LAVA CI

LAVA is a system for functional testing of boards including deploying custom bootloaders and kernels. This is particularly relevant to testing Mesa because we often need to change kernels for UAPI changes (and this lets us do full testing of a new kernel during development), and our workloads can easily take down boards when mistakes are made (kernel oopses, OOMs that take out critical system services).

Mesa-LAVA software architecture

The gitlab-runner will run on some host that has access to the LAVA lab, with tags like “lava-mesa-boardname” to control only taking in jobs for the hardware that the LAVA lab contains. The gitlab-runner spawns a Docker container with lava-cli in it, and connects to the LAVA lab using a predefined token to submit jobs under a specific device type.

The LAVA instance manages scheduling those jobs to the boards present. For a job, it will deploy the kernel, device tree, and the ramdisk containing the CTS.

Deploying a new Mesa-LAVA lab

You’ll want to start with setting up your LAVA instance and getting some boards booting using test jobs. Start with the stock QEMU examples to make sure your instance works at all. Then, you’ll need to define your actual boards.

The device type in lava-gitlab-ci.yml is the device type you create in your LAVA instance, which doesn’t have to match the board’s name in /etc/lava-dispatcher/device-types. You create your boards under that device type and the Mesa jobs will be scheduled to any of them. Instantiate your boards by creating them in the UI or at the command line attached to that device type, then populate their dictionary (using an “extends” line probably referencing the board’s template in /etc/lava-dispatcher/device-types). Now, go find a relevant healthcheck job for your board as a test job definition, or cobble something together from a board that boots using the same boot_method and some public images, and figure out how to get your boards booting.

Once you can boot your board using a custom job definition, it’s time to connect Mesa CI to it. Install gitlab-runner and register as a shared runner (you’ll need a GitLab admin for help with this). The runner must have a tag (like “mesa-lava-db410c”) to restrict the jobs it takes or it will grab random jobs from tasks across gitlab.freedesktop.org, and your runner isn’t ready for that.

The runner will be running an ARM Docker image (we haven’t done any x86 LAVA yet, so that isn’t documented). If your host for the gitlab-runner is x86, then you’ll need to install qemu-user-static and the binfmt support.

The Docker image will need access to the lava instance. If it’s on a public network it should be fine. If you’re running the LAVA instance on localhost, you’ll need to set network_mode="host" in /etc/gitlab-runner/config.toml so it can access localhost. Create a gitlab-runner user in your LAVA instance, log in under that user on the web interface, and create an API token. Copy that into a lavacli.yaml:

default:
  token: <token contents>
  uri: <URL to the instance>
  username: gitlab-runner

Add a volume mount of that lavacli.yaml to /etc/gitlab-runner/config.toml so that the Docker container can access it. You probably have a volumes = ["/cache"] already, so now it would be:

volumes = ["/home/anholt/lava-config/lavacli.yaml:/root/.config/lavacli.yaml", "/cache"]

Note that this token is visible to anybody that can submit MRs to Mesa! It is not an actual secret. We could just bake it into the GitLab CI yml, but this way the current method of connecting to the LAVA instance is separated from the Mesa branches (particularly relevant as we have many stable branches all using CI).

Now it’s time to define your test runner in .gitlab-ci/lava-gitlab-ci.yml.