From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: GET_RNG_SEED hypercall ABI? (Re: [PATCH v5 0/5] random,x86,kvm: Rework arch RNG seeds and get some from kvm) Date: Fri, 29 Aug 2014 08:36:47 +0200 Message-ID: <54001F7F.5030206@redhat.com> References: <20140828141704.GI18167@minantech.com> <53FF8722.6080302@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: 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: Andy Lutomirski Cc: X86 ML , Theodore Ts'o , Kees Cook , kvm list , Konrad Rzeszutek Wilk , Gleb Natapov , Andrew Honig , Haiyang Zhang , Raghavendra K T , "linux-kernel@vger.kernel.org" , Linux Virtualization , Daniel Borkmann , Bandan Das , Srivatsa Vaddagiri , Alok Kataria , "H. Peter Anvin" List-Id: virtualization@lists.linuxfoundation.org Il 29/08/2014 02:13, Andy Lutomirski ha scritto: > Hmm. Then, assuming that someone manages to allocate a > cross-hypervisor MSR number for this, what am I supposed to do in the > KVM code? Just make it available unconditionally? I don't see why > that wouldn't work reliably, but it seems like an odd design. The odd part of it is what Gleb mentioned. > Also, the one and only native feature flag I tested (rdtscp) actually > does work: RDTSCP seems to send #UD if QEMU is passed -cpu > host,-rdtscp. True, and I'm not sure why. There are a couple others. I was thinking more of things like SSE, AVX or DE (that affects the availability of a bit in CR4). Paolo From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752851AbaH2GhU (ORCPT ); Fri, 29 Aug 2014 02:37:20 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50675 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751785AbaH2GhQ (ORCPT ); Fri, 29 Aug 2014 02:37:16 -0400 Message-ID: <54001F7F.5030206@redhat.com> Date: Fri, 29 Aug 2014 08:36:47 +0200 From: Paolo Bonzini User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.0 MIME-Version: 1.0 To: Andy Lutomirski CC: Gleb Natapov , Raghavendra K T , "Theodore Ts'o" , Kees Cook , kvm list , Konrad Rzeszutek Wilk , Bandan Das , Andrew Honig , Haiyang Zhang , X86 ML , "linux-kernel@vger.kernel.org" , Linux Virtualization , Daniel Borkmann , Srivatsa Vaddagiri , "H. Peter Anvin" , Alok Kataria Subject: Re: GET_RNG_SEED hypercall ABI? (Re: [PATCH v5 0/5] random,x86,kvm: Rework arch RNG seeds and get some from kvm) References: <20140828141704.GI18167@minantech.com> <53FF8722.6080302@redhat.com> In-Reply-To: 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 Il 29/08/2014 02:13, Andy Lutomirski ha scritto: > Hmm. Then, assuming that someone manages to allocate a > cross-hypervisor MSR number for this, what am I supposed to do in the > KVM code? Just make it available unconditionally? I don't see why > that wouldn't work reliably, but it seems like an odd design. The odd part of it is what Gleb mentioned. > Also, the one and only native feature flag I tested (rdtscp) actually > does work: RDTSCP seems to send #UD if QEMU is passed -cpu > host,-rdtscp. True, and I'm not sure why. There are a couple others. I was thinking more of things like SSE, AVX or DE (that affects the availability of a bit in CR4). Paolo