Re: [Qemu-devel] [PATCH] xen: use a common function for pv and hvm guest backend register calls

[Stefano Stabellini]

On Wed, 3 Aug 2016, Juergen Gross wrote:
> On 02/08/16 20:27, Stefano Stabellini wrote:
> > On Tue, 2 Aug 2016, Juergen Gross wrote:
> >> Instead of calling xen_be_register() for each supported backend type
> >> for hvm and pv guests in their machine init functions use a common
> >> function in order not to have to add new backends twice.
> >>
> >> This at once fixes the error that hvm domains couldn't use the qusb
> >> backend.
> >>
> >> Signed-off-by: Juergen Gross <address@hidden>
> >> ---
> >> Is it on purpose the qnic and vfb backends are not registered for HVM?
> > 
> > Yes, it is on purpose: there is no code in any toolstacks to use qnic,
> > and the presence of vfb can cause problems to Linux HVM guests (or at
> > least it used to), additionally vfb for HVM guests is also disabled in
> > libxl.
> > 
> > In general, it is a good idea to disable code that is not supposed to be
> > used.
> > 
> > Can qusb be used with HVM guests with libxl/xl?
> 
> Yes. You have to specify "type=qusb" for usbctrl, then it will work.
> I have verified that.

Good, thanks.