I hope there is (or will be) a way to use io_uring for the sorts of purposes that the syscall boundary is currently used for. The example I have in mind is https://rr-project.org/ which uses the syscall boundary to isolate nondeterminism in order to implement record/replay debugging. I'm not sure how it can accomplish the same thing with io_uring; it would need to be informed of all updates to the shared pages or something?