[PATCH] perf/x86/msr: add support for MSR_IA32_THERM_STATUS

[Stephane Eranian]

This patch adds support for the Digital Readout provided by the
IA32_THERM_STATUS MSR (0x19C) on Intel X86 processors. The readout
shows the number of degrees Celcius to the TCC (critical temperature)
supported by the processor. Thus, the larger, the better.

The perf_event support is provided via the msr PMU. The new
logical event is called cpu_thermal_margin. It comes with a unit and
snapshot files. The event shows the current temprature distance (margin).
It is not an accumulating event. The unit is degree C. The event
is provided per logical CPU to make things simpler but it is the
same for both hyper-threads sharing a physical core.

$ perf stat -I 1000 -a -A -e msr/cpu_thermal_margin/

This will print the temperature for all logical CPUs.
             time CPU                counts unit events
     1.000123741 CPU0                    38 C    msr/cpu_thermal_margin/
     1.000161837 CPU1                    37 C    msr/cpu_thermal_margin/
     1.000187906 CPU2                    36 C    msr/cpu_thermal_margin/
     1.000189046 CPU3                    39 C    msr/cpu_thermal_margin/
     1.000283044 CPU4                    40 C    msr/cpu_thermal_margin/
     1.000344297 CPU5                    40 C    msr/cpu_thermal_margin/
     1.000365832 CPU6                    39 C    msr/cpu_thermal_margin/
     ...

In case the temperature margin cannot be read, the reported value would be -1.

Works on all processors supporting the Digital Readout (dtherm in cpuinfo)

Signed-off-by: Stephane Eranian <eranian@xxxxxxxxxx>

---
 arch/x86/events/msr.c | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/arch/x86/events/msr.c b/arch/x86/events/msr.c
index 14efaa0e8684..0be15b9b2376 100644
--- a/arch/x86/events/msr.c
+++ b/arch/x86/events/msr.c
@@ -10,7 +10,9 @@ enum perf_msr_id {
 	PERF_MSR_SMI			= 4,
 	PERF_MSR_PTSC			= 5,
 	PERF_MSR_IRPERF			= 6,
-
+	PERF_MSR_THERM			= 7,
+	PERF_MSR_THERM_SNAP		= 8,
+	PERF_MSR_THERM_UNIT		= 9,
 	PERF_MSR_EVENT_MAX,
 };
 
@@ -29,6 +31,12 @@ static bool test_irperf(int idx)
 	return boot_cpu_has(X86_FEATURE_IRPERF);
 }
 
+static bool test_therm_status(int idx)
+{
+	return boot_cpu_has(X86_FEATURE_DTHERM);
+}
+
+
 static bool test_intel(int idx)
 {
 	if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL ||
@@ -102,6 +110,9 @@ PMU_EVENT_ATTR_STRING(pperf,  evattr_pperf,  "event=0x03");
 PMU_EVENT_ATTR_STRING(smi,    evattr_smi,    "event=0x04");
 PMU_EVENT_ATTR_STRING(ptsc,   evattr_ptsc,   "event=0x05");
 PMU_EVENT_ATTR_STRING(irperf, evattr_irperf, "event=0x06");
+PMU_EVENT_ATTR_STRING(cpu_thermal_margin, evattr_therm, "event=0x07");
+PMU_EVENT_ATTR_STRING(cpu_thermal_margin.snapshot, evattr_therm_snap, "1");
+PMU_EVENT_ATTR_STRING(cpu_thermal_margin.unit, evattr_therm_unit, "C");
 
 static struct perf_msr msr[] = {
 	[PERF_MSR_TSC]    = { 0,		&evattr_tsc,	NULL,		 },
@@ -111,6 +122,9 @@ static struct perf_msr msr[] = {
 	[PERF_MSR_SMI]    = { MSR_SMI_COUNT,	&evattr_smi,	test_intel,	 },
 	[PERF_MSR_PTSC]   = { MSR_F15H_PTSC,	&evattr_ptsc,	test_ptsc,	 },
 	[PERF_MSR_IRPERF] = { MSR_F17H_IRPERF,	&evattr_irperf,	test_irperf,	 },
+	[PERF_MSR_THERM] = { MSR_IA32_THERM_STATUS, &evattr_therm,	     test_therm_status, },
+	[PERF_MSR_THERM_SNAP] = { MSR_IA32_THERM_STATUS, &evattr_therm_snap, test_therm_status, },
+	[PERF_MSR_THERM_UNIT] = { MSR_IA32_THERM_STATUS, &evattr_therm_unit, test_therm_status, },
 };
 
 static struct attribute *events_attrs[PERF_MSR_EVENT_MAX + 1] = {
@@ -193,10 +207,15 @@ static void msr_event_update(struct perf_event *event)
 		goto again;
 
 	delta = now - prev;
-	if (unlikely(event->hw.event_base == MSR_SMI_COUNT))
+	if (unlikely(event->hw.event_base == MSR_SMI_COUNT)) {
 		delta = sign_extend64(delta, 31);
-
-	local64_add(delta, &event->count);
+		local64_add(delta, &event->count);
+	} else if (unlikely(event->hw.event_base == MSR_IA32_THERM_STATUS)) {
+		/* if valid, extract digital readout, other set to -1 */
+		now = now & (1ULL << 31) ? (now >> 16) & 0x3f :  -1;
+		local64_set(&event->count, now);
+	} else
+		local64_add(delta, &event->count);
 }
 
 static void msr_event_start(struct perf_event *event, int flags)
-- 
2.7.4