ASM_NOP3          421 include/asm-x86/system.h 	alternative(ASM_NOP3, "mfence", X86_FEATURE_MFENCE_RDTSC);
ASM_NOP3          422 include/asm-x86/system.h 	alternative(ASM_NOP3, "lfence", X86_FEATURE_LFENCE_RDTSC);