On Thu, Sep 18, 2014 at 7:43 AM, H. Peter Anvin <hpa@xxxxxxxxx> wrote: > 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. Agreed. KVM currently puts 0 in 0x40000000.EAX, meaning that a feature bit in Microsoft's leaf 0x40000003 would probably not work well for KVM. I don't expect that Microsoft wants to start claiming to be KVM for the purpose of using a KVM-style feature bit, so, if we went the CPUID route, we would probably need something new. --Andy > > -hpa > > -- Andy Lutomirski AMA Capital Management, LLC -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
