linux-kernel - [PATCH] perf/x86/intel: Hide Topdown metrics events if slots is not enumerated

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Date:   Thu, 22 Sep 2022 13:15:05 -0700
From:   kan.liang@...ux.intel.com
To:     peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
        namhyung@...nel.org, joe.jin@...cle.com, likexu@...cent.com,
        dongli.zhang@...cle.com, Kan Liang <kan.liang@...ux.intel.com>
Subject: [PATCH] perf/x86/intel: Hide Topdown metrics events if slots is not enumerated

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

The below error is observed on Ice Lake VM.

$ perf stat
Error:
The sys_perf_event_open() syscall returned with 22 (Invalid argument)
for event (slots).
/bin/dmesg | grep -i perf may provide additional information.

In a virtualization env, the Topdown metrics and the slots event haven't
been supported yet. The guest CPUID doesn't enumerate them. However, the
current kernel unconditionally exposes the slots event and the Topdown
metrics events to sysfs, which misleads the perf tool and triggers the
error.

Hide the perf metrics topdown events and the slots event if the slots
event is not enumerated.

The big core of a hybrid platform can also supports the perf-metrics
feature. Fix the hybrid platform as well.

Reported-by: Dongli Zhang <dongli.zhang@...cle.com>
Tested-by: Dongli Zhang <dongli.zhang@...cle.com>
Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
---
 arch/x86/events/intel/core.c | 33 ++++++++++++++++++++++++++++++++-
 1 file changed, 32 insertions(+), 1 deletion(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index b16c91ac9219..a0a62b67c440 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -5335,6 +5335,19 @@ static struct attribute *intel_pmu_attrs[] = {
 	NULL,
 };
 
+static umode_t
+td_is_visible(struct kobject *kobj, struct attribute *attr, int i)
+{
+	/*
+	 * Hide the perf metrics topdown events
+	 * if the slots is not enumerated.
+	 */
+	if (x86_pmu.num_topdown_events)
+		return (x86_pmu.intel_ctrl & INTEL_PMC_MSK_FIXED_SLOTS) ? attr->mode : 0;
+
+	return attr->mode;
+}
+
 static umode_t
 tsx_is_visible(struct kobject *kobj, struct attribute *attr, int i)
 {
@@ -5370,6 +5383,7 @@ default_is_visible(struct kobject *kobj, struct attribute *attr, int i)
 
 static struct attribute_group group_events_td  = {
 	.name = "events",
+	.is_visible = td_is_visible,
 };
 
 static struct attribute_group group_events_mem = {
@@ -5522,6 +5536,23 @@ static inline int hybrid_find_supported_cpu(struct x86_hybrid_pmu *pmu)
 	return (cpu >= nr_cpu_ids) ? -1 : cpu;
 }
 
+static umode_t hybrid_td_is_visible(struct kobject *kobj,
+					struct attribute *attr, int i)
+{
+	struct device *dev = kobj_to_dev(kobj);
+	struct x86_hybrid_pmu *pmu =
+		 container_of(dev_get_drvdata(dev), struct x86_hybrid_pmu, pmu);
+
+	if (!is_attr_for_this_pmu(kobj, attr))
+		return 0;
+
+	/* Only check the big core which supports perf metrics */
+	if (pmu->cpu_type == hybrid_big)
+		return (pmu->intel_ctrl & INTEL_PMC_MSK_FIXED_SLOTS) ? attr->mode : 0;
+
+	return attr->mode;
+}
+
 static umode_t hybrid_tsx_is_visible(struct kobject *kobj,
 				     struct attribute *attr, int i)
 {
@@ -5548,7 +5579,7 @@ static umode_t hybrid_format_is_visible(struct kobject *kobj,
 
 static struct attribute_group hybrid_group_events_td  = {
 	.name		= "events",
-	.is_visible	= hybrid_events_is_visible,
+	.is_visible	= hybrid_td_is_visible,
 };
 
 static struct attribute_group hybrid_group_events_mem = {
-- 
2.35.1