LAST_USER_MM_L1D_FLUSH
#define LAST_USER_MM_SPEC_MASK (LAST_USER_MM_IBPB | LAST_USER_MM_L1D_FLUSH)
if (prev_mm & LAST_USER_MM_L1D_FLUSH)
if (likely(!(next_mm & LAST_USER_MM_L1D_FLUSH)))
if (unlikely((prev_mm | next_mm) & LAST_USER_MM_L1D_FLUSH))