Re: [Xen-devel] Does XEN use TUN/TAP interface?

[Daniel Stodden <stodden@xxxxxxxxxx>]

On Sun, 2008-03-16 at 17:41 +0000, Daniel P. Berrange wrote:

> > > Whether it is a separate hypervisor / Dom0, or a combined HV+Dom0 is not
> > > really relevant to this question. In both cases the driver backends are 
> > > in the Linux host OS and not the hypervisor itself.
> > 
> > Using TUN/TAP is absolutely pointless if the peer is not running in
> > userland. Because connecting userspace to a network interface is the
> > whole point there. 
> > 
> > And this is why the VMM type matters to answer the question.
> 
> No the distinction here is between kernel space & user space backends, not
> between host OS and hypervisor. The hypervisor doesn't get involved in the
> driver backends - it is delegated to the host OS to take care of.

Okay, you're certainly right. I hereby correct myself:

TUN/TAP is used when the VMM part doing I/O virtualization is in
userspace.  Whether the part of the VMM doing I/O virtualization ends up
as userspace on a UNIX system with TUN/TAP support depends on the VMM
type, with the exception of a type I VMM which is quite different from a
typical type I VMM in that it is delegating I/O virtualization to a
guest OS running QEMU.

Much better, thank you.

Kind Regards,
Daniel

-- 
Daniel Stodden
LRR     -      Lehrstuhl für Rechnertechnik und Rechnerorganisation
Institut für Informatik der TU München             D-85748 Garching
http://www.lrr.in.tum.de/~stodden         mailto:stodden@xxxxxxxxxx
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