linux-kernel - Re: random(4) driver questions

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Date:	Mon, 27 Jun 2011 11:08:13 -0400
From:	Sasha Levin <levinsasha928@...il.com>
To:	Ted Ts'o <tytso@....edu>
Cc:	Sandy Harris <sandyinchina@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: random(4) driver questions

On Mon, 2011-06-27 at 10:54 -0400, Ted Ts'o wrote:
> > What happens to /dev/random when it runs on
> > a virtual machine and all the things it relies on
> > for entropy get virtualised away?
> > 
> > The server that the VM is hosted on will usually
> > have plenty of entropy, often a hardware RNG.
> > Is there an interface that makes that visible
> > from the VM? Perhaps a virtual "hardware"
> > RNG driven by /dev/urandom on the host?
> 
> Yes, paravirtualizing the random number generator would be a big help.
> Probably what I would do is to periodically add entropy from the host
> OS to the guest OS, via some paravirt channel.  This would add a new
> "catastrophic reseeding", and if the virtual guest can mix in some
> other unknown material, again that can only help.

virtio has a 'virtio-rng' device which does just that.

-- 

Sasha.

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