perf/x86/intel/ds: Fix x86_pmu_stop warning for large PEBS
[ Upstream commit5.4-rM2-2.2.x-imx-squashed35d1ce6bec
] A warning as below may be triggered when sampling with large PEBS. [ 410.411250] perf: interrupt took too long (72145 > 71975), lowering kernel.perf_event_max_sample_rate to 2000 [ 410.724923] ------------[ cut here ]------------ [ 410.729822] WARNING: CPU: 0 PID: 16397 at arch/x86/events/core.c:1422 x86_pmu_stop+0x95/0xa0 [ 410.933811] x86_pmu_del+0x50/0x150 [ 410.937304] event_sched_out.isra.0+0xbc/0x210 [ 410.941751] group_sched_out.part.0+0x53/0xd0 [ 410.946111] ctx_sched_out+0x193/0x270 [ 410.949862] __perf_event_task_sched_out+0x32c/0x890 [ 410.954827] ? set_next_entity+0x98/0x2d0 [ 410.958841] __schedule+0x592/0x9c0 [ 410.962332] schedule+0x5f/0xd0 [ 410.965477] exit_to_usermode_loop+0x73/0x120 [ 410.969837] prepare_exit_to_usermode+0xcd/0xf0 [ 410.974369] ret_from_intr+0x2a/0x3a [ 410.977946] RIP: 0033:0x40123c [ 411.079661] ---[ end trace bc83adaea7bb664a ]--- In the non-overflow context, e.g., context switch, with large PEBS, perf may stop an event twice. An example is below. //max_samples_per_tick is adjusted to 2 //NMI is triggered intel_pmu_handle_irq() handle_pmi_common() drain_pebs() __intel_pmu_pebs_event() perf_event_overflow() __perf_event_account_interrupt() hwc->interrupts = 1 return 0 //A context switch happens right after the NMI. //In the same tick, the perf_throttled_seq is not changed. perf_event_task_sched_out() perf_pmu_sched_task() intel_pmu_drain_pebs_buffer() __intel_pmu_pebs_event() perf_event_overflow() __perf_event_account_interrupt() ++hwc->interrupts >= max_samples_per_tick return 1 x86_pmu_stop(); # First stop perf_event_context_sched_out() task_ctx_sched_out() ctx_sched_out() event_sched_out() x86_pmu_del() x86_pmu_stop(); # Second stop and trigger the warning Perf should only invoke the perf_event_overflow() in the overflow context. Current drain_pebs() is called from: - handle_pmi_common() -- overflow context - intel_pmu_pebs_sched_task() -- non-overflow context - intel_pmu_pebs_disable() -- non-overflow context - intel_pmu_auto_reload_read() -- possible overflow context With PERF_SAMPLE_READ + PERF_FORMAT_GROUP, the function may be invoked in the NMI handler. But, before calling the function, the PEBS buffer has already been drained. The __intel_pmu_pebs_event() will not be called in the possible overflow context. To fix the issue, an indicator is required to distinguish between the overflow context aka handle_pmi_common() and other cases. The dummy regs pointer can be used as the indicator. In the non-overflow context, perf should treat the last record the same as other PEBS records, and doesn't invoke the generic overflow handler. Fixes:21509084f9
("perf/x86/intel: Handle multiple records in the PEBS buffer") Reported-by: Like Xu <like.xu@linux.intel.com> Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Kan Liang <kan.liang@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Like Xu <like.xu@linux.intel.com> Link: https://lkml.kernel.org/r/20200902210649.2743-1-kan.liang@linux.intel.com Signed-off-by: Sasha Levin <sashal@kernel.org>
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@ -669,9 +669,7 @@ unlock:
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static inline void intel_pmu_drain_pebs_buffer(void)
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{
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struct pt_regs regs;
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x86_pmu.drain_pebs(®s);
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x86_pmu.drain_pebs(NULL);
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}
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/*
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@ -1736,6 +1734,7 @@ static void __intel_pmu_pebs_event(struct perf_event *event,
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struct x86_perf_regs perf_regs;
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struct pt_regs *regs = &perf_regs.regs;
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void *at = get_next_pebs_record_by_bit(base, top, bit);
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struct pt_regs dummy_iregs;
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if (hwc->flags & PERF_X86_EVENT_AUTO_RELOAD) {
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/*
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@ -1748,6 +1747,9 @@ static void __intel_pmu_pebs_event(struct perf_event *event,
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} else if (!intel_pmu_save_and_restart(event))
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return;
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if (!iregs)
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iregs = &dummy_iregs;
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while (count > 1) {
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setup_sample(event, iregs, at, &data, regs);
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perf_event_output(event, &data, regs);
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@ -1757,16 +1759,22 @@ static void __intel_pmu_pebs_event(struct perf_event *event,
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}
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setup_sample(event, iregs, at, &data, regs);
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/*
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* All but the last records are processed.
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* The last one is left to be able to call the overflow handler.
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*/
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if (perf_event_overflow(event, &data, regs)) {
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x86_pmu_stop(event, 0);
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return;
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if (iregs == &dummy_iregs) {
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/*
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* The PEBS records may be drained in the non-overflow context,
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* e.g., large PEBS + context switch. Perf should treat the
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* last record the same as other PEBS records, and doesn't
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* invoke the generic overflow handler.
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*/
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perf_event_output(event, &data, regs);
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} else {
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/*
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* All but the last records are processed.
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* The last one is left to be able to call the overflow handler.
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*/
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if (perf_event_overflow(event, &data, regs))
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x86_pmu_stop(event, 0);
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}
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}
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static void intel_pmu_drain_pebs_core(struct pt_regs *iregs)
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