perf/x86/intel: Only check the group flag for X86 leader

A warning in intel_pmu_lbr_counters_reorder() may be triggered by below
perf command.

perf record -e "{cpu-clock,cycles/call-graph="lbr"/}" -- sleep 1

It's because the group is mistakenly treated as a branch counter group.

The hw.flags of the leader are used to determine whether a group is a
branch counters group. However, the hw.flags is only available for a
hardware event. The field to store the flags is a union type. For a
software event, it's a hrtimer. The corresponding bit may be set if the
leader is a software event.

For a branch counter group and other groups that have a group flag
(e.g., topdown, PEBS counters snapshotting, and ACR), the leader must
be a X86 event. Check the X86 event before checking the flag.
The patch only fixes the issue for the branch counter group.
The following patch will fix the other groups.

There may be an alternative way to fix the issue by moving the hw.flags
out of the union type. It should work for now. But it's still possible
that the flags will be used by other types of events later. As long as
that type of event is used as a leader, a similar issue will be
triggered. So the alternative way is dropped.

Fixes: 33744916196b ("perf/x86/intel: Support branch counters logging")
Closes: https://lore.kernel.org/lkml/20250412091423.1839809-1-luogengkun@huaweicloud.com/
Reported-by: Luo Gengkun <luogengkun@huaweicloud.com>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20250424134718.311934-2-kan.liang@linux.intel.com

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 3a4f031d2f4401d63982a68f958a2499dff720e4..139ad80d1df34f17d71389e3d250ff7d0984ffa4 100644 (file)
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -754,7 +754,7 @@ void x86_pmu_enable_all(int added)
        }
 }
 
-static inline int is_x86_event(struct perf_event *event)
+int is_x86_event(struct perf_event *event)
 {
        int i;
 

diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index 2c0ce0e9545e50ddfa217cf9e9a2dac48d30ae6e..4237c379cdc53b58e19d3b2394deab9b7ae5e694 100644 (file)
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -110,9 +110,16 @@ static inline bool is_topdown_event(struct perf_event *event)
        return is_metric_event(event) || is_slots_event(event);
 }
 
+int is_x86_event(struct perf_event *event);
+
+static inline bool check_leader_group(struct perf_event *leader, int flags)
+{
+       return is_x86_event(leader) ? !!(leader->hw.flags & flags) : false;
+}
+
 static inline bool is_branch_counters_group(struct perf_event *event)
 {
-       return event->group_leader->hw.flags & PERF_X86_EVENT_BRANCH_COUNTERS;
+       return check_leader_group(event->group_leader, PERF_X86_EVENT_BRANCH_COUNTERS);
 }
 
 static inline bool is_pebs_counter_event_group(struct perf_event *event)