| Message ID | 20230913125956.3652667-1-tero.kristo@linux.intel.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Delegated to: | BPF |
| Headers | show |
| Series | None | expand |
On Wed, Sep 13, 2023 at 03:59:56PM +0300, Tero Kristo wrote: > Per-package perf events are typically registered with a single CPU only, > however they can be read across all the CPUs within the package. > Currently perf_event_read maps the event CPU according to the topology > information to avoid an unnecessary SMP call, however > perf_event_read_local deals with hard values and rejects a read with a > failure if the CPU is not the one exactly registered. Allow similar > mapping within the perf_event_read_local if the perf event in question > can support this. > > This allows users like BPF code to read the package perf events properly > across different CPUs within a package. > > Signed-off-by: Tero Kristo <tero.kristo@linux.intel.com> > --- > v2: > * prevent illegal array access in case event->oncpu == -1 > * split the event->cpu / event->oncpu handling to their own variables > > kernel/events/core.c | 18 +++++++++++++++--- > 1 file changed, 15 insertions(+), 3 deletions(-) > > diff --git a/kernel/events/core.c b/kernel/events/core.c > index 4c72a41f11af..6b343bac0a71 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -4425,6 +4425,9 @@ static int __perf_event_read_cpu(struct perf_event *event, int event_cpu) > { > u16 local_pkg, event_pkg; > > + if (event_cpu < 0 || event_cpu >= nr_cpu_ids) > + return event_cpu; if ((unsigned)event_cpu >= nr_cpu_ids) return event_cpu; As you could also find at the current __perf_event_read_cpu() callsite. > + > if (event->group_caps & PERF_EV_CAP_READ_ACTIVE_PKG) { > int local_cpu = smp_processor_id(); > > @@ -4528,6 +4531,8 @@ int perf_event_read_local(struct perf_event *event, u64 *value, > { > unsigned long flags; > int ret = 0; > + int event_cpu; > + int event_oncpu; You wrecked the x-mas tree :-) I'll fix both up. Thanks!
diff --git a/kernel/events/core.c b/kernel/events/core.c index 4c72a41f11af..6b343bac0a71 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -4425,6 +4425,9 @@ static int __perf_event_read_cpu(struct perf_event *event, int event_cpu) { u16 local_pkg, event_pkg; + if (event_cpu < 0 || event_cpu >= nr_cpu_ids) + return event_cpu; + if (event->group_caps & PERF_EV_CAP_READ_ACTIVE_PKG) { int local_cpu = smp_processor_id(); @@ -4528,6 +4531,8 @@ int perf_event_read_local(struct perf_event *event, u64 *value, { unsigned long flags; int ret = 0; + int event_cpu; + int event_oncpu; /* * Disabling interrupts avoids all counter scheduling (context @@ -4551,15 +4556,22 @@ int perf_event_read_local(struct perf_event *event, u64 *value, goto out; } + /* + * Get the event CPU numbers, and adjust them to local if the event is + * a per-package event that can be read locally + */ + event_oncpu = __perf_event_read_cpu(event, event->oncpu); + event_cpu = __perf_event_read_cpu(event, event->cpu); + /* If this is a per-CPU event, it must be for this CPU */ if (!(event->attach_state & PERF_ATTACH_TASK) && - event->cpu != smp_processor_id()) { + event_cpu != smp_processor_id()) { ret = -EINVAL; goto out; } /* If this is a pinned event it must be running on this CPU */ - if (event->attr.pinned && event->oncpu != smp_processor_id()) { + if (event->attr.pinned && event_oncpu != smp_processor_id()) { ret = -EBUSY; goto out; } @@ -4569,7 +4581,7 @@ int perf_event_read_local(struct perf_event *event, u64 *value, * or local to this CPU. Furthermore it means its ACTIVE (otherwise * oncpu == -1). */ - if (event->oncpu == smp_processor_id()) + if (event_oncpu == smp_processor_id()) event->pmu->read(event); *value = local64_read(&event->count);
Per-package perf events are typically registered with a single CPU only, however they can be read across all the CPUs within the package. Currently perf_event_read maps the event CPU according to the topology information to avoid an unnecessary SMP call, however perf_event_read_local deals with hard values and rejects a read with a failure if the CPU is not the one exactly registered. Allow similar mapping within the perf_event_read_local if the perf event in question can support this. This allows users like BPF code to read the package perf events properly across different CPUs within a package. Signed-off-by: Tero Kristo <tero.kristo@linux.intel.com> --- v2: * prevent illegal array access in case event->oncpu == -1 * split the event->cpu / event->oncpu handling to their own variables kernel/events/core.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-)