ACTLR_EL as implementation defined.
Apple adds an IMPDEF
s3_6_c15_c14_6 and effectively implements VHE semantics. This does not seem to violate the architecture, since the register contents are IMPDEF anyway so nothing says they can't alias ACTLR_EL1 and ACTLR_EL2 together in EL2.
ACTLR_EL1 is trapped by
HCR_EL2.TACR. It is also trapped by
HACR_EL2<0> (which has all the controls for fine-grained Apple IMPDEF stuff).
AIDR_EL1 contains feature bits for Apple IMPDEF functionality. It is identical in EL1 and EL2 and is trapped by