Call trace observed during boot: Faulting instruction address: 0xc000000000248340 cpu 0x0: Vector: 380 (Data Access Out of Range) at [c000000ff66fb850] pc: c000000000248340: event_function_call+0x50/0x1f0 lr: c00000000024878c: perf_remove_from_context+0x3c/0x100 sp: c000000ff66fbad0 msr: 9000000000009033 dar: 7d20e2a6f92d03c0 current = 0xc000000ff6679200 paca = 0xc00000000fd40000 softe: 0 irq_happened: 0x01 pid = 14, comm = cpuhp/0 Linux version 4.14.0-rc2-42789-ge8eae4b (rgrimm@XXXX) (gcc version 5.4.0 20160609 (Ubuntu/IBM 5.4.0-6ubuntu1~16.04.4)) #1 SMP Thu Nov 16 14:35:14 CST 2017 enter ? for help [c000000ff66fbb80] c00000000024878c perf_remove_from_context+0x3c/0x100 [c000000ff66fbbc0] c00000000024e84c perf_pmu_migrate_context+0x10c/0x380 [c000000ff66fbc60] c0000000000ca050 ppc_nest_imc_cpu_offline+0x1b0/0x210 [c000000ff66fbcb0] c0000000000d5d54 cpuhp_invoke_callback+0x194/0x620 [c000000ff66fbd20] c0000000000d702c cpuhp_thread_fun+0x7c/0x1b0 [c000000ff66fbd60] c00000000010ad90 smpboot_thread_fn+0x290/0x2a0 [c000000ff66fbdc0] c000000000104818 kthread+0x168/0x1b0 [c000000ff66fbe30] c00000000000b5a0 ret_from_kernel_thread+0x5c/0xbc While registering the cpuhotplug callbacks for nest-imc, if we fail in the cpuhotplug online path for any random node in a multi node system (because the opal call to stop nest-imc counters fails for that node), ppc_nest_imc_cpu_offline() will get invoked for other nodes who successfully returned from cpuhotplug online path. This call trace is generated since in the ppc_nest_imc_cpu_offline() path we are trying to migrate the event context, when nest-imc counters are not even initialized. Patch to add a check to ensure that nest-imc is registered before migrating the event context.
Note: Madhavan Srinivasan has recently send a skiboot patch to have a check in the skiboot code to make sure that the microcode is initialized in all the chips, before enabling the nest units. https://patchwork.ozlabs.org/patch/844047/ (v2) Signed-off-by: Anju T Sudhakar <a...@linux.vnet.ibm.com> Reviewed-by: Madhavan Srinivasan <ma...@linux.vnet.ibm.com> --- arch/powerpc/perf/imc-pmu.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/arch/powerpc/perf/imc-pmu.c b/arch/powerpc/perf/imc-pmu.c index 0ead3cd..9daa1c3 100644 --- a/arch/powerpc/perf/imc-pmu.c +++ b/arch/powerpc/perf/imc-pmu.c @@ -309,6 +309,20 @@ static int ppc_nest_imc_cpu_offline(unsigned int cpu) if (!cpumask_test_and_clear_cpu(cpu, &nest_imc_cpumask)) return 0; + /* + * Check whether nest_imc is registered. We could end up here + * if the cpuhotplug callback registration fails. i.e, callback + * invokes the offline path for all successfully registered nodes. + * At this stage, nest_imc pmu will not be registered and we + * should return here. + * + * We return with a zero since this is not an offline failure. + * And cpuhp_setup_state() returns the actual failure reason + * to the caller, which inturn will call the cleanup routine. + */ + if (!nest_pmus) + return 0; + /* * Now that this cpu is one of the designated, * find a next cpu a) which is online and b) in same chip. -- 2.7.4