I have 3 windows VMs with each passing through 2 USB ports (one mouse, one keyboard).  Since all devices are identical, I have to use:

    <hostdev mode='subsystem' type='usb' managed='yes'>
      <source>
        <address bus='3' device='10'/>
      </source>
      <address type='usb' bus='0' port='1'/>
    </hostdev>
    <hostdev mode='subsystem' type='usb' managed='yes'>
      <source>
        <address bus='3' device='11'/>
      </source>
      <address type='usb' bus='0' port='2'/>
    </hostdev>

..to assign all my devices.  When I go to add another new USB device (a headset), I add the following:

    <hostdev mode='subsystem' type='usb' managed='yes'>
      <source>
        <address bus='3' device='16'/>
      </source>
      <address type='usb' bus='0' port='3'/>
    </hostdev>

and I get "internal error: No free USB ports".

 

If I use the Libvirt Hotplug USB plugin, I get  "error: internal error: No free USB ports" so I dont think I'm messing up the XML.

I have plenty of free usb ports on the motherboard.  Here is lsusb -t output:

/:  Bus 04.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/6p, 5000M
    |__ Port 5: Dev 2, If 0, Class=Hub, Driver=hub/4p, 5000M
/:  Bus 03.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/15p, 480M
    |__ Port 3: Dev 15, If 0, Class=Human Interface Device, Driver=usbfs, 1.5M
    |__ Port 3: Dev 15, If 1, Class=Human Interface Device, Driver=usbfs, 1.5M
    |__ Port 4: Dev 14, If 2, Class=Human Interface Device, Driver=usbfs, 12M
    |__ Port 4: Dev 14, If 0, Class=Human Interface Device, Driver=usbfs, 12M
    |__ Port 4: Dev 14, If 1, Class=Human Interface Device, Driver=usbfs, 12M
    |__ Port 7: Dev 16, If 0, Class=Audio, Driver=, 12M
    |__ Port 7: Dev 16, If 3, Class=Human Interface Device, Driver=usbhid, 12M
    |__ Port 7: Dev 16, If 1, Class=Audio, Driver=, 12M
    |__ Port 7: Dev 16, If 2, Class=Audio, Driver=, 12M
    |__ Port 9: Dev 4, If 0, Class=Hub, Driver=hub/4p, 480M
        |__ Port 3: Dev 12, If 1, Class=Human Interface Device, Driver=usbfs, 1.5M
        |__ Port 3: Dev 12, If 0, Class=Human Interface Device, Driver=usbfs, 1.5M
        |__ Port 4: Dev 13, If 1, Class=Human Interface Device, Driver=usbfs, 12M
        |__ Port 4: Dev 13, If 2, Class=Human Interface Device, Driver=usbfs, 12M
        |__ Port 4: Dev 13, If 0, Class=Human Interface Device, Driver=usbfs, 12M
    |__ Port 11: Dev 10, If 0, Class=Human Interface Device, Driver=usbhid, 1.5M
    |__ Port 11: Dev 10, If 1, Class=Human Interface Device, Driver=usbhid, 1.5M
    |__ Port 12: Dev 11, If 0, Class=Human Interface Device, Driver=usbhid, 12M
    |__ Port 12: Dev 11, If 1, Class=Human Interface Device, Driver=usbhid, 12M
    |__ Port 12: Dev 11, If 2, Class=Human Interface Device, Driver=usbhid, 12M
    |__ Port 14: Dev 9, If 0, Class=Mass Storage, Driver=usb-storage, 480M
/:  Bus 02.Port 1: Dev 1, Class=root_hub, Driver=ehci-pci/2p, 480M
    |__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/8p, 480M
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=ehci-pci/2p, 480M
    |__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/6p, 480M

I've read that libvirt has a limitation of 6 usb per VM, but I'm only use 2 each (although that makes it 6 total before I try adding the headset).

Personally, id get a pcie usb3 card and pass that through to each vm... less headaches with limitations of passing individual usb ports. 

44 minutes ago, billington.mark said:

Personally, id get a pcie usb3 card and pass that through to each vm... less headaches with limitations of passing individual usb ports. 

 

I dont have any free PCIe slots to add one, otherwise I would.

I found the solution so figured I'd come back and post it so others seeing the same error dont have to wonder what happened.

 

I went back to where I pulled the code for adding devices when you have more than one with the same name, VM USB Passthrough Multiple Devices with the same Vendor/Product

 

 I had to take out the: 

<address type='usb' bus='0' port='2'/>

for each device that I had already added.  Unraid will add that part back in and fix it up automagically.

Edited September 10, 20178 yr by bigwah