Re: [Qemu-devel] [PATCH v2 2/2] Add dbus-vmstate object

[Marc-André Lureau]

Hi

On Thu, Aug 22, 2019 at 2:56 PM Dr. David Alan Gilbert
<address@hidden> wrote:
>
> * Marc-André Lureau (address@hidden) wrote:
> > 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.
>
> I'll leave the main review to someone who understands the details of
> DBUS, however from the migration side:
>
> > Signed-off-by: Marc-André Lureau <address@hidden>
>
> <snip>
>
> > +
> > +static int
> > +dbus_load_state(QEMUFile *f, void *opaque, int version_id)
> > +{
> > +    DBusVMState *self = DBUS_VMSTATE(opaque);
> > +    uint8_t *data = NULL;
> > +    int ret = -1;
> > +    char id[256];
> > +    unsigned int size;
>
> Higher level question; do you actually need a separate ID, or does
> the ID that's stored by the migration code in the section name
> give you enough uniqueness?


The ID stored in migration section name is based on the handler ID:
TYPE_DBUS_VMSTATE "-" handler_id

By design, handler_id must be unique (and documented as such).

Do you see a problem with that approach?

>
> > +    if (qemu_get_counted_string(f, id) == 0) {
> > +        error_report("Invalid vmstate Id");
> > +        goto end;
>
> I generally prefer to include something telling me where the error has
> come from, just to make it easier to track down if I see the error in
> a log; e.g. use __func__

ok

>
> > +    }
> > +
> > +    if (g_strcmp0(id, self->id)) {
> > +        error_report("Invalid vmstate Id: %s != %s", id, self->id);
> > +        goto end;
> > +    }
> > +
> > +    size = qemu_get_be32(f);
> > +    if (size > DBUS_VMSTATE_SIZE_LIMIT) {
> > +        error_report("Invalid vmstate size: %u", size);
> > +        goto end;
> > +    }
> > +
> > +    data = g_malloc(size);
> > +    if (qemu_get_buffer(f, data, size) != size) {
> > +        error_report("Failed to read %u bytes", size);
> > +        goto end;
> > +    }
> > +
> > +    if (dbus_load_state_proxy(self->proxy, data, size) < 0) {
> > +        error_report("Failed to restore Id '%s'", id);
> > +        goto end;
> > +    }
> > +
> > +    ret = 0;
> > +
> > +end:
> > +    g_clear_pointer(&data, g_free);
> > +    return ret;
> > +}
> > +
> > +static void
> > +dbus_save_state(QEMUFile *f, void *opaque)
> > +{
> > +    DBusVMState *self = DBUS_VMSTATE(opaque);
> > +    GVariant *result = NULL, *child = NULL;
> > +    const uint8_t *data;
> > +    size_t size;
> > +    GError *err = NULL;
> > +
> > +    result = g_dbus_proxy_call_sync(self->proxy, "Save",
> > +                                    NULL, G_DBUS_CALL_FLAGS_NO_AUTO_START,
> > +                                    -1, NULL, &err);
> > +    if (!result) {
> > +        error_report("Failed to Save: %s", err->message);
> > +        g_clear_error(&err);
> > +        goto end;
> > +    }
> > +
> > +    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");
> > +        goto end;
> > +    }
> > +    if (size > DBUS_VMSTATE_SIZE_LIMIT) {
> > +        error_report("Too much vmstate data to save: %zu", size);
> > +        goto end;
> > +    }
> > +
> > +    qemu_put_counted_string(f, self->id);
> > +    qemu_put_be32(f, size);
> > +    qemu_put_buffer(f, data, size);
> > +
> > +end:
> > +    g_clear_pointer(&child, g_variant_unref);
> > +    g_clear_pointer(&result, g_variant_unref);
> > +}
> > +
> > +static const SaveVMHandlers savevm_handlers = {
> > +    .save_state = dbus_save_state,
> > +    .load_state = dbus_load_state,
> > +};
> > +
> > +static void
> > +dbus_vmstate_complete(UserCreatable *uc, Error **errp)
> > +{
> > +    DBusVMState *self = DBUS_VMSTATE(uc);
> > +    GError *err = NULL;
> > +    GDBusConnection *bus = NULL;
> > +    GDBusProxy *proxy = NULL;
> > +    char *idstr = NULL;
> > +
> > +    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,
> > +               NULL, NULL, &err);
> > +    if (err) {
> > +        error_setg(errp, "failed to connect to DBus: '%s'", err->message);
> > +        g_clear_error(&err);
> > +        return;
> > +    }
> > +
> > +    self->bus = bus;
> > +
> > +    proxy = g_dbus_proxy_new_sync(bus,
> > +                G_DBUS_PROXY_FLAGS_NONE,
> > +                (GDBusInterfaceInfo *) &vmstate1_interface_info,
> > +                NULL,
> > +                "/org/qemu/VMState1",
> > +                "org.qemu.VMState1",
> > +                NULL, &err);
> > +
> > +    if (err) {
> > +        error_setg(errp, "failed to create DBus proxy: '%s'", 
> > err->message);
> > +        g_clear_error(&err);
> > +        return;
> > +    }
> > +
> > +    self->proxy = proxy;
> > +
> > +    self->id = dbus_proxy_get_id(proxy, &err);
> > +    if (!self->id) {
> > +        error_setg(errp, "failed to get DBus Id: '%s'", err->message);
> > +        g_clear_error(&err);
> > +        return;
> > +    }
> > +
> > +    idstr = get_idstr(self);
> > +    if (register_savevm_live(NULL, idstr, 0, 0,
> > +                             &savevm_handlers, self) < 0) {
> > +        error_setg(errp, "Failed to register savevm handler");
> > +    }
>
> Can you try and avoid register_savevm_live if possible and just wire a
> vmsd onto the class like most other devices? We don't have many
> register_savevm_live calls, and I'd like to get them down to just the
> iterative devices.

Sure if I could, but it's not a device.

Perhaps we could have a qom interface for vmsd users? I can try that eventually.

thanks

> Dave
>
>
> > +    g_free(idstr);
> > +}
> > +
> > +static void
> > +dbus_vmstate_finalize(Object *o)
> > +{
> > +    DBusVMState *self = DBUS_VMSTATE(o);
> > +    char *idstr = get_idstr(self);
> > +
> > +    unregister_savevm(NULL, idstr, self);
> > +
> > +    g_clear_object(&self->bus);
> > +    g_clear_object(&self->proxy);
> > +    g_free(self->dbus_addr);
> > +    g_free(self->id);
> > +    g_free(idstr);
> > +}
> > +
> > +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 void
> > +dbus_vmstate_class_init(ObjectClass *oc, void *data)
> > +{
> > +    UserCreatableClass *ucc = USER_CREATABLE_CLASS(oc);
> > +
> > +    ucc->complete = dbus_vmstate_complete;
> > +
> > +    object_class_property_add_str(oc, "addr",
> > +                                  get_dbus_addr, set_dbus_addr,
> > +                                  &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 },
> > +        { }
> > +    }
> > +};
> > +
> > +static void
> > +register_types(void)
> > +{
> > +    type_register_static(&dbus_vmstate_info);
> > +}
> > +
> > +type_init(register_types);
> > diff --git a/configure b/configure
> > index 714e7fb6a1..e5b34f5ca7 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
> > @@ -6830,6 +6836,7 @@ 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..4a32a183fb
> > --- /dev/null
> > +++ b/docs/interop/dbus-vmstate.rst
> > @@ -0,0 +1,63 @@
> > +============
> > +DBus VMState
> > +============
> > +
> > +Introduction
> > +============
> > +
> > +Helper processes may have their state migrated with the help of
> > +QEMU "dbus-vmstate" objects.
> > +
> > +At this point, the connection to the helper is done in DBus
> > +peer-to-peer mode (no initial Hello, and no bus name for
> > +communication). The helper must be listening to the given address.
> > +
> > +Helper may save arbitrary data to be transferred in the migration
> > +stream and restored/loaded on destination.
> > +
> > +The data amount to be transferred is limited to 1Mb. The state must be
> > +saved quickly (a few seconds maximum). (DBus imposes a time limit on
> > +reply anyway, and migration would fail if the data isn't given quickly
> > +enough)
> > +
> > +Interface
> > +=========
> > +
> > +On /org/qemu/VMState1 object path:
> > +
> > +.. 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 utf8 encoded string that identifies the helper uniquely.
> > +Must be <256 bytes.
> > +
> > +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 load
> > +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 b4bfcab417..6bb173cfa6 100644
> > --- a/docs/interop/index.rst
> > +++ b/docs/interop/index.rst
> > @@ -13,6 +13,7 @@ Contents:
> >     :maxdepth: 2
> >
> >     bitmaps
> > +   dbus-vmstate
> >     live-block-operations
> >     pr-helper
> >     vhost-user
> > diff --git a/tests/Makefile.include b/tests/Makefile.include
> > index fd7fdb8658..2c610086a7 100644
> > --- a/tests/Makefile.include
> > +++ b/tests/Makefile.include
> > @@ -157,7 +157,9 @@ 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)
> > @@ -618,6 +620,18 @@ 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-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 $(test-qapi-obj-y) 
> > tests/test-qapi-events.o
> > @@ -820,6 +834,7 @@ tests/test-filter-mirror$(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
> > @@ -1172,6 +1187,7 @@ 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-test.c b/tests/dbus-vmstate-test.c
> > new file mode 100644
> > index 0000000000..45d44916d2
> > --- /dev/null
> > +++ b/tests/dbus-vmstate-test.c
> > @@ -0,0 +1,371 @@
> > +#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;
> > +    GDBusObjectManagerServer *om;
> > +    GDBusServer *server;
> > +} TestServer;
> > +
> > +typedef struct Test {
> > +    bool migrate_fail;
> > +    TestServer srcA;
> > +    TestServer dstA;
> > +    TestServer srcB;
> > +    TestServer dstB;
> > +    GMainLoop *loop, *dbus_loop;
> > +    QTestState *src_qemu;
> > +} Test;
> > +
> > +GMutex mutex;
> > +GCond cond;
> > +
> > +static gboolean
> > +vmstate_load(VMState1 *object, GDBusMethodInvocation *invocation,
> > +             const gchar *arg_data, gpointer user_data)
> > +{
> > +    TestServer *h = user_data;
> > +    GVariant *args, *var;
> > +    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_variant_unref(var);
> > +
> > +    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 void
> > +connection_closed(GDBusConnection *connection,
> > +                  gboolean remote_peer_vanished,
> > +                  GError *Error,
> > +                  gpointer user_data)
> > +{
> > +    TestServer *h = user_data;
> > +
> > +    g_clear_object(&h->om);
> > +    g_clear_object(&connection);
> > +}
> > +
> > +static GDBusObjectManagerServer *
> > +get_omserver(GDBusConnection *conn, gpointer user_data)
> > +{
> > +    TestServer *h = user_data;
> > +    GDBusObjectManagerServer *om;
> > +    GDBusObjectSkeleton *sk;
> > +    VMState1 *v;
> > +
> > +    om = g_dbus_object_manager_server_new("/org/qemu");
> > +    sk = g_dbus_object_skeleton_new("/org/qemu/VMState1");
> > +
> > +    v = vmstate1_skeleton_new();
> > +    g_object_set(v, "id", h->id->name, NULL);
> > +    g_signal_connect(v, "handle-load", G_CALLBACK(vmstate_load), 
> > user_data);
> > +    g_signal_connect(v, "handle-save", G_CALLBACK(vmstate_save), 
> > user_data);
> > +
> > +    g_dbus_object_skeleton_add_interface(sk, G_DBUS_INTERFACE_SKELETON(v));
> > +    g_dbus_object_manager_server_export(om, sk);
> > +    g_dbus_object_manager_server_set_connection(om, conn);
> > +
> > +    g_clear_object(&v);
> > +    g_clear_object(&sk);
> > +
> > +    return om;
> > +}
> > +
> > +static gboolean
> > +on_new_connection(GDBusServer *server,
> > +                  GDBusConnection *connection,
> > +                  gpointer user_data)
> > +{
> > +    TestServer *h = user_data;
> > +
> > +    g_object_ref(connection);
> > +    g_signal_connect(connection, "closed",
> > +                     G_CALLBACK(connection_closed), user_data);
> > +    h->om = get_omserver(connection, user_data);
> > +
> > +    return TRUE;
> > +}
> > +
> > +static gboolean
> > +allow_mechanism_cb(GDBusAuthObserver *observer,
> > +                   const gchar *mechanism,
> > +                   gpointer user_data)
> > +{
> > +    return g_strcmp0(mechanism, "EXTERNAL") == 0;
> > +}
> > +
> > +static gboolean
> > +authorize_authenticated_peer_cb(GDBusAuthObserver *observer,
> > +                                GIOStream *stream,
> > +                                GCredentials *credentials,
> > +                                gpointer user_data)
> > +{
> > +    gboolean authorized = FALSE;
> > +
> > +    if (credentials != NULL) {
> > +        GCredentials *own_credentials = g_credentials_new();
> > +
> > +        if (g_credentials_is_same_user(credentials, own_credentials, 
> > NULL)) {
> > +            authorized = TRUE;
> > +        }
> > +
> > +        g_clear_object(&own_credentials);
> > +    }
> > +
> > +    return authorized;
> > +}
> > +
> > +static GDBusServer *
> > +server_start(TestServer *h, const char *p, const TestServerId *id)
> > +{
> > +    GDBusAuthObserver *observer = NULL;
> > +    GDBusServer *server = NULL;
> > +    gchar *guid = NULL;
> > +    GError *error = NULL;
> > +    char *addr = NULL;
> > +
> > +    h->id = id;
> > +    addr = g_strdup_printf("unix:path=%s/dbus-%s%s", workdir, p, 
> > h->id->name);
> > +    guid = g_dbus_generate_guid();
> > +    observer = g_dbus_auth_observer_new();
> > +    g_signal_connect(observer, "allow-mechanism",
> > +                     G_CALLBACK(allow_mechanism_cb), h);
> > +    g_signal_connect(observer, "authorize-authenticated-peer",
> > +                     G_CALLBACK(authorize_authenticated_peer_cb), h);
> > +
> > +    server = g_dbus_server_new_sync(addr,
> > +                                    G_DBUS_SERVER_FLAGS_NONE,
> > +                                    guid,
> > +                                    observer,
> > +                                    NULL, /* GCancellable */
> > +                                    &error);
> > +    g_dbus_server_start(server);
> > +    g_clear_object(&observer);
> > +    g_free(guid);
> > +
> > +    if (server == NULL) {
> > +        g_printerr("Error creating server at address %s: %s\n",
> > +                   addr, error->message);
> > +        g_error_free(error);
> > +        return NULL;
> > +    }
> > +
> > +    g_signal_connect(server, "new-connection",
> > +                     G_CALLBACK(on_new_connection), h);
> > +
> > +    g_free(addr);
> > +    return server;
> > +}
> > +
> > +
> > +static gpointer
> > +dbus_thread(gpointer p)
> > +{
> > +    Test *test = p;
> > +    GMainContext *context = g_main_context_new();
> > +    GMainLoop *loop = g_main_loop_new(context, FALSE);
> > +
> > +    g_main_context_push_thread_default(context);
> > +
> > +    g_mutex_lock(&mutex);
> > +    test->srcA.server = server_start(&test->srcA, "src", &idA);
> > +    test->srcB.server = server_start(&test->srcB, "src", &idB);
> > +    test->dstA.server = server_start(&test->dstA, "dst", &idA);
> > +    test->dstB.server = server_start(&test->dstB, "dst", &idB);
> > +    test->dbus_loop = loop;
> > +    g_cond_signal(&cond);
> > +    g_mutex_unlock(&mutex);
> > +
> > +    g_main_loop_run(loop);
> > +
> > +    g_main_loop_unref(loop);
> > +    g_main_context_unref(context);
> > +
> > +    g_mutex_lock(&mutex);
> > +    g_clear_object(&test->srcA.server);
> > +    g_clear_object(&test->srcB.server);
> > +    g_clear_object(&test->dstA.server);
> > +    g_clear_object(&test->dstB.server);
> > +    g_mutex_unlock(&mutex);
> > +
> > +    return NULL;
> > +}
> > +
> > +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);
> > +}
> > +
> > +static void
> > +test_dbus_vmstate(Test *test)
> > +{
> > +    QTestState *src_qemu = NULL, *dst_qemu = NULL;
> > +    char *src_qemu_args = NULL, *dst_qemu_args = NULL;
> > +    char *uri = g_strdup_printf("unix:%s/migsocket", workdir);
> > +    GThread *t = g_thread_new("dbus", dbus_thread, test);
> > +
> > +    g_mutex_lock(&mutex);
> > +    while (!test->dbus_loop) {
> > +        g_cond_wait(&cond, &mutex);
> > +    }
> > +
> > +    src_qemu_args =
> > +        g_strdup_printf("-object dbus-vmstate,id=dvA,addr=%s "
> > +                        "-object dbus-vmstate,id=dvB,addr=%s",
> > +                        
> > g_dbus_server_get_client_address(test->srcA.server),
> > +                        
> > g_dbus_server_get_client_address(test->srcB.server));
> > +
> > +
> > +    dst_qemu_args =
> > +        g_strdup_printf("-object dbus-vmstate,id=dvA,addr=%s "
> > +                        "-object dbus-vmstate,id=dvB,addr=%s "
> > +                        "-incoming %s",
> > +                        
> > g_dbus_server_get_client_address(test->dstA.server),
> > +                        
> > g_dbus_server_get_client_address(test->dstB.server),
> > +                        uri);
> > +
> > +    src_qemu = qtest_init(src_qemu_args);
> > +    dst_qemu = qtest_init(dst_qemu_args);
> > +
> > +    test->loop = g_main_loop_new(NULL, TRUE);
> > +
> > +    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);
> > +
> > +    g_free(uri);
> > +    qtest_quit(dst_qemu);
> > +    qtest_quit(src_qemu);
> > +    g_free(dst_qemu_args);
> > +    g_free(src_qemu_args);
> > +
> > +    g_main_loop_quit(test->dbus_loop);
> > +    g_mutex_unlock(&mutex);
> > +
> > +    g_thread_join(t);
> > +}
> > +
> > +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_migrate(void)
> > +{
> > +    Test test = { };
> > +
> > +    test_dbus_vmstate(&test);
> > +
> > +    check_migrated(&test.srcA, &test.dstA);
> > +    check_migrated(&test.srcB, &test.dstB);
> > +}
> > +
> > +int
> > +main(int argc, char **argv)
> > +{
> > +    GError *err = NULL;
> > +    int ret;
> > +
> > +    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);
> > +    }
> > +
> > +    qtest_add_func("/dbus-vmstate/migrate",
> > +                   test_dbus_vmstate_migrate);
> > +
> > +    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.rc1
> >
> --
> Dr. David Alan Gilbert / address@hidden / Manchester, UK