Re: [Qemu-discuss] Can't remove libvirt USB controller via QEMU, but can via virsh

[Jakob Bohm]

On 11/08/2015 00:33, james harvey wrote:
> Using libvirt 1.2.18 (-1 Arch) and QEMU git-master (2.4.0.r40384.2d69736).
>
> Installed using Q35 chipset.
>
> Using managedsave/start is unusable due to a non-stop repeating
> uhci_hcd error.  (Fills tty0 screen every 0.003 kernel seconds with
> errors.)
>
> QEMU won't let me remove the USB controller -- remove is grayed out.
>
> virsh edit allows me to remove them, which lets me use managedsave/start.
>
> QEMU only lets me remove the USB redirection entries, which didn't help.
Last time I checked (has been some time though) qemu
did not have a GUI that can gray out anything.

There are 2 ways in which libvirt (including virsh)
can add/remove devices from qemu:

A) By changing the (long) list of devices and other
  options on the qemu command line when starting qemu,
  this is reflected in the output of the command

virsh domxml-to-native qemu-argv /path/to/guestconfig.xml

B) By using the monitor and qml sockets to "hotplug"
  devices on a running guest.

I am quite confident that the usb controller can be
removed by simply omitting it (and all usb devices
needing it) from the qemu command line (method A),
but I don't know if it can be done with method B,
(except that it must be possible if libvirt/virsh
does it without rebooting the guest).

Note that older versions of libvirt refused to remove
the USB tablet it uses for mouse movements, and thus
the USB controller, which was quite annoying.

Enjoy

Jakob
--
Jakob Bohm, CIO, Partner, WiseMo A/S.  https://www.wisemo.com
Transformervej 29, 2860 Søborg, Denmark.  Direct +45 31 13 16 10
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