Finding out if "Unrestricted Guest" supported at runtime

[johndoe31415]

Hi there,

is there an option to find out at runtime (e.g. with means of CPUID or something else) if the "Unrestricted Guest" feature is supported on the CPU? In the developer manual I can only find which flags control the UG feature (i.e. "25.8. Unrestricted Guests" ff), but I don't see anywhere how to determine if the feature is actually supported. Historically, at which processor family was "Unrestricted Guest" introduced? Is there a easy way to tell which processors contian the feature from the timeline?

Best regards,
Joe

[Tracy_Camp · Accepted solution]

There are a series of MSRs that tell you if a given CPU supports the '1' setting of unrestricted guest and a number of other virtualization features. The specific MSR is IA32_VMX_PROCBASED_CTLS2 and I believe unrestricted guest is bit 7 in the secondary proc controls VMCS field.

[johndoe31415]

Perfect, thank you very much!