Re: [Xen-devel] [PATCH v6 1/2] libxl: Introduce functions to add and remove USB devices to an HVM guest

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Thu, Apr 25, 2013 at 08:44:58AM +0100, Ian Campbell wrote:
> On Wed, 2013-04-24 at 18:49 +0100, Pasi Kärkkäinen wrote:
> > On Wed, Apr 24, 2013 at 04:51:46PM +0100, Ian Campbell wrote:
> > > On Wed, 2013-04-24 at 16:45 +0100, George Dunlap wrote:
> > > > On 24/04/13 14:51, Ian Campbell wrote:
> > > > > On Wed, 2013-04-24 at 14:32 +0100, George Dunlap wrote:
> > > > >
> > > > >> There's also the translation of "AUTO" protocol into PV or HVM, and
> > > > > This made me wonder, how is libxl_device_usb_protocol different from 
> > > > > the
> > > > > type of the domain? Can you (or is the intention) use PV with an HVM
> > > > > domain? I suppose DEVICEMODEL is HVM only?
> > > > 
> > > > The intention is to allow HVM guests to use either DEVICEMODEL or PV as 
> > > > protocols.
> > > > 
> > > > > Is "protocol" really the right word for this? I'd half expect it to 
> > > > > mean
> > > > > USB 1.0 vs 2.0 vs 3.0. For NICS we call this Enum libxl_nic_type. FWIW
> > > > 
> > > > But we're already using 'type' for the device type. :-)
> > > > 
> > > > I think for nics it makes sense to call it a 'type', as for NICs we 
> > > > refer to the *emulated device* as a NIC, or the PV device as a NIC, 
> > > > which is then (virtually) plugged into a bridge somewhere.  But in this 
> > > > case I don't think it makes sense, as it's the actual host device you 
> > > > care about, and the way the guest talks to it is either via PV or qemu. 
> > > >  
> > > > "Protocol" may not be the very best option, but at least it gives you 
> > > > the idea of a conduit.
> > > 
> > > It's more like a "method" then?
> > > 
> > 
> > "protocol" reminded me about something.. when using devicemodel/qemu method,
> > do we currently allow specifying if the usb device should be connected to 
> > usb2 (ehci) or usb3 (xhci) virtual controller?
> 
> Perhaps EMU_USB2 and EMU_USB3 would be preferable names to DEVICEMODEL?
> 
> Not sure which the current devicemodel mode uses, the code doesn't
> appear to ask qemu for one or the other explicitly, I'd imagine the
> default would be USB2? The qmeu manpage only mentions UHCI.
>

I think you're able to set the (virtual) usb controller for each device on the 
qemu cmdline,
but dunno if qemu has any built-in logic to decide which virtual usb controller 
to attach to if none is specified.. 
like automatically attach usb3 device from the host to virtual usb3/xhci 
controller? 

-- Pasi
 

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