On Thu, Mar 26, 2020 at 2:07 PM Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote: > The second concern was pruning, but iirc the experiments were inconclusive. > selftests/bpf only has old fb progs. Hence, I think, the step zero is for > everyone to contribute their bpf programs written in C. If we have both > cilium and cloudflare progs as selftests it will help a lot to guide such long > lasting verifier decisions. How would you like to handle program changes over time for this? In Cilium community we periodically rebuild bpf-next VM images for testing, and run every pull request against those images[0]. We also test against specific older kernels, currently 4.9 and 4.19. This allows us to get some sense for the impact of upstream changes while developing Cilium features, but unfortunately doesn't allow everyone using kernel selftests to get that feedback at least from the kernel tree. We also have a verifier complexity test script where we compile with the maximum number of features (to ideally generate the most complex programs possible) then attempt to load all of the various programs, and output the complexity count that the kernel reports[1,2] which we can track over time. However Cilium BPF programs are actively developing and even if we merge these programs into the kernel tree, they will get out-of-date quickly. Up until recently everything was verifying fine compiling with LLVM7 and loading into bpf-next. Over the past month we started noticing new issues not with the existing implementation, but in *new* BPF features. As we increased complexity, our CI started failing against bpf-next[3] while they loaded fine on older kernels. We ended up mitigating by upgrading to LLVM-10. Long story short, there's several moving parts; changing BPF program implementations, changing the compiler toolchain, changing the kernel verifier. So my question is basically, where's the line of responsibility for what the kernel selftests are responsible for vs integration tests? How do we maintain those over time as the BPF programs and compiler changes? Do we just parachute the ~11K LoC of Cilium datapath into the kernel tree once per cycle? Or should Cilium autobuild a verifier-test docker image that kernel testing scripts can pull & run? Or would it be helpful to have a separate GitHub project similar to libbpf that pulls out kernel selftests, Cilium progs, fb progs, cloudflare progs, etc automatically and centralizes a generic suite of BPF verifier integration tests? Some other option? [0] https://github.com/cilium/packer-ci-build [1] https://github.com/cilium/cilium/blob/master/test/bpf/check-complexity.sh [2] https://github.com/cilium/cilium/blob/master/test/bpf/verifier-test.sh [3] https://github.com/cilium/cilium/issues/10517
