The core_pmu does not define cpu_* callbacks, which handles allocation of 'struct cpu_hw_events::shared_regs' data, initialization of debug store and PMU_FL_EXCL_CNTRS counters.
While this probably won't happen on bare metal, virtual CPU can define x86_pmu.extra_regs together with PMU version 1 and thus be using core_pmu -> using shared_regs data without it being allocated. That could could leave to following panic: BUG: unable to handle kernel NULL pointer dereference at (null) IP: [<ffffffff8152cd4f>] _spin_lock_irqsave+0x1f/0x40 SNIP [<ffffffff81024bd9>] __intel_shared_reg_get_constraints+0x69/0x1e0 [<ffffffff81024deb>] intel_get_event_constraints+0x9b/0x180 [<ffffffff8101e815>] x86_schedule_events+0x75/0x1d0 [<ffffffff810586dc>] ? check_preempt_curr+0x7c/0x90 [<ffffffff810649fe>] ? try_to_wake_up+0x24e/0x3e0 [<ffffffff81064ba2>] ? default_wake_function+0x12/0x20 [<ffffffff8109eb16>] ? autoremove_wake_function+0x16/0x40 [<ffffffff810577e9>] ? __wake_up_common+0x59/0x90 [<ffffffff811a9517>] ? __d_lookup+0xa7/0x150 [<ffffffff8119db5f>] ? do_lookup+0x9f/0x230 [<ffffffff811a993a>] ? dput+0x9a/0x150 [<ffffffff8119c8f5>] ? path_to_nameidata+0x25/0x60 [<ffffffff8119e90a>] ? __link_path_walk+0x7da/0x1000 [<ffffffff8101d8f9>] ? x86_pmu_add+0xb9/0x170 [<ffffffff8101d7a7>] x86_pmu_commit_txn+0x67/0xc0 [<ffffffff811b07b0>] ? mntput_no_expire+0x30/0x110 [<ffffffff8119c731>] ? path_put+0x31/0x40 [<ffffffff8107c297>] ? current_fs_time+0x27/0x30 [<ffffffff8117d170>] ? mem_cgroup_get_reclaim_stat_from_page+0x20/0x70 [<ffffffff8111b7aa>] group_sched_in+0x13a/0x170 [<ffffffff81014a29>] ? sched_clock+0x9/0x10 [<ffffffff8111bac8>] ctx_sched_in+0x2e8/0x330 [<ffffffff8111bb7b>] perf_event_sched_in+0x6b/0xb0 [<ffffffff8111bc36>] perf_event_context_sched_in+0x76/0xc0 [<ffffffff8111eb3b>] perf_event_comm+0x1bb/0x2e0 [<ffffffff81195ee9>] set_task_comm+0x69/0x80 [<ffffffff81195fe1>] setup_new_exec+0xe1/0x2e0 [<ffffffff811ea68e>] load_elf_binary+0x3ce/0x1ab0 Adding cpu_(prepare|starting|dying) for core_pmu to have shared_regs data allocated for core_pmu. AFAICS there's no harm to initialize debug store and PMU_FL_EXCL_CNTRS either for core_pmu. Signed-off-by: Jiri Olsa <[email protected]> --- arch/x86/kernel/cpu/perf_event_intel.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c index 9da2400c2ec3..0a61a9a021de 100644 --- a/arch/x86/kernel/cpu/perf_event_intel.c +++ b/arch/x86/kernel/cpu/perf_event_intel.c @@ -2533,6 +2533,10 @@ ssize_t intel_event_sysfs_show(char *page, u64 config) return x86_event_sysfs_show(page, config, event); } +static int intel_pmu_cpu_prepare(int cpu); +static void intel_pmu_cpu_starting(int cpu); +static void intel_pmu_cpu_dying(int cpu); + static __initconst const struct x86_pmu core_pmu = { .name = "core", .handle_irq = x86_pmu_handle_irq, @@ -2559,6 +2563,9 @@ static __initconst const struct x86_pmu core_pmu = { .guest_get_msrs = core_guest_get_msrs, .format_attrs = intel_arch_formats_attr, .events_sysfs_show = intel_event_sysfs_show, + .cpu_prepare = intel_pmu_cpu_prepare, + .cpu_starting = intel_pmu_cpu_starting, + .cpu_dying = intel_pmu_cpu_dying, }; struct intel_shared_regs *allocate_shared_regs(int cpu) -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
