linux-kernel - [V2 PATCH] perf/x86/intel: Don't enable freeze-on-smi for PerfMon V1

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Date:   Wed, 25 Apr 2018 14:57:17 -0400
From:   kan.liang@...ux.intel.com
To:     peterz@...radead.org, tglx@...utronix.de, mingo@...hat.com,
        linux-kernel@...r.kernel.org
Cc:     acme@...hat.com, eranian@...gle.com, ak@...ux.intel.com,
        Kan Liang <kan.liang@...ux.intel.com>
Subject: [V2 PATCH] perf/x86/intel: Don't enable freeze-on-smi for PerfMon V1

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

The SMM freeze feature was introduced since PerfMon V2. But the current
code unconditionally enables the feature for all platforms. It can
generate #GP exception, if the related FREEZE_WHILE_SMM bit is set for
the machine with PerfMon V1.

To disable the feature for PerfMon V1, perf needs to
- Remove the freeze_on_smi sysfs entry by moving intel_pmu_attrs to
  intel_pmu, which is only applied to PerfMon V2 and later.
- Check the PerfMon version before flipping the SMM bit when starting CPU

Fixes: 6089327f5424 ("perf/x86: Add sysfs entry to freeze counters on SMI")
Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
---

Change since V1
- Modified the changelog.

 arch/x86/events/intel/core.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 4f2a5c7..08be8ed 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3346,7 +3346,8 @@ static void intel_pmu_cpu_starting(int cpu)
 
 	cpuc->lbr_sel = NULL;
 
-	flip_smm_bit(&x86_pmu.attr_freeze_on_smi);
+	if (x86_pmu.version > 1)
+		flip_smm_bit(&x86_pmu.attr_freeze_on_smi);
 
 	if (!cpuc->shared_regs)
 		return;
@@ -3509,6 +3510,8 @@ static __initconst const struct x86_pmu core_pmu = {
 	.cpu_dying		= intel_pmu_cpu_dying,
 };
 
+static struct attribute *intel_pmu_attrs[];
+
 static __initconst const struct x86_pmu intel_pmu = {
 	.name			= "Intel",
 	.handle_irq		= intel_pmu_handle_irq,
@@ -3540,6 +3543,8 @@ static __initconst const struct x86_pmu intel_pmu = {
 	.format_attrs		= intel_arch3_formats_attr,
 	.events_sysfs_show	= intel_event_sysfs_show,
 
+	.attrs			= intel_pmu_attrs,
+
 	.cpu_prepare		= intel_pmu_cpu_prepare,
 	.cpu_starting		= intel_pmu_cpu_starting,
 	.cpu_dying		= intel_pmu_cpu_dying,
@@ -3918,8 +3923,6 @@ __init int intel_pmu_init(void)
 
 	x86_pmu.max_pebs_events		= min_t(unsigned, MAX_PEBS_EVENTS, x86_pmu.num_counters);
 
-
-	x86_pmu.attrs			= intel_pmu_attrs;
 	/*
 	 * Quirk: v2 perfmon does not report fixed-purpose events, so
 	 * assume at least 3 events, when not running in a hypervisor:
-- 
2.4.11