rust-vmm-ci/README.md

# rust-vmm-ci

The `rust-vmm-ci` repository contains [integration tests](#integration-tests)
and [Buildkite pipeline](#buildkite-pipeline) definitions that are used for
running the CI for all rust-vmm crates.

Having a centralized place for the tests is one of the enablers for keeping the
same quality standard for all crates in rust-vmm.

## Getting Started with rust-vmm-ci

To run the integration tests defined in the pipeline as part of the CI:

1. Add rust-vmm-ci as a git submodule to your repository

```bash
# Add rust-vmm-ci as a submodule. This will point to the latest rust-vmm-ci
# commit from the master branch. The following command will also add a
# `.gitmodules` file and the `rust-vmm-ci` to the index.
git submodule add https://github.com/rust-vmm/rust-vmm-ci.git
# Commit the changes to your repository so that the CI can run using the
# rust-vmm-ci pipeline and tests.
git commit -s -m "Added rust-vmm-ci as submodule"
```

2. Create the coverage test configuration file named coverage_config.json in
the root of the repository. One example of the configuration file can be found
in [coverage_config.json.sample](coverage_config.json.sample).

The json must have the following fields:
- *coverage_score*: The coverage of the repository.
- *exclude_path*: This field is used for excluding files from the report. It
  should be used to exclude autogenerated files. Files in *exclude_path* are
  separated by one coma. If the repository does not have any autogenerated
  files, *exclude_path* should be an empty string.
- *crate_features*: `cargo kcov` does not build crate features by default. To
  get the coverage report including optional features these need to be
  specified in *crate_features* separated by coma. If the crate does not have
  any features, this field should be empty.

This file is required for the coverage integration so it needs to be added
to the repository as well.

3. Create a new pipeline definition in Buildkite. For this step ask one of the
rust-vmm Buildkite [admins](CODEOWNERS) to create one for you. Add a pipeline
step that is uploading the rust-vmm-ci pipeline:

```bash
buildkite-agent pipeline upload rust-vmm-ci/.buildkite/pipeline.yml
```

4. The code owner of the repository will have to setup a WebHook for triggering
the CI on Pull Requests and pushes.

## Buildkite Pipeline

The [Buildkite](https://buildkite.com) pipeline is the definition of tests to
be run as part of the CI. It includes steps for running unit tests and linters
(including coding style checks), and computing the coverage.

 Currently the tests can run on Linux x86_64 and aarch64 hosts.

Example of step that checks the build:

```yaml
steps:
  - label: "build-gnu-x86"
    commands:
     - cargo build --release
    retry:
      automatic: false
    agents:
      platform: x86_64.metal
    plugins:
      - docker#v3.0.1:
          image: "rustvmm/dev:v3"
          always-pull: true
```

To see all steps in the pipeline check the
[.buikite/pipeline.yml](.buildkite/pipeline.yml) file.

### Custom Pipeline

Some crates might need to test functionality that is specific to that
particular component and thus cannot be added to the common pipeline.

In this situation, the repositories need to create a custom pipeline (besides
the rust-vmm-ci pipeline) and add it in the repository. The preferred path for
the custom pipeline is `.buildkite/pipeline.yml`.

For example to test the build with one non-default
[feature](https://doc.rust-lang.org/1.19.0/book/first-edition/conditional-compilation.html)
enabled, the following step can be added in the custom pipeline under
`.buildkite/pipeline.yml`.

```yaml
steps:
  - label: "build-gnu-x86-bzimage"
    commands:
     - cargo build --release --features bzimage
    retry:
      automatic: false
    agents:
      platform: x86_64.metal
    plugins:
      - docker#v3.0.1:
          image: "rustvmm/dev:v3"
always-pull: true
```

### Custom Repository Hooks

The integration tests of some repositories have dependencies on external
resources. One example is
[linux-loader](https://github.com/rust-vmm/linux-loader/) which needs to
download a bzImage before running the unit tests. Because this is specific
to the linux-loader crate, the logic for downloading the required resources
cannot be part of the common pipeline. The mechanism used here is
[Repository Hooks](https://buildkite.com/docs/agent/v3/hooks#repository-hooks).
The hooks are defined per repository and live in the crate repository under
`.buildkite/hooks`.

Example of post-checkout hook that downloads and extracts a bzImage:

```bash
#!/bin/bash

DEB_NAME="linux-image-4.9.0-9-amd64_4.9.168-1_amd64.deb"
DEB_URL="http://ftp.debian.org/debian/pool/main/l/linux/${DEB_NAME}"

REPO_PATH="${BUILDKITE_BUILD_CHECKOUT_PATH}"
DEB_PATH="${REPO_PATH}/${DEB_NAME}"
EXTRACT_PATH="${REPO_PATH}/src/bzimage-archive"
BZIMAGE_PATH="${EXTRACT_PATH}/boot/vmlinuz-4.9.0-9-amd64"

mkdir -p ${EXTRACT_PATH}

wget ${DEB_URL} -P ${REPO_PATH}
dpkg-deb -x ${DEB_PATH} ${EXTRACT_PATH}

mv ${BZIMAGE_PATH} ${REPO_PATH}/src/bzimage
rm -r ${EXTRACT_PATH}
rm -f ${DEB_PATH}
```

In this example the post-checkout hook downloads a deb image, extracts the
contents of it and places it in `linux-loader/src/bzimage`. The unit tests
will use the relative path `src/bzimage` which does not depend on the image
being downloaded.

## Integration Tests

In addition to the one-liner tests defined in the
[Builkite Pipeline](#buildkite-pipeline), the rust-vmm-ci also has more
complex tests defined in [integration_tests](integration_tests).

### Test Profiles

The integration tests support two test profiles:
- **devel**: this is the recommended profile for running the integration tests
  on a local development machine.
- **ci** (default option): this is the profile used when running the
  integration tests as part of the the Continuous Integration (CI).

The test profiles are applicable to tests that run using pytest. Currently only
the [coverage test](tests/test_coverage.py) follows this model as all the other
integration tests are run using the
[Buildkite pipeline](https://buildkite.com/rust-vmm/kvm-ioctls-ci).

The difference between is declaring tests as passed or failed:
- with the **devel** profile the coverage test passes if the current coverage
  is equal or higher than the upstream coverage value. In case the current
  coverage is higher, the coverage file is updated to the new coverage value.
- with the **ci** profile the coverage test passes only if the current coverage
  is equal to the upstream coverage value.

Further details about the coverage test can be found in the
[Adaptive Coverage](#adaptive-coverage) section.

### Adaptive Coverage

The line coverage is saved in [tests/coverage](tests/coverage). To update the
coverage before submitting a PR, run the coverage test:

```bash
docker run --device=/dev/kvm \
           -it \
           --security-opt seccomp=unconfined \
           --volume $(pwd)/kvm-ioctls:/kvm-ioctls \
           rustvmm/dev:v3
cd kvm-ioctls/
pytest --profile=devel tests/test_coverage.py
```

If the PR coverage is higher than the upstream coverage, the coverage file
needs to be manually added to the commit before submitting the PR:

```bash
git add tests/coverage
```

Failing to do so will generate a fail on the CI pipeline when publishing the
PR.

**NOTE:** The coverage file is only updated in the `devel` test profile. In
the `ci` profile the coverage test will fail if the current coverage is higher
than the coverage reported in [tests/coverage](tests/coverage)