[skissane]

So my understanding – if you run VirtualBox on macOS, and you choose macOS as Guest OS type when creating your VM, it automatically turns GetKeyFromRealSMC on. That means you are using option (2) by default. You can always switch to option (1) instead if you want to, but if you are virtualising macOS-on-macOS, there is little reason to.

From reading the VirtualBox source code [0] – it also automatically enables GetKeyFromRealSMC if it detects Apple hardware, even if the host OS isn't macOS. So, if you install Windows on your Mac, and then create a macOS VM in VirtualBox, it will automatically select option (2) as well. (I think, they actually include the code to talk to the Apple SMC in their Windows and Linux kernel drivers too.)

(Note I haven't actually tried doing this myself, this is just what I gather from the source.)

[0] https://github.com/mdaniel/virtualbox-org-svn-vbox-trunk/blo...

[yjftsjthsd-h]

> but if you are virtualising macOS-on-macOS, there is little reason to.

Not needing to run a kext just to retrieve a known hardcoded string seems like a very good reason.

[skissane]

You don't need to use a kext. You can instead use IOKit to talk to the AppleSMC driver over a Mach port. Works even without root: https://gist.github.com/vagelim/dd5be2802ecb097b81cf07711f6a...

VirtualBox has code to do the above. But it also has code in one of its kexts to do it by talking directly to the hardware, in case (for whatever reason) this API doesn't work; it tries IOKit first and then calls the kext as a fallback. And, the kext doesn't solely exist to talk to the SMC, it does a bunch of other things too. I'm not sure whether VirtualBox works without its kexts, but if it doesn't, it isn't because of this reason.

(When I wrote my original comment above, I didn't know you could do this through the IOKit API, although I've since edited that comment to mention it.)