Shuah, On Wed, Jun 23, 2021 at 12:08:48PM -0600, Shuah Khan wrote: > On 6/23/21 8:26 AM, Vitaly Chikunov wrote: > > Do kselftests require to be backward-compatible? > > Kselftests from the latest kernel can run on older kernels. In that > respect they are backward compatible. > > It is possible that a newly added test is for a new feature and new > API and as a result could be skipped on older kernels. > > > > > I see Documentation/dev-tools/kselftest.rst does not require this, but > > maybe it's assumed like in other test suites (or in perf). > > > > | In general, the rules for selftests are > > | > > | * Do as much as you can if you're not root; > > | > > | * Don't take too long; > > | > > | * Don't break the build on any architecture, and > > | > > | * Don't cause the top-level "make run_tests" to fail if your feature is > > | unconfigured. > > > > Correct. We don't explicitly state that the tests are backward > compatible, however they are. We don't do any revision checks. > We keep adding new tests and enhancements to existing tests in > every release. New tests depend on new kernel features and headers > and they could fail to build. However the suite will build the tests > it can build and will run the test it can run. > > > For example LTP says: > > > > | LTP test should be as backward compatible as possible. [...] > > | > > | Therefore LTP test for more current features should be able to cope with older > > | systems. > > > > Also, (it's said[1]) perf, even though in kernel tree, is supposed to work > > properly on any (older/newer) version of Linux. > > > > Can you clarify this point in kselftest.rst? > > > > I think, this would be useful for future kselftests developers, users, > > and packagers. (Currently, I package for ALT Linux kselftests (and perf) > > from the latest mainline branch, so people could test even older kernels > > with the latest kselftests. > > > > If there is policy to be backward-compatible kselftests in the future > > could reach a state where users would run them in all pass mode (without > > selecting only working tests). This, in turn, would increase [ease of] > > usability of tests and thus frequency of their run and consequentially > > quality kernel testing overall. > > > > The policy is kselftests from new kernel can run on older kernels. > Tests that don't meet dependencies and privileges to run are skipped. > We do have newer tests that don't fail gracefully if dependencies aren't > met and those cases are considered as bugs. > > We have a wide range of tests in the suite. Some tests are at the > granularity of a specific system call flag. It would be difficult to isolate > all pass. What we can come close to is skipping tests that don't > meet dependencies consistently and we strive to do this and consider the > ones that don't meet as bugs and fix them. > > Hope this gives you a context around backward compatibility. Thanks much for the detailed explanation! Vitaly,
