Saturday, June 24, 2017

[Update] seL4/RISC-V SMP support | seL4/RISC-V Tutorials Release

Updates (since 03062017)


A new unofficial 24062017 release of seL4, libraries and seL4 Tutorials.

  • SMP support, tested on Spike with 2 - 9 cores:
    • seL4 is using a big kernel lock.
    • Only reschedule IPI (set affinity) is provided.
    • Relying on SBI to do other remote operations.
    • SBI doesn't provide VADDR-> ASID -> HART operation.
    • Using tp register to hold per-core IPC buffer addresses.
  • Ported seL4-tutorias to RISC-V. This means:
    • People can learn more about both seL4/RISC-V doing the tutorials.
    • Lack of RISC-V/Spike user-level timer (or another S-timer) is an issue. seL4 (being a microkernel) is not supposed to provide a timer API, rather, user-level apps should have their own HW timer and device drivers.
  • More tests are passing on sel4test now after:
    • SMP support.
    • Re-adding a supervisor timer (for seL4 scheduling).
    • [154/154] Tests pass (8 more tests pass after multicore and timer support).
    • All libraries, kernel are rebased to latest seL4's revisions.

seL4 Tutorials 


sel4-tutorials [1] is the first recommended entry point for people who want to learn and get hands-on experience on seL4 and its libraries.  This repo [1] contains slides, docs and code tutorials with commented instructions and tasks that take you from writing a seL4 hello world application to doing IPC in a multithreading environment, now on RISC-V.

hello-3 exercise showing 2 threads doing IPC communication




seL4test is a comprehensive unit and functional testing suite for seL4 and can be useful when porting to new platforms or adding new features.

It can be used as a reference how to develop a big project on seL4. A new riscv_smp_defconfig config file for RISC-V is added to test SMP support. Instructions how to run it are provided in this blog post.

For this release that contains SMP, use:

$repo init -u -m sel4test-24062017.xml



This work is my personal/independent effort (during spare time) and it's not related to Data61/CSIRO/TS Group (that maintains seL4), until it gets upstream.