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Re: [Xen-users] Status of USB in xl toolstack

On 04/08/2014 09:31 AM, Ian Campbell wrote:
I don't know what George plans and you've dropped the CC so he is
unlikely to see the question. I've put it back and left the quotes

I don't believe you need to reboot the host to use PCI passthrough, in
most cases you can dynamically rebind. There are helpers in xl to do
this, or you can poke at sysfs directly.

I think it would be unlikely that rebooting the host would be necessary
for USB passthrough.

So there are several ways to get your USB device to your guest:
1. PCI pass-through of the host USB controller
2. passing through a host USB device via qemu emulation
3. passing through a host USB device via PVUSB

#1 is available and pretty well understood. It has never required booting your host -- you could always dynamically assign a device to pciback after you've booted. Before 4.2 this required a bunch of manual frobbing about in sysfs; since 4.2 there are some convenient xl commands to do so. See the wiki page here:


In #2, qemu emulates the USB controller, but passes the USB commands through to the host device. This has been available as a static configuration for a long time; as of at least 4.3 you could pass in arbitrary numbers of devices. Depending on your USB device, if you do #2 you may need to set the "usbversion" in your config file as well.

There is no way to do USB "hot-plug" for this mode yet -- I have a patch series that's functional, but still needs to be tweaked to get the interface right.

In #3, usbback passes the USB commands through to the host device. This requires pcifront in your guest and pciback in your domU and dom0 respectively. There is no xl support for this yet, but as with pci pass-through, there are ways you can make this happen manually by frobbing about with xenstore.

Hopefully that gives you some options.


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