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From: Paul Brook <paul@codesourcery.com>
Date: Sun, 1 Jul 2012 23:06:36 +0100
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Subject: Re: [Qemu-devel] [RFC PATCH 0/4] virtio-rng and RngBackend
	infrastructure (v2)
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To: qemu-devel@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>, Anthony Liguori <aliguori@us.ibm.com>, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, Markus Armbruster <armbru@redhat.com>, Amit Shah <amit.shah@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Andreas Faerber <afaerber@suse.de>

> This series depends on my QOM -object series that I just posted.
> 
> In Amit's thread on virtio-rng, danpb mentioned that we really ought to
> have a proper RNG backend infrastructure and of course he's correct on
> that.
> 
> Now that we have QOM, I wanted to demonstrate how we can use QOM to
> construct a complete backend without adding any new infrastructure.
> 
> I've now implemented a urandom and egd backend and tested them.  I think
> the first three patches are ready to go.

I never really understood why this exists in the first place.  It's a simple 
readonly charcter device.  IMHO you should be using virtio-serial.  This is 
virtio-console v.s. virtio-serial all over again.
The only thing close to a reason I've heard is that guest OS is incompetent 
and can't source random rata from a serial device.

Even accepting the pointless guest device, I see absolutely no reason to have 
special infrastructure for this within qemu.  Character devices do everything 
you need.  Creating annother "read stream of data" API is needless duplication 
and only going to reintroduce bugs we already fixed in the character device 
layer.

Paul