From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: Standardizing an MSR or other hypercall to get an RNG seed? Date: Thu, 18 Sep 2014 17:58:25 +0200 Message-ID: <541B0121.8040503@redhat.com> References: <2aa00301e9af4826b5781e01709f81e7@BY2PR0301MB0711.namprd03.prod.outlook.com> <541AEF7D.2010007@zytor.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 , "H. Peter Anvin" Cc: Gleb Natapov , Theodore Ts'o , kvm list , Linux Virtualization List-Id: virtualization@lists.linuxfoundation.org Il 18/09/2014 17:44, Andy Lutomirski ha scritto: > Slight correction: QEMU/KVM has optional support for Hyper-V feature > enumeration. Ideally the RNG seed mechanism would be enabled by > default, but I don't know whether the QEMU maintainers would be okay > with enabling the Hyper-V cpuid mechanism in a default configuration. Some guests cannot find the KVM leaves at 0x40000100, so it wouldn't be great. And I also don't know what VMware folks would think, but I think they would be even less thrilled than me. Note that even if there is no well-defined CPUID leaf, and the main detection mechanism is #GP, each hypervisor is free to define a CPUID bit of its own. However, if it's going to be an architectural (Intel-defined) MSR, I think the right place for a feature bit is in the low leaves (like EAX=7, ECX=0). Paolo