Re: [Xen-users] Is it safe to use qemu's QMP socket for controlling a Xen HVM?

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2014-09-24 at 20:00 +0200, Manfred Haertel, DB3HM wrote:
> Xen starts a qemu process on Domain 0 for every HVM.
> 
> This qemu has a QMP socket at /var/run/xen, which is used by xl for some 
> controlling purposes.
>
> Is it safe if I send commands to the QMP socket by myself? E.g. to add 
> an USB device to the HVM dynamically (which is currently not possible 
> otherwise when using the xl toolstack).

I think the QMP socket needs to be consider private to its owner, more
so because I'm reasonably sure that someone else using the socket will
confuse libxl if not qemu.

There's a syntax  you can use in xl.cfg files to pass more options to
the device model, I think you can use that to create your own QMP socket
to use.

Of course depending on what you do you may also end up confusing libxl
down the road (probably not with a USB plug though).

NB there are patches floating around on xen-devel to add native USB
support to the libxl/xl, although they don't seem to be going to make
the 4.5 release, hopefully for 4.6!

Ian.



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