MSR_HV_HYPERCALL
hc_orig = rdmsr(MSR_HV_HYPERCALL);
wrmsr(MSR_HV_HYPERCALL, hc);
hc = rdmsr(MSR_HV_HYPERCALL);
hc = rdmsr(MSR_HV_HYPERCALL);
wrmsr(MSR_HV_HYPERCALL, (hc & MSR_HV_HYPERCALL_RSVD_MASK));