Merge tag 'perf-urgent-2025-05-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull misc perf fixes from Ingo Molnar:

 - Require group events for branch counter groups and
   PEBS counter snapshotting groups to be x86 events.

 - Fix the handling of counter-snapshotting of non-precise
   events, where counter values may move backwards a bit,
   temporarily, confusing the code.

 - Restrict perf/KVM PEBS to guest-owned events.

* tag 'perf-urgent-2025-05-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/x86/intel: KVM: Mask PEBS_ENABLE loaded for guest with vCPU's value.
  perf/x86/intel/ds: Fix counter backwards of non-precise events counters-snapshotting
  perf/x86/intel: Check the X86 leader for pebs_counter_event_group
  perf/x86/intel: Only check the group flag for X86 leader

Author: torvalds

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;
 

arch/x86/events/intel/core.c

@@ -4395,7 +4395,7 @@ static struct perf_guest_switch_msr *intel_guest_get_msrs(int *nr, void *data)
 	arr[pebs_enable] = (struct perf_guest_switch_msr){
 		.msr = MSR_IA32_PEBS_ENABLE,
 		.host = cpuc->pebs_enabled & ~cpuc->intel_ctrl_guest_mask,
-		.guest = pebs_mask & ~cpuc->intel_ctrl_host_mask,
+		.guest = pebs_mask & ~cpuc->intel_ctrl_host_mask & kvm_pmu->pebs_enable,
 	};
 
 	if (arr[pebs_enable].host) {

arch/x86/events/intel/ds.c

@@ -2379,8 +2379,25 @@ __intel_pmu_pebs_last_event(struct perf_event *event,
 			 */
 			intel_pmu_save_and_restart_reload(event, count);
 		}
-	} else
-		intel_pmu_save_and_restart(event);
+	} else {
+		/*
+		 * For a non-precise event, it's possible the
+		 * counters-snapshotting records a positive value for the
+		 * overflowed event. Then the HW auto-reload mechanism
+		 * reset the counter to 0 immediately, because the
+		 * pebs_event_reset is cleared if the PERF_X86_EVENT_AUTO_RELOAD
+		 * is not set. The counter backwards may be observed in a
+		 * PMI handler.
+		 *
+		 * Since the event value has been updated when processing the
+		 * counters-snapshotting record, only needs to set the new
+		 * period for the counter.
+		 */
+		if (is_pebs_counter_event_group(event))
+			static_call(x86_pmu_set_period)(event);
+		else
+			intel_pmu_save_and_restart(event);
+	}
 }
 
 static __always_inline void

arch/x86/events/perf_event.h

@@ -110,14 +110,21 @@ 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)
 {
-	return event->group_leader->hw.flags & PERF_X86_EVENT_PEBS_CNTR;
+	return check_leader_group(event->group_leader, PERF_X86_EVENT_PEBS_CNTR);
 }
 
 struct amd_nb {