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Microkit Release 2.1.0

2025-11-26

This release contains various bug fixes, quality-of-life changes, features, and new board support.

There are no breaking changes.

Feature changes

  • Initial x86-64 support.
    • This means that Microkit now supports all 64-bit architectures of seL4.
  • Transition to using capDL for system initialisation.
    • While this is a significant internal change, there should be no difference for users of Microkit.
    • However, this does mean we can now mark the seL4 RFC for Microkit as ‘implemented’!
  • Update to 14.0.0 of seL4.
    • With the changes for the transition to capDL, we no longer need patches to the kernel.
  • Add support for multi-core systems on all platforms.
    • For now, the default configurations of Microkit are still using the uni-core variant of seL4. A different value to --config is required to use the SMP variant.
    • See the manual section for more details.
  • Add new setvar_id attribute similar to setvar_vaddr but for any system description elements that have an identifier associated with them (e.g channel ends).
  • Add new --image-type argument to the tool to specify system image format that will be produced.
    • For ARM and RISC-V support we have only supported emitting a raw binary. We now support ELFs and (on RISC-V) the uImage format.
    • On RISC-V platforms, when booting with U-Boot (e.g on the Star64) the binary format does not receive the expected arguments for booting (hart ID). The binary was working by coincidence and only for the uImage Linux format does U-Boot pass the hart ID when booting the image. For this reason all RISC-V hardware platforms (other than our supported FPGA platforms) default to uImage now to prevent booting issues.
    • See the manual section for all details.
  • Enable KernelAllowSMCCalls by default for all ARM platforms.
    • This means that all Microkit systems can make use of the PD SMC feature by default rather than having to change the kernel configuration and then build the SDK from source.
  • Increase the default PD stack size from 0x1000 to 0x2000.
  • Add different memory configurations for Raspberry Pi 4B.
    • Previously only 1GB was supported, now 2GB, 4GB and 8GB variants are available.
  • Support building the SDK using LLVM instead of GCC.
    • GCC still remains the default for now, but this does give the option for people to use LLVM when building Microkit from source.
  • Default to using Python 3.12 when building from source.
  • Update Nix flake to use Nix 25.05.

Bug fixes

  • Fixed the libmicrokit linker script to avoid the IPC buffer symbol potentially overlapping with loadable segments.
  • Fixes and improvements to error checking on the system description.
  • Add missing inline to certain libmicrokit calls to fix warnings on newer C compilers.

Board support

  • Compulab IOT-GATE-IMX8PLUS
  • Serengeti
  • SiFive Premier P550
  • Ultra96v2
  • x86-64 generic targets

Upgrade notes

There are no breaking changes in this release, but for users it is important to note that there was a significant internal change (transition to capDL) that may lead to regressions.

We have fixed all regressions that we have found, but there may be some we have missed. If you notice any unexpected behaviour, please open an issue on GitHub.

Due to the capDL changes, the boot log output has slightly changed, so if you have scripts that rely on the certain debug UART output you might have to update them.

Instead of this boot log:

Booting all finished, dropped to user space
MON|INFO: Microkit Bootstrap
MON|INFO: bootinfo untyped list matches expected list
MON|INFO: Number of bootstrap invocations: 0x0000000a
MON|INFO: Number of system invocations:    0x00000228
MON|INFO: completed bootstrap invocations
MON|INFO: completed system invocations

you’ll instead see this:

Booting all finished, dropped to user space
INFO  [sel4_capdl_initializer::initialize] Starting CapDL initializer
INFO  [sel4_capdl_initializer::initialize] Starting threads
MON|INFO: Microkit Monitor started!

before your Microkit system starts.

Full changelog

Use git log 2.0.1..2.1.0 in https://github.com/seL4/microkit/

More details

See the documentation or ask on the mailing list!

Other releases

See the full list of Microkit releases.