The really important question that remains after reading the kgraft presentation is, of course, if "getties" really is the plural of "getty"?
(PS. Note that the presentation somewhat ambigously refers to the 'World view' checking code as 'trampoline'. This can indeed safely be removed once everything is done. The JMP at the start of the original function will remain, however. Also note that if they had more cooperation from the compiler like the Windows hotpatch scheme, instead of ftrace piggybacking on the GCC profiling code, they could presumably do this without any delay whatsoever on the other CPUs, but I suspect this was evaluated and rejected for various reasons.)