VMCALL

if not in_vmx:
    fault(UD)
if vmx_nonroot:
    vm_exit(18, 0)               # the hypercall: what the call means
                                 # is the hypervisor's to define
if CPL > 0 or seam:
    fault(GP, 0)
ctl = msr[IA32_SMM_MONITOR_CTL]  # MSEG's base in bits 31:12
dual = msr[IA32_VMX_BASIC] >> 49 & 1
p = current_vmcs
if in_smm or not dual or not ctl & 1:
    vm_fail(1)                   # in the hypervisor, VMCALL calls
                                 # the SMM-transfer monitor alone
elif dual_monitor:
    vm_exit(18, 0)               # an SMM VM exit, to the monitor
                                 # (34.15.2)
elif p == NO_VMCS:
    vm_fail_invalid()
elif launched(p):
    vm_fail(19)
elif not exit_controls_ok():
    vm_fail(20)                  # 34.15.6.1
else:
    mseg = ctl & 0xFFFFF000
    rev = msr[IA32_VMX_MISC] >> 32
    if phys_read(mseg, 32) != rev:
        vm_fail(22)              # MSEG's revision identifier
    elif phys_read(mseg + 4, 32) != 1:
        vm_fail(24)              # the monitor's features: 64-bit
                                 # mode needs bit 0, the rest 0
    else:
        vm_exit(18, 0)           # an SMM VM exit that activates
                                 # the dual-monitor treatment
                                 # (34.15.6)