Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754309Ab3JBOiS (ORCPT ); Wed, 2 Oct 2013 10:38:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:11640 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753409Ab3JBOiO (ORCPT ); Wed, 2 Oct 2013 10:38:14 -0400 Message-ID: <524C2FDB.4080203@redhat.com> Date: Wed, 02 Oct 2013 16:38:19 +0200 From: Paolo Bonzini User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130923 Thunderbird/17.0.9 MIME-Version: 1.0 To: Alexander Graf CC: Michael Ellerman , Gleb Natapov , Benjamin Herrenschmidt , Paul Mackerras , linux-kernel@vger.kernel.org, mpm@selenic.com, herbert@gondor.hengli.com.au, linuxppc-dev@ozlabs.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, tytso@mit.edu Subject: Re: [PATCH 3/3] KVM: PPC: Book3S: Add support for hwrng found on some powernv systems References: <5243F933.7000907@redhat.com> <20131001083426.GB27484@concordia> <20131001083908.GA17294@redhat.com> <1380620338.645.22.camel@pasglop> <524AAFAA.3010801@redhat.com> <20131002050940.GA25363@drongo> <524BDD73.3020106@redhat.com> <1380704789.645.57.camel@pasglop> <668E4650-BC22-4CBF-A282-E7875DF29DB6@suse.de> <3CBF5732-E7EE-4C96-8132-6D7B77270DAF@suse.de> <20131002100224.GF17294@redhat.com> <1380722275.12149.28.camel@concordia> <029A8D6C-C23C-42B2-8C26-D76B59E2C9DD@suse.de> <524C2EAE.7090209@redhat.com> In-Reply-To: X-Enigmail-Version: 1.5.2 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 928 Lines: 21 Il 02/10/2013 16:36, Alexander Graf ha scritto: >> > >> > With Michael's earlier patch in this series, the hwrng is accessible by >> > host userspace via /dev/hwrng, no? > Yes, but there's not token from user space that gets passed into the > kernel to check whether access is ok or not. So while QEMU may not have > permission to open /dev/hwrng it could spawn a guest that opens it, > drains all entropy out of it and thus stall other processes which try to > fetch entropy, no? > > Maybe I haven't fully grasped the interface yet though :). Yes, that's right. I don't think it's a huge problem, but it's another point in favor of just doing the hypercall in userspace. Paolo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/