From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: [PATCH 1/2] rngd: add udev rule to source from hwrng if virtio-rng present Date: Mon, 11 Aug 2014 09:50:20 -0700 Message-ID: <53E8F44C.7030803@linux.intel.com> References: <53E3D3FF.70707@linux.intel.com> <20140808090715.GG14400@grmbl.mre> <53E54533.8030109@linux.intel.com> <20140811071527.GB4184@grmbl.mre> <20140811133030.GA27247@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140811133030.GA27247@lst.de> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Torsten Duwe , Amit Shah Cc: jgarzik@bitpay.com, Ricardo Neri , linux-kernel@vger.kernel.org, Virtualization List List-Id: virtualization@lists.linuxfoundation.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