Hi,

> > Another useful thing would be to not create the xen platform device in case
> > "-nodefaults" was specified on the command line (that switch turns off a bunch
> > of other devices present by default: vga, nic, cdrom, ...).
> 
> Currently looks 'xen-platform' itself can't be created, not those devices existed on that.

The error message looks more like libxl tries to hot-unplug the xen
platform device.

Attached patch (untested!) hooks up the xen platform device to the
default device code we have in qemu.  Two effects:

  (1) As mentioned above the device will not be created in case
      -nodefaults  is specified on the command line.
  (2) Autocreating the device is also turned off in case xen-platform
      is added manually via -device.

With the patch applied you should be able to move the xen-platform
device to some other place with a simple 'qemu -device
xen-platform,addr=$slot'.

cheers,
  Gerd