Re: [Qemu-devel] [RFC] QEMU Dbus support - a proposal management API

["Blue Swirl" <blauwirbel@gmail.com>]

On 12/10/07, Yuval Kashtan <yuvalkashtan@gmail.com> wrote:
> Hello All,
> Attached is a proposed patch which adds DBus support to QEMU. DBus is a
> standard message bus for linux
> (http://www.freedesktop.org/wiki/Software/dbus )
> The idea behind this is to allow for external programs such as controlling
> GUI or HyperVisors to communicate and control QEMU, in a standard manner.
> Although it is possible to connect to the monitor, an API is more standard,
> theres no need to parse texts and error messages, no internationalization
> problems and in general is a much better idea.
>
> Implementation:
> This is done by creating a DBus server from QEMU which raise signals and act
> upon methods.
> Methods mainly implement same logic as the current command line options and
> monitor does.
>
> How to use:
> To enable DBus support you'll have to add --enable-dbus when you execure
> configure script.
> Then when you execute QEMU, you'll have to add -dbus-service <service_name>
> where service_name follows the DBus naming convention ( xxx.xxx.xxx....)
> To support QEMU configuration through DBus,  you'll also have to add
> -dbus_configuration which will cause QEMU to wait until ConfigDone is called
> through the DBus interface. this allows external programs time to call DBus
> methods starting with Config_ which changes configuration (just as the CLI
> does) thus enabling invocation of QEMU without parameters (beside the DBus
> ones).
> With that, we have implemented a nice python script that reads VM's
> configuration from INI file.
>
> To compile this you will also have to compile the attached freedesktop.org
> dsrv library (it is also attach for those who can't handle GIT) from:
> git://people.freedesktop.org/~shaharf/dsrv
>
> Features:
> Currently support was added to all important CLI configuration and some
> online monitor functions (such as connecting and disconnecting usb devices).
> configuration methods begins with Config_ prefix and monitor ones with
> Monitor_.
> For a complete list you can just execute qemu and connect with dbus-viewer
> to see what is supported.
>
>
> All the dbus handling routines can be found in dbus-monitor.c.
> I have two different implementations of this:
> 1) A single threaded version. which comply to the qemu standard of not
> opening additional threads.
> 2) A multi threaded version which open an additional, single, thread which
> handles all the DBus load. I actually believe this version is better as it
> allows QEMU to continue execution of guest operations even when there are
> DBus methods/signals to handle, whereas in the first option, DBus is
> integrated into QEMU mainloop. Also this makes it possible to monitor even
> during long operations (like monitoring the progress of savevm)
>
>
> Please comment both on the idea of management API and the proposed
> implementation.
>
>
> Attached are:
> RFC-QEMU-Dbus.patch - patch file including all necessary changes to qemu.
> was made against QEMU HEAD as of 23/9 morning.
> RFC-QEMU-Dbus-Interface.xml - the xml description of the DBus interface that
> I suggest.
> dsrv.tar.gz.txt - the dbus server library.

I have no idea if this is useful. I would have tried the patch, but it
does not apply to current CVS. Other comments:

When configure is invoked with --enable-dbus, it should check for DBUS
libraries and abort if not found.

The coding style in monitor-dbus.c is different from what is commonly
used in Qemu. Some long lines could be shortened.

Enabling of DEBUG_ACPI and other ACPI changes are probably not
directly needed so they should be in separate patches.

Only commands are included, how about reading values and statistics?