Re: usb devices in domU

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Thu, Apr 16, 2015 at 07:36:21AM -0600, Brook Milligan wrote:
> Thank you very much.
> 
> On Apr 16, 2015, at 1:41 AM, Manuel Bouyer wrote:
> > It should be possible for a HVM guest.
> > In the guest's config file:
> > usb=1
> > usbdevice=[ 'tablet', 'host:09fb:6001' ]
> > 
> > 09fb:6001 being the vendor and device ID or your USB device
> > in dom0. You may need to disable drivers in dom0 so that
> > your device is attached to ugen (I don't remember).
> 
> What if the device is not permanently connected?  In this particular case, Windows does not even have a driver for it; the device is detected by an application only when the app is run.  Does this mean that some controller is what needs to be passed through?

I don't remember, but the qemu-dm in dom0 can probably detect when the
device is connected, and pass it to the domU. 

> 
> > This has worked for me at last with Xen 4.1. The above was to
> > pass the Altera USBblaster to a linux guest where I could program the
> > FPGA with altera's tools. It did work, but was very slow ?
> 
> Does this imply that passed-through USB devices suffer performance degradation?  The one I need access to has some pretty strict speed requirements; for example, it must have USB 3.0 speeds.  Will that be possible with a dom0 intervening?

Probably not, as the this goes through an emulated USB controller (by qemu-dm)
on the domU side.
In this case you can try to pass the USB controller itself.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--