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Subject[PATCH 1/3] perf/x86: add sysfs entry to freeze counter on SMI
Date
From: Kan Liang <Kan.liang@intel.com>

When setting FREEZE_WHILE_SMM bit in IA32_DEBUGCTL, all performance
counters will be effected. There is no way to do per-counter freeze
on smi. So it should not use the per-event interface (e.g. ioctl or
event attribute) to set FREEZE_WHILE_SMM bit.

Adds sysfs entry /sys/device/cpu/freeze_on_smi to set FREEZE_WHILE_SMM
bit in IA32_DEBUGCTL. When set, freezes perfmon and trace messages
while in SMM.
Value has to be 0 or 1. It will be applied to all possible cpus.

Signed-off-by: Kan Liang <Kan.liang@intel.com>
---
arch/x86/events/core.c | 10 +++++++++
arch/x86/events/intel/core.c | 48 ++++++++++++++++++++++++++++++++++++++++
arch/x86/events/perf_event.h | 3 +++
arch/x86/include/asm/msr-index.h | 1 +
4 files changed, 62 insertions(+)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 349d4d1..c16fb50 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -1750,6 +1750,8 @@ ssize_t x86_event_sysfs_show(char *page, u64 config, u64 event)
return ret;
}

+static struct attribute_group x86_pmu_attr_group;
+
static int __init init_hw_perf_events(void)
{
struct x86_pmu_quirk *quirk;
@@ -1813,6 +1815,14 @@ static int __init init_hw_perf_events(void)
x86_pmu_events_group.attrs = tmp;
}

+ if (x86_pmu.attrs) {
+ struct attribute **tmp;
+
+ tmp = merge_attr(x86_pmu_attr_group.attrs, x86_pmu.attrs);
+ if (!WARN_ON(!tmp))
+ x86_pmu_attr_group.attrs = tmp;
+ }
+
pr_info("... version: %d\n", x86_pmu.version);
pr_info("... bit width: %d\n", x86_pmu.cntval_bits);
pr_info("... generic registers: %d\n", x86_pmu.num_counters);
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 4244bed..a99a4ea 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3595,6 +3595,52 @@ static struct attribute *hsw_events_attrs[] = {
NULL
};

+static ssize_t freeze_on_smi_show(struct device *cdev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ return sprintf(buf, "%d\n", x86_pmu.attr_freeze_on_smi);
+}
+
+static ssize_t freeze_on_smi_store(struct device *cdev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ unsigned long val;
+ u64 debugctlmsr;
+ ssize_t ret;
+ int cpu;
+
+ ret = kstrtoul(buf, 0, &val);
+ if (ret)
+ return ret;
+
+ if (val > 1)
+ return -EINVAL;
+
+ if (x86_pmu.attr_freeze_on_smi == val)
+ return count;
+
+ for_each_possible_cpu(cpu) {
+ rdmsrl_on_cpu(cpu, MSR_IA32_DEBUGCTLMSR, &debugctlmsr);
+ if (val)
+ wrmsrl_on_cpu(cpu, MSR_IA32_DEBUGCTLMSR, debugctlmsr | DEBUGCTLMSR_FREEZE_WHILE_SMM);
+ else
+ wrmsrl_on_cpu(cpu, MSR_IA32_DEBUGCTLMSR, debugctlmsr & ~DEBUGCTLMSR_FREEZE_WHILE_SMM);
+ }
+
+ x86_pmu.attr_freeze_on_smi = val;
+
+ return count;
+}
+
+static DEVICE_ATTR_RW(freeze_on_smi);
+
+static struct attribute *intel_pmu_attrs[] = {
+ &dev_attr_freeze_on_smi.attr,
+ NULL,
+};
+
__init int intel_pmu_init(void)
{
union cpuid10_edx edx;
@@ -3641,6 +3687,8 @@ __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:
diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index bcbb1d2..110cb9b0 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -561,6 +561,9 @@ struct x86_pmu {
ssize_t (*events_sysfs_show)(char *page, u64 config);
struct attribute **cpu_events;

+ int attr_freeze_on_smi;
+ struct attribute **attrs;
+
/*
* CPU Hotplug hooks
*/
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index d8b5f8a..26c861f 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -134,6 +134,7 @@
#define DEBUGCTLMSR_BTS_OFF_OS (1UL << 9)
#define DEBUGCTLMSR_BTS_OFF_USR (1UL << 10)
#define DEBUGCTLMSR_FREEZE_LBRS_ON_PMI (1UL << 11)
+#define DEBUGCTLMSR_FREEZE_WHILE_SMM (1UL << 14)

#define MSR_PEBS_FRONTEND 0x000003f7

--
2.7.4
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