On Thu, Sep 18, 2014 at 11:58 AM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > >> > Actually, that MSR address range has been reserved for that purpose, along >> > with: >> > - CPUID.EAX=1 -> ECX bit 31 (always returns 0 on bare metal) >> > - CPUID.EAX=4000_00xxH leaves (i.e. HYPERVISOR CPUID) >> >> I don't know whether this is documented anywhere, but Linux tries to >> detect a hypervisor by searching CPUID leaves 0x400xyz00 for >> "KVMKVMKVM\0\0\0", so at least Linux can handle the KVM leaves being >> in a somewhat variable location. >> >> Do we consider this mechanism to work across all hypervisors and >> guests? That is, could we put something like "CrossHVPara\0" >> somewhere in that range, where each hypervisor would be free to decide >> exactly where it ends up? > > That's also possible, but extending the hypervisor CPUID range > beywond 400000FFH is not officially sanctioned by Intel. > > Xen started doing that in order to expose both Hyper-V and Xen > CPUID leaves, and KVM followed the practice. > Whoops. Might Intel be willing to extend that range to 0x40000000 - 0x400fffff? And would Microsoft be okay with using this mechanism for discovery? Do we have anyone from VMware in this thread? I don't have any VMware contacts. --Andy -- 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
