Thanks for the quick, informative reply. I noticed that Microkit also explicitly requires EL2 support and has comments to that effect in its build tool (and gives an error if you try to turn it off in the build config). In order for seL4 to act has a hypervisor and therefore be able to have virtual machines on Microkit it needs to be in EL2. The work the Microkit tool has to do changes a bit for hyp vs non-hyp mode, I mainly put that error there so people changing the source wouldn’t expect non-hyp to work. If there is some use-case where the limitation of requiring seL4 to run at EL2 instead of EL1 is blocking I would be happy to help remove that limitation. Right now I am not aware of any such case. Microkit isn't well-suited for my purposes, except as a reference for how to create a system build, Just out of curiosity is that because you’re trying to build a more dynamic system than Microkit can handle right now or some other reason? If is something more specific I’d be happy to try help fix it. Microkit SDK itself to download the ARM GCC cross-compiler tools for aarch64-none-elf, which seems like a slightly more appropriate build target than the aarch64-unknown-linux-gnu tools from someone's Homebrew repo that the Microkit tutorial recommended. For the tutorial my goal was to get people up and running as quickly as possible which means installing the toolchain from a package manager, the aarch64-none-elf toolchain is not in any popular package managers (apt. homebrew etc) other than Nix as far as I am aware. Even with a good internet connection it takes a really long time to download for some reason. Maybe Clang for the tutorial would be better suited than an ARM Linux toolchain, and then making Microkit build with LLVM by default (right now it’s an option when building from source). I know the Raspberry Pi 5 that I want to support can run 32-bit ARM code at EL0 only, which is all I need. I have added Raspberry Pi 5B support here [1] but only for 64-bt. [1]: https://github.com/seL4/seL4/pull/1515. Ivan This email and any files transmitted with it may contain confidential information. If you believe you have received this email or any of its contents in error, please notify me immediately by return email and destroy this email. Do not use, disseminate, forward, print or copy any contents of an email received in error.