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> The CPU ID registers say EL3 does not exist. Thank you for mentioning this. I retract my earlier (GP) comment. I didn't know that ARM chips self-declared t
by KirillPanov 5y ago
> The CPU ID registers say EL3 does not exist.
Thank you for mentioning this. I retract my earlier (GP) comment.
I didn't know that ARM chips self-declared their support for EL3 with register bits that could be read! But yes, they do:
https://www.kernel.org/doc/html/latest/arm64/cpu-feature-registers.html https://www.kernel.org/doc/html/latest/arm64/cpu-feature-reg...
These bits amount to Apple saying "there is no EL3" and constitute one of the few pieces of official documentation attributable to Apple.
PS, if you're maintaining any kind of list of "why the M1 is more trustworthy than chip XYZ", the fact that there is a MSR-like bit declaring that the feature doesn't exist should definitely go on that list. Just to make it clear that EL3 not existing was something declared by the chip rather than assumed by the reverse engineers.