[2.5.70] Config options for PS/2 console

Which config options are *required* for PS/2 keyboard support?

With 2.5.70 (or 2.5.69) I cannot use remote console redirection of a Siemens Primergy H450 system. Some keys are dead, others result in error messages such as:

atkbd.c: Unknown key (set 0, scancode 0xed, on isa0060/serio0) pressed.

2.4.x worked fine (but I didn't enable special input support or things like that).