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

["Daniel P. Berrange" <berrange@xxxxxxxxxx>]

On Sun, Mar 16, 2008 at 06:21:51PM +0100, Daniel Stodden wrote:
> On Sun, 2008-03-16 at 17:12 +0000, Daniel P. Berrange wrote:
> > On Sun, Mar 16, 2008 at 05:50:19PM +0100, Daniel Stodden wrote:
> > > On Sun, 2008-03-16 at 15:52 +0100, Pavel Muller wrote:
> > > > Hello,
> > > > I want to ask if XEN use TUP/TAP interfaces or use other interface?
> > > 
> > > No. TUN/TAP is typically used for hosted VMs. Broadly speaking, it's
> > > only useful if a significant part of the VMM is running in user mode on
> > > top of a native Linux, as is the case with VMware Workstation,
> > > VirtualBox, UserModeLinux etc.
> > > 
> > > Xen is a hypervisor, running below all OSes on bare hardware. The
> > > network virtualization is based on a Linux OS (dom0), but the guests
> > > aren't running on top of that, but rather as siblings on a common
> > > virtualization layer.
> > 
> > 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.

Dan.
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