linux-kernel - [tip: perf/core] perf/x86/amd: Make Zen3 branch sampling opt-in

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Date:   Tue, 05 Apr 2022 08:36:39 -0000
From:   "tip-bot2 for Stephane Eranian" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Stephane Eranian <eranian@...gle.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: perf/core] perf/x86/amd: Make Zen3 branch sampling opt-in

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

Commit-ID:     cc37e520a236069c0de0e7ea455082fa11c73b12
Gitweb:        https://git.kernel.org/tip/cc37e520a236069c0de0e7ea455082fa11c73b12
Author:        Stephane Eranian <eranian@...gle.com>
AuthorDate:    Tue, 22 Mar 2022 15:15:11 -07:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Tue, 05 Apr 2022 10:24:38 +02:00

perf/x86/amd: Make Zen3 branch sampling opt-in

Add a kernel config option CONFIG_PERF_EVENTS_AMD_BRS
to make the support for AMD Zen3 Branch Sampling (BRS) an opt-in
compile time option.

Signed-off-by: Stephane Eranian <eranian@...gle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lore.kernel.org/r/20220322221517.2510440-8-eranian@google.com
---
 arch/x86/events/Kconfig      |  8 ++++++-
 arch/x86/events/amd/Makefile |  3 +-
 arch/x86/events/perf_event.h | 49 +++++++++++++++++++++++++++--------
 3 files changed, 49 insertions(+), 11 deletions(-)

diff --git a/arch/x86/events/Kconfig b/arch/x86/events/Kconfig
index d6cdfe6..09c5696 100644
--- a/arch/x86/events/Kconfig
+++ b/arch/x86/events/Kconfig
@@ -44,4 +44,12 @@ config PERF_EVENTS_AMD_UNCORE
 
 	  To compile this driver as a module, choose M here: the
 	  module will be called 'amd-uncore'.
+
+config PERF_EVENTS_AMD_BRS
+	depends on PERF_EVENTS && CPU_SUP_AMD
+	bool "AMD Zen3 Branch Sampling support"
+	help
+	  Enable AMD Zen3 branch sampling support (BRS) which samples up to
+	  16 consecutive taken branches in registers.
+
 endmenu
diff --git a/arch/x86/events/amd/Makefile b/arch/x86/events/amd/Makefile
index cf323ff..b9f5d46 100644
--- a/arch/x86/events/amd/Makefile
+++ b/arch/x86/events/amd/Makefile
@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
-obj-$(CONFIG_CPU_SUP_AMD)		+= core.o brs.o
+obj-$(CONFIG_CPU_SUP_AMD)		+= core.o
+obj-$(CONFIG_PERF_EVENTS_AMD_BRS)	+= brs.o
 obj-$(CONFIG_PERF_EVENTS_AMD_POWER)	+= power.o
 obj-$(CONFIG_X86_LOCAL_APIC)		+= ibs.o
 obj-$(CONFIG_PERF_EVENTS_AMD_UNCORE)	+= amd-uncore.o
diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index d91ff2c..ef27aee 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -1218,6 +1218,8 @@ static inline bool fixed_counter_disabled(int i, struct pmu *pmu)
 #ifdef CONFIG_CPU_SUP_AMD
 
 int amd_pmu_init(void);
+
+#ifdef CONFIG_PERF_EVENTS_AMD_BRS
 int amd_brs_init(void);
 void amd_brs_disable(void);
 void amd_brs_enable(void);
@@ -1252,25 +1254,52 @@ static inline void amd_pmu_brs_del(struct perf_event *event)
 
 void amd_pmu_brs_sched_task(struct perf_event_context *ctx, bool sched_in);
 
-/*
- * check if BRS is activated on the CPU
- * active defined as it has non-zero users and DBG_EXT_CFG.BRSEN=1
- */
-static inline bool amd_brs_active(void)
+static inline s64 amd_brs_adjust_period(s64 period)
 {
-	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+	if (period > x86_pmu.lbr_nr)
+		return period - x86_pmu.lbr_nr;
 
-	return cpuc->brs_active;
+	return period;
+}
+#else
+static inline int amd_brs_init(void)
+{
+	return 0;
 }
+static inline void amd_brs_disable(void) {}
+static inline void amd_brs_enable(void) {}
+static inline void amd_brs_drain(void) {}
+static inline void amd_brs_lopwr_init(void) {}
+static inline void amd_brs_disable_all(void) {}
+static inline int amd_brs_setup_filter(struct perf_event *event)
+{
+	return 0;
+}
+static inline void amd_brs_reset(void) {}
 
-static inline s64 amd_brs_adjust_period(s64 period)
+static inline void amd_pmu_brs_add(struct perf_event *event)
 {
-	if (period > x86_pmu.lbr_nr)
-		return period - x86_pmu.lbr_nr;
+}
+
+static inline void amd_pmu_brs_del(struct perf_event *event)
+{
+}
+
+static inline void amd_pmu_brs_sched_task(struct perf_event_context *ctx, bool sched_in)
+{
+}
 
+static inline s64 amd_brs_adjust_period(s64 period)
+{
 	return period;
 }
 
+static inline void amd_brs_enable_all(void)
+{
+}
+
+#endif
+
 #else /* CONFIG_CPU_SUP_AMD */
 
 static inline int amd_pmu_init(void)