[00/11] qdev: Add JSON -device and fix QMP device_add

Message

Kevin Wolf Sept. 24, 2021, 9:04 a.m. UTC

It's still a long way until we'll have QAPIfied devices, but there are
some improvements that we can already make now to make the future switch
easier.

One important part of this is having code paths without QemuOpts, which
we want to get rid of and replace with the keyval parser in the long
run. This series adds support for JSON syntax to -device, which bypasses
QemuOpts.

While we're not using QAPI yet, devices are based on QOM, so we already
do have type checks and an implied schema. JSON syntax supported now can
be supported by QAPI later and regarding command line compatibility,
actually switching to it becomes an implementation detail this way (of
course, it will still add valuable user-visible features like
introspection and documentation).

Apart from making things more future proof, this also immediately adds
a way to do non-scalar properties on the command line. nvme could have
used list support recently, and the lack of it in -device led to some
rather unnatural solution in the first version (doing the relationship
between a device and objects backwards) and loss of features in the
following. With this series, using a list as a device property should be
possible without any weird tricks.

Unfortunately, even QMP device_add goes through QemuOpts before this
series, which destroys any type safety QOM provides and also can't
support non-scalar properties. This is a bug that is fixed during this
series, but that is technically an incompatible change. A similar change
was made for netdev_add in commit db2a380c84.

libvirt needs to make sure that it actually always passes the right
type, because passing a wrong type will start to fail after this
series. I hope that libvirt already does things correctly, so this
won't cause any trouble, but if it does, there is the option of using
the QemuOpts-less code path only for JSON -device and going through a
deprecation period for QMP device_add.

Kevin Wolf (11):
  qom: Reduce use of error_propagate()
  iotests/245: Fix type for iothread property
  iotests/051: Fix typo
  qdev: Avoid using string visitor for properties
  qdev: Make DeviceState.id independent of QemuOpts
  qdev: Add Error parameter to qdev_set_id()
  qemu-option: Allow deleting opts during qemu_opts_foreach()
  qdev: Base object creation on QDict rather than QemuOpts
  qdev: Avoid QemuOpts in QMP device_add
  vl: Enable JSON syntax for -device
  Deprecate stable non-JSON -device and -object

 qapi/qdev.json                      | 15 +++--
 docs/about/deprecated.rst           | 11 ++++
 include/hw/qdev-core.h              | 10 ++--
 include/monitor/qdev.h              |  2 +-
 hw/arm/virt.c                       |  2 +-
 hw/core/qdev.c                      |  6 +-
 hw/net/virtio-net.c                 |  4 +-
 hw/pci-bridge/pci_expander_bridge.c |  2 +-
 hw/ppc/e500.c                       |  2 +-
 hw/vfio/pci.c                       |  4 +-
 hw/xen/xen-legacy-backend.c         |  3 +-
 qom/object.c                        |  7 +--
 qom/object_interfaces.c             | 17 ++----
 softmmu/qdev-monitor.c              | 90 +++++++++++++++++------------
 softmmu/vl.c                        | 58 ++++++++++++++++---
 util/qemu-option.c                  |  4 +-
 tests/qemu-iotests/051              |  2 +-
 tests/qemu-iotests/051.pc.out       |  4 +-
 tests/qemu-iotests/245              |  4 +-
 19 files changed, 161 insertions(+), 86 deletions(-)