[fedora-virt] USB passthrough

Robert L Cochran cochranb at speakeasy.net
Mon Jun 29 20:32:33 UTC 2009

This is precisely what I brought up on this list weeks ago -- USB device 
pass through. Thanks to work done by Mark and also Dan Walsh, I'm 
succeeding with something called a USB BUB developed by Paul Badger of 
moderndevice.com and Brian Riley of wulfden.org. The BUB is essentially 
an FTDI FT232RL-based uart. I use it to program my Freeduino devices, 
which I purchase as kits from Brian. I expect to pass other USB devices 
through to my Ubuntu guest as well.

Thanks again to Mark and Dan for the fantastic support when I both 
complained and filed a bug related to USB device passthrough.

Bob Cochran

On 06/29/2009 06:19 AM, Mark McLoughlin wrote:
> Hey,
> At FUDCon yesterday, Paul asked me about how to get KVM USB device
> passthrough working and I had to admit I'd never tried it.
> So, after some poking with F-11, here's what I found:
>    1) You need selinux-policy-targeted-3.6.12-55.fc11 or later
>    2) Make sure the virt_use_usb SELinux boolean is enabled, which it
>       should be by default:
>         $>  getsebool virt_use_usb
>         virt_use_usb -->  on
>         $>  setsebool -P virt_use_usb on
>    3) Plug your device in, and if it's a USB mass storage device, make
>       sure it's not mounted in the host
>    4) In virt-manager, open the VM window, go to the details tap,
>       clock 'Add hardware', select 'Phyiscal host device', choose
>       'USB device', then the device you wish to passthrough
>    5) Take a peek at the device in the guest XML config
>         $>  virsh dumpxml xp
>         ...
>         <devices>
>           ...
>           <hostdev mode='subsystem' type='usb' managed='yes'>
>             <source>
>               <vendor id='0x0dda'/>
>               <product id='0x0001'/>
>             </source>
>           </hostdev>
>         </devices>
>    6) Start the guest and check whether the guest can see it. If not,
>       check /var/log/libvirt/qemu/$guest.log because qemu will happily
>       start up even if the device cannot be assigned.
>    7) It sucks that the device has to be plugged in before you start
>       the guest; qemu now has a "autoconnect" mode which probably
>       makes sense for libvirt to use by default, see bug #508645
> Cheers,
> Mark.
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