From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752879AbaHKQxv (ORCPT ); Mon, 11 Aug 2014 12:53:51 -0400 Received: from mga02.intel.com ([134.134.136.20]:12059 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751512AbaHKQxu (ORCPT ); Mon, 11 Aug 2014 12:53:50 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.01,843,1400050800"; d="scan'208";a="586534018" Message-ID: <53E8F44C.7030803@linux.intel.com> Date: Mon, 11 Aug 2014 09:50:20 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.7.0 MIME-Version: 1.0 To: Torsten Duwe , Amit Shah CC: jgarzik@bitpay.com, Virtualization List , Amos Kong , Rusty Russell , linux-kernel@vger.kernel.org, Ricardo Neri Subject: Re: [PATCH 1/2] rngd: add udev rule to source from hwrng if virtio-rng present References: <53E3D3FF.70707@linux.intel.com> <20140808090715.GG14400@grmbl.mre> <53E54533.8030109@linux.intel.com> <20140811071527.GB4184@grmbl.mre> <20140811133030.GA27247@lst.de> In-Reply-To: <20140811133030.GA27247@lst.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/11/2014 06:30 AM, Torsten Duwe wrote: > On Mon, Aug 11, 2014 at 12:45:27PM +0530, Amit Shah wrote: >> >> What's the suggested value for rng->quality, though, for virtio-rng >> that I can use to ensure the kthread starts? >> >> Should I use the 700 (70%) as proposed in the original patchset? I'm >> not exactly sure how that value will be used as well.. > > There is no such thing as a suggested value, every number is wrong > to some degree. The quality is an estimation of how random your > source really is; it's a property of your hardware. If the device is > virtual you're in trouble ;-) > > Either you have a way to query the underlying real hardware, or > you do your whitening and entropy estimation in the backend driver -- > then you can claim 100%. > virtio-rng I feel we could rank at 100%; it is supposed to feed /dev/random-quality randomness from the VMM. If the VMM is hostile you have already lost anyway. -hpa