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* [Qemu-devel] [PATCH v3 0/6] Add dbus-vmstate
@ 2019-09-12 12:25 Marc-André Lureau
  2019-09-12 12:25 ` [Qemu-devel] [PATCH v3 1/6] migration: fix vmdesc leak on vmstate_save() error Marc-André Lureau
                   ` (6 more replies)
  0 siblings, 7 replies; 32+ messages in thread
From: Marc-André Lureau @ 2019-09-12 12:25 UTC (permalink / raw)
  To: qemu-devel
  Cc: berrange, quintela, mprivozn, dgilbert, Marc-André Lureau,
	pbonzini

Hi,

With external processes or helpers participating to the VM support, it
becomes necessary to handle their migration. Various options exist to
transfer their state:
1) as the VM memory, RAM or devices (we could say that's how
   vhost-user devices can be handled today, they are expected to
   restore from ring state)
2) other "vmstate" (as with TPM emulator state blobs)
3) left to be handled by management layer

1) is not practical, since an external processes may legitimatelly
need arbitrary state date to back a device or a service, or may not
even have an associated device.

2) needs ad-hoc code for each helper, but is simple and working

3) is complicated for management layer, QEMU has the migration timing

The proposed "dbus-vmstate" object will connect to a given D-Bus
address, and save/load from org.qemu.VMState1 owners on migration.

Thus helpers can easily have their state migrated with QEMU, without
implementing ad-hoc support (such as done for TPM emulation)

D-Bus is ubiquitous on Linux (it is systemd IPC), and can be made to
work on various other OSes. There are several implementations and good
bindings for various languages.  (the tests/dbus-vmstate-test.c is a
good example of how simple the implementation of services can be, even
in C)

dbus-vmstate is put into use by the libvirt series "[PATCH 00/23] Use
a slirp helper process".

v3:
- after various discussions on helper processes, we settled on a
  preference for having a bus for communications. This version is
  actually v1 updated.
- added a dbus.rst document to describe D-Bus recommendations for QEMU
- added dbus-vmstate-daemon.sh to play with the dbus-daemon configuration
  (although it is not very useful in the context of a single UID)
- added a new vmstate interface, so that any object can implement
  VMStateDescription, and converted dbus-vmstate
- added "migration: fix vmdesc leak on vmstate_save() error"
- convert to g_auto

v2:
- D-Bus is most common and practical through a bus, but it requires a
  daemon to be running. I argue that the benefits outweight the cost
  of running an extra daemon in v1 in the context of multi-process
  qemu, but it is also possible to connect in p2p mode as done in this
  new version.

Marc-André Lureau (6):
  migration: fix vmdesc leak on vmstate_save() error
  vmstate: add qom interface to get id
  vmstate: replace DeviceState with VMStateIf
  tests: add qtest_expect_exit_status()
  docs: start a document to describe D-Bus usage
  Add dbus-vmstate object

 MAINTAINERS                   |   6 +
 backends/Makefile.objs        |   4 +
 backends/dbus-vmstate.c       | 530 ++++++++++++++++++++++++++++++++++
 configure                     |   7 +
 docs/devel/migration.rst      |   2 +-
 docs/interop/dbus-vmstate.rst |  68 +++++
 docs/interop/dbus.rst         |  73 +++++
 docs/interop/index.rst        |   2 +
 hw/block/onenand.c            |   2 +-
 hw/core/Makefile.objs         |   1 +
 hw/core/qdev.c                |  21 +-
 hw/core/vmstate-if.c          |  23 ++
 hw/ide/cmd646.c               |   2 +-
 hw/ide/isa.c                  |   2 +-
 hw/ide/piix.c                 |   2 +-
 hw/ide/via.c                  |   2 +-
 hw/misc/max111x.c             |   2 +-
 hw/net/eepro100.c             |   4 +-
 hw/net/vmxnet3.c              |   2 +-
 hw/nvram/eeprom93xx.c         |   4 +-
 hw/ppc/spapr_drc.c            |   9 +-
 hw/ppc/spapr_iommu.c          |   4 +-
 hw/s390x/s390-skeys.c         |   2 +-
 include/hw/vmstate-if.h       |  32 ++
 include/migration/register.h  |   6 +-
 include/migration/vmstate.h   |  10 +-
 migration/qjson.h             |   2 +
 migration/savevm.c            |  29 +-
 stubs/vmstate.c               |   4 +-
 tests/Makefile.include        |  20 +-
 tests/dbus-vmstate-daemon.sh  |  95 ++++++
 tests/dbus-vmstate-test.c     | 386 +++++++++++++++++++++++++
 tests/dbus-vmstate1.xml       |  12 +
 tests/libqtest.c              |  41 +--
 tests/libqtest.h              |   9 +
 35 files changed, 1355 insertions(+), 65 deletions(-)
 create mode 100644 backends/dbus-vmstate.c
 create mode 100644 docs/interop/dbus-vmstate.rst
 create mode 100644 docs/interop/dbus.rst
 create mode 100644 hw/core/vmstate-if.c
 create mode 100644 include/hw/vmstate-if.h
 create mode 100755 tests/dbus-vmstate-daemon.sh
 create mode 100644 tests/dbus-vmstate-test.c
 create mode 100644 tests/dbus-vmstate1.xml

-- 
2.23.0



^ permalink raw reply	[flat|nested] 32+ messages in thread

end of thread, other threads:[~2019-09-25  9:50 UTC | newest]

Thread overview: 32+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2019-09-12 12:25 [Qemu-devel] [PATCH v3 0/6] Add dbus-vmstate Marc-André Lureau
2019-09-12 12:25 ` [Qemu-devel] [PATCH v3 1/6] migration: fix vmdesc leak on vmstate_save() error Marc-André Lureau
2019-09-13 13:29   ` Dr. David Alan Gilbert
2019-09-17 12:31   ` Daniel P. Berrangé
2019-09-25  9:49   ` Dr. David Alan Gilbert
2019-09-12 12:25 ` [Qemu-devel] [PATCH v3 2/6] vmstate: add qom interface to get id Marc-André Lureau
2019-09-16  9:54   ` Dr. David Alan Gilbert
2019-09-17 12:33   ` Daniel P. Berrangé
2019-09-12 12:25 ` [Qemu-devel] [PATCH v3 3/6] vmstate: replace DeviceState with VMStateIf Marc-André Lureau
2019-09-12 16:18   ` Halil Pasic
2019-09-13  7:12     ` Marc-André Lureau
2019-09-16  9:06   ` Dr. David Alan Gilbert
2019-09-17 12:35   ` Daniel P. Berrangé
2019-09-12 12:25 ` [Qemu-devel] [PATCH v3 4/6] tests: add qtest_expect_exit_status() Marc-André Lureau
2019-09-13 13:33   ` Dr. David Alan Gilbert
2019-09-17 12:36   ` Daniel P. Berrangé
2019-09-12 12:25 ` [Qemu-devel] [PATCH v3 5/6] docs: start a document to describe D-Bus usage Marc-André Lureau
2019-09-16 10:00   ` Dr. David Alan Gilbert
2019-09-16 10:57     ` Marc-André Lureau
2019-09-16 13:15       ` Dr. David Alan Gilbert
2019-09-16 19:13         ` Marc-André Lureau
2019-09-17  8:12           ` Dr. David Alan Gilbert
2019-09-17  8:23             ` Marc-André Lureau
2019-09-17 12:47     ` Daniel P. Berrangé
2019-09-17 13:03       ` Dr. David Alan Gilbert
2019-09-19  9:23     ` Stefan Hajnoczi
2019-09-17 13:07   ` Daniel P. Berrangé
2019-09-12 12:25 ` [Qemu-devel] [PATCH v3 6/6] Add dbus-vmstate object Marc-André Lureau
2019-09-12 14:29   ` Eric Blake
2019-09-16 10:43   ` Dr. David Alan Gilbert
2019-09-17 13:21   ` Daniel P. Berrangé
2019-09-12 13:50 ` [Qemu-devel] [PATCH v3 0/6] Add dbus-vmstate no-reply

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