Hafnium has 4 main kinds of tests:

  1. Host tests
    • Unit tests of core functionality, e.g. page table manipulation.
    • Source in src/*_test.cc.
    • Using the Google Test framework, built against ‘fake’ architecture (src/arch/fake).
  2. Arch tests
    • Architecture-specific unit tests, e.g. MMU setup.
    • Source under test/arch.
    • Using our own hftest framework, with standalone_main.c.
    • Build own hypervisor image, run in EL2.
  3. VM API tests
    • Exercise hypervisor API from both primary and secondary VMs.
    • Source under test/vmapi.
    • Tests are run from the primary VM under a normal build of the Hafnium hypervisor, possibly communicating with a helper service in one or more secondary VMs.
    • Using our own hftest framework, with standalone_main.c for the primary VM and hftest_service.c for secondary VMs.
    • Build own primary and secondary VMs, run in EL1 under actual Hafnium image.
  4. Linux tests
    • Exercise the Hafnium Linux kernel module.
    • Source under test/linux.
    • Tests are run from userspace (PID 1) under Linux in the primary VM under Hafnium, possibly with other secondary VMs.
    • Using our own hftest framework, with linux_main.c.

Host tests run directly on the host machine where they are built, whereas the other 3 types can run under an emulator such as QEMU, or on real hardware.


Presubmit builds everything, runs all tests and checks the source for formatting and lint errors. This can be run locally with:


Or to just run the tests after having built everything manually run:


QEMU tests

These tests boot Hafnium on QEMU and the VMs make calls to Hafnium to test its behaviour. They can also be run on the Arm FVP and in some cases on real hardware.


Having a framework for tests makes them easier to read and write. hftest is a framework to meet the needs of VM based tests for Hafnium. It consists of:

  • assertions
  • test declarations
  • base VM image
  • driver script

Assertions should be familiar from other testing libraries. They make use of C11's _Generic expressions for type genericity.

Test declarations name the test and the suite that the test is part of. Declarations are converted into descriptors stored in the .hftest section of the VM image which allows the image to inspect the structure of the tests it contains. The linker sorts the descriptors by their symbol name which is how descriptors from the same suite are grouped together for easier parsing.

The base VM image offers a command line interface, via the bootargs, to query the tests in the image and to run specific tests. The driver script uses this interface to execute tests, each with a fresh QEMU boot to give a fresh environment.