perf/core: Allow reading package events from perf_event_read_local

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>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230913125956.3652667-1-tero.kristo@linux.intel.com

diff --git a/kernel/events/core.c b/kernel/events/core.c
index af569196d7604bd35b084dee09f41d557d2205a6..708d474c2ede947f9b7d52ab23a2c1c22adadb4d 100644 (file)
--- 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 ((unsigned)event_cpu >= nr_cpu_ids)
+               return event_cpu;
+
        if (event->group_caps & PERF_EV_CAP_READ_ACTIVE_PKG) {
                int local_cpu = smp_processor_id();
 
@@ -4527,6 +4530,8 @@ int perf_event_read_local(struct perf_event *event, u64 *value,
                          u64 *enabled, u64 *running)
 {
        unsigned long flags;
+       int event_oncpu;
+       int event_cpu;
        int ret = 0;
 
        /*
@@ -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);