=== Introduction === Testing is paradoxically one of BPF's great strengths as well as one of it's current weaknesses. Fortunately, this weakness is not too far from being corrected. BPF_PROG_RUN is somewhat of a double edged sword. On the one hand, you can run reproducibly run progs in near-production context. On the other hand, since BPF is so deeply intertwined with the running kernel, you must make the kernel you run tests on as close to your production kernel as possible to get full testing benefits. This is going to be more of an issue going forward through the growth of kfuncs because kfuncs do not possess a stable ABI [5]. Proper testing should be encouraged at a community-wide level in order to avoid accidental surprises and potential loss of faith in BPF "stability". Most successful kernel-dependent projects deploy some form of virtual-machine-based testing [1][2][3][4] to solve the above issues. However, there are two problems with this: 1. VM-based testing is not quite common knowledge yet and remains somewhat of a dark art to successfully implement. 2. Multiple implementations of what is essentially the same thing is somewhat of a drain on resources. (These are not necessarily bad things -- it is useful and necessary to explore a problem space before settling on best practices) vmtest [0] aims to solve both problems. === Goals === I'd like to do a short presentation on the design and ideas behind vmtest. I'd also like to show a quick demo. It shouldn't take very long. I'll probably also share what I'd like to implement next. I don't know what that's going to be at time of writing b/c I'm probably going to get to it before LSFMMBPF. For the rest of the time I'd like to discuss what the community would like to see in vmtest. And to hear what it'd take to see adoption from other projects. Obviously no one can be required to adopt vmtest but I think it'll save everyone a good deal of effort if done correctly. Thanks, Daniel [0]: https://github.com/danobi/vmtest [1]: https://github.com/cilium/ebpf/blob/master/run-tests.sh [2]: https://github.com/osandov/drgn/tree/main/vmtest [3]: https://github.com/libbpf/ci/blob/master/run-qemu/run.sh [4]: https://github.com/torvalds/linux/blob/master/tools/testing/selftests/bpf/vmtest.sh [5]: https://github.com/torvalds/linux/commit/16c294a6aad86
