FLAT_RING3_CS64    21 arch/x86/include/asm/xen/interface_64.h #define FLAT_KERNEL_CS64 FLAT_RING3_CS64
FLAT_RING3_CS64    31 arch/x86/include/asm/xen/interface_64.h #define FLAT_USER_CS64 FLAT_RING3_CS64