From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: "H. Peter Anvin" <hpa@zytor.com>, Theodore Tso <tytso@mit.edu>,
Herbert Xu <herbert@gondor.apana.org.au>,
Jeff Garzik <jeff@garzik.org>,
LKML <linux-kernel@vger.kernel.org>,
virtualization@lists.linux-foundation.org,
Christian Borntraeger <borntraeger@de.ibm.com>,
Matt Mackall <mpm@selenic.com>,
Johannes Berg <johannes@sipsolutions.net>
Subject: Re: [PATCH 2/2] lguest: virtio-rng support
Date: Mon, 19 May 2008 10:45:23 +0100 [thread overview]
Message-ID: <48314C33.7010604@goop.org> (raw)
In-Reply-To: <200805191928.13043.rusty@rustcorp.com.au>
Rusty Russell wrote:
> Unfortunately not. Hardware randomness devices export /dev/hwrng, and it's up
> to userspace to feed that into /dev/random (or not). That's usually done by
> rngd, which at least on my system, assumes 1 bit of entropy per bit of data
> from /dev/hwrng by default.
>
> I was a little surprised that this decision was exported to userspace, but if
> you're not prepared to unconditionally trust hw rngs, it makes sense to palm
> it off.
Yeah, that's a bit of a pity. Hardware rngs can often generate really
crappy randomness, which needs tons of processing to remove noise like
50/60hz hum, etc.
> We could write a boutique device for virtualization which *did* feed
> directly, but that would be a little gauche.
>
Well, yes, we can certainly do any amount of processing we like to the
stuff provided to guests, so that the 1:1 bits/entropy ratio is as true
as we can make it.
J
next prev parent reply other threads:[~2008-05-19 9:45 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-15 18:48 Virt RNG? Jeff Garzik
2008-05-15 19:53 ` Jeremy Fitzhardinge
2008-05-15 20:26 ` Dor Laor
2008-05-15 20:31 ` Christian Borntraeger
2008-05-15 20:44 ` Jeff Garzik
2008-05-15 20:43 ` Jeff Dike
2008-05-15 23:43 ` Rusty Russell
2008-05-16 0:07 ` Henrique de Moraes Holschuh
2008-05-16 5:31 ` [PATCH 1/2] virtio: hardware random device Rusty Russell
2008-05-16 5:39 ` [PATCH 2/2] lguest: virtio-rng support Rusty Russell
2008-05-16 10:49 ` Johannes Berg
2008-05-16 20:25 ` H. Peter Anvin
2008-05-17 4:46 ` Rusty Russell
2008-05-17 4:50 ` H. Peter Anvin
2008-05-17 6:28 ` Rusty Russell
2008-05-17 6:43 ` Herbert Xu
2008-05-17 7:43 ` Christian Borntraeger
2008-05-17 15:56 ` H. Peter Anvin
2008-05-17 7:47 ` Jeremy Fitzhardinge
2008-05-19 9:05 ` Rusty Russell
2008-05-19 9:10 ` Jeremy Fitzhardinge
2008-05-19 9:28 ` Rusty Russell
2008-05-19 9:45 ` Jeremy Fitzhardinge [this message]
2008-05-17 15:57 ` H. Peter Anvin
2008-05-16 7:31 ` [PATCH 1/2] virtio: hardware random device Christian Borntraeger
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