On Fri, Aug 21, 2020 at 12:57:54PM -0700, kan.li...@linux.intel.com wrote: > diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c > index 0f3d01562ded..fa08d810dcd2 100644 > --- a/arch/x86/events/core.c > +++ b/arch/x86/events/core.c > @@ -1440,7 +1440,10 @@ static void x86_pmu_start(struct perf_event *event, > int flags) > > cpuc->events[idx] = event; > __set_bit(idx, cpuc->active_mask); > - __set_bit(idx, cpuc->running); > + /* The cpuc->running is only used by the P4 PMU */ > + if (!cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON) && > + (boot_cpu_data.x86 == 0xf)) > + __set_bit(idx, cpuc->running); > x86_pmu.enable(event); > perf_event_update_userpage(event); > }
Yuck! Use a static_branch() or something. This is a gnarly nest of code that runs 99.9% of the time to conclude a negative. IOW a complete waste of cycles for everybody not running a P4 space heater. > @@ -1544,6 +1547,9 @@ static void x86_pmu_del(struct perf_event *event, int > flags) > if (cpuc->txn_flags & PERF_PMU_TXN_ADD) > goto do_del; > > + if (READ_ONCE(x86_pmu.attr_rdpmc) && x86_pmu.sched_task && > + test_bit(event->hw.idx, cpuc->active_mask)) > + __set_bit(event->hw.idx, cpuc->dirty); And that too seems like an overly complicated set of tests and branches. This should be effectivly true for the 99% common case. > @@ -2219,11 +2225,45 @@ static int x86_pmu_event_init(struct perf_event > *event) > return err; > } > > +void x86_pmu_clear_dirty_counters(void) > +{ > + struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events); > + int i; > + > + if (bitmap_empty(cpuc->dirty, X86_PMC_IDX_MAX)) > + return; > + > + /* Don't need to clear the assigned counter. */ > + for (i = 0; i < cpuc->n_events; i++) > + __clear_bit(cpuc->assign[i], cpuc->dirty); > + > + for_each_set_bit(i, cpuc->dirty, X86_PMC_IDX_MAX) { > + /* Metrics events don't have corresponding HW counters. */ > + if (is_metric_idx(i)) > + continue; > + else if (i >= INTEL_PMC_IDX_FIXED) > + wrmsrl(MSR_ARCH_PERFMON_FIXED_CTR0 + (i - > INTEL_PMC_IDX_FIXED), 0); > + else > + wrmsrl(x86_pmu_event_addr(i), 0); > + } > + > + bitmap_zero(cpuc->dirty, X86_PMC_IDX_MAX); > +} The bitmap_{empty,zero}() do indeed compile into single instructions, neat! > static void x86_pmu_event_mapped(struct perf_event *event, struct mm_struct > *mm) > { > if (!(event->hw.flags & PERF_X86_EVENT_RDPMC_ALLOWED)) > return; > > + /* > + * Enable sched_task() for the RDPMC task, > + * and clear the existing dirty counters. > + */ > + if (x86_pmu.sched_task && event->hw.target && > !is_sampling_event(event)) { > + perf_sched_cb_inc(event->ctx->pmu); > + x86_pmu_clear_dirty_counters(); > + } I'm failing to see the correctness of the !is_sampling_event() part there. > /* > * This function relies on not being called concurrently in two > * tasks in the same mm. Otherwise one task could observe > @@ -2246,6 +2286,9 @@ static void x86_pmu_event_unmapped(struct perf_event > *event, struct mm_struct *m > if (!(event->hw.flags & PERF_X86_EVENT_RDPMC_ALLOWED)) > return; > > + if (x86_pmu.sched_task && event->hw.target && !is_sampling_event(event)) > + perf_sched_cb_dec(event->ctx->pmu); > + Idem. > if (atomic_dec_and_test(&mm->context.perf_rdpmc_allowed)) > on_each_cpu_mask(mm_cpumask(mm), cr4_update_pce, NULL, 1); > } > diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c > index c72e4904e056..e67713bfa33a 100644 > --- a/arch/x86/events/intel/core.c > +++ b/arch/x86/events/intel/core.c > @@ -4166,11 +4166,39 @@ static void intel_pmu_cpu_dead(int cpu) > intel_cpuc_finish(&per_cpu(cpu_hw_events, cpu)); > } > > +static void intel_pmu_rdpmc_sched_task(struct perf_event_context *ctx) > +{ > + struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events); > + struct perf_event *event; > + > + if (bitmap_empty(cpuc->dirty, X86_PMC_IDX_MAX)) > + return; > + > + /* > + * If the new task has the RDPMC enabled, clear the dirty counters to > + * prevent the potential leak. If the new task doesn't have the RDPMC > + * enabled, do nothing. > + */ > + list_for_each_entry(event, &ctx->event_list, event_entry) { > + if (event->hw.target && > + (event->hw.flags & PERF_X86_EVENT_RDPMC_ALLOWED) && > + !is_sampling_event(event) && > + atomic_read(&event->mmap_count)) > + break; > + } > + if (&event->event_entry == &ctx->event_list) > + return; That's horrific, what's wrong with something like: if (!atomic_read(¤t->mm->context.perf_rdpmc_allowed)) return; > + > + x86_pmu_clear_dirty_counters(); > +} How is this Intel specific code? IIRC AMD has RDPMC too.