linux-kernel - [PATCH v0 2/3] perf/x86/intel/pt: Export cpu frequency ratios needed by PT decoders

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Date:	Thu, 28 Apr 2016 18:35:45 +0300
From:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
	Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
	linux-kernel@...r.kernel.org, vince@...ter.net, eranian@...gle.com,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Mathieu Poirier <mathieu.poirier@...aro.org>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: [PATCH v0 2/3] perf/x86/intel/pt: Export cpu frequency ratios needed by PT decoders

In order for Intel PT decoders to infer correct crystal clock and bus
frequencies that are required to correctly decode timing information
from a PT stream (MTC and CBR packets), export them as sysfs attributes:

  * max_nonturbo_ratio: ratio between the invariant TSC and base clock;
  * tsc_art_ratio: TSC to core crystal clock ratio.

Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
---
 arch/x86/events/intel/pt.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++
 arch/x86/events/intel/pt.h |  6 ++++++
 2 files changed, 60 insertions(+)

diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
index e88915ff98..bf0b0fe33d 100644
--- a/arch/x86/events/intel/pt.c
+++ b/arch/x86/events/intel/pt.c
@@ -125,9 +125,46 @@ static struct attribute_group pt_format_group = {
 	.attrs	= pt_formats_attr,
 };
 
+static ssize_t
+pt_timing_attr_show(struct device *dev, struct device_attribute *attr,
+		    char *page)
+{
+	struct perf_pmu_events_attr *pmu_attr =
+		container_of(attr, struct perf_pmu_events_attr, attr);
+
+	switch (pmu_attr->id) {
+	case 0:
+		return sprintf(page, "%lu\n", pt_pmu.max_nonturbo_ratio);
+	case 1:
+		return sprintf(page, "%u:%u\n",
+			       pt_pmu.tsc_art_num,
+			       pt_pmu.tsc_art_den);
+	default:
+		break;
+	}
+
+	return -EINVAL;
+}
+
+PMU_EVENT_ATTR(max_nonturbo_ratio, timing_attr_max_nonturbo_ratio, 0,
+	       pt_timing_attr_show);
+PMU_EVENT_ATTR(tsc_art_ratio, timing_attr_tsc_art_ratio, 1,
+	       pt_timing_attr_show);
+
+static struct attribute *pt_timing_attr[] = {
+	&timing_attr_max_nonturbo_ratio.attr.attr,
+	&timing_attr_tsc_art_ratio.attr.attr,
+	NULL,
+};
+
+static struct attribute_group pt_timing_group = {
+	.attrs	= pt_timing_attr,
+};
+
 static const struct attribute_group *pt_attr_groups[] = {
 	&pt_cap_group,
 	&pt_format_group,
+	&pt_timing_group,
 	NULL,
 };
 
@@ -140,6 +177,23 @@ static int __init pt_pmu_hw_init(void)
 	int ret;
 	long i;
 
+	rdmsrl(MSR_PLATFORM_INFO, reg);
+	pt_pmu.max_nonturbo_ratio = (reg & 0xff00) >> 8;
+
+	/*
+	 * if available, read in TSC to core crystal clock ratio,
+	 * otherwise, zero for numerator stands for "not enumerated"
+	 * as per SDM
+	 */
+	if (boot_cpu_data.cpuid_level >= CPUID_TSC_LEAF) {
+		u32 eax, ebx, ecx, edx;
+
+		cpuid(CPUID_TSC_LEAF, &eax, &ebx, &ecx, &edx);
+
+		pt_pmu.tsc_art_num = ebx;
+		pt_pmu.tsc_art_den = eax;
+	}
+
 	if (boot_cpu_has(X86_FEATURE_VMX)) {
 		/*
 		 * Intel SDM, 36.5 "Tracing post-VMXON" says that
diff --git a/arch/x86/events/intel/pt.h b/arch/x86/events/intel/pt.h
index 3abb5f5ccc..e5385b1fa0 100644
--- a/arch/x86/events/intel/pt.h
+++ b/arch/x86/events/intel/pt.h
@@ -48,6 +48,9 @@ struct topa_entry {
 #define PT_CPUID_LEAVES		2
 #define PT_CPUID_REGS_NUM	4 /* number of regsters (eax, ebx, ecx, edx) */
 
+/* TSC to Core Crystal Clock Ratio */
+#define CPUID_TSC_LEAF		0x15
+
 enum pt_capabilities {
 	PT_CAP_max_subleaf = 0,
 	PT_CAP_cr3_filtering,
@@ -66,6 +69,9 @@ struct pt_pmu {
 	struct pmu		pmu;
 	u32			caps[PT_CPUID_REGS_NUM * PT_CPUID_LEAVES];
 	bool			vmx;
+	unsigned long		max_nonturbo_ratio;
+	unsigned int		tsc_art_num;
+	unsigned int		tsc_art_den;
 };
 
 /**
-- 
2.8.0.rc3