VMFUNC

if not vmx_nonroot:
    fault(UD)                    # outside a guest (and on AMD's
                                 # processors, which have no VMX)
p = current_vmcs
pri = vmcs_read(p, 0x4002)       # processor-based controls; bit
sec = 0                          # 31 activates the secondary ones
if pri >> 31:
    sec = vmcs_read(p, 0x401E)
if not sec >> 13 & 1 or eax > 63:
    fault(UD)                    # VM functions off, or past 63
if not vmcs_read(p, 0x2018) >> eax & 1:
    vm_exit(59)                  # a function the hypervisor did not
                                 # enable
if eax == 0:                     # EPTP switching (28.5.7.3)
    if ecx > 511:
        vm_exit(59)
    a = vmcs_read(p, 0x2024)     # the EPTP list, 512 entries
    e = phys_read(a + 8 * ecx, 64)
    old = vmcs_read(p, 0x201A)   # EPTP
    walk = (e ^ old) >> 3 & 7    # another page-walk length
    if not eptp_ok(e) or walk:
        vm_exit(59)              # or an EPTP that a VM entry would
                                 # refuse
    vmcs_write(p, 0x201A, e)     # the guest's memory, translated by
                                 # other EPT paging structures
    ctls = msr[IA32_VMX_PROCBASED_CTLS2]
    if ctls >> 50 & 1:           # EPT-violation #VE may be 1: the
        vmcs_write(p, 0x0004, ecx)  # EPTP index
# no other VM function is defined; one that is enabled but not
# defined does what the SDM does not say