[Xen-devel] Re: Error recovery in Xen's paravirtualizing USB driver for Linux

[Pete Zaitcev <zaitcev@xxxxxxxxxx>]

On Wed, 07 Dec 2005 18:31:17 +0000, harry <harry@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx> 
wrote:

>     This 'USB split driver' has a 'front-end' in the Linux kernel
> running in a guest domain of the hypervisor and a 'back-end' in the
> Linux kernel running in a device driver domain (usually the special
> privilidged domain 0).

Why don't you just let guest 0 to own the controller? This is what
the guest 0 is for, as far as I know.

If you create special stub drivers in the hypervisor, you might as
well create virtual USB controllers for nonzero guests.

> o - The back-end uses usb_register to register itself as a driver
> matching all USB IDs so it gets probed for every USB device that is
> connected.  When a USB device is probed for a configured port, the
> driver claims all the interfaces for the device.

Ewww! Ewww!

You are just going to hit all the difficulties the vmware guy hit,
perhaps minus the size limitation in usbfs since you are bypassing it.

I would expect that the scheme you're proposing were employed to
let non-zero guests to drive some virtualized devices, but not for
the guest zero.

-- Pete

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