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

["Yuval Kashtan" <yuvalkashtan@gmail.com>]

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Some answers:
- If there is interest I can re-create the patch so it will work against the
current head. I thought to receive some comments about it first..
- thanks for the styling and configuration remarks, I will certainly fix
these. But before I invest more time in it, I would like to hear what ppl
think in general of management API? How do you like DBus as the
infrastructure for that? and what do you think of the proposed
implementation?
- Currently only commands are implemented (with very few getters), but of
course this can be further extended to include values reading and
statistics.
- This is very useful when you want to manage and control QEMU, for instance
developing a GUI to attach and detach usb devices or controlling more than
one instance of QEMU from a single management point, receiving parameters
externally and more.


On Dec 10, 2007 10:51 PM, Blue Swirl <blauwirbel@gmail.com> wrote:

> 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?
>
>
>


-- 
Sincerly,
Yuval Kashtan

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