| Message ID | 20191211134506.1803403-6-marcandre.lureau@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Add dbus-vmstate | expand |
On Wed, Dec 11, 2019 at 05:45:03PM +0400, Marc-André Lureau wrote: > When instantiated, this object will connect to the given D-Bus bus > "addr". During migration, it will take/restore the data from > org.qemu.VMState1 instances. See documentation for details. > > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com> > --- > MAINTAINERS | 2 + > backends/Makefile.objs | 4 + > backends/dbus-vmstate.c | 496 ++++++++++++++++++++++++++++++++++ > docs/interop/dbus-vmstate.rst | 74 +++++ > docs/interop/dbus.rst | 5 + > docs/interop/index.rst | 1 + > 6 files changed, 582 insertions(+) > create mode 100644 backends/dbus-vmstate.c > create mode 100644 docs/interop/dbus-vmstate.rst > > diff --git a/MAINTAINERS b/MAINTAINERS > index f08fb4f24e..7af80d0c1d 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -2202,9 +2202,11 @@ F: qapi/migration.json > D-Bus > M: Marc-André Lureau <marcandre.lureau@redhat.com> > S: Maintained > +F: backends/dbus-vmstate.c > F: util/dbus.c > F: include/qemu/dbus.h > F: docs/interop/dbus.rst > +F: docs/interop/dbus-vmstate.rst > > Seccomp > M: Eduardo Otubo <otubo@redhat.com> > 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..059dd420b8 > --- /dev/null > +++ b/backends/dbus-vmstate.c > @@ -0,0 +1,496 @@ > +/* > + * QEMU dbus-vmstate > + * > + * Copyright (C) 2019 Red Hat Inc > + * > + * Authors: > + * Marc-André Lureau <marcandre.lureau@redhat.com> > + * > + * 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/dbus.h" > +#include "qemu/error-report.h" > +#include "qapi/error.h" > +#include "qom/object_interfaces.h" > +#include "qapi/qmp/qerror.h" > +#include "migration/vmstate.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; > +}; > + Not an objection to your patch here. This just reminds me that we ought to follow GLib's lead and implement some helper macros to automate all this tedious boilerplate. So we can just do something simple like: QOM_DECLARE_FINAL_TYPE(DBusVMState, dbus_vmstate, DBUS_VMSATE, Object) and an equiv to do the TypeInfo declaration & registration. > +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 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(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 = qemu_dbus_get_queued_owners(self->bus, "org.qemu.VMState1"); > + if (!names) { > + 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: %" G_GSIZE_FORMAT, 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); > + } This is a bit of a bike-shed comment, but I'm curious if you considered using GVariant for the serializing data vs the data output stream ? I feel like GVariant is enforcing more structure & safety on the data serialization process, which could be appealing. > +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; Can use g_autoptr for this > + 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); Why not just use self->bus directly. > + if (err) { > + error_setg(errp, "failed to connect to DBus: '%s'", err->message); > + g_clear_error(&err); Missing return here, as we don't want to register vmstate handler if we fail. > + } > + > + self->bus = bus; > + > + if (vmstate_register(VMSTATE_IF(self), -1, &dbus_vmstate, self) < 0) { > + error_setg(errp, "Failed to register vmstate"); > + } > +} > diff --git a/docs/interop/dbus-vmstate.rst b/docs/interop/dbus-vmstate.rst > new file mode 100644 > index 0000000000..8693891640 > --- /dev/null > +++ b/docs/interop/dbus-vmstate.rst > @@ -0,0 +1,74 @@ > +============= > +D-Bus VMState > +============= > + > +Introduction > +============ > + > +The QEMU dbus-vmstate object's 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 A few seconds is too long IMHO. I think the expectation ought to be a small fraction of a second. Anything longer than that suggests there is some extra synchronization work needing beyond serailizing state, which might suggest the need for a separate DBus call. eg a way to tell the backend to "quiesce" itself perhaps For now we can keep it simple and just say that this method should not do anything except seriailize state in a fraction of a second. > +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 comma-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. (maximum 256 bytes > +including terminating NUL byte) > + > +.. note:: > + > + The helper ID namespace is a separate namespace. In particular, it is not > + related to QEMU "id" used in -object/-device objects. Are there any expectations here on a scheme ? I feel leaving it unspecified is probably a mistake. Should it follow a DBUs like reverse.domain.name.style ? > + > +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. Regards, Daniel
* Marc-André Lureau (marcandre.lureau@redhat.com) wrote: <snip> Generally from the migration side I'm OK; I don't know that much glib stuff as you're using, so I'll leave that to Dan. > + 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); Generally can you put either the function name or something in the error to point us in the right direction; then if a user gets an error and it says dbus_vmstate_post_load: Failed to get proxies (e.g. by using %s: ...__func__) then any random qemu dev will be able to resolve the blame pointer quickly and not trying to guess which proxies we're talking about. You might also like to add some trace_ calls to watch what is going on. Dave > + 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: %" G_GSIZE_FORMAT, 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/docs/interop/dbus-vmstate.rst b/docs/interop/dbus-vmstate.rst > new file mode 100644 > index 0000000000..8693891640 > --- /dev/null > +++ b/docs/interop/dbus-vmstate.rst > @@ -0,0 +1,74 @@ > +============= > +D-Bus VMState > +============= > + > +Introduction > +============ > + > +The QEMU dbus-vmstate object's 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 comma-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. (maximum 256 bytes > +including terminating NUL byte) > + > +.. note:: > + > + The helper ID namespace is a separate namespace. In particular, it is not > + related to QEMU "id" used in -object/-device objects. > + > +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/dbus.rst b/docs/interop/dbus.rst > index 3d760e4882..d9af608dc9 100644 > --- a/docs/interop/dbus.rst > +++ b/docs/interop/dbus.rst > @@ -97,3 +97,8 @@ the "D-Bus API Design Guidelines": > https://dbus.freedesktop.org/doc/dbus-api-design.html > > The "org.qemu.*" prefix is reserved for the QEMU project. > + > +QEMU Interfaces > +=============== > + > +:doc:`dbus-vmstate` > diff --git a/docs/interop/index.rst b/docs/interop/index.rst > index ded134ea75..049387ac6d 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 > qemu-ga > -- > 2.24.0.308.g228f53135a > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
Hi On Thu, Dec 12, 2019 at 4:03 PM Daniel P. Berrangé <berrange@redhat.com> wrote: > > On Wed, Dec 11, 2019 at 05:45:03PM +0400, Marc-André Lureau wrote: > > When instantiated, this object will connect to the given D-Bus bus > > "addr". During migration, it will take/restore the data from > > org.qemu.VMState1 instances. See documentation for details. > > > > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com> > > --- > > MAINTAINERS | 2 + > > backends/Makefile.objs | 4 + > > backends/dbus-vmstate.c | 496 ++++++++++++++++++++++++++++++++++ > > docs/interop/dbus-vmstate.rst | 74 +++++ > > docs/interop/dbus.rst | 5 + > > docs/interop/index.rst | 1 + > > 6 files changed, 582 insertions(+) > > create mode 100644 backends/dbus-vmstate.c > > create mode 100644 docs/interop/dbus-vmstate.rst > > > > diff --git a/MAINTAINERS b/MAINTAINERS > > index f08fb4f24e..7af80d0c1d 100644 > > --- a/MAINTAINERS > > +++ b/MAINTAINERS > > @@ -2202,9 +2202,11 @@ F: qapi/migration.json > > D-Bus > > M: Marc-André Lureau <marcandre.lureau@redhat.com> > > S: Maintained > > +F: backends/dbus-vmstate.c > > F: util/dbus.c > > F: include/qemu/dbus.h > > F: docs/interop/dbus.rst > > +F: docs/interop/dbus-vmstate.rst > > > > Seccomp > > M: Eduardo Otubo <otubo@redhat.com> > > 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..059dd420b8 > > --- /dev/null > > +++ b/backends/dbus-vmstate.c > > @@ -0,0 +1,496 @@ > > +/* > > + * QEMU dbus-vmstate > > + * > > + * Copyright (C) 2019 Red Hat Inc > > + * > > + * Authors: > > + * Marc-André Lureau <marcandre.lureau@redhat.com> > > + * > > + * 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/dbus.h" > > +#include "qemu/error-report.h" > > +#include "qapi/error.h" > > +#include "qom/object_interfaces.h" > > +#include "qapi/qmp/qerror.h" > > +#include "migration/vmstate.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; > > +}; > > + > > Not an objection to your patch here. This just reminds me that we > ought to follow GLib's lead and implement some helper macros to > automate all this tedious boilerplate. So we can just do something > simple like: > > QOM_DECLARE_FINAL_TYPE(DBusVMState, dbus_vmstate, DBUS_VMSATE, Object) > > and an equiv to do the TypeInfo declaration & registration. > > > +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 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(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 = qemu_dbus_get_queued_owners(self->bus, "org.qemu.VMState1"); > > + if (!names) { > > + 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: %" G_GSIZE_FORMAT, 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); > > + } > > This is a bit of a bike-shed comment, but I'm curious if you > considered using GVariant for the serializing data vs the > data output stream ? I feel like GVariant is enforcing more > structure & safety on the data serialization process, which > could be appealing. > No I haven't thought about it. I don't know if it's worth it for a string + u32. > > +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; > > Can use g_autoptr for this yes, thanks > > > + 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); > > Why not just use self->bus directly. That works too, thanks > > > + if (err) { > > + error_setg(errp, "failed to connect to DBus: '%s'", err->message); > > + g_clear_error(&err); > > Missing return here, as we don't want to register vmstate handler > if we fail. ok > > > + } > > + > > + self->bus = bus; > > + > > + if (vmstate_register(VMSTATE_IF(self), -1, &dbus_vmstate, self) < 0) { > > + error_setg(errp, "Failed to register vmstate"); > > + } > > +} > > > > diff --git a/docs/interop/dbus-vmstate.rst b/docs/interop/dbus-vmstate.rst > > new file mode 100644 > > index 0000000000..8693891640 > > --- /dev/null > > +++ b/docs/interop/dbus-vmstate.rst > > @@ -0,0 +1,74 @@ > > +============= > > +D-Bus VMState > > +============= > > + > > +Introduction > > +============ > > + > > +The QEMU dbus-vmstate object's 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 > > A few seconds is too long IMHO. I think the expectation ought to > be a small fraction of a second. > > Anything longer than that suggests there is some extra synchronization > work needing beyond serailizing state, which might suggest the need > for a separate DBus call. eg a way to tell the backend to "quiesce" > itself perhaps > > For now we can keep it simple and just say that this method should > not do anything except seriailize state in a fraction of a second. ok > > > +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 comma-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. (maximum 256 bytes > > +including terminating NUL byte) > > + > > +.. note:: > > + > > + The helper ID namespace is a separate namespace. In particular, it is not > > + related to QEMU "id" used in -object/-device objects. > > Are there any expectations here on a scheme ? I feel leaving it > unspecified is probably a mistake. Should it follow a DBUs like > reverse.domain.name.style ? In general, it should follow the associated qemu object/device id. > > > + > > +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. > > Regards, > Daniel > -- > |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| > |: https://libvirt.org -o- https://fstop138.berrange.com :| > |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :| > >
diff --git a/MAINTAINERS b/MAINTAINERS index f08fb4f24e..7af80d0c1d 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -2202,9 +2202,11 @@ F: qapi/migration.json D-Bus M: Marc-André Lureau <marcandre.lureau@redhat.com> S: Maintained +F: backends/dbus-vmstate.c F: util/dbus.c F: include/qemu/dbus.h F: docs/interop/dbus.rst +F: docs/interop/dbus-vmstate.rst Seccomp M: Eduardo Otubo <otubo@redhat.com> 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..059dd420b8 --- /dev/null +++ b/backends/dbus-vmstate.c @@ -0,0 +1,496 @@ +/* + * QEMU dbus-vmstate + * + * Copyright (C) 2019 Red Hat Inc + * + * Authors: + * Marc-André Lureau <marcandre.lureau@redhat.com> + * + * 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/dbus.h" +#include "qemu/error-report.h" +#include "qapi/error.h" +#include "qom/object_interfaces.h" +#include "qapi/qmp/qerror.h" +#include "migration/vmstate.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 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(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 = qemu_dbus_get_queued_owners(self->bus, "org.qemu.VMState1"); + if (!names) { + 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: %" G_GSIZE_FORMAT, 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/docs/interop/dbus-vmstate.rst b/docs/interop/dbus-vmstate.rst new file mode 100644 index 0000000000..8693891640 --- /dev/null +++ b/docs/interop/dbus-vmstate.rst @@ -0,0 +1,74 @@ +============= +D-Bus VMState +============= + +Introduction +============ + +The QEMU dbus-vmstate object's 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 comma-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. (maximum 256 bytes +including terminating NUL byte) + +.. note:: + + The helper ID namespace is a separate namespace. In particular, it is not + related to QEMU "id" used in -object/-device objects. + +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/dbus.rst b/docs/interop/dbus.rst index 3d760e4882..d9af608dc9 100644 --- a/docs/interop/dbus.rst +++ b/docs/interop/dbus.rst @@ -97,3 +97,8 @@ the "D-Bus API Design Guidelines": https://dbus.freedesktop.org/doc/dbus-api-design.html The "org.qemu.*" prefix is reserved for the QEMU project. + +QEMU Interfaces +=============== + +:doc:`dbus-vmstate` diff --git a/docs/interop/index.rst b/docs/interop/index.rst index ded134ea75..049387ac6d 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 qemu-ga
When instantiated, this object will connect to the given D-Bus bus "addr". During migration, it will take/restore the data from org.qemu.VMState1 instances. See documentation for details. Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com> --- MAINTAINERS | 2 + backends/Makefile.objs | 4 + backends/dbus-vmstate.c | 496 ++++++++++++++++++++++++++++++++++ docs/interop/dbus-vmstate.rst | 74 +++++ docs/interop/dbus.rst | 5 + docs/interop/index.rst | 1 + 6 files changed, 582 insertions(+) create mode 100644 backends/dbus-vmstate.c create mode 100644 docs/interop/dbus-vmstate.rst