Yeah, a no-op pkey_alloc flag tied to this patch to provide a way to
detect if pkey state is preserved on fork, since kernels without the
patch would report EINVAL. Something like
PKEY_ASSERT_FORK_INHERIT_STATE would make sense. Otherwise, it's
going to be quite painful to adopt this in userspace software without kernel
version checks. Most software can't accept causing a crash / abort
after forking in environments not applying all the stable kernel
patches, or in fresh OS installs that aren't fully updated + rebooted yet.
