LAST_USER_MM_IBPB
#define LAST_USER_MM_SPEC_MASK (LAST_USER_MM_IBPB | LAST_USER_MM_L1D_FLUSH)
#define LAST_USER_MM_INIT LAST_USER_MM_IBPB
(next_mm | prev_mm) & LAST_USER_MM_IBPB)