Hi ppc-dev list, We noticed that our kpatch integration tests started failing on ppc64le when targeting the upstream v6.4 kernel, and then confirmed that the in-tree livepatching kselftests similarly fail, too. From the kselftest results, it appears that livepatch transitions are no longer completing. Looking at the commit logs for v6.4, there looks to be some churn in the powerpc stack layout code -- I am suspicious that "reliable" stack unwinding may be left untested/broken after those changes. AFAICT, the livepatching subsystem is the only user of this interface in kernel/livepatch/transition.c :: klp_check_stack()'s call to stack_trace_save_tsk_reliable(). As such, the livepatching kselftests are probably the only way to test reliable unwinding. Unfortunately, git bisect isn't cooperating (we keep falling into a long span of non-bootable commits, despite efforts to `git bisect skip` over them), so we don't have an offending commit or patchset to point to. A few other details: - Test machine is a Power 9 9009-42A (IBM Power System S924) - Reproducable with v6.4, v6.5 - Minimal repro: -- Build with CONFIG_TEST_LIVEPATCH=m -- Run tools/testing/selftests/livepatch/test-livepatch.sh If this has already been report or fixed, please send any pointers to threads / commits. If not, I can provide any other info to help reproduce. Thanks, -- Joe
