> RHEL used 64k page size on aarch64 for a while. I believe we have switched back to 4k.

Last I checked, at least CentOS 8 (which should be the same as RHEL 8) is still using 64k pages (search at https://git.centos.org/rpms/kernel/blob/c8/f/SOURCES/kernel-... for CONFIG_ARM64_64K_PAGES=y).

And AFAIK, to access the maximum amount of physical memory in AARCH64 (52-bit physical addresses, instead of 48 bit physical addresses), you must use 64k pages. Since RHEL is normally used on servers, it makes sense to want to be able to access huge amounts of physical memory; that's probably the true reason (or even the sole reason) RHEL uses 64k pages on AARCH64.