linux-kernel - [tip: perf/core] perf/x86/intel/pt: Add a capability and config bit for disabling TNTs

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Date:   Wed, 16 Feb 2022 14:57:58 -0000
From:   "tip-bot2 for Alexander Shishkin" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: perf/core] perf/x86/intel/pt: Add a capability and config bit
 for disabling TNTs

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     161a9a33702a2e65a4118dacb449505ac8ce3122
Gitweb:        https://git.kernel.org/tip/161a9a33702a2e65a4118dacb449505ac8ce3122
Author:        Alexander Shishkin <alexander.shishkin@...ux.intel.com>
AuthorDate:    Wed, 26 Jan 2022 12:48:15 +02:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Tue, 15 Feb 2022 17:47:11 +01:00

perf/x86/intel/pt: Add a capability and config bit for disabling TNTs

As of Intel SDM (https://www.intel.com/sdm) version 076, there is a new
Intel PT feature called TNT-Disable which is enabled config bit 55.

TNT-Disable disables Taken-Not-Taken packets to reduce the tracing
overhead, but with the result that exact control flow information is
lost.

Add a capability and config bit for TNT-Disable.

Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Adrian Hunter <adrian.hunter@...el.com>
Link: https://lore.kernel.org/r/20220126104815.2807416-3-adrian.hunter@intel.com
---
 arch/x86/events/intel/pt.c       | 8 ++++++++
 arch/x86/include/asm/intel_pt.h  | 1 +
 arch/x86/include/asm/msr-index.h | 1 +
 3 files changed, 10 insertions(+)

diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
index f339c88..aa66c0c 100644
--- a/arch/x86/events/intel/pt.c
+++ b/arch/x86/events/intel/pt.c
@@ -60,6 +60,7 @@ static struct pt_cap_desc {
 	PT_CAP(ptwrite,			0, CPUID_EBX, BIT(4)),
 	PT_CAP(power_event_trace,	0, CPUID_EBX, BIT(5)),
 	PT_CAP(event_trace,		0, CPUID_EBX, BIT(7)),
+	PT_CAP(tnt_disable,		0, CPUID_EBX, BIT(8)),
 	PT_CAP(topa_output,		0, CPUID_ECX, BIT(0)),
 	PT_CAP(topa_multiple_entries,	0, CPUID_ECX, BIT(1)),
 	PT_CAP(single_range_output,	0, CPUID_ECX, BIT(2)),
@@ -112,6 +113,7 @@ PMU_FORMAT_ATTR(noretcomp,	"config:11"	);
 PMU_FORMAT_ATTR(ptw,		"config:12"	);
 PMU_FORMAT_ATTR(branch,		"config:13"	);
 PMU_FORMAT_ATTR(event,		"config:31"	);
+PMU_FORMAT_ATTR(notnt,		"config:55"	);
 PMU_FORMAT_ATTR(mtc_period,	"config:14-17"	);
 PMU_FORMAT_ATTR(cyc_thresh,	"config:19-22"	);
 PMU_FORMAT_ATTR(psb_period,	"config:24-27"	);
@@ -121,6 +123,7 @@ static struct attribute *pt_formats_attr[] = {
 	&format_attr_cyc.attr,
 	&format_attr_pwr_evt.attr,
 	&format_attr_event.attr,
+	&format_attr_notnt.attr,
 	&format_attr_fup_on_ptw.attr,
 	&format_attr_mtc.attr,
 	&format_attr_tsc.attr,
@@ -302,6 +305,7 @@ fail:
 			RTIT_CTL_MTC		| \
 			RTIT_CTL_PWR_EVT_EN	| \
 			RTIT_CTL_EVENT_EN	| \
+			RTIT_CTL_NOTNT		| \
 			RTIT_CTL_FUP_ON_PTW	| \
 			RTIT_CTL_PTW_EN)
 
@@ -360,6 +364,10 @@ static bool pt_event_valid(struct perf_event *event)
 	    !intel_pt_validate_hw_cap(PT_CAP_event_trace))
 		return false;
 
+	if (config & RTIT_CTL_NOTNT &&
+	    !intel_pt_validate_hw_cap(PT_CAP_tnt_disable))
+		return false;
+
 	if (config & RTIT_CTL_PTW) {
 		if (!intel_pt_validate_hw_cap(PT_CAP_ptwrite))
 			return false;
diff --git a/arch/x86/include/asm/intel_pt.h b/arch/x86/include/asm/intel_pt.h
index d1ef9cb..c796e9b 100644
--- a/arch/x86/include/asm/intel_pt.h
+++ b/arch/x86/include/asm/intel_pt.h
@@ -14,6 +14,7 @@ enum pt_capabilities {
 	PT_CAP_ptwrite,
 	PT_CAP_power_event_trace,
 	PT_CAP_event_trace,
+	PT_CAP_tnt_disable,
 	PT_CAP_topa_output,
 	PT_CAP_topa_multiple_entries,
 	PT_CAP_single_range_output,
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 79b392d..efd34cf 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -206,6 +206,7 @@
 #define RTIT_CTL_PTW_EN			BIT(12)
 #define RTIT_CTL_BRANCH_EN		BIT(13)
 #define RTIT_CTL_EVENT_EN		BIT(31)
+#define RTIT_CTL_NOTNT			BIT_ULL(55)
 #define RTIT_CTL_MTC_RANGE_OFFSET	14
 #define RTIT_CTL_MTC_RANGE		(0x0full << RTIT_CTL_MTC_RANGE_OFFSET)
 #define RTIT_CTL_CYC_THRESH_OFFSET	19