type=ioemu? (was: Re: NetBSD in an HVM instance can't see outside world)

[Johan Ihren <johani%johani.org@localhost>]

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Hi,

On 3 Sep 2008, at 19:34, Manuel Bouyer wrote:

> > vif = [ 'mac=00:16:3d:00:00:13, bridge=bridge0, type=ioemu' ]
>
> This should create a tap interface in the dom0, in addition to the  
> usual
> xvif. Please check that the tap interface is up, and was added to  
> bridge0

Exactly what does the "type=ioemu" stuff mean? And why is the tap  
needed for networking? And what does it do in this context (i.e. I  
know that a tap is a virtual Ethernet in the DOM0, but at least for PV  
the xvif is all that's needed).

Googling reveals lots of Linux references of unclear relevance to  
NetBSD/Xen so I'm a bit confused.

And, while on the subject of ioemu, I see things like:

> disk = [ 'file:/xen/windows/winxp.img,ioemu:hda,w', 'phy:/dev/ 
> cd0a,ioemu:hdb:cdrom,r' ]

So how is that different from not using the "ioemu:" part in front of  
the VDEV (i.e. "hda" here)?

Just extracting a few pieces from my pool of "unknowledge" ;-)

Johan

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