Fascinating, thank you. It seems strange that the C1-Pro/C1-Ultra TRM mention that ID_AA64PFR1_EL1[11:8] should still be non-zero even when BROADCASTMTE is low.

edit: Oh, I guess Linux does emulate the feature registers, doh. Since that user is booting with arm64.nomte, the kernel is changing those feature bits to zero! This probably explains the confusion here about hardware support: in Linux userspace, you still trap for system register reads, and this is just abstracted away from you...

https://github.com/torvalds/linux/blob/841e384b841a3d89c50b4...