CPUID_NOX
if (cpu_feature[2] & CPUID_NOX)
pmap_pg_nx = (cpu_feature[2] & CPUID_NOX ? PTE_NX : 0);
if (cpu_feature[2] & CPUID_NOX)
xpmap_pg_nx = (descs[3] & CPUID_NOX) ? PTE_NX : 0;
if ((cpu_feature[2] & CPUID_NOX) && !(prot & VM_PROT_EXECUTE))