips/mips_malta.c
+++ b/hw/mips/mips_malta.c
@@ -568,7 +568,7 @@
     memory_region_add_subregion(address_space, base, &s->iomem_lo);
     memory_region_add_subregion(address_space, base + 0xa00, &s->iomem_hi);
 
-    chr = qemu_chr_new("fpga", "vc:320x200");
+    chr = qemu_chr_new("fpga", "vc:320x200", NULL);
     qemu_chr_fe_init(&s->display, chr, NULL);
     qemu_chr_fe_set_handlers(&s->display, NULL, NULL,
                              malta_fgpa_display_event, NULL, s, NULL, true);
diff --git a/hw/usb/dev-serial.c b/hw/usb/dev-serial.c
index 98d1ca3..03c3bcd 100644
--- a/hw/usb/dev-serial.c
+++ b/hw/usb/dev-serial.c
@@ -514,7 +514,7 @@
     USBDevice *dev;
     Chardev *cdrv;
 
-    cdrv = qemu_chr_new("braille", "braille");
+    cdrv = qemu_chr_new("braille", "braille", NULL);
     if (!cdrv)
         return NULL;
 
diff --git a/include/chardev/char.h b/include/chardev/char.h
index 014566c..c0b57f7 100644
--- a/include/chardev/char.h
+++ b/include/chardev/char.h
@@ -73,6 +73,7 @@
 /**
  * qemu_chr_new_from_opts:
  * @opts: see qemu-config.c for a list of valid options
+ * @context: the #GMainContext to be used at initialization time
  *
  * Create a new character backend from a QemuOpts list.
  *
@@ -81,6 +82,7 @@
  *                            or left untouched in case of help option
  */
 Chardev *qemu_chr_new_from_opts(QemuOpts *opts,
+                                GMainContext *context,
                                 Error **errp);
 
 /**
@@ -106,25 +108,29 @@
  * qemu_chr_new:
  * @label: the name of the backend
  * @filename: the URI
+ * @context: the #GMainContext to be used at initialization time
  *
  * Create a new character backend from a URI.
  * Do not implicitly initialize a monitor if the chardev is muxed.
  *
  * Returns: a new character backend
  */
-Chardev *qemu_chr_new(const char *label, const char *filename);
+Chardev *qemu_chr_new(const char *label, const char *filename,
+                      GMainContext *context);
 
 /**
  * qemu_chr_new_mux_mon:
  * @label: the name of the backend
  * @filename: the URI
+ * @context: the #GMainContext to be used at initialization time
  *
  * Create a new character backend from a URI.
  * Implicitly initialize a monitor if the chardev is muxed.
  *
  * Returns: a new character backend
  */
-Chardev *qemu_chr_new_mux_mon(const char *label, const char *filename);
+Chardev *qemu_chr_new_mux_mon(const char *label, const char *filename,
+                              GMainContext *context);
 
 /**
 * qemu_chr_change:
@@ -146,6 +152,7 @@
  * @label: the name of the backend
  * @filename: the URI
  * @permit_mux_mon: if chardev is muxed, initialize a monitor
+ * @context: the #GMainContext to be used at initialization time
  *
  * Create a new character backend from a URI.
  * Character device communications are not written
@@ -154,7 +161,7 @@
  * Returns: a new character backend
  */
 Chardev *qemu_chr_new_noreplay(const char *label, const char *filename,
-                               bool permit_mux_mon);
+                               bool permit_mux_mon, GMainContext *context);
 
 /**
  * qemu_chr_be_can_write:
@@ -272,7 +279,8 @@
 } ChardevClass;
 
 Chardev *qemu_chardev_new(const char *id, const char *typename,
-                          ChardevBackend *backend, Error **errp);
+                          ChardevBackend *backend, GMainContext *context,
+                          Error **errp);
 
 extern int term_escape_char;
 
diff --git a/net/slirp.c b/net/slirp.c
index 7a16d8d..4ec989b 100644
--- a/net/slirp.c
+++ b/net/slirp.c
@@ -927,7 +927,7 @@
          * FIXME: sure we want to support implicit
          * muxed monitors here?
          */
-        Chardev *chr = qemu_chr_new_mux_mon(buf, p);
+        Chardev *chr = qemu_chr_new_mux_mon(buf, p, NULL);
 
         if (!chr) {
             error_setg(errp, "Could not open guest forwarding device '%s'",
diff --git a/qtest.c b/qtest.c
index 60988c8..5271417 100644
--- a/qtest.c
+++ b/qtest.c
@@ -763,7 +763,7 @@
 {
     Chardev *chr;
 
-    chr = qemu_chr_new("qtest", qtest_chrdev);
+    chr = qemu_chr_new("qtest", qtest_chrdev, NULL);
 
     if (chr == NULL) {
         error_setg(errp, "Failed to initialize device for qtest: \"%s\"",
diff --git a/tests/test-char.c b/tests/test-char.c
index 82579e6..63b4d32 100644
--- a/tests/test-char.c
+++ b/tests/test-char.c
@@ -86,7 +86,7 @@
                             1, &error_abort);
     qemu_opt_set(opts, "backend", "console", &error_abort);
 
-    chr = qemu_chr_new_from_opts(opts, NULL);
+    chr = qemu_chr_new_from_opts(opts, NULL, NULL);
     g_assert_nonnull(chr);
 
     qemu_chr_write_all(chr, (const uint8_t *)"CONSOLE", 7);
@@ -108,7 +108,7 @@
     CharBackend be;
     int ret;
 
-    chr = qemu_chr_new("label", "stdio");
+    chr = qemu_chr_new("label", "stdio", NULL);
     g_assert_nonnull(chr);
 
     qemu_chr_fe_init(&be, chr, &error_abort);
@@ -139,7 +139,7 @@
     qemu_opt_set(opts, "backend", "ringbuf", &error_abort);
 
     qemu_opt_set(opts, "size", "5", &error_abort);
-    chr = qemu_chr_new_from_opts(opts, NULL);
+    chr = qemu_chr_new_from_opts(opts, NULL, NULL);
     g_assert_null(chr);
     qemu_opts_del(opts);
 
@@ -147,7 +147,7 @@
                             1, &error_abort);
     qemu_opt_set(opts, "backend", "ringbuf", &error_abort);
     qemu_opt_set(opts, "size", "2", &error_abort);
-    chr = qemu_chr_new_from_opts(opts, &error_abort);
+    chr = qemu_chr_new_from_opts(opts, NULL, &error_abort);
     g_assert_nonnull(chr);
     qemu_opts_del(opts);
 
@@ -170,7 +170,7 @@
                             1, &error_abort);
     qemu_opt_set(opts, "backend", "memory", &error_abort);
     qemu_opt_set(opts, "size", "2", &error_abort);
-    chr = qemu_chr_new_from_opts(opts, NULL);
+    chr = qemu_chr_new_from_opts(opts, NULL, NULL);
     g_assert_nonnull(chr);
     object_unparent(OBJECT(chr));
     qemu_opts_del(opts);
@@ -189,7 +189,7 @@
     qemu_opt_set(opts, "backend", "ringbuf", &error_abort);
     qemu_opt_set(opts, "size", "128", &error_abort);
     qemu_opt_set(opts, "mux", "on", &error_abort);
-    chr = qemu_chr_new_from_opts(opts, &error_abort);
+    chr = qemu_chr_new_from_opts(opts, NULL, &error_abort);
     g_assert_nonnull(chr);
     qemu_opts_del(opts);
 
@@ -412,7 +412,7 @@
     CharBackend client_be;
     Chardev *chr_client;
     Chardev *chr = qemu_chr_new("server",
-                                "websocket:127.0.0.1:0,server,nowait");
+                                "websocket:127.0.0.1:0,server,nowait", NULL);
     const char handshake[] = "GET / HTTP/1.1\r\n"
                              "Upgrade: websocket\r\n"
                              "Connection: Upgrade\r\n"
@@ -436,7 +436,7 @@
     qemu_chr_fe_set_handlers(&be, websock_server_can_read, websock_server_read,
                              NULL, NULL, chr, NULL, true);
 
-    chr_client = qemu_chr_new("client", tmp);
+    chr_client = qemu_chr_new("client", tmp, NULL);
     qemu_chr_fe_init(&client_be, chr_client, &error_abort);
     qemu_chr_fe_set_handlers(&client_be, websock_client_can_read,
                              websock_client_read,
@@ -482,7 +482,7 @@
     }
 
     tmp = g_strdup_printf("pipe:%s", pipe);
-    chr = qemu_chr_new("pipe", tmp);
+    chr = qemu_chr_new("pipe", tmp, NULL);
     g_assert_nonnull(chr);
     g_free(tmp);
 
@@ -586,7 +586,7 @@
         int port;
         sock = make_udp_socket(&port);
         tmp = g_strdup_printf("udp:127.0.0.1:%d", port);
-        chr = qemu_chr_new("client", tmp);
+        chr = qemu_chr_new("client", tmp, NULL);
         g_assert_nonnull(chr);
 
         be = g_alloca(sizeof(CharBackend));
@@ -764,7 +764,7 @@
     opts = qemu_opts_parse_noisily(qemu_find_opts("chardev"),
                                    optstr, true);
     g_assert_nonnull(opts);
-    chr = qemu_chr_new_from_opts(opts, &error_abort);
+    chr = qemu_chr_new_from_opts(opts, NULL, &error_abort);
     qemu_opts_del(opts);
     g_assert_nonnull(chr);
     g_assert(!object_property_get_bool(OBJECT(chr), "connected", &error_abort));
@@ -914,7 +914,7 @@
     opts = qemu_opts_parse_noisily(qemu_find_opts("chardev"),
                                    optstr, true);
     g_assert_nonnull(opts);
-    chr = qemu_chr_new_from_opts(opts, &error_abort);
+    chr = qemu_chr_new_from_opts(opts, NULL, &error_abort);
     qemu_opts_del(opts);
     g_assert_nonnull(chr);
 
@@ -1015,14 +1015,14 @@
     qemu_opt_set(opts, "backend", "serial", &error_abort);
     qemu_opt_set(opts, "path", "/dev/null", &error_abort);
 
-    chr = qemu_chr_new_from_opts(opts, NULL);
+    chr = qemu_chr_new_from_opts(opts, NULL, NULL);
     g_assert_nonnull(chr);
     /* TODO: add more tests with a pty */
     object_unparent(OBJECT(chr));
 
     /* test tty alias */
     qemu_opt_set(opts, "backend", "tty", &error_abort);
-    chr = qemu_chr_new_from_opts(opts, NULL);
+    chr = qemu_chr_new_from_opts(opts, NULL, NULL);
     g_assert_nonnull(chr);
     object_unparent(OBJECT(chr));
 
@@ -1055,7 +1055,7 @@
     g_assert_cmpint(ret, ==, 8);
 
     chr = qemu_chardev_new("label-file", TYPE_CHARDEV_FILE, &backend,
-                           &error_abort);
+                           NULL, &error_abort);
 
     qemu_chr_fe_init(&be, chr, &error_abort);
     qemu_chr_fe_set_handlers(&be,
@@ -1109,7 +1109,7 @@
         out = g_build_filename(tmp_path, "out", NULL);
         file.out = out;
         chr = qemu_chardev_new(NULL, TYPE_CHARDEV_FILE, &backend,
-                               &error_abort);
+                               NULL, &error_abort);
     }
     ret = qemu_chr_write_all(chr, (uint8_t *)"hello!", 6);
     g_assert_cmpint(ret, ==, 6);
@@ -1144,7 +1144,7 @@
     chr = qemu_chr_find("label-null");
     g_assert_null(chr);
 
-    chr = qemu_chr_new("label-null", "null");
+    chr = qemu_chr_new("label-null", "null", NULL);
     chr = qemu_chr_find("label-null");
     g_assert_nonnull(chr);
 
@@ -1181,7 +1181,7 @@
 {
     Chardev *chr;
     g_setenv("QTEST_SILENT_ERRORS", "1", 1);
-    chr = qemu_chr_new("label-invalid", "invalid");
+    chr = qemu_chr_new("label-invalid", "invalid", NULL);
     g_assert_null(chr);
     g_unsetenv("QTEST_SILENT_ERRORS");
 }
@@ -1215,7 +1215,7 @@
 
     chr_args = g_strdup_printf("udp:127.0.0.1:%d", port);
 
-    chr = qemu_chr_new("chardev", chr_args);
+    chr = qemu_chr_new("chardev", chr_args, NULL);
     qemu_chr_fe_init(&be, chr, &error_abort);
 
     /* check that chardev operates correctly */
diff --git a/tests/vhost-user-test.c b/tests/vhost-user-test.c
index 7d5f234..d961bd0 100644
--- a/tests/vhost-user-test.c
+++ b/tests/vhost-user-test.c
@@ -519,7 +519,7 @@
     Chardev *chr;
 
     chr_path = g_strdup_printf("unix:%s%s", server->socket_path, opt);
-    chr = qemu_chr_new(server->chr_name, chr_path);
+    chr = qemu_chr_new(server->chr_name, chr_path, NULL);
     g_free(chr_path);
 
     g_assert_nonnull(chr);
diff --git a/vl.c b/vl.c
index 9e4dba7..ea794ec 100644
--- a/vl.c
+++ b/vl.c
@@ -2302,7 +2302,7 @@
 {
     Error *local_err = NULL;
 
-    if (!qemu_chr_new_from_opts(opts, &local_err)) {
+    if (!qemu_chr_new_from_opts(opts, NULL, &local_err)) {
         if (local_err) {
             error_propagate(errp, local_err);
             return -1;
@@ -2440,7 +2440,7 @@
     snprintf(label, sizeof(label), "serial%d", index);
     serial_hds = g_renew(Chardev *, serial_hds, index + 1);
 
-    serial_hds[index] = qemu_chr_new_mux_mon(label, devname);
+    serial_hds[index] = qemu_chr_new_mux_mon(label, devname, NULL);
     if (!serial_hds[index]) {
         error_report("could not connect serial device"
                      " to character backend '%s'", devname);
@@ -2476,7 +2476,7 @@
         exit(1);
     }
     snprintf(label, sizeof(label), "parallel%d", index);
-    parallel_hds[index] = qemu_chr_new_mux_mon(label, devname);
+    parallel_hds[index] = qemu_chr_new_mux_mon(label, devname, NULL);
     if (!parallel_hds[index]) {
         error_report("could not connect parallel device"
                      " to character backend '%s'", devname);
@@ -2490,7 +2490,7 @@
 {
     QemuOpts *opts;
 
-    if (!qemu_chr_new_mux_mon("debugcon", devname)) {
+    if (!qemu_chr_new_mux_mon("debugcon", devname, NULL)) {
         error_report("invalid character backend '%s'", devname);
         exit(1);
     }