On Thu, Mar 31, 2022 at 04:05:38PM +0000, Szabolcs Nagy wrote:

> i think it's slightly better to treat ZA like TPIDR2,
> so only clear if CLONE_SETTLS is set.

> otherwise in principle the child can return to the frame
> where ZA was used and expect it to work (it's hard to
> come up with a reason why would some code do that, but
> this is valid in a single-threaded fork child).

From an implementation point of view it's a bit clearer if we just
always preserve PSTATE.ZA and ZA contents on clone() and clear them on
exec.  Do you see a problem with that?