On Fri, Nov 7, 2025, at 15:19, Yeoreum Yun wrote:
On Thu, Nov 6, 2025, at 10:40, Yeoreum Yun wrote:
apply FEAT_LSUI instruction to emulate deprecated swpX instruction.
Can you explain in the changrelog why you do this?
In particular, is this a performance optimization or is this required for correctness in some scenario?
I think the main purpose using for this is to "remove the toggling the PSTATE.PAN" bit. so that remove some *potential* problem which can happen when PAN bit is cleared.
Ok, I see. This should definitely be part of the commit log for the patch in addition to the cover letter.
also, though swpb might add some complexity, but swp can get a little bit of benifit by removing the ll/sc way and reduce the amount of instructions.
This part I think you can ignore in the patch description, unless there is an additional problem with possibly mixing ll/sc and lse atomics that you are trying to solve.
Arnd