Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754126Ab3JBOhh (ORCPT ); Wed, 2 Oct 2013 10:37:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:14992 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753767Ab3JBOhe (ORCPT ); Wed, 2 Oct 2013 10:37:34 -0400 Date: Wed, 2 Oct 2013 17:37:20 +0300 From: Gleb Natapov To: Paolo Bonzini Cc: Alexander Graf , Michael Ellerman , 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 Message-ID: <20131002143720.GK17294@redhat.com> References: <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <524C2EAE.7090209@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1139 Lines: 26 On Wed, Oct 02, 2013 at 04:33:18PM +0200, Paolo Bonzini wrote: > Il 02/10/2013 16:08, Alexander Graf ha scritto: > > > The hwrng is accessible by host userspace via /dev/mem. > > > > A guest should live on the same permission level as a user space > > application. If you run QEMU as UID 1000 without access to /dev/mem, why > > should the guest suddenly be able to directly access a memory location > > (MMIO) it couldn't access directly through a normal user space interface. > > > > It's basically a layering violation. > > With Michael's earlier patch in this series, the hwrng is accessible by > host userspace via /dev/hwrng, no? > Access to which can be controlled by its permission. Permission of /dev/kvm may be different. If we route hypercall via userspace and configure qemu to get entropy from /dev/hwrng everything will fall nicely together (except performance). -- Gleb. -- 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/