[libvirt-users] Host should not touch passed-through USB device, how?

[Daniel P. Berrange]

On Tue, Jun 01, 2010 at 12:49:05PM -0400, Cole Robinson wrote:
> On 05/28/2010 02:09 PM, Andreas Ntaflos wrote:
> > Hello list, 
> > 
> > this may be off topic but it is closely related to my Libvirt adventures 
> > so maybe you can help me.
> > 
> > I want to pass a USB device (a USB Huawei E620 modem) through to a KVM 
> > guest. Pass-through in general works fine and the modem is visible in 
> > the guest. However, the host still sees it and sometimes tries to access 
> > it (such modems seem to also be USB storage devices). This naturally 
> > leads to conflicts and I believe this crashed the guest very badly 
> > yesterday.
> > 
> > So I am looking for a way to make sure the host passes through the USB 
> > device (in its entirety) without trying to touch it and claim it as its 
> > own. Preferably without disabling the USB storage subsystem completely 
> > on the host.
> > 
> > Any ideas? Is there a best practice for such things in the Libvirt 
> > world? Or any other world? 
> > 
> 
> For PCI devices, libvirt automatically performs a device reset and some
> other voodoo to make sure the host doesn't try to use the device. Maybe
> there is something similar that libvirt can do for USB devices as well?
> I'm not very knowledgable about that stuff so I can't say for certain.

Yes there is the same. We need to finish implementing identical infrastructure
to that used for PCI devices. We need to do resets and bind/unbind host device
drivers, and implement the so called 'managed' mode.

Daniel
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