[virt-tools-list] Problem accessing USB devices under a VM running Windows 10

[Jeffery Small]

I'm on an Xubuntu 16.10 system running the latest version of QEMU-KVM
(1.2.6.1).  I have a VM running Windows 10, which is launched from
virt-manager.

Question #1:

With the OS not running, from the Hardware Details page I have used "Add
Hardware" to attach a USB flash drive.  In the hardware list it shows
up as "USB 058f:6387" and the details show "Device: 002:003 Alcor Micro
Corp. Flash Drive".

Nevertheless, when I launch the Windows 10 OS, File Explorer does not see
this device.  I've also looked in Device Manager and can see no reference
to the flash drive.

Any clue as to the nature of the problem and what must be done to make this
visible to the Windows OS?  I am doing this with a flash drive as a test in
order to get device attachment working.  Ultimately, I will be attaching a
usb dongle key to the port which must be seen by a program running in this
environment.


Question #2:

There was no problem adding the Alcor flash drive and it is the only device
I have added manually, but when I attempt to add another flash drive or my
attached phone, virt-manager reports:

  "Error adding device: internal error: No free USB ports"

Error details:

  Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/addhardware.py", line 1343, in _add_device
  self.vm.add_device(self._dev)
  File "/usr/share/virt-manager/virtManager/domain.py", line 568, in add_device
  self._redefine_xmlobj(xmlobj)
  File "/usr/share/virt-manager/virtManager/libvirtobject.py", line 389, in _redefine_xmlobj
  self._define(newxml)
  File "/usr/share/virt-manager/virtManager/domain.py", line 1094, in _define
  self.conn.define_domain(newxml)
  File "/usr/share/virt-manager/virtManager/connection.py", line 677, in define_domain
  return self._backend.defineXML(xml)
  File "/usr/lib/python2.7/dist-packages/libvirt.py", line 3800, in defineXML
  if ret is None:raise libvirtError('virDomainDefineXML() failed', conn=self)
  libvirtError: internal error: No free USB ports

Having support for only one external USB port is surprising.  Can you
point me to any documentation that indicates how to address this problem
and add additional ports?

Thanks for you assistance.

Regards,
--
Jeffery Small