> But it did remind me that on some platforms writing "2" to > /proc/sys/abi/cp15_barrier will enable hw support for these > instructions, since some platforms do support them even thought they > are deprecated. It's certainly worth investigating what your hardware > supports.
Not necessarily disagreeing with the content of that but the terminology seems wrong: I don't have a reference to hand but I'm fairly sure that hardware is *required* to support a "deprecated" instruction. "Deprecated" usually means something like: unless you know what you're doing you probably shouldn't use this feature because it might perform badly and it might not be available in a future version (of the Arm architecture in this case).
