Merge tag 'ui-pull-request' of https://gitlab.com/marcandre.lureau/qemu into staging

UI/chardev-related patch queue

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* tag 'ui-pull-request' of https://gitlab.com/marcandre.lureau/qemu:
  dbus: add -audio dbus nsamples option
  plugins: fix -Werror=maybe-uninitialized false-positive
  ui/dbus: clarify the kind of win32 handle that is shared
  ui/dbus: on win32, allow ANONYMOUS with p2p
  qemu-options.hx: describe hub chardev and aggregation of several backends
  tests/unit/test-char: add unit tests for hub chardev backend
  chardev/char-hub: implement backend chardev aggregator
  chardev/char-pty: send CHR_EVENT_CLOSED on disconnect

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

15 files changed, 923 insertions, 19 deletions

diff --git a/audio/dbusaudio.c b/audio/dbusaudio.c
index 095e739..b44fdd1 100644
--- a/audio/dbusaudio.c
+++ b/audio/dbusaudio.c
@@ -43,9 +43,10 @@
 
 #define DBUS_DISPLAY1_AUDIO_PATH DBUS_DISPLAY1_ROOT "/Audio"
 
-#define DBUS_AUDIO_NSAMPLES 1024 /* could be configured? */
+#define DBUS_DEFAULT_AUDIO_NSAMPLES 480
 
 typedef struct DBusAudio {
+    Audiodev *dev;
     GDBusObjectManagerServer *server;
     bool p2p;
     GDBusObjectSkeleton *audio;
@@ -151,6 +152,18 @@ dbus_init_out_listener(QemuDBusDisplay1AudioOutListener *listener,
         G_DBUS_CALL_FLAGS_NONE, -1, NULL, NULL, NULL);
 }
 
+static guint
+dbus_audio_get_nsamples(DBusAudio *da)
+{
+    AudiodevDBusOptions *opts = &da->dev->u.dbus;
+
+    if (opts->has_nsamples && opts->nsamples) {
+        return opts->nsamples;
+    } else {
+        return DBUS_DEFAULT_AUDIO_NSAMPLES;
+    }
+}
+
 static int
 dbus_init_out(HWVoiceOut *hw, struct audsettings *as, void *drv_opaque)
 {
@@ -160,7 +173,7 @@ dbus_init_out(HWVoiceOut *hw, struct audsettings *as, void *drv_opaque)
     QemuDBusDisplay1AudioOutListener *listener = NULL;
 
     audio_pcm_init_info(&hw->info, as);
-    hw->samples = DBUS_AUDIO_NSAMPLES;
+    hw->samples = dbus_audio_get_nsamples(da);
     audio_rate_start(&vo->rate);
 
     g_hash_table_iter_init(&iter, da->out_listeners);
@@ -274,7 +287,7 @@ dbus_init_in(HWVoiceIn *hw, struct audsettings *as, void *drv_opaque)
     QemuDBusDisplay1AudioInListener *listener = NULL;
 
     audio_pcm_init_info(&hw->info, as);
-    hw->samples = DBUS_AUDIO_NSAMPLES;
+    hw->samples = dbus_audio_get_nsamples(da);
     audio_rate_start(&vo->rate);
 
     g_hash_table_iter_init(&iter, da->in_listeners);
@@ -399,6 +412,7 @@ dbus_audio_init(Audiodev *dev, Error **errp)
 {
     DBusAudio *da = g_new0(DBusAudio, 1);
 
+    da->dev = dev;
     da->out_listeners = g_hash_table_new_full(g_str_hash, g_str_equal,
                                                 g_free, g_object_unref);
     da->in_listeners = g_hash_table_new_full(g_str_hash, g_str_equal,
@@ -524,11 +538,17 @@ dbus_audio_register_listener(AudioState *s,
             );
     }
 
+    GDBusConnectionFlags flags =
+        G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_SERVER;
+#ifdef WIN32
+    flags |= G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_ALLOW_ANONYMOUS;
+#endif
+
     listener_conn =
         g_dbus_connection_new_sync(
             G_IO_STREAM(socket_conn),
             guid,
-            G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_SERVER,
+            flags,
             NULL, NULL, &err);
     if (err) {
         error_report("Failed to setup peer connection: %s", err->message);
@@ -646,6 +666,7 @@ dbus_audio_set_server(AudioState *s, GDBusObjectManagerServer *server, bool p2p)
                      "swapped-signal::handle-register-out-listener",
                      dbus_audio_register_out_listener, s,
                      NULL);
+    qemu_dbus_display1_audio_set_nsamples(da->iface, dbus_audio_get_nsamples(da));
 
     g_dbus_object_skeleton_add_interface(G_DBUS_OBJECT_SKELETON(da->audio),
                                          G_DBUS_INTERFACE_SKELETON(da->iface));
diff --git a/chardev/char-hub.c b/chardev/char-hub.c
new file mode 100644
index 0000000..3a4aae3
--- /dev/null
+++ b/chardev/char-hub.c
@@ -0,0 +1,301 @@
+/*
+ * QEMU Character Hub Device
+ *
+ * Author: Roman Penyaev <r.peniaev@gmail.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "qemu/option.h"
+#include "chardev/char.h"
+#include "chardev-internal.h"
+
+/*
+ * Character hub device aggregates input from multiple backend devices
+ * and forwards it to a single frontend device. Additionally, hub
+ * device takes the output from the frontend device and sends it back
+ * to all the connected backend devices.
+ */
+
+/*
+ * Write to all backends. Different backend devices accept data with
+ * various rate, so it is quite possible that one device returns less,
+ * then others. In this case we return minimum to the caller,
+ * expecting caller will repeat operation soon. When repeat happens
+ * send to the devices which consume data faster must be avoided
+ * for obvious reasons not to send data, which was already sent.
+ * Called with chr_write_lock held.
+ */
+static int hub_chr_write(Chardev *chr, const uint8_t *buf, int len)
+{
+    HubChardev *d = HUB_CHARDEV(chr);
+    int r, i, ret = len;
+    unsigned int written;
+
+    /* Invalidate index on every write */
+    d->be_eagain_ind = -1;
+
+    for (i = 0; i < d->be_cnt; i++) {
+        if (!d->backends[i].be.chr->be_open) {
+            /* Skip closed backend */
+            continue;
+        }
+        written = d->be_written[i] - d->be_min_written;
+        if (written) {
+            /* Written in the previous call so take into account */
+            ret = MIN(written, ret);
+            continue;
+        }
+        r = qemu_chr_fe_write(&d->backends[i].be, buf, len);
+        if (r < 0) {
+            if (errno == EAGAIN) {
+                /* Set index and expect to be called soon on watch wake up */
+                d->be_eagain_ind = i;
+            }
+            return r;
+        }
+        d->be_written[i] += r;
+        ret = MIN(r, ret);
+    }
+    d->be_min_written += ret;
+
+
+    return ret;
+}
+
+static int hub_chr_can_read(void *opaque)
+{
+    HubCharBackend *backend = opaque;
+    CharBackend *fe = backend->hub->parent.be;
+
+    if (fe && fe->chr_can_read) {
+        return fe->chr_can_read(fe->opaque);
+    }
+
+    return 0;
+}
+
+static void hub_chr_read(void *opaque, const uint8_t *buf, int size)
+{
+    HubCharBackend *backend = opaque;
+    CharBackend *fe = backend->hub->parent.be;
+
+    if (fe && fe->chr_read) {
+        fe->chr_read(fe->opaque, buf, size);
+    }
+}
+
+static void hub_chr_event(void *opaque, QEMUChrEvent event)
+{
+    HubCharBackend *backend = opaque;
+    HubChardev *d = backend->hub;
+    CharBackend *fe = d->parent.be;
+
+    if (event == CHR_EVENT_OPENED) {
+        /*
+         * Catch up with what was already written while this backend
+         * was closed
+         */
+        d->be_written[backend->be_ind] = d->be_min_written;
+
+        if (d->be_event_opened_cnt++) {
+            /* Ignore subsequent open events from other backends */
+            return;
+        }
+    } else if (event == CHR_EVENT_CLOSED) {
+        if (!d->be_event_opened_cnt) {
+            /* Don't go below zero. Probably assert is better */
+            return;
+        }
+        if (--d->be_event_opened_cnt) {
+            /* Serve only the last one close event */
+            return;
+        }
+    }
+
+    if (fe && fe->chr_event) {
+        fe->chr_event(fe->opaque, event);
+    }
+}
+
+static GSource *hub_chr_add_watch(Chardev *s, GIOCondition cond)
+{
+    HubChardev *d = HUB_CHARDEV(s);
+    Chardev *chr;
+    ChardevClass *cc;
+
+    if (d->be_eagain_ind == -1) {
+        return NULL;
+    }
+
+    assert(d->be_eagain_ind < d->be_cnt);
+    chr = qemu_chr_fe_get_driver(&d->backends[d->be_eagain_ind].be);
+    cc = CHARDEV_GET_CLASS(chr);
+    if (!cc->chr_add_watch) {
+        return NULL;
+    }
+
+    return cc->chr_add_watch(chr, cond);
+}
+
+static bool hub_chr_attach_chardev(HubChardev *d, Chardev *chr,
+                                   Error **errp)
+{
+    bool ret;
+
+    if (d->be_cnt >= MAX_HUB) {
+        error_setg(errp, "hub: too many uses of chardevs '%s'"
+                   " (maximum is " stringify(MAX_HUB) ")",
+                   d->parent.label);
+        return false;
+    }
+    ret = qemu_chr_fe_init(&d->backends[d->be_cnt].be, chr, errp);
+    if (ret) {
+        d->backends[d->be_cnt].hub = d;
+        d->backends[d->be_cnt].be_ind = d->be_cnt;
+        d->be_cnt += 1;
+    }
+
+    return ret;
+}
+
+static void char_hub_finalize(Object *obj)
+{
+    HubChardev *d = HUB_CHARDEV(obj);
+    int i;
+
+    for (i = 0; i < d->be_cnt; i++) {
+        qemu_chr_fe_deinit(&d->backends[i].be, false);
+    }
+}
+
+static void hub_chr_update_read_handlers(Chardev *chr)
+{
+    HubChardev *d = HUB_CHARDEV(chr);
+    int i;
+
+    for (i = 0; i < d->be_cnt; i++) {
+        qemu_chr_fe_set_handlers_full(&d->backends[i].be,
+                                      hub_chr_can_read,
+                                      hub_chr_read,
+                                      hub_chr_event,
+                                      NULL,
+                                      &d->backends[i],
+                                      chr->gcontext, true, false);
+    }
+}
+
+static void qemu_chr_open_hub(Chardev *chr,
+                                 ChardevBackend *backend,
+                                 bool *be_opened,
+                                 Error **errp)
+{
+    ChardevHub *hub = backend->u.hub.data;
+    HubChardev *d = HUB_CHARDEV(chr);
+    strList *list = hub->chardevs;
+
+    d->be_eagain_ind = -1;
+
+    if (list == NULL) {
+        error_setg(errp, "hub: 'chardevs' list is not defined");
+        return;
+    }
+
+    while (list) {
+        Chardev *s;
+
+        s = qemu_chr_find(list->value);
+        if (s == NULL) {
+            error_setg(errp, "hub: chardev can't be found by id '%s'",
+                       list->value);
+            return;
+        }
+        if (CHARDEV_IS_HUB(s) || CHARDEV_IS_MUX(s)) {
+            error_setg(errp, "hub: multiplexers and hub devices can't be "
+                       "stacked, check chardev '%s', chardev should not "
+                       "be a hub device or have 'mux=on' enabled",
+                       list->value);
+            return;
+        }
+        if (!hub_chr_attach_chardev(d, s, errp)) {
+            return;
+        }
+        list = list->next;
+    }
+
+    /* Closed until an explicit event from backend */
+    *be_opened = false;
+}
+
+static void qemu_chr_parse_hub(QemuOpts *opts, ChardevBackend *backend,
+                                  Error **errp)
+{
+    ChardevHub *hub;
+    strList **tail;
+    int i;
+
+    backend->type = CHARDEV_BACKEND_KIND_HUB;
+    hub = backend->u.hub.data = g_new0(ChardevHub, 1);
+    qemu_chr_parse_common(opts, qapi_ChardevHub_base(hub));
+
+    tail = &hub->chardevs;
+
+    for (i = 0; i < MAX_HUB; i++) {
+        char optbuf[16];
+        const char *dev;
+
+        snprintf(optbuf, sizeof(optbuf), "chardevs.%u", i);
+        dev = qemu_opt_get(opts, optbuf);
+        if (!dev) {
+            break;
+        }
+
+        QAPI_LIST_APPEND(tail, g_strdup(dev));
+    }
+}
+
+static void char_hub_class_init(ObjectClass *oc, void *data)
+{
+    ChardevClass *cc = CHARDEV_CLASS(oc);
+
+    cc->parse = qemu_chr_parse_hub;
+    cc->open = qemu_chr_open_hub;
+    cc->chr_write = hub_chr_write;
+    cc->chr_add_watch = hub_chr_add_watch;
+    /* We handle events from backends only */
+    cc->chr_be_event = NULL;
+    cc->chr_update_read_handler = hub_chr_update_read_handlers;
+}
+
+static const TypeInfo char_hub_type_info = {
+    .name = TYPE_CHARDEV_HUB,
+    .parent = TYPE_CHARDEV,
+    .class_init = char_hub_class_init,
+    .instance_size = sizeof(HubChardev),
+    .instance_finalize = char_hub_finalize,
+};
+
+static void register_types(void)
+{
+    type_register_static(&char_hub_type_info);
+}
+
+type_init(register_types);
diff --git a/chardev/char-pty.c b/chardev/char-pty.c
index cbb21b7..6a2c1dc 100644
--- a/chardev/char-pty.c
+++ b/chardev/char-pty.c
@@ -181,6 +181,9 @@ static void pty_chr_state(Chardev *chr, int connected)
 
     if (!connected) {
         remove_fd_in_watch(chr);
+        if (s->connected) {
+            qemu_chr_be_event(chr, CHR_EVENT_CLOSED);
+        }
         s->connected = 0;
         /* (re-)connect poll interval for idle guests: once per second.
          * We check more frequently in case the guests sends data to
@@ -215,7 +218,6 @@ static void char_pty_finalize(Object *obj)
     pty_chr_state(chr, 0);
     object_unref(OBJECT(s->ioc));
     pty_chr_timer_cancel(s);
-    qemu_chr_be_event(chr, CHR_EVENT_CLOSED);
 }
 
 #if defined HAVE_PTY_H
diff --git a/chardev/char.c b/chardev/char.c
index 7705da5..5a9e976 100644
--- a/chardev/char.c
+++ b/chardev/char.c
@@ -943,7 +943,26 @@ QemuOptsList qemu_chardev_opts = {
         },{
             .name = "chardev",
             .type = QEMU_OPT_STRING,
+        },
+        /*
+         * Multiplexer options. Follows QAPI array syntax.
+         * See MAX_HUB macro to obtain array capacity.
+         */
+        {
+            .name = "chardevs.0",
+            .type = QEMU_OPT_STRING,
+        },{
+            .name = "chardevs.1",
+            .type = QEMU_OPT_STRING,
         },{
+            .name = "chardevs.2",
+            .type = QEMU_OPT_STRING,
+        },{
+            .name = "chardevs.3",
+            .type = QEMU_OPT_STRING,
+        },
+
+        {
             .name = "append",
             .type = QEMU_OPT_BOOL,
         },{
@@ -1106,8 +1125,8 @@ ChardevReturn *qmp_chardev_change(const char *id, ChardevBackend *backend,
         return NULL;
     }
 
-    if (CHARDEV_IS_MUX(chr)) {
-        error_setg(errp, "Mux device hotswap not supported yet");
+    if (CHARDEV_IS_MUX(chr) || CHARDEV_IS_HUB(chr)) {
+        error_setg(errp, "For mux or hub device hotswap is not supported yet");
         return NULL;
     }
 
diff --git a/chardev/chardev-internal.h b/chardev/chardev-internal.h
index 853807f..9752dd7 100644
--- a/chardev/chardev-internal.h
+++ b/chardev/chardev-internal.h
@@ -29,13 +29,16 @@
 #include "chardev/char-fe.h"
 #include "qom/object.h"
 
+#define MAX_HUB 4
 #define MAX_MUX 4
 #define MUX_BUFFER_SIZE 32 /* Must be a power of 2.  */
 #define MUX_BUFFER_MASK (MUX_BUFFER_SIZE - 1)
 
 struct MuxChardev {
     Chardev parent;
+    /* Linked frontends */
     CharBackend *backends[MAX_MUX];
+    /* Linked backend */
     CharBackend chr;
     unsigned long mux_bitset;
     int focus;
@@ -53,11 +56,57 @@ struct MuxChardev {
     int64_t timestamps_start;
 };
 typedef struct MuxChardev MuxChardev;
+typedef struct HubChardev HubChardev;
+typedef struct HubCharBackend HubCharBackend;
+
+/*
+ * Back-pointer on a hub, actual backend and its index in
+ * `hub->backends` array
+ */
+struct HubCharBackend {
+    HubChardev   *hub;
+    CharBackend  be;
+    unsigned int be_ind;
+};
+
+struct HubChardev {
+    Chardev parent;
+    /* Linked backends */
+    HubCharBackend backends[MAX_HUB];
+    /*
+     * Number of backends attached to this hub. Once attached, a
+     * backend can't be detached, so the counter is only increasing.
+     * To safely remove a backend, hub has to be removed first.
+     */
+    unsigned int be_cnt;
+    /*
+     * Number of CHR_EVEN_OPENED events from all backends. Needed to
+     * send CHR_EVEN_CLOSED only when counter goes to zero.
+     */
+    unsigned int be_event_opened_cnt;
+    /*
+     * Counters of written bytes from a single frontend device
+     * to multiple backend devices.
+     */
+    unsigned int be_written[MAX_HUB];
+    unsigned int be_min_written;
+    /*
+     * Index of a backend device which got EAGAIN on last write,
+     * -1 is invalid index.
+     */
+    int be_eagain_ind;
+};
+typedef struct HubChardev HubChardev;
 
 DECLARE_INSTANCE_CHECKER(MuxChardev, MUX_CHARDEV,
                          TYPE_CHARDEV_MUX)
-#define CHARDEV_IS_MUX(chr)                             \
+DECLARE_INSTANCE_CHECKER(HubChardev, HUB_CHARDEV,
+                         TYPE_CHARDEV_HUB)
+
+#define CHARDEV_IS_MUX(chr)                                \
     object_dynamic_cast(OBJECT(chr), TYPE_CHARDEV_MUX)
+#define CHARDEV_IS_HUB(chr)                                \
+    object_dynamic_cast(OBJECT(chr), TYPE_CHARDEV_HUB)
 
 bool mux_chr_attach_frontend(MuxChardev *d, CharBackend *b,
                              unsigned int *tag, Error **errp);
diff --git a/chardev/meson.build b/chardev/meson.build
index 70070a8..56ee39a 100644
--- a/chardev/meson.build
+++ b/chardev/meson.build
@@ -3,6 +3,7 @@ chardev_ss.add(files(
   'char-file.c',
   'char-io.c',
   'char-mux.c',
+  'char-hub.c',
   'char-null.c',
   'char-pipe.c',
   'char-ringbuf.c',
diff --git a/contrib/plugins/cache.c b/contrib/plugins/cache.c
index 7baff86..7cfd3df 100644
--- a/contrib/plugins/cache.c
+++ b/contrib/plugins/cache.c
@@ -603,7 +603,7 @@ static int l2_cmp(gconstpointer a, gconstpointer b)
 static void log_stats(void)
 {
     int i;
-    Cache *icache, *dcache, *l2_cache;
+    Cache *icache, *dcache, *l2_cache = NULL;
 
     g_autoptr(GString) rep = g_string_new("core #, data accesses, data misses,"
                                           " dmiss rate, insn accesses,"
diff --git a/include/chardev/char.h b/include/chardev/char.h
index 01df55f..429852f 100644
--- a/include/chardev/char.h
+++ b/include/chardev/char.h
@@ -232,6 +232,7 @@ OBJECT_DECLARE_TYPE(Chardev, ChardevClass, CHARDEV)
 
 #define TYPE_CHARDEV_NULL "chardev-null"
 #define TYPE_CHARDEV_MUX "chardev-mux"
+#define TYPE_CHARDEV_HUB "chardev-hub"
 #define TYPE_CHARDEV_RINGBUF "chardev-ringbuf"
 #define TYPE_CHARDEV_PTY "chardev-pty"
 #define TYPE_CHARDEV_CONSOLE "chardev-console"
diff --git a/qapi/audio.json b/qapi/audio.json
index 519697c..dd5a58d 100644
--- a/qapi/audio.json
+++ b/qapi/audio.json
@@ -66,6 +66,26 @@
     '*out': 'AudiodevPerDirectionOptions' } }
 
 ##
+# @AudiodevDBusOptions:
+#
+# Options of the D-Bus audio backend.
+#
+# @in: options of the capture stream
+#
+# @out: options of the playback stream
+#
+# @nsamples: set the number of samples per read/write calls (default to 480,
+# 10ms at 48kHz).
+#
+# Since: 10.0
+##
+{ 'struct': 'AudiodevDBusOptions',
+  'data': {
+    '*in':  'AudiodevPerDirectionOptions',
+    '*out': 'AudiodevPerDirectionOptions',
+    '*nsamples': 'uint32'} }
+
+##
 # @AudiodevAlsaPerDirectionOptions:
 #
 # Options of the ALSA backend that are used for both playback and
@@ -490,7 +510,7 @@
                    'if': 'CONFIG_AUDIO_ALSA' },
     'coreaudio': { 'type': 'AudiodevCoreaudioOptions',
                    'if': 'CONFIG_AUDIO_COREAUDIO' },
-    'dbus':      { 'type': 'AudiodevGenericOptions',
+    'dbus':      { 'type': 'AudiodevDBusOptions',
                    'if': 'CONFIG_DBUS_DISPLAY' },
     'dsound':    { 'type': 'AudiodevDsoundOptions',
                    'if': 'CONFIG_AUDIO_DSOUND' },
diff --git a/qapi/char.json b/qapi/char.json
index e045354..f02b66c 100644
--- a/qapi/char.json
+++ b/qapi/char.json
@@ -333,6 +333,19 @@
   'base': 'ChardevCommon' }
 
 ##
+# @ChardevHub:
+#
+# Configuration info for hub chardevs.
+#
+# @chardevs: List of chardev IDs, which should be added to this hub
+#
+# Since: 10.0
+##
+{ 'struct': 'ChardevHub',
+  'data': { 'chardevs': ['str'] },
+  'base': 'ChardevCommon' }
+
+##
 # @ChardevStdio:
 #
 # Configuration info for stdio chardevs.
@@ -479,6 +492,8 @@
 #
 # @mux: (since 1.5)
 #
+# @hub: (since 10.0)
+#
 # @msmouse: emulated Microsoft serial mouse (since 1.5)
 #
 # @wctablet: emulated Wacom Penpartner serial tablet (since 2.9)
@@ -521,6 +536,7 @@
             'pty',
             'null',
             'mux',
+            'hub',
             'msmouse',
             'wctablet',
             { 'name': 'braille', 'if': 'CONFIG_BRLAPI' },
@@ -596,6 +612,16 @@
   'data': { 'data': 'ChardevMux' } }
 
 ##
+# @ChardevHubWrapper:
+#
+# @data: Configuration info for hub chardevs
+#
+# Since: 10.0
+##
+{ 'struct': 'ChardevHubWrapper',
+  'data': { 'data': 'ChardevHub' } }
+
+##
 # @ChardevStdioWrapper:
 #
 # @data: Configuration info for stdio chardevs
@@ -703,6 +729,7 @@
             'pty': 'ChardevPtyWrapper',
             'null': 'ChardevCommonWrapper',
             'mux': 'ChardevMuxWrapper',
+            'hub': 'ChardevHubWrapper',
             'msmouse': 'ChardevCommonWrapper',
             'wctablet': 'ChardevCommonWrapper',
             'braille': { 'type': 'ChardevCommonWrapper',
diff --git a/qemu-options.hx b/qemu-options.hx
index d19bf53..ec0090d 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3733,7 +3733,7 @@ SRST
 The general form of a character device option is:
 
 ``-chardev backend,id=id[,mux=on|off][,options]``
-    Backend is one of: ``null``, ``socket``, ``udp``, ``msmouse``,
+    Backend is one of: ``null``, ``socket``, ``udp``, ``msmouse``, ``hub``,
     ``vc``, ``ringbuf``, ``file``, ``pipe``, ``console``, ``serial``,
     ``pty``, ``stdio``, ``braille``, ``parallel``,
     ``spicevmc``, ``spiceport``. The specific backend will determine the
@@ -3790,9 +3790,10 @@ The general form of a character device option is:
     the QEMU monitor, and ``-nographic`` also multiplexes the console
     and the monitor to stdio.
 
-    There is currently no support for multiplexing in the other
-    direction (where a single QEMU front end takes input and output from
-    multiple chardevs).
+    If you need to aggregate data in the opposite direction (where one
+    QEMU frontend interface receives input and output from multiple
+    backend chardev devices), please refer to the paragraph below
+    regarding chardev ``hub`` aggregator device configuration.
 
     Every backend supports the ``logfile`` option, which supplies the
     path to a file to record all data transmitted via the backend. The
@@ -3892,6 +3893,46 @@ The available backends are:
     Forward QEMU's emulated msmouse events to the guest. ``msmouse``
     does not take any options.
 
+``-chardev hub,id=id,chardevs.0=id[,chardevs.N=id]``
+    Explicitly create chardev backend hub device with the possibility
+    to aggregate input from multiple backend devices and forward it to
+    a single frontend device. Additionally, ``hub`` device takes the
+    output from the frontend device and sends it back to all the
+    connected backend devices. This allows for seamless interaction
+    between different backend devices and a single frontend
+    interface. Aggregation supported for up to 4 chardev
+    devices. (Since 10.0)
+
+    For example, the following is a use case of 2 backend devices:
+    virtual console ``vc0`` and a pseudo TTY ``pty0`` connected to
+    a single virtio hvc console frontend device with a hub ``hub0``
+    help. Virtual console renders text to an image, which can be
+    shared over the VNC protocol. In turn, pty backend provides
+    bidirectional communication to the virtio hvc console over the
+    pseudo TTY file. The example configuration can be as follows:
+
+    ::
+
+       -chardev pty,path=/tmp/pty,id=pty0 \
+       -chardev vc,id=vc0 \
+       -chardev hub,id=hub0,chardevs.0=pty0,chardevs.1=vc0 \
+       -device virtconsole,chardev=hub0 \
+       -vnc 0.0.0.0:0
+
+    Once QEMU starts VNC client and any TTY emulator can be used to
+    control a single hvc console:
+
+    ::
+
+       # Start TTY emulator
+       tio /tmp/pty
+
+       # Start VNC client and switch to virtual console Ctrl-Alt-2
+       vncviewer :0
+
+    Several frontend devices is not supported. Stacking of multiplexers
+    and hub devices is not supported as well.
+
 ``-chardev vc,id=id[[,width=width][,height=height]][[,cols=cols][,rows=rows]]``
     Connect to a QEMU text console. ``vc`` may optionally be given a
     specific size.
diff --git a/tests/unit/test-char.c b/tests/unit/test-char.c
index 98a60d8..85b350a 100644
--- a/tests/unit/test-char.c
+++ b/tests/unit/test-char.c
@@ -359,6 +359,403 @@ static void char_mux_test(void)
     qmp_chardev_remove("mux-label", &error_abort);
 }
 
+static void char_hub_test(void)
+{
+    QemuOpts *opts;
+    Chardev *hub, *chr1, *chr2, *base;
+    char *data;
+    FeHandler h = { 0, false, 0, false, };
+    Error *error = NULL;
+    CharBackend chr_be;
+    int ret, i;
+
+#define RB_SIZE 128
+
+    /*
+     * Create invalid hub
+     * 1. Create hub without a 'chardevs.N' defined (expect error)
+     */
+    opts = qemu_opts_create(qemu_find_opts("chardev"), "hub0",
+                            1, &error_abort);
+    qemu_opt_set(opts, "backend", "hub", &error_abort);
+    hub = qemu_chr_new_from_opts(opts, NULL, &error);
+    g_assert_cmpstr(error_get_pretty(error), ==,
+                    "hub: 'chardevs' list is not defined");
+    error_free(error);
+    error = NULL;
+    qemu_opts_del(opts);
+
+    /*
+     * Create invalid hub
+     * 1. Create chardev with embedded mux: 'mux=on'
+     * 2. Create hub which refers mux
+     * 3. Create hub which refers chardev already attached
+     *    to the mux (already in use, expect error)
+     */
+    opts = qemu_opts_create(qemu_find_opts("chardev"), "chr0",
+                            1, &error_abort);
+    qemu_opt_set(opts, "mux", "on", &error_abort);
+    qemu_opt_set(opts, "backend", "ringbuf", &error_abort);
+    qemu_opt_set(opts, "size", stringify(RB_SIZE), &error_abort);
+    base = qemu_chr_new_from_opts(opts, NULL, &error_abort);
+    g_assert_nonnull(base);
+    qemu_opts_del(opts);
+
+    opts = qemu_opts_create(qemu_find_opts("chardev"), "hub0",
+                            1, &error_abort);
+    qemu_opt_set(opts, "backend", "hub", &error_abort);
+    qemu_opt_set(opts, "chardevs.0", "chr0", &error_abort);
+    hub = qemu_chr_new_from_opts(opts, NULL, &error);
+    g_assert_cmpstr(error_get_pretty(error), ==,
+                    "hub: multiplexers and hub devices can't be "
+                    "stacked, check chardev 'chr0', chardev should "
+                    "not be a hub device or have 'mux=on' enabled");
+    error_free(error);
+    error = NULL;
+    qemu_opts_del(opts);
+
+    opts = qemu_opts_create(qemu_find_opts("chardev"), "hub0",
+                            1, &error_abort);
+    qemu_opt_set(opts, "backend", "hub", &error_abort);
+    qemu_opt_set(opts, "chardevs.0", "chr0-base", &error_abort);
+    hub = qemu_chr_new_from_opts(opts, NULL, &error);
+    g_assert_cmpstr(error_get_pretty(error), ==,
+                    "chardev 'chr0-base' is already in use");
+    error_free(error);
+    error = NULL;
+    qemu_opts_del(opts);
+
+    /* Finalize chr0 */
+    qmp_chardev_remove("chr0", &error_abort);
+
+    /*
+     * Create invalid hub with more than maximum allowed backends
+     * 1. Create more than maximum allowed 'chardevs.%d' options for
+     *    hub (expect error)
+     */
+    opts = qemu_opts_create(qemu_find_opts("chardev"), "hub0",
+                            1, &error_abort);
+    for (i = 0; i < 10; i++) {
+        char key[32], val[32];
+
+        snprintf(key, sizeof(key), "chardevs.%d", i);
+        snprintf(val, sizeof(val), "chr%d", i);
+        qemu_opt_set(opts, key, val, &error);
+        if (error) {
+            char buf[64];
+
+            snprintf(buf, sizeof(buf), "Invalid parameter 'chardevs.%d'", i);
+            g_assert_cmpstr(error_get_pretty(error), ==, buf);
+            error_free(error);
+            break;
+        }
+    }
+    g_assert_nonnull(error);
+    error = NULL;
+    qemu_opts_del(opts);
+
+    /*
+     * Create hub with 2 backend chardevs and 1 frontend and perform
+     * data aggregation
+     * 1. Create 2 ringbuf backend chardevs
+     * 2. Create 1 frontend
+     * 3. Create hub which refers 2 backend chardevs
+     * 4. Attach hub to a frontend
+     * 5. Attach hub to a frontend second time (expect error)
+     * 6. Perform data aggregation
+     * 7. Remove chr1 ("chr1 is busy", expect error)
+     * 8. Remove hub0 ("hub0 is busy", expect error);
+     * 9. Finilize frontend, hub and backend chardevs in correct order
+     */
+
+    /* Create first chardev */
+    opts = qemu_opts_create(qemu_find_opts("chardev"), "chr1",
+                            1, &error_abort);
+    qemu_opt_set(opts, "backend", "ringbuf", &error_abort);
+    qemu_opt_set(opts, "size", stringify(RB_SIZE), &error_abort);
+    chr1 = qemu_chr_new_from_opts(opts, NULL, &error_abort);
+    g_assert_nonnull(chr1);
+    qemu_opts_del(opts);
+
+    /* Create second chardev */
+    opts = qemu_opts_create(qemu_find_opts("chardev"), "chr2",
+                            1, &error_abort);
+    qemu_opt_set(opts, "backend", "ringbuf", &error_abort);
+    qemu_opt_set(opts, "size", stringify(RB_SIZE), &error_abort);
+    chr2 = qemu_chr_new_from_opts(opts, NULL, &error_abort);
+    g_assert_nonnull(chr2);
+    qemu_opts_del(opts);
+
+    /* Create hub0 and refer 2 backend chardevs */
+    opts = qemu_opts_create(qemu_find_opts("chardev"), "hub0",
+                            1, &error_abort);
+    qemu_opt_set(opts, "backend", "hub", &error_abort);
+    qemu_opt_set(opts, "chardevs.0", "chr1", &error_abort);
+    qemu_opt_set(opts, "chardevs.1", "chr2", &error_abort);
+    hub = qemu_chr_new_from_opts(opts, NULL, &error_abort);
+    g_assert_nonnull(hub);
+    qemu_opts_del(opts);
+
+    /* Attach hub to a frontend */
+    qemu_chr_fe_init(&chr_be, hub, &error_abort);
+    qemu_chr_fe_set_handlers(&chr_be,
+                             fe_can_read,
+                             fe_read,
+                             fe_event,
+                             NULL,
+                             &h,
+                             NULL, true);
+
+    /* Fails second time */
+    qemu_chr_fe_init(&chr_be, hub, &error);
+    g_assert_cmpstr(error_get_pretty(error), ==, "chardev 'hub0' is already in use");
+    error_free(error);
+    error = NULL;
+
+    /* Write to backend, chr1 */
+    base = qemu_chr_find("chr1");
+    g_assert_cmpint(qemu_chr_be_can_write(base), !=, 0);
+
+    qemu_chr_be_write(base, (void *)"hello", 6);
+    g_assert_cmpint(h.read_count, ==, 6);
+    g_assert_cmpstr(h.read_buf, ==, "hello");
+    h.read_count = 0;
+
+    /* Write to backend, chr2 */
+    base = qemu_chr_find("chr2");
+    g_assert_cmpint(qemu_chr_be_can_write(base), !=, 0);
+
+    qemu_chr_be_write(base, (void *)"olleh", 6);
+    g_assert_cmpint(h.read_count, ==, 6);
+    g_assert_cmpstr(h.read_buf, ==, "olleh");
+    h.read_count = 0;
+
+    /* Write to frontend, chr_be */
+    ret = qemu_chr_fe_write(&chr_be, (void *)"heyhey", 6);
+    g_assert_cmpint(ret, ==, 6);
+
+    data = qmp_ringbuf_read("chr1", RB_SIZE, false, 0, &error_abort);
+    g_assert_cmpint(strlen(data), ==, 6);
+    g_assert_cmpstr(data, ==, "heyhey");
+    g_free(data);
+
+    data = qmp_ringbuf_read("chr2", RB_SIZE, false, 0, &error_abort);
+    g_assert_cmpint(strlen(data), ==, 6);
+    g_assert_cmpstr(data, ==, "heyhey");
+    g_free(data);
+
+    /* Can't be removed, depends on hub0 */
+    qmp_chardev_remove("chr1", &error);
+    g_assert_cmpstr(error_get_pretty(error), ==, "Chardev 'chr1' is busy");
+    error_free(error);
+    error = NULL;
+
+    /* Can't be removed, depends on frontend chr_be */
+    qmp_chardev_remove("hub0", &error);
+    g_assert_cmpstr(error_get_pretty(error), ==, "Chardev 'hub0' is busy");
+    error_free(error);
+    error = NULL;
+
+    /* Finalize frontend */
+    qemu_chr_fe_deinit(&chr_be, false);
+
+    /* Finalize hub0 */
+    qmp_chardev_remove("hub0", &error_abort);
+
+    /* Finalize backend chardevs */
+    qmp_chardev_remove("chr1", &error_abort);
+    qmp_chardev_remove("chr2", &error_abort);
+
+#ifndef _WIN32
+    /*
+     * Create 3 backend chardevs to simulate EAGAIN and watcher.
+     * Mainly copied from char_pipe_test().
+     * 1. Create 2 ringbuf backend chardevs
+     * 2. Create 1 pipe backend chardev
+     * 3. Create 1 frontend
+     * 4. Create hub which refers 2 backend chardevs
+     * 5. Attach hub to a frontend
+     * 6. Perform data aggregation and check watcher
+     * 7. Finilize frontend, hub and backend chardevs in correct order
+     */
+    {
+        gchar *tmp_path = g_dir_make_tmp("qemu-test-char.XXXXXX", NULL);
+        gchar *in, *out, *pipe = g_build_filename(tmp_path, "pipe", NULL);
+        Chardev *chr3;
+        int fd, len;
+        char buf[128];
+
+        in = g_strdup_printf("%s.in", pipe);
+        if (mkfifo(in, 0600) < 0) {
+            abort();
+        }
+        out = g_strdup_printf("%s.out", pipe);
+        if (mkfifo(out, 0600) < 0) {
+            abort();
+        }
+
+        /* Create first chardev */
+        opts = qemu_opts_create(qemu_find_opts("chardev"), "chr1",
+                                1, &error_abort);
+        qemu_opt_set(opts, "backend", "ringbuf", &error_abort);
+        qemu_opt_set(opts, "size", stringify(RB_SIZE), &error_abort);
+        chr1 = qemu_chr_new_from_opts(opts, NULL, &error_abort);
+        g_assert_nonnull(chr1);
+        qemu_opts_del(opts);
+
+        /* Create second chardev */
+        opts = qemu_opts_create(qemu_find_opts("chardev"), "chr2",
+                                1, &error_abort);
+        qemu_opt_set(opts, "backend", "ringbuf", &error_abort);
+        qemu_opt_set(opts, "size", stringify(RB_SIZE), &error_abort);
+        chr2 = qemu_chr_new_from_opts(opts, NULL, &error_abort);
+        g_assert_nonnull(chr2);
+        qemu_opts_del(opts);
+
+        /* Create third chardev */
+        opts = qemu_opts_create(qemu_find_opts("chardev"), "chr3",
+                                1, &error_abort);
+        qemu_opt_set(opts, "backend", "pipe", &error_abort);
+        qemu_opt_set(opts, "path", pipe, &error_abort);
+        chr3 = qemu_chr_new_from_opts(opts, NULL, &error_abort);
+        g_assert_nonnull(chr3);
+
+        /* Create hub0 and refer 3 backend chardevs */
+        opts = qemu_opts_create(qemu_find_opts("chardev"), "hub0",
+                                1, &error_abort);
+        qemu_opt_set(opts, "backend", "hub", &error_abort);
+        qemu_opt_set(opts, "chardevs.0", "chr1", &error_abort);
+        qemu_opt_set(opts, "chardevs.1", "chr2", &error_abort);
+        qemu_opt_set(opts, "chardevs.2", "chr3", &error_abort);
+        hub = qemu_chr_new_from_opts(opts, NULL, &error_abort);
+        g_assert_nonnull(hub);
+        qemu_opts_del(opts);
+
+        /* Attach hub to a frontend */
+        qemu_chr_fe_init(&chr_be, hub, &error_abort);
+        qemu_chr_fe_set_handlers(&chr_be,
+                                 fe_can_read,
+                                 fe_read,
+                                 fe_event,
+                                 NULL,
+                                 &h,
+                                 NULL, true);
+
+        /* Write to frontend, chr_be */
+        ret = qemu_chr_fe_write(&chr_be, (void *)"thisis", 6);
+        g_assert_cmpint(ret, ==, 6);
+
+        data = qmp_ringbuf_read("chr1", RB_SIZE, false, 0, &error_abort);
+        g_assert_cmpint(strlen(data), ==, 6);
+        g_assert_cmpstr(data, ==, "thisis");
+        g_free(data);
+
+        data = qmp_ringbuf_read("chr2", RB_SIZE, false, 0, &error_abort);
+        g_assert_cmpint(strlen(data), ==, 6);
+        g_assert_cmpstr(data, ==, "thisis");
+        g_free(data);
+
+        fd = open(out, O_RDWR);
+        ret = read(fd, buf, sizeof(buf));
+        g_assert_cmpint(ret, ==, 6);
+        buf[ret] = 0;
+        g_assert_cmpstr(buf, ==, "thisis");
+        close(fd);
+
+        /* Add watch. 0 indicates no watches if nothing to wait for */
+        ret = qemu_chr_fe_add_watch(&chr_be, G_IO_OUT | G_IO_HUP,
+                                    NULL, NULL);
+        g_assert_cmpint(ret, ==, 0);
+
+        /*
+         * Write to frontend, chr_be, until EAGAIN. Make sure length is
+         * power of two to fit nicely the whole pipe buffer.
+         */
+        len = 0;
+        while ((ret = qemu_chr_fe_write(&chr_be, (void *)"thisisit", 8))
+               != -1) {
+            len += ret;
+        }
+        g_assert_cmpint(errno, ==, EAGAIN);
+
+        /* Further all writes should cause EAGAIN */
+        ret = qemu_chr_fe_write(&chr_be, (void *)"b", 1);
+        g_assert_cmpint(ret, ==, -1);
+        g_assert_cmpint(errno, ==, EAGAIN);
+
+        /*
+         * Add watch. Non 0 indicates we have a blocked chardev, which
+         * can wakes us up when write is possible.
+         */
+        ret = qemu_chr_fe_add_watch(&chr_be, G_IO_OUT | G_IO_HUP,
+                                    NULL, NULL);
+        g_assert_cmpint(ret, !=, 0);
+        g_source_remove(ret);
+
+        /* Drain pipe and ring buffers */
+        fd = open(out, O_RDWR);
+        while ((ret = read(fd, buf, MIN(sizeof(buf), len))) != -1 && len > 0) {
+            len -= ret;
+        }
+        close(fd);
+
+        data = qmp_ringbuf_read("chr1", RB_SIZE, false, 0, &error_abort);
+        g_assert_cmpint(strlen(data), ==, 128);
+        g_free(data);
+
+        data = qmp_ringbuf_read("chr2", RB_SIZE, false, 0, &error_abort);
+        g_assert_cmpint(strlen(data), ==, 128);
+        g_free(data);
+
+        /*
+         * Now we are good to go, first repeat "lost" sequence, which
+         * was already consumed and drained by the ring buffers, but
+         * pipe have not recieved that yet.
+         */
+        ret = qemu_chr_fe_write(&chr_be, (void *)"thisisit", 8);
+        g_assert_cmpint(ret, ==, 8);
+
+        ret = qemu_chr_fe_write(&chr_be, (void *)"streamisrestored", 16);
+        g_assert_cmpint(ret, ==, 16);
+
+        data = qmp_ringbuf_read("chr1", RB_SIZE, false, 0, &error_abort);
+        g_assert_cmpint(strlen(data), ==, 16);
+        /* Only last 16 bytes, see big comment above */
+        g_assert_cmpstr(data, ==, "streamisrestored");
+        g_free(data);
+
+        data = qmp_ringbuf_read("chr2", RB_SIZE, false, 0, &error_abort);
+        g_assert_cmpint(strlen(data), ==, 16);
+        /* Only last 16 bytes, see big comment above */
+        g_assert_cmpstr(data, ==, "streamisrestored");
+        g_free(data);
+
+        fd = open(out, O_RDWR);
+        ret = read(fd, buf, sizeof(buf));
+        g_assert_cmpint(ret, ==, 24);
+        buf[ret] = 0;
+        /* Both 8 and 16 bytes */
+        g_assert_cmpstr(buf, ==, "thisisitstreamisrestored");
+        close(fd);
+
+        g_free(in);
+        g_free(out);
+        g_free(tmp_path);
+        g_free(pipe);
+
+        /* Finalize frontend */
+        qemu_chr_fe_deinit(&chr_be, false);
+
+        /* Finalize hub0 */
+        qmp_chardev_remove("hub0", &error_abort);
+
+        /* Finalize backend chardevs */
+        qmp_chardev_remove("chr1", &error_abort);
+        qmp_chardev_remove("chr2", &error_abort);
+        qmp_chardev_remove("chr3", &error_abort);
+    }
+#endif
+}
 
 static void websock_server_read(void *opaque, const uint8_t *buf, int size)
 {
@@ -1507,6 +1904,7 @@ int main(int argc, char **argv)
     g_test_add_func("/char/invalid", char_invalid_test);
     g_test_add_func("/char/ringbuf", char_ringbuf_test);
     g_test_add_func("/char/mux", char_mux_test);
+    g_test_add_func("/char/hub", char_hub_test);
 #ifdef _WIN32
     g_test_add_func("/char/console/subprocess", char_console_test_subprocess);
     g_test_add_func("/char/console", char_console_test);
diff --git a/ui/dbus-console.c b/ui/dbus-console.c
index 5eb1d40..85e215e 100644
--- a/ui/dbus-console.c
+++ b/ui/dbus-console.c
@@ -305,10 +305,16 @@ dbus_console_register_listener(DBusDisplayConsole *ddc,
 #endif
     );
 
+    GDBusConnectionFlags flags =
+        G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_SERVER;
+#ifdef WIN32
+    flags |= G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_ALLOW_ANONYMOUS;
+#endif
+
     listener_conn = g_dbus_connection_new_sync(
         G_IO_STREAM(socket_conn),
         guid,
-        G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_SERVER,
+        flags,
         NULL, NULL, &err);
     if (err) {
         error_report("Failed to setup peer connection: %s", err->message);
diff --git a/ui/dbus-display1.xml b/ui/dbus-display1.xml
index e70f284..72deefa 100644
--- a/ui/dbus-display1.xml
+++ b/ui/dbus-display1.xml
@@ -527,14 +527,14 @@
   <interface name="org.qemu.Display1.Listener.Win32.Map">
     <!--
         ScanoutMap:
-        @handle: the shared map handle value.
+        @handle: the shared file mapping handle value (not a file handle)
         @offset: mapping offset.
         @width: display width, in pixels.
         @height: display height, in pixels.
         @stride: stride, in bytes.
         @pixman_format: image format (ex: ``PIXMAN_X8R8G8B8``).
 
-        Resize and update the display content with a shared map.
+        Resize and update the display content with a shared file mapping object.
     -->
     <method name="ScanoutMap">
       <arg type="t" name="handle" direction="in"/>
@@ -774,6 +774,18 @@
     </method>
 
     <!--
+        NSamples:
+
+        The number of samples per read/write frames. (for example the default is
+        480, or 10ms at 48kHz)
+
+        (earlier version of the display interface do not provide this property)
+    -->
+    <property name="NSamples" type="u" access="read">
+      <annotation name="org.freedesktop.DBus.Property.EmitsChangedSignal" value="const"/>
+    </property>
+
+    <!--
         Interfaces:
 
         This property lists extra interfaces provided by the
diff --git a/ui/dbus.c b/ui/dbus.c
index 7b258c6..2eb03aa 100644
--- a/ui/dbus.c
+++ b/ui/dbus.c
@@ -317,11 +317,17 @@ dbus_display_add_client(int csock, Error **errp)
     conn = g_socket_connection_factory_create_connection(socket);
 
     dbus_display->add_client_cancellable = g_cancellable_new();
+    GDBusConnectionFlags flags =
+        G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_SERVER |
+        G_DBUS_CONNECTION_FLAGS_DELAY_MESSAGE_PROCESSING;
+
+#ifdef WIN32
+    flags |= G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_ALLOW_ANONYMOUS;
+#endif
 
     g_dbus_connection_new(G_IO_STREAM(conn),
                           guid,
-                          G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_SERVER |
-                          G_DBUS_CONNECTION_FLAGS_DELAY_MESSAGE_PROCESSING,
+                          flags,
                           NULL,
                           dbus_display->add_client_cancellable,
                           dbus_display_add_client_ready,