linux-kernel - Re: [RFC PATCH] hwrng: sysfs entry rng_seed_kernel, was: "Re: [PATCH v2 1/2] hwrng: fetch randomness only after device init"

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Message-ID: <20140711132626.GB17415@grmbl.mre>
Date:	Fri, 11 Jul 2014 18:56:26 +0530
From:	Amit Shah <amit.shah@...hat.com>
To:	Jason Cooper <jason@...edaemon.net>
Cc:	linux-kernel@...r.kernel.org,
	Virtualization List <virtualization@...ts.linux-foundation.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	herbert@...dor.apana.org.au, keescook@...omium.org,
	stable@...r.kernel.org
Subject: Re: [RFC PATCH] hwrng: sysfs entry rng_seed_kernel, was: "Re: [PATCH
 v2 1/2] hwrng: fetch randomness only after device init"

On (Wed) 09 Jul 2014 [12:07:25], Jason Cooper wrote:
> Amit, Kees,

(snip)

> I'm cooling to the idea of the init function for virtio-rng, and it
> might be best just to admit that there's no way to seed the entropy pool
> from the virtio-rng at probe time.  After all, once userspace is up, the
> system should take advantage of /dev/hwrng for the generation of
> long-term keys.  Either via rngd feeding /dev/random, or directly.
> 
> As for the follow-on patch you asked about, I think that's fine.  More
> entropy can't hurt.
> 
> The below patch might be worth considering so that the user of a system
> with only virtio-rng can kick the entropy pool as they see fit.  It's
> probably not too kosher as is, but if the idea is liked, I could clean
> it up and submit.
> 
> The advantage is that users don't need to have rngd installed and
> running on the system in order to jump-start the entropy pool.

... so a udev rule that looks for the new sysfs file, and asks the
kernel to do its thing?

And maybe even a patch to rngd that looks for this file and does a
similar thing?

There's also the option to use a delayed workqueue item, that will
succeed if probe has finished.  This method doesn't have userspace
dependencies.

Thanks,

		Amit
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