Re: [Xen-devel] [PATCH v3 2/6] libxl: do not add a vkb backend to hvm guests

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 25 Jun 2015, Ian Campbell wrote:
> On Tue, 2015-06-16 at 16:39 +0100, Stefano Stabellini wrote:
> > On Tue, 16 Jun 2015, Wei Liu wrote:
> > > On Wed, Jun 10, 2015 at 11:09:50AM +0100, Stefano Stabellini wrote:
> > > > When QEMU restricts its xenstore connection, it cannot provide PV
> > > > backends. A separate QEMU instance is required to provide PV backends in
> > > > userspace, such as qdisk. With two separate instances, it is not
> > > > possible to take advantage of vkb for mouse and keyboard, as the QEMU
> > > > that emulates the graphic card (the device model), would be separate
> > > > from the QEMU running the vkb backend (PV QEMU).
> > > > 
> > > 
> > > The question is that how would this affect the non-split setup.
> > 
> > vkb is useful because emulating usb forces QEMU to wake up more often.
> > However there is no way around it.
> 
> Does pvfb+vkb continue to work due to code somewhere else?

Yes, it continues to work as usual for PV guests.


> Do we think anyone will actually be using emulated VGA + PV input
> devices?

VGA + PV input only works with Linux and is only useful for power
efficiency, because if you disable usb emulation in QEMU, then QEMU
would be able to wake up less often. Given that usb emulation is still
on by default, I don't think that this change will have a big impact.

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