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

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

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
> untrimmed.
>
> 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:
http://wiki.xenproject.org/wiki/Xen_PCI_Passthrough

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.

 -George


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