From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: Standardizing an MSR or other hypercall to get an RNG seed? Date: Thu, 18 Sep 2014 07:43:09 -0700 Message-ID: <541AEF7D.2010007@zytor.com> References: <2aa00301e9af4826b5781e01709f81e7@BY2PR0301MB0711.namprd03.prod.outlook.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Gleb Natapov , Paolo Bonzini , Theodore Ts'o To: KY Srinivasan , Andy Lutomirski , Linux Virtualization , kvm list Return-path: In-Reply-To: <2aa00301e9af4826b5781e01709f81e7@BY2PR0301MB0711.namprd03.prod.outlook.com> 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 List-Id: kvm.vger.kernel.org On 09/18/2014 07:40 AM, KY Srinivasan wrote: >> >> The main questions are what MSR index to use and how to detect the >> presence of the MSR. I've played with two approaches: >> >> 1. Use CPUID to detect the presence of this feature. This is very easy for >> KVM to implement by using a KVM-specific CPUID feature. The problem is >> that this will necessarily be KVM-specific, as the guest must first probe for >> KVM and then probe for the KVM feature. I doubt that Hyper-V, for >> example, wants to claim to be KVM. If we could standardize a non- >> hypervisor-specific CPUID feature, then this problem would go away. > > We would prefer a CPUID feature bit to detect this feature. > I guess if we're introducing the concept of pan-OS MSRs we could also have pan-OS CPUID. The real issue is to get a single non-conflicting standard. -hpa