On Thu, Sep 18, 2014 at 8:38 AM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: > 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. 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. --Andy > > --Andy > >> >> -hpa >> >> > > > > -- > Andy Lutomirski > AMA Capital Management, LLC -- 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
