The later verions of the KAISER pathces (pre-PTI) allowed the user/kernel shared areas to be GLOBAL. The thought was that this would reduce the TLB overhead of keeping two copies of these mappings.
During the switch over to PTI, we seem to have lost our ability to have GLOBAL mappings. This adds them back. Did we have some reason for leaving out global pages entirely? We _should_ have all the TLB flushing mechanics in place to handle these already since all of our kernel mapping changes have to know how to flush global pages regardless. Cc: Andy Lutomirski <l...@kernel.org> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Kees Cook <keesc...@google.com> Cc: Hugh Dickins <hu...@google.com> Cc: Juergen Gross <jgr...@suse.com> Cc: x...@kernel.org