linux-kernel - [PATCH V6 11/14] perf/x86/intel: Disable sample-read the slots and metrics events

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Date:   Fri, 17 Jul 2020 07:05:51 -0700
From:   kan.liang@...ux.intel.com
To:     peterz@...radead.org, acme@...hat.com, mingo@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     jolsa@...nel.org, eranian@...gle.com,
        alexander.shishkin@...ux.intel.com, ak@...ux.intel.com,
        Kan Liang <kan.liang@...ux.intel.com>
Subject: [PATCH V6 11/14] perf/x86/intel: Disable sample-read the slots and metrics events

From: Kan Liang <kan.liang@...ux.intel.com>

Users fail to sample-read the slots and metrics events, e.g.,
perf record -e '{slots, topdown-retiring}:S'.

When reading the metrics event, the fixed counter 3 (slots) has to be
reset, which impacts the sampling of the slots event.

Add a specific validate_group() support to reject the case and error out
for Ice Lake.

An alternative fix may unconditionally disable slots sampling, but it's
not a decent fix. Users may want to only sample the slot events
without the topdown metrics events.

Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
---
 arch/x86/events/core.c       |  4 ++++
 arch/x86/events/intel/core.c | 20 ++++++++++++++++++++
 arch/x86/events/perf_event.h |  2 ++
 3 files changed, 26 insertions(+)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index c25dde095bca..7a4c26b89cbf 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -2176,7 +2176,11 @@ static int validate_group(struct perf_event *event)
 
 	fake_cpuc->n_events = 0;
 	ret = x86_pmu.schedule_events(fake_cpuc, n, NULL);
+	if (ret)
+		goto out;
 
+	if (x86_pmu.validate_group)
+		ret = x86_pmu.validate_group(fake_cpuc, n);
 out:
 	free_fake_cpuc(fake_cpuc);
 	return ret;
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index dd3d9f3f2162..bcd96d7fb6ec 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -4576,6 +4576,25 @@ static __init void intel_ht_bug(void)
 	x86_pmu.stop_scheduling = intel_stop_scheduling;
 }
 
+static int icl_validate_group(struct cpu_hw_events *cpuc, int n)
+{
+	bool has_sampling_slots = false, has_metrics = false;
+	struct perf_event *e;
+	int i;
+
+	for (i = 0; i < n; i++) {
+		e = cpuc->event_list[i];
+		if (is_slots_event(e) && is_sampling_event(e))
+			has_sampling_slots = true;
+
+		if (is_metric_event(e))
+			has_metrics = true;
+	}
+	if (unlikely(has_sampling_slots && has_metrics))
+		return -EINVAL;
+	return 0;
+}
+
 EVENT_ATTR_STR(mem-loads,	mem_ld_hsw,	"event=0xcd,umask=0x1,ldlat=3");
 EVENT_ATTR_STR(mem-stores,	mem_st_hsw,	"event=0xd0,umask=0x82")
 
@@ -5437,6 +5456,7 @@ __init int intel_pmu_init(void)
 		intel_pmu_pebs_data_source_skl(pmem);
 		x86_pmu.update_topdown_event = icl_update_topdown_event;
 		x86_pmu.set_topdown_event_period = icl_set_topdown_event_period;
+		x86_pmu.validate_group = icl_validate_group;
 		pr_cont("Icelake events, ");
 		name = "icelake";
 		break;
diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index 8100c21205e8..acd85baeabd8 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -677,6 +677,8 @@ struct x86_pmu {
 	int		perfctr_second_write;
 	u64		(*limit_period)(struct perf_event *event, u64 l);
 
+	int		(*validate_group)(struct cpu_hw_events *cpuc, int n);
+
 	/* PMI handler bits */
 	unsigned int	late_ack		:1,
 			enabled_ack		:1,
-- 
2.17.1