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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] Re: [PATCH 9/9] Introduce VLANClientState::cleanup()
Date: Tue, 28 Apr 2009 19:28:31 +0100
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To: qemu-devel@nongnu.org
Cc: Mark McLoughlin <markmc@redhat.com>, Anthony Liguori <aliguori@us.ibm.com>, Marcelo Tosatti <mtosatti@redhat.com>, Markus Armbruster <armbru@redhat.com>

On Tuesday 28 April 2009, Anthony Liguori wrote:
> Paul Brook wrote:
> > Hmm, in that case I don't understand your distinction between frontend
> > and backend.
>
> In the case of networking, they don't have to be distinct because all
> you need to do is have two "front-ends" and flip the TX/RX queues.
> Although even in this case, someone has to own the MAC address so it's
> not purely symmetric.

I'm still not understanding. Ethernet devices are fundamentally based around a 
bus architecture. "flip the TX/RX queues" only makes sense if you're talking 
about a point-point connection. For ethernet devices I see no reason to 
distinguish between "host" devices (slirp, vde, tap) and "guest" devices. 
They may be created for different reasons, but they're all doing 
fundamentally the same thing.

> In the general case, that isn't always true for devices.  Consider block
> devices, for instance.

You mean the API we expose to the devices v.s. the API we expose to the image 
file backends? Or do you mean different layers like ide/scsi v.s. internal 
block devices?

Paul