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In the past we've > stubbed out some tests based on clang version, can we do the same > here? LLVM has 6-month development cycle vs. kernel 8-10 weeks. With this, sometimes we implemented some features which is suitable for *latest* kernel version but has an adverse impact on old kernels. > > This build breakage tends to happen with every major kernel release. > Is there a way to avoid this? FWIW some CI builds fail because of > this, however I have no idea where these reports go / why they aren't > taken into account: https://lkml.org/lkml/2021/6/22/987 First always check tools/testing/selftests/bpf/README.rst which should contain most, if not all, possible breakages and how to mitigate them, e.g., which llvm patch is responsible and if you checkout a llvm repo upto and without that patch, you might be okay. We can also maintain a list of llvm sha commits which have been tested to work for a particular kernel version. Further, if we really want, we could have a forked llvm-project repo with tags for each kernel release. This way, people can checkout the repo/tag and build for particular kernel release selftests. > > It would be nice if there was some combination of (easily available > clang release) x (stable kernel versions) that allows to compile BPF > selftests successfully. > > Lorenz >