NX/XD & LAHF/SAHF

NX/XD 

The AMD No eXecute (NX) and the Intel eXecute Disable (XD)

                 NX/XD is enabled or disabled in the server BIOS and is typically found under Processor options and labeled as something like “Execute Disable Bit”, “NX Technology” or “XD Support”.

               A vital aspect of virtualization is isolation -- preventing application code in one VM from accessing the memory space used by other VMs. The idea is that when a memory area is marked as non-executable, the processor will refuse to run any code in those protected areas. This prevents one VM from affecting another VM.

LAHF/SAHF

              LAHF stands for Load AH from Flags and SAHF stands for Store AH into Flags.

              LAHF & SAHF are used to load and store instructions for certain status flags. similar to NX/XD which can be enabled or disabled in the server BIOS, support for LAHF/SAHF is typically tied into the Virtualization Technology (VT) option in a server BIOS which is often referred to Intel VT or AMD-V which is their respective support for virtualization CPU technology.