[Qemu-devel] [PATCH v3 6/6] Add dbus-vmstate object

[Marc-André Lureau]

When instanciated, this object will connect to the given D-Bus
bus. During migration, it will take the data from org.qemu.VMState1
instances.

See documentation for further details.

Signed-off-by: Marc-André Lureau <address@hidden>
---
 MAINTAINERS                   |   6 +
 backends/Makefile.objs        |   4 +
 backends/dbus-vmstate.c       | 530 ++++++++++++++++++++++++++++++++++
 configure                     |   7 +
 docs/interop/dbus-vmstate.rst |  68 +++++
 docs/interop/index.rst        |   1 +
 tests/Makefile.include        |  19 +-
 tests/dbus-vmstate-daemon.sh  |  95 ++++++
 tests/dbus-vmstate-test.c     | 386 +++++++++++++++++++++++++
 tests/dbus-vmstate1.xml       |  12 +
 10 files changed, 1127 insertions(+), 1 deletion(-)
 create mode 100644 backends/dbus-vmstate.c
 create mode 100644 docs/interop/dbus-vmstate.rst
 create mode 100755 tests/dbus-vmstate-daemon.sh
 create mode 100644 tests/dbus-vmstate-test.c
 create mode 100644 tests/dbus-vmstate1.xml

diff --git a/MAINTAINERS b/MAINTAINERS
index 50eaf005f4..f641870c40 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2153,6 +2153,12 @@ F: tests/migration-test.c
 F: docs/devel/migration.rst
 F: qapi/migration.json
 
+DBus VMState
+M: Marc-André Lureau <address@hidden>
+S: Maintained
+F: backends/dbus-vmstate.c
+F: tests/dbus-vmstate*
+
 Seccomp
 M: Eduardo Otubo <address@hidden>
 S: Supported
diff --git a/backends/Makefile.objs b/backends/Makefile.objs
index f0691116e8..28a847cd57 100644
--- a/backends/Makefile.objs
+++ b/backends/Makefile.objs
@@ -17,3 +17,7 @@ endif
 common-obj-$(call land,$(CONFIG_VHOST_USER),$(CONFIG_VIRTIO)) += vhost-user.o
 
 common-obj-$(CONFIG_LINUX) += hostmem-memfd.o
+
+common-obj-$(CONFIG_GIO) += dbus-vmstate.o
+dbus-vmstate.o-cflags = $(GIO_CFLAGS)
+dbus-vmstate.o-libs = $(GIO_LIBS)
diff --git a/backends/dbus-vmstate.c b/backends/dbus-vmstate.c
new file mode 100644
index 0000000000..559f5430c5
--- /dev/null
+++ b/backends/dbus-vmstate.c
@@ -0,0 +1,530 @@
+/*
+ * QEMU dbus-vmstate
+ *
+ * Copyright (C) 2019 Red Hat Inc
+ *
+ * Authors:
+ *  Marc-André Lureau <address@hidden>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/units.h"
+#include "qemu/error-report.h"
+#include "qapi/error.h"
+#include "qom/object_interfaces.h"
+#include "qapi/qmp/qerror.h"
+#include "migration/vmstate.h"
+#include <gio/gio.h>
+
+typedef struct DBusVMState DBusVMState;
+typedef struct DBusVMStateClass DBusVMStateClass;
+
+#define TYPE_DBUS_VMSTATE "dbus-vmstate"
+#define DBUS_VMSTATE(obj)                                \
+    OBJECT_CHECK(DBusVMState, (obj), TYPE_DBUS_VMSTATE)
+#define DBUS_VMSTATE_GET_CLASS(obj)                              \
+    OBJECT_GET_CLASS(DBusVMStateClass, (obj), TYPE_DBUS_VMSTATE)
+#define DBUS_VMSTATE_CLASS(klass)                                    \
+    OBJECT_CLASS_CHECK(DBusVMStateClass, (klass), TYPE_DBUS_VMSTATE)
+
+struct DBusVMStateClass {
+    ObjectClass parent_class;
+};
+
+struct DBusVMState {
+    Object parent;
+
+    GDBusConnection *bus;
+    char *dbus_addr;
+    char *id_list;
+
+    uint32_t data_size;
+    uint8_t *data;
+};
+
+static const GDBusPropertyInfo vmstate_property_info[] = {
+    { -1, (char *) "Id", (char *) "s",
+      G_DBUS_PROPERTY_INFO_FLAGS_READABLE, NULL },
+};
+
+static const GDBusPropertyInfo * const vmstate_property_info_pointers[] = {
+    &vmstate_property_info[0],
+    NULL
+};
+
+static const GDBusInterfaceInfo vmstate1_interface_info = {
+    -1,
+    (char *) "org.qemu.VMState1",
+    (GDBusMethodInfo **) NULL,
+    (GDBusSignalInfo **) NULL,
+    (GDBusPropertyInfo **) &vmstate_property_info_pointers,
+    NULL,
+};
+
+#define DBUS_VMSTATE_SIZE_LIMIT (1 * MiB)
+
+static char **
+dbus_get_vmstate1_names(DBusVMState *self, GError **err)
+{
+    g_autoptr(GDBusProxy) proxy = NULL;
+    g_autoptr(GVariant) result = NULL;
+    g_autoptr(GVariant) child = NULL;
+
+    proxy = g_dbus_proxy_new_sync(self->bus, G_DBUS_PROXY_FLAGS_NONE, NULL,
+                                  "org.freedesktop.DBus",
+                                  "/org/freedesktop/DBus",
+                                  "org.freedesktop.DBus",
+                                  NULL, err);
+    if (!proxy) {
+        return NULL;
+    }
+
+    result = g_dbus_proxy_call_sync(proxy, "ListQueuedOwners",
+                                    g_variant_new("(s)", "org.qemu.VMState1"),
+                                    G_DBUS_CALL_FLAGS_NO_AUTO_START,
+                                    -1, NULL, err);
+    if (!result) {
+        return NULL;
+    }
+
+    child = g_variant_get_child_value(result, 0);
+    return g_variant_dup_strv(child, NULL);
+}
+
+static GHashTable *
+get_id_list_set(DBusVMState *self)
+{
+    g_auto(GStrv) ids = NULL;
+    g_autoptr(GHashTable) set = NULL;
+    int i;
+
+    if (!self->id_list) {
+        return NULL;
+    }
+
+    ids = g_strsplit(self->id_list, ",", -1);
+    set = g_hash_table_new_full(g_str_hash, g_str_equal, g_free, NULL);
+    for (i = 0; ids[i]; i++) {
+        g_hash_table_add(set, ids[i]);
+        ids[i] = NULL;
+    }
+
+    return g_steal_pointer(&set);
+}
+
+static GHashTable *
+dbus_get_proxies(DBusVMState *self, GError **err)
+{
+    g_autoptr(GError) local_err = NULL;
+    g_autoptr(GHashTable) proxies = NULL;
+    g_autoptr(GHashTable) ids = NULL;
+    g_auto(GStrv) names = NULL;
+    size_t i;
+
+    ids = get_id_list_set(self);
+    proxies = g_hash_table_new_full(g_str_hash, g_str_equal,
+                                    g_free, g_object_unref);
+
+    names = dbus_get_vmstate1_names(self, &local_err);
+    if (!names) {
+        if (g_error_matches(local_err,
+                            G_DBUS_ERROR, G_DBUS_ERROR_NAME_HAS_NO_OWNER)) {
+            return proxies;
+        }
+        g_propagate_error(err, local_err);
+        return NULL;
+    }
+
+    for (i = 0; names[i]; i++) {
+        g_autoptr(GDBusProxy) proxy = NULL;
+        g_autoptr(GVariant) result = NULL;
+        g_autofree char *id = NULL;
+        size_t size;
+
+        proxy = g_dbus_proxy_new_sync(self->bus, G_DBUS_PROXY_FLAGS_NONE,
+                    (GDBusInterfaceInfo *) &vmstate1_interface_info,
+                    names[i],
+                    "/org/qemu/VMState1",
+                    "org.qemu.VMState1",
+                    NULL, err);
+        if (!proxy) {
+            return NULL;
+        }
+
+        result = g_dbus_proxy_get_cached_property(proxy, "Id");
+        if (!result) {
+            g_set_error_literal(err, G_IO_ERROR, G_IO_ERROR_FAILED,
+                                "VMState Id property is missing.");
+            return NULL;
+        }
+
+        id = g_variant_dup_string(result, &size);
+        if (ids && !g_hash_table_remove(ids, id)) {
+            g_clear_pointer(&id, g_free);
+            g_clear_object(&proxy);
+            continue;
+        }
+        if (size == 0 || size >= 256) {
+            g_set_error(err, G_IO_ERROR, G_IO_ERROR_FAILED,
+                        "VMState Id '%s' is invalid.", id);
+            return NULL;
+        }
+
+        if (!g_hash_table_insert(proxies, id, proxy)) {
+            g_set_error(err, G_IO_ERROR, G_IO_ERROR_FAILED,
+                        "Duplicated VMState Id '%s'", id);
+            return NULL;
+        }
+        id = NULL;
+        proxy = NULL;
+
+        g_clear_pointer(&result, g_variant_unref);
+    }
+
+    if (ids) {
+        g_autofree char **left = NULL;
+
+        left = (char **)g_hash_table_get_keys_as_array(ids, NULL);
+        if (*left) {
+            g_autofree char *leftids = g_strjoinv(",", left);
+            g_set_error(err, G_IO_ERROR, G_IO_ERROR_FAILED,
+                        "Required VMState Id are missing: %s", leftids);
+            return NULL;
+        }
+    }
+
+    return g_steal_pointer(&proxies);
+}
+
+static int
+dbus_load_state_proxy(GDBusProxy *proxy, const uint8_t *data, size_t size)
+{
+    g_autoptr(GError) err = NULL;
+    g_autoptr(GVariant) result = NULL;
+    g_autoptr(GVariant) value = NULL;
+
+    value = g_variant_new_fixed_array(G_VARIANT_TYPE_BYTE,
+                                      data, size, sizeof(char));
+    result = g_dbus_proxy_call_sync(proxy, "Load",
+                                    g_variant_new("(@ay)",
+                                                  g_steal_pointer(&value)),
+                                    G_DBUS_CALL_FLAGS_NO_AUTO_START,
+                                    -1, NULL, &err);
+    if (!result) {
+        error_report("Failed to Load: %s", err->message);
+        return -1;
+    }
+
+    return 0;
+}
+
+static int dbus_vmstate_post_load(void *opaque, int version_id)
+{
+    DBusVMState *self = DBUS_VMSTATE(opaque);
+    g_autoptr(GInputStream) m = NULL;
+    g_autoptr(GDataInputStream) s = NULL;
+    g_autoptr(GError) err = NULL;
+    g_autoptr(GHashTable) proxies = NULL;
+    uint32_t nelem;
+
+    proxies = dbus_get_proxies(self, &err);
+    if (!proxies) {
+        error_report("Failed to get proxies: %s", err->message);
+        return -1;
+    }
+
+    m = g_memory_input_stream_new_from_data(self->data, self->data_size, NULL);
+    s = g_data_input_stream_new(m);
+    g_data_input_stream_set_byte_order(s, G_DATA_STREAM_BYTE_ORDER_BIG_ENDIAN);
+
+    nelem = g_data_input_stream_read_uint32(s, NULL, &err);
+    if (err) {
+        goto error;
+    }
+
+    while (nelem > 0) {
+        GDBusProxy *proxy = NULL;
+        uint32_t len;
+        gsize bytes_read, avail;
+        char id[256];
+
+        len = g_data_input_stream_read_uint32(s, NULL, &err);
+        if (err) {
+            goto error;
+        }
+        if (len >= 256) {
+            error_report("Invalid DBus vmstate proxy name %u", len);
+            return -1;
+        }
+        if (!g_input_stream_read_all(G_INPUT_STREAM(s), id, len,
+                                     &bytes_read, NULL, &err)) {
+            goto error;
+        }
+        g_return_val_if_fail(bytes_read == len, -1);
+        id[len] = 0;
+
+        proxy = g_hash_table_lookup(proxies, id);
+        if (!proxy) {
+            error_report("Failed to find proxy Id '%s'", id);
+            return -1;
+        }
+
+        len = g_data_input_stream_read_uint32(s, NULL, &err);
+        avail = g_buffered_input_stream_get_available(
+            G_BUFFERED_INPUT_STREAM(s));
+
+        if (len > DBUS_VMSTATE_SIZE_LIMIT || len > avail) {
+            error_report("Invalid vmstate size: %u", len);
+            return -1;
+        }
+
+        if (dbus_load_state_proxy(proxy,
+                g_buffered_input_stream_peek_buffer(G_BUFFERED_INPUT_STREAM(s),
+                                                    NULL),
+                len) < 0) {
+            error_report("Failed to restore Id '%s'", id);
+            return -1;
+        }
+
+        if (!g_seekable_seek(G_SEEKABLE(s), len, G_SEEK_CUR, NULL, &err)) {
+            goto error;
+        }
+
+        nelem -= 1;
+    }
+
+    return 0;
+
+error:
+    error_report("Failed to read from stream: %s", err->message);
+    return -1;
+}
+
+static void
+dbus_save_state_proxy(gpointer key,
+                      gpointer value,
+                      gpointer user_data)
+{
+    GDataOutputStream *s = user_data;
+    const char *id = key;
+    GDBusProxy *proxy = value;
+    g_autoptr(GVariant) result = NULL;
+    g_autoptr(GVariant) child = NULL;
+    g_autoptr(GError) err = NULL;
+    const uint8_t *data;
+    gsize size;
+
+    result = g_dbus_proxy_call_sync(proxy, "Save",
+                                    NULL, G_DBUS_CALL_FLAGS_NO_AUTO_START,
+                                    -1, NULL, &err);
+    if (!result) {
+        error_report("Failed to Save: %s", err->message);
+        return;
+    }
+
+    child = g_variant_get_child_value(result, 0);
+    data = g_variant_get_fixed_array(child, &size, sizeof(char));
+    if (!data) {
+        error_report("Failed to Save: not a byte array");
+        return;
+    }
+    if (size > DBUS_VMSTATE_SIZE_LIMIT) {
+        error_report("Too large vmstate data to save: %lu", size);
+        return;
+    }
+
+    if (!g_data_output_stream_put_uint32(s, strlen(id), NULL, &err) ||
+        !g_data_output_stream_put_string(s, id, NULL, &err) ||
+        !g_data_output_stream_put_uint32(s, size, NULL, &err) ||
+        !g_output_stream_write_all(G_OUTPUT_STREAM(s),
+                                   data, size, NULL, NULL, &err)) {
+        error_report("Failed to write to stream: %s", err->message);
+    }
+}
+
+static int dbus_vmstate_pre_save(void *opaque)
+{
+    DBusVMState *self = DBUS_VMSTATE(opaque);
+    g_autoptr(GOutputStream) m = NULL;
+    g_autoptr(GDataOutputStream) s = NULL;
+    g_autoptr(GHashTable) proxies = NULL;
+    g_autoptr(GError) err = NULL;
+
+    proxies = dbus_get_proxies(self, &err);
+    if (!proxies) {
+        error_report("Failed to get proxies: %s", err->message);
+        return -1;
+    }
+
+    m = g_memory_output_stream_new_resizable();
+    s = g_data_output_stream_new(m);
+    g_data_output_stream_set_byte_order(s, 
G_DATA_STREAM_BYTE_ORDER_BIG_ENDIAN);
+
+    if (!g_data_output_stream_put_uint32(s, g_hash_table_size(proxies),
+                                         NULL, &err)) {
+        error_report("Failed to write to stream: %s", err->message);
+        return -1;
+    }
+
+    g_hash_table_foreach(proxies, dbus_save_state_proxy, s);
+
+    if (g_memory_output_stream_get_size(G_MEMORY_OUTPUT_STREAM(m))
+        > UINT32_MAX) {
+        error_report("DBus vmstate buffer is too large");
+        return -1;
+    }
+
+    if (!g_output_stream_close(G_OUTPUT_STREAM(m), NULL, &err)) {
+        error_report("Failed to close stream: %s", err->message);
+        return -1;
+    }
+
+    g_free(self->data);
+    self->data_size =
+        g_memory_output_stream_get_size(G_MEMORY_OUTPUT_STREAM(m));
+    self->data =
+        g_memory_output_stream_steal_data(G_MEMORY_OUTPUT_STREAM(m));
+
+    return 0;
+}
+
+static const VMStateDescription dbus_vmstate = {
+    .name = TYPE_DBUS_VMSTATE,
+    .version_id = 0,
+    .pre_save = dbus_vmstate_pre_save,
+    .post_load = dbus_vmstate_post_load,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT32(data_size, DBusVMState),
+        VMSTATE_VBUFFER_ALLOC_UINT32(data, DBusVMState, 0, 0, data_size),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static void
+dbus_vmstate_complete(UserCreatable *uc, Error **errp)
+{
+    DBusVMState *self = DBUS_VMSTATE(uc);
+    GError *err = NULL;
+    GDBusConnection *bus;
+
+    if (!object_resolve_path_type("", TYPE_DBUS_VMSTATE, NULL)) {
+        error_setg(errp, "There is already an instance of %s",
+                   TYPE_DBUS_VMSTATE);
+        return;
+    }
+
+    if (!self->dbus_addr) {
+        error_setg(errp, QERR_MISSING_PARAMETER, "addr");
+        return;
+    }
+
+    bus = g_dbus_connection_new_for_address_sync(self->dbus_addr,
+             G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_CLIENT |
+             G_DBUS_CONNECTION_FLAGS_MESSAGE_BUS_CONNECTION,
+             NULL, NULL, &err);
+    if (err) {
+        error_setg(errp, "failed to connect to DBus: '%s'", err->message);
+        g_clear_error(&err);
+    }
+
+    self->bus = bus;
+
+    if (vmstate_register(VMSTATE_IF(self), -1, &dbus_vmstate, self) < 0) {
+        error_setg(errp, "Failed to register vmstate");
+    }
+}
+
+static void
+dbus_vmstate_finalize(Object *o)
+{
+    DBusVMState *self = DBUS_VMSTATE(o);
+
+    vmstate_unregister(VMSTATE_IF(self), &dbus_vmstate, self);
+
+    g_clear_object(&self->bus);
+    g_free(self->dbus_addr);
+    g_free(self->id_list);
+    g_free(self->data);
+}
+
+static char *
+get_dbus_addr(Object *o, Error **errp)
+{
+    DBusVMState *self = DBUS_VMSTATE(o);
+
+    return g_strdup(self->dbus_addr);
+}
+
+static void
+set_dbus_addr(Object *o, const char *str, Error **errp)
+{
+    DBusVMState *self = DBUS_VMSTATE(o);
+
+    g_free(self->dbus_addr);
+    self->dbus_addr = g_strdup(str);
+}
+
+static char *
+get_id_list(Object *o, Error **errp)
+{
+    DBusVMState *self = DBUS_VMSTATE(o);
+
+    return g_strdup(self->id_list);
+}
+
+static void
+set_id_list(Object *o, const char *str, Error **errp)
+{
+    DBusVMState *self = DBUS_VMSTATE(o);
+
+    g_free(self->id_list);
+    self->id_list = g_strdup(str);
+}
+
+static char *
+dbus_vmstate_get_id(VMStateIf *vmif)
+{
+    return g_strdup(TYPE_DBUS_VMSTATE);
+}
+
+static void
+dbus_vmstate_class_init(ObjectClass *oc, void *data)
+{
+    UserCreatableClass *ucc = USER_CREATABLE_CLASS(oc);
+    VMStateIfClass *vc = VMSTATE_IF_CLASS(oc);
+
+    ucc->complete = dbus_vmstate_complete;
+    vc->get_id = dbus_vmstate_get_id;
+
+    object_class_property_add_str(oc, "addr",
+                                  get_dbus_addr, set_dbus_addr,
+                                  &error_abort);
+    object_class_property_add_str(oc, "id-list",
+                                  get_id_list, set_id_list,
+                                  &error_abort);
+}
+
+static const TypeInfo dbus_vmstate_info = {
+    .name = TYPE_DBUS_VMSTATE,
+    .parent = TYPE_OBJECT,
+    .instance_size = sizeof(DBusVMState),
+    .instance_finalize = dbus_vmstate_finalize,
+    .class_size = sizeof(DBusVMStateClass),
+    .class_init = dbus_vmstate_class_init,
+    .interfaces = (InterfaceInfo[]) {
+        { TYPE_USER_CREATABLE },
+        { TYPE_VMSTATE_IF },
+        { }
+    }
+};
+
+static void
+register_types(void)
+{
+    type_register_static(&dbus_vmstate_info);
+}
+
+type_init(register_types);
diff --git a/configure b/configure
index 95134c0180..0a6eb2ebcd 100755
--- a/configure
+++ b/configure
@@ -3665,10 +3665,16 @@ if $pkg_config --atleast-version=$glib_req_ver gio-2.0; 
then
     gio=yes
     gio_cflags=$($pkg_config --cflags gio-2.0)
     gio_libs=$($pkg_config --libs gio-2.0)
+    gdbus_codegen=$($pkg_config --variable=gdbus_codegen gio-2.0)
 else
     gio=no
 fi
 
+if $pkg_config --atleast-version=$glib_req_ver gio-unix-2.0; then
+    gio_cflags="$gio_cflags $($pkg_config --cflags gio-unix-2.0)"
+    gio_libs="$gio_libs $($pkg_config --libs gio-unix-2.0)"
+fi
+
 # Sanity check that the current size_t matches the
 # size that glib thinks it should be. This catches
 # problems on multi-arch where people try to build
@@ -6831,6 +6837,7 @@ if test "$gio" = "yes" ; then
     echo "CONFIG_GIO=y" >> $config_host_mak
     echo "GIO_CFLAGS=$gio_cflags" >> $config_host_mak
     echo "GIO_LIBS=$gio_libs" >> $config_host_mak
+    echo "GDBUS_CODEGEN=$gdbus_codegen" >> $config_host_mak
 fi
 echo "CONFIG_TLS_PRIORITY=\"$tls_priority\"" >> $config_host_mak
 if test "$gnutls" = "yes" ; then
diff --git a/docs/interop/dbus-vmstate.rst b/docs/interop/dbus-vmstate.rst
new file mode 100644
index 0000000000..78070be1bd
--- /dev/null
+++ b/docs/interop/dbus-vmstate.rst
@@ -0,0 +1,68 @@
+=============
+D-Bus VMState
+=============
+
+Introduction
+============
+
+The QEMU dbus-vmstate object aim is to migrate helpers data running on
+a QEMU D-Bus bus. (refer to the :doc:`dbus` document for
+recommendation on D-Bus usage)
+
+Upon migration, QEMU will go through the queue of
+``org.qemu.VMState1`` D-Bus name owners and query their ``Id``. It
+must be unique among the helpers.
+
+It will then save arbitrary data of each Id to be transferred in the
+migration stream and restored/loaded at the corresponding destination
+helper.
+
+The data amount to be transferred is limited to 1Mb. The state must be
+saved quickly (a few seconds maximum). (D-Bus imposes a time limit on
+reply anyway, and migration would fail if data isn't given quickly
+enough)
+
+dbus-vmstate object can be configured with the expected list of
+helpers by setting its ``id-list`` property, with a coma-separated
+``Id`` list.
+
+Interface
+=========
+
+On object path ``/org/qemu/VMState1``, the following
+``org.qemu.VMState1`` interface should be implemented:
+
+.. code:: xml
+
+  <interface name="org.qemu.VMState1">
+    <property name="Id" type="s" access="read"/>
+    <method name="Load">
+      <arg type="ay" name="data" direction="in"/>
+    </method>
+    <method name="Save">
+      <arg type="ay" name="data" direction="out"/>
+    </method>
+  </interface>
+
+"Id" property
+-------------
+
+A string that identifies the helper uniquely.
+
+Load(in u8[] bytes) method
+--------------------------
+
+The method called on destination with the state to restore.
+
+The helper may be initially started in a waiting state (with
+an --incoming argument for example), and it may resume on success.
+
+An error may be returned to the caller.
+
+Save(out u8[] bytes) method
+---------------------------
+
+The method called on the source to get the current state to be
+migrated. The helper should continue to run normally.
+
+An error may be returned to the caller.
diff --git a/docs/interop/index.rst b/docs/interop/index.rst
index fa4478ce2e..75832f44ac 100644
--- a/docs/interop/index.rst
+++ b/docs/interop/index.rst
@@ -14,6 +14,7 @@ Contents:
 
    bitmaps
    dbus
+   dbus-vmstate
    live-block-operations
    pr-helper
    vhost-user
diff --git a/tests/Makefile.include b/tests/Makefile.include
index d4502a30eb..eb40e8a5e7 100644
--- a/tests/Makefile.include
+++ b/tests/Makefile.include
@@ -158,7 +158,9 @@ check-qtest-pci-$(CONFIG_RTL8139_PCI) += 
tests/rtl8139-test$(EXESUF)
 check-qtest-pci-$(CONFIG_VGA) += tests/display-vga-test$(EXESUF)
 check-qtest-pci-$(CONFIG_HDA) += tests/intel-hda-test$(EXESUF)
 check-qtest-pci-$(CONFIG_IVSHMEM_DEVICE) += tests/ivshmem-test$(EXESUF)
-
+ifneq ($(GDBUS_CODEGEN),)
+check-qtest-pci-$(CONFIG_GIO) += tests/dbus-vmstate-test$(EXESUF)
+endif
 check-qtest-i386-$(CONFIG_ISA_TESTDEV) = tests/endianness-test$(EXESUF)
 check-qtest-i386-y += tests/fdc-test$(EXESUF)
 check-qtest-i386-y += tests/ide-test$(EXESUF)
@@ -620,6 +622,19 @@ tests/qapi-schema/doc-good.test.texi: 
$(SRC_PATH)/tests/qapi-schema/doc-good.jso
        @mv tests/qapi-schema/doc-good-qapi-doc.texi $@
        @rm -f tests/qapi-schema/doc-good-qapi-*.[ch] 
tests/qapi-schema/doc-good-qmp-*.[ch]
 
+tests/dbus-vmstate1.h tests/dbus-vmstate1.c: tests/dbus-vmstate1-gen-timestamp 
;
+tests/dbus-vmstate1-gen-timestamp: $(SRC_PATH)/tests/dbus-vmstate1.xml
+       $(call quiet-command,$(GDBUS_CODEGEN) $< \
+               --interface-prefix org.qemu --generate-c-code 
tests/dbus-vmstate1, \
+               "GEN","$(@:%-timestamp=%)")
+       @>$@
+
+tests/dbus-vmstate-test.o-cflags := -DSRCDIR="$(SRC_PATH)"
+tests/dbus-vmstate1.o-cflags := $(GIO_CFLAGS)
+tests/dbus-vmstate1.o-libs := $(GIO_LIBS)
+
+tests/dbus-vmstate-test.o: tests/dbus-vmstate1.h
+
 tests/test-string-output-visitor$(EXESUF): tests/test-string-output-visitor.o 
$(test-qapi-obj-y)
 tests/test-string-input-visitor$(EXESUF): tests/test-string-input-visitor.o 
$(test-qapi-obj-y)
 tests/test-qmp-event$(EXESUF): tests/test-qmp-event.o $(test-qapi-obj-y) 
tests/test-qapi-events.o
@@ -822,6 +837,7 @@ tests/test-filter-mirror$(EXESUF): 
tests/test-filter-mirror.o $(qtest-obj-y)
 tests/test-filter-redirector$(EXESUF): tests/test-filter-redirector.o 
$(qtest-obj-y)
 tests/test-x86-cpuid-compat$(EXESUF): tests/test-x86-cpuid-compat.o 
$(qtest-obj-y)
 tests/ivshmem-test$(EXESUF): tests/ivshmem-test.o 
contrib/ivshmem-server/ivshmem-server.o $(libqos-pc-obj-y) $(libqos-spapr-obj-y)
+tests/dbus-vmstate-test$(EXESUF): tests/dbus-vmstate-test.o 
tests/dbus-vmstate1.o $(libqos-pc-obj-y) $(libqos-spapr-obj-y)
 tests/vhost-user-bridge$(EXESUF): tests/vhost-user-bridge.o $(test-util-obj-y) 
libvhost-user.a
 tests/test-uuid$(EXESUF): tests/test-uuid.o $(test-util-obj-y)
 tests/test-arm-mptimer$(EXESUF): tests/test-arm-mptimer.o
@@ -1176,6 +1192,7 @@ check-clean:
        rm -rf $(check-unit-y) tests/*.o $(QEMU_IOTESTS_HELPERS-y)
        rm -rf $(sort $(foreach target,$(SYSEMU_TARGET_LIST), 
$(check-qtest-$(target)-y)) $(check-qtest-generic-y))
        rm -f tests/test-qapi-gen-timestamp
+       rm -f tests/dbus-vmstate1-gen-timestamp
        rm -rf $(TESTS_VENV_DIR) $(TESTS_RESULTS_DIR)
 
 clean: check-clean
diff --git a/tests/dbus-vmstate-daemon.sh b/tests/dbus-vmstate-daemon.sh
new file mode 100755
index 0000000000..c4394ac918
--- /dev/null
+++ b/tests/dbus-vmstate-daemon.sh
@@ -0,0 +1,95 @@
+#!/bin/sh
+
+# dbus-daemon wrapper script for dbus-vmstate testing
+#
+# This script allows to tweak the dbus-daemon policy during the test
+# to test different configurations.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <http://www.gnu.org/licenses/>.
+#
+# Copyright (C) 2019 Red Hat, Inc.
+
+write_config()
+{
+    CONF="$1"
+    cat > "$CONF" <<EOF
+<busconfig>
+  <type>session</type>
+  <listen>unix:tmpdir=/tmp</listen>
+
+  <policy context="default">
+     <!-- Holes must be punched in service configuration files for
+          name ownership and sending method calls -->
+     <deny own="*"/>
+     <deny send_type="method_call"/>
+
+     <!-- Signals and reply messages (method returns, errors) are allowed
+          by default -->
+     <allow send_type="signal"/>
+     <allow send_requested_reply="true" send_type="method_return"/>
+     <allow send_requested_reply="true" send_type="error"/>
+
+     <!-- All messages may be received by default -->
+     <allow receive_type="method_call"/>
+     <allow receive_type="method_return"/>
+     <allow receive_type="error"/>
+     <allow receive_type="signal"/>
+
+     <!-- Allow anyone to talk to the message bus -->
+     <allow send_destination="org.freedesktop.DBus"
+            send_interface="org.freedesktop.DBus" />
+     <allow send_destination="org.freedesktop.DBus"
+            send_interface="org.freedesktop.DBus.Introspectable"/>
+     <allow send_destination="org.freedesktop.DBus"
+            send_interface="org.freedesktop.DBus.Properties"/>
+     <!-- But disallow some specific bus services -->
+     <deny send_destination="org.freedesktop.DBus"
+           send_interface="org.freedesktop.DBus"
+           send_member="UpdateActivationEnvironment"/>
+     <deny send_destination="org.freedesktop.DBus"
+           send_interface="org.freedesktop.DBus.Debug.Stats"/>
+     <deny send_destination="org.freedesktop.DBus"
+           send_interface="org.freedesktop.systemd1.Activator"/>
+
+     <allow own="org.qemu.VMState1"/>
+     <allow send_destination="org.qemu.VMState1"/>
+     <allow receive_sender="org.qemu.VMState1"/>
+
+  </policy>
+
+  <include if_selinux_enabled="yes"
+   selinux_root_relative="yes">contexts/dbus_contexts</include>
+
+</busconfig>
+EOF
+}
+
+ARGS=
+for arg in "$@"
+do
+    case $arg in
+        --config-file=*)
+          CONF="${arg#*=}"
+          write_config "$CONF"
+          ARGS="$ARGS $1"
+          shift
+        ;;
+        *)
+          ARGS="$ARGS $1"
+          shift
+        ;;
+    esac
+done
+
+exec dbus-daemon $ARGS
diff --git a/tests/dbus-vmstate-test.c b/tests/dbus-vmstate-test.c
new file mode 100644
index 0000000000..bcf2372e15
--- /dev/null
+++ b/tests/dbus-vmstate-test.c
@@ -0,0 +1,386 @@
+#include "qemu/osdep.h"
+#include <glib/gstdio.h>
+#include <gio/gio.h>
+#include "libqtest.h"
+#include "qemu-common.h"
+#include "dbus-vmstate1.h"
+
+static char *workdir;
+
+typedef struct TestServerId {
+    const char *name;
+    const char *data;
+    size_t size;
+} TestServerId;
+
+static const TestServerId idA = {
+    "idA", "I'am\0idA!", sizeof("I'am\0idA!")
+};
+
+static const TestServerId idB = {
+    "idB", "I'am\0idB!", sizeof("I'am\0idB!")
+};
+
+typedef struct TestServer {
+    const TestServerId *id;
+    bool save_called;
+    bool load_called;
+} TestServer;
+
+typedef struct Test {
+    const char *id_list;
+    bool migrate_fail;
+    bool without_dst_b;
+    TestServer srcA;
+    TestServer dstA;
+    TestServer srcB;
+    TestServer dstB;
+    GMainLoop *loop;
+    QTestState *src_qemu;
+} Test;
+
+static gboolean
+vmstate_load(VMState1 *object, GDBusMethodInvocation *invocation,
+             const gchar *arg_data, gpointer user_data)
+{
+    TestServer *h = user_data;
+    g_autoptr(GVariant) var = NULL;
+    GVariant *args;
+    const uint8_t *data;
+    size_t size;
+
+    args = g_dbus_method_invocation_get_parameters(invocation);
+    var = g_variant_get_child_value(args, 0);
+    data = g_variant_get_fixed_array(var, &size, sizeof(char));
+    g_assert_cmpuint(size, ==, h->id->size);
+    g_assert(!memcmp(data, h->id->data, h->id->size));
+    h->load_called = true;
+
+    g_dbus_method_invocation_return_value(invocation, g_variant_new("()"));
+    return TRUE;
+}
+
+static gboolean
+vmstate_save(VMState1 *object, GDBusMethodInvocation *invocation,
+             gpointer user_data)
+{
+    TestServer *h = user_data;
+    GVariant *var;
+
+    var = g_variant_new_fixed_array(G_VARIANT_TYPE_BYTE,
+                                    h->id->data, h->id->size, sizeof(char));
+    g_dbus_method_invocation_return_value(invocation,
+                                          g_variant_new("(@ay)", var));
+    h->save_called = true;
+
+    return TRUE;
+}
+
+static gboolean
+wait_for_migration_complete(gpointer user_data)
+{
+    Test *test = user_data;
+    QDict *rsp_return;
+    bool stop = false;
+    const char *status;
+
+    qtest_qmp_send(test->src_qemu, "{ 'execute': 'query-migrate' }");
+    rsp_return = qtest_qmp_receive_success(test->src_qemu, NULL, NULL);
+    status = qdict_get_str(rsp_return, "status");
+    if (g_str_equal(status, "completed") || g_str_equal(status, "failed")) {
+        stop = true;
+        g_assert_cmpstr(status, ==,
+                        test->migrate_fail ? "failed" : "completed");
+    }
+    qobject_unref(rsp_return);
+
+    if (stop) {
+        g_main_loop_quit(test->loop);
+    }
+    return stop ? G_SOURCE_REMOVE : G_SOURCE_CONTINUE;
+}
+
+static void migrate(QTestState *who, const char *uri)
+{
+    QDict *args, *rsp;
+
+    args = qdict_new();
+    qdict_put_str(args, "uri", uri);
+
+    rsp = qtest_qmp(who, "{ 'execute': 'migrate', 'arguments': %p }", args);
+
+    g_assert(qdict_haskey(rsp, "return"));
+    qobject_unref(rsp);
+}
+
+typedef struct WaitNamed {
+    GMainLoop *loop;
+    bool named;
+} WaitNamed;
+
+static void
+named_cb(GDBusConnection *connection,
+         const gchar *name,
+         gpointer user_data)
+{
+    WaitNamed *t = user_data;
+
+    t->named = true;
+    g_main_loop_quit(t->loop);
+}
+
+static GDBusConnection *
+get_connection(Test *test, guint *ownid)
+{
+    g_autofree gchar *addr = NULL;
+    WaitNamed *wait;
+    GError *err = NULL;
+    GDBusConnection *c;
+
+    wait = g_new0(WaitNamed, 1);
+    wait->loop = test->loop;
+    addr = g_dbus_address_get_for_bus_sync(G_BUS_TYPE_SESSION, NULL, &err);
+    g_assert_no_error(err);
+
+    c = g_dbus_connection_new_for_address_sync(
+        addr,
+        G_DBUS_CONNECTION_FLAGS_MESSAGE_BUS_CONNECTION |
+        G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_CLIENT,
+        NULL, NULL, &err);
+    g_assert_no_error(err);
+    *ownid = g_bus_own_name_on_connection(c, "org.qemu.VMState1",
+                                          G_BUS_NAME_OWNER_FLAGS_NONE,
+                                          named_cb, named_cb, wait, g_free);
+    if (!wait->named) {
+        g_main_loop_run(wait->loop);
+    }
+
+    return c;
+}
+
+static GDBusObjectManagerServer *
+get_server(GDBusConnection *conn, TestServer *s, const TestServerId *id)
+{
+    g_autoptr(GDBusObjectSkeleton) sk = NULL;
+    g_autoptr(VMState1Skeleton) v = NULL;
+    GDBusObjectManagerServer *os;
+
+    s->id = id;
+    os = g_dbus_object_manager_server_new("/org/qemu");
+    sk = g_dbus_object_skeleton_new("/org/qemu/VMState1");
+
+    v = VMSTATE1_SKELETON(vmstate1_skeleton_new());
+    g_object_set(v, "id", id->name, NULL);
+
+    g_signal_connect(v, "handle-load", G_CALLBACK(vmstate_load), s);
+    g_signal_connect(v, "handle-save", G_CALLBACK(vmstate_save), s);
+
+    g_dbus_object_skeleton_add_interface(sk, G_DBUS_INTERFACE_SKELETON(v));
+    g_dbus_object_manager_server_export(os, sk);
+    g_dbus_object_manager_server_set_connection(os, conn);
+
+    return os;
+}
+
+static void
+set_id_list(Test *test, QTestState *s)
+{
+    if (!test->id_list) {
+        return;
+    }
+
+    g_assert(!qmp_rsp_is_err(qtest_qmp(s,
+        "{ 'execute': 'qom-set', 'arguments': "
+        "{ 'path': '/objects/dv', 'property': 'id-list', 'value': %s } }",
+        test->id_list)));
+}
+static void
+test_dbus_vmstate(Test *test)
+{
+    g_autofree char *src_qemu_args = NULL;
+    g_autofree char *dst_qemu_args = NULL;
+    g_autoptr(GTestDBus) srcbus = NULL;
+    g_autoptr(GTestDBus) dstbus = NULL;
+    g_autoptr(GDBusConnection) srcconnA = NULL;
+    g_autoptr(GDBusConnection) srcconnB = NULL;
+    g_autoptr(GDBusConnection) dstconnA = NULL;
+    g_autoptr(GDBusConnection) dstconnB = NULL;
+    g_autoptr(GDBusObjectManagerServer) srcserverA = NULL;
+    g_autoptr(GDBusObjectManagerServer) srcserverB = NULL;
+    g_autoptr(GDBusObjectManagerServer) dstserverA = NULL;
+    g_autoptr(GDBusObjectManagerServer) dstserverB = NULL;
+    g_auto(GStrv) srcaddr = NULL;
+    g_auto(GStrv) dstaddr = NULL;
+    g_autofree char *uri = NULL;
+    QTestState *src_qemu = NULL, *dst_qemu = NULL;
+    guint ownsrcA, ownsrcB, owndstA, owndstB;
+
+    uri = g_strdup_printf("unix:%s/migsocket", workdir);
+
+    test->loop = g_main_loop_new(NULL, TRUE);
+
+    srcbus = g_test_dbus_new(G_TEST_DBUS_NONE);
+    g_test_dbus_up(srcbus);
+    srcconnA = get_connection(test, &ownsrcA);
+    srcserverA = get_server(srcconnA, &test->srcA, &idA);
+    srcconnB = get_connection(test, &ownsrcB);
+    srcserverB = get_server(srcconnB, &test->srcB, &idB);
+
+    /* remove ,guid=foo part */
+    srcaddr = g_strsplit(g_test_dbus_get_bus_address(srcbus), ",", 2);
+    src_qemu_args =
+        g_strdup_printf("-object dbus-vmstate,id=dv,addr=%s", srcaddr[0]);
+
+    dstbus = g_test_dbus_new(G_TEST_DBUS_NONE);
+    g_test_dbus_up(dstbus);
+    dstconnA = get_connection(test, &owndstA);
+    dstserverA = get_server(dstconnA, &test->dstA, &idA);
+    if (!test->without_dst_b) {
+        dstconnB = get_connection(test, &owndstB);
+        dstserverB = get_server(dstconnB, &test->dstB, &idB);
+    }
+
+    dstaddr = g_strsplit(g_test_dbus_get_bus_address(dstbus), ",", 2);
+    dst_qemu_args =
+        g_strdup_printf("-object dbus-vmstate,id=dv,addr=%s -incoming %s",
+                        dstaddr[0], uri);
+
+    src_qemu = qtest_init(src_qemu_args);
+    dst_qemu = qtest_init(dst_qemu_args);
+    set_id_list(test, src_qemu);
+    set_id_list(test, dst_qemu);
+
+    migrate(src_qemu, uri);
+    test->src_qemu = src_qemu;
+    g_timeout_add_seconds(1, wait_for_migration_complete, test);
+
+    g_main_loop_run(test->loop);
+    g_main_loop_unref(test->loop);
+
+    if (test->migrate_fail) {
+        qtest_expect_exit_status(dst_qemu, 1);
+    }
+    qtest_quit(dst_qemu);
+    qtest_quit(src_qemu);
+    g_bus_unown_name(ownsrcA);
+    g_bus_unown_name(ownsrcB);
+    g_bus_unown_name(owndstA);
+    if (!test->without_dst_b) {
+        g_bus_unown_name(owndstB);
+    }
+}
+
+static void
+check_not_migrated(TestServer *s, TestServer *d)
+{
+    assert(!s->save_called);
+    assert(!s->load_called);
+    assert(!d->save_called);
+    assert(!d->load_called);
+}
+
+static void
+check_migrated(TestServer *s, TestServer *d)
+{
+    assert(s->save_called);
+    assert(!s->load_called);
+    assert(!d->save_called);
+    assert(d->load_called);
+}
+
+static void
+test_dbus_vmstate_without_list(void)
+{
+    Test test = { 0, };
+
+    test_dbus_vmstate(&test);
+
+    check_migrated(&test.srcA, &test.dstA);
+    check_migrated(&test.srcB, &test.dstB);
+}
+
+static void
+test_dbus_vmstate_with_list(void)
+{
+    Test test = { .id_list = "idA,idB" };
+
+    test_dbus_vmstate(&test);
+
+    check_migrated(&test.srcA, &test.dstA);
+    check_migrated(&test.srcB, &test.dstB);
+}
+
+static void
+test_dbus_vmstate_only_a(void)
+{
+    Test test = { .id_list = "idA" };
+
+    test_dbus_vmstate(&test);
+
+    check_migrated(&test.srcA, &test.dstA);
+    check_not_migrated(&test.srcB, &test.dstB);
+}
+
+static void
+test_dbus_vmstate_missing_src(void)
+{
+    Test test = { .id_list = "idA,idC", .migrate_fail = true };
+
+    test_dbus_vmstate(&test);
+    check_not_migrated(&test.srcA, &test.dstA);
+    check_not_migrated(&test.srcB, &test.dstB);
+}
+
+static void
+test_dbus_vmstate_missing_dst(void)
+{
+    Test test = { .id_list = "idA,idB",
+                  .without_dst_b = true,
+                  .migrate_fail = true };
+
+    test_dbus_vmstate(&test);
+
+    assert(test.srcA.save_called);
+    assert(test.srcB.save_called);
+    assert(!test.dstB.save_called);
+}
+
+int
+main(int argc, char **argv)
+{
+    GError *err = NULL;
+    g_autofree char *dbus_daemon = NULL;
+    int ret;
+
+    dbus_daemon = g_build_filename(G_STRINGIFY(SRCDIR),
+                                   "tests",
+                                   "dbus-vmstate-daemon.sh",
+                                   NULL);
+    g_setenv("G_TEST_DBUS_DAEMON", dbus_daemon, true);
+
+    g_test_init(&argc, &argv, NULL);
+
+    workdir = g_dir_make_tmp("dbus-vmstate-test-XXXXXX", &err);
+    if (!workdir) {
+        g_error("Unable to create temporary dir: %s\n", err->message);
+        exit(1);
+    }
+
+    qtest_add_func("/dbus-vmstate/without-list",
+                   test_dbus_vmstate_without_list);
+    qtest_add_func("/dbus-vmstate/with-list",
+                   test_dbus_vmstate_with_list);
+    qtest_add_func("/dbus-vmstate/only-a",
+                   test_dbus_vmstate_only_a);
+    qtest_add_func("/dbus-vmstate/missing-src",
+                   test_dbus_vmstate_missing_src);
+    qtest_add_func("/dbus-vmstate/missing-dst",
+                   test_dbus_vmstate_missing_dst);
+
+    ret = g_test_run();
+
+    rmdir(workdir);
+    g_free(workdir);
+
+    return ret;
+}
diff --git a/tests/dbus-vmstate1.xml b/tests/dbus-vmstate1.xml
new file mode 100644
index 0000000000..cc8563be4c
--- /dev/null
+++ b/tests/dbus-vmstate1.xml
@@ -0,0 +1,12 @@
+<?xml version="1.0"?>
+<node name="/" xmlns:doc="http://www.freedesktop.org/dbus/1.0/doc.dtd";>
+  <interface name="org.qemu.VMState1">
+    <property name="Id" type="s" access="read"/>
+    <method name="Load">
+      <arg type="ay" name="data" direction="in"/>
+    </method>
+    <method name="Save">
+      <arg type="ay" name="data" direction="out"/>
+    </method>
+  </interface>
+</node>
-- 
2.23.0