linux-kernel - Re: [PATCH v5 0/5] random,x86,kvm: Rework arch RNG seeds and get some from kvm

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Message-ID: <20140813143209.GD6437@thunk.org>
Date:	Wed, 13 Aug 2014 10:32:09 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Andy Lutomirski <luto@...capital.net>,
	kvm list <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Kees Cook <keescook@...omium.org>, X86 ML <x86@...nel.org>,
	Daniel Borkmann <dborkman@...hat.com>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	Gleb Natapov <gleb@...nel.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Bandan Das <bsd@...hat.com>, Andrew Honig <ahonig@...gle.com>
Subject: Re: [PATCH v5 0/5] random,x86,kvm: Rework arch RNG seeds and get
 some from kvm

On Wed, Aug 13, 2014 at 12:48:41AM -0700, H. Peter Anvin wrote:
> The proposed arch_get_rng_seed() is not really what it claims to be; it
> most definitely does not produce seed-grade randomness, instead it seems
> to be an arch function for best-effort initialization of the entropy
> pools -- which is fine, it is just something quite different.

Without getting into an argument about which definition of "seed" is
correct --- it's certainly confusing and different form the RDSEED
usage of the word "seed".

Do we expect that anyone else besides arch_get_rnd_seed() would
actually want to use it?  I'd argue no; we want the rest of the kernel
to either use get_random_bytes() or prandom_u32().  Given that, maybe
we should just call it arch_random_init(), and expect that the only
user of this interface would be drivers/char/random.c?

					- Ted
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