linux-kernel - [PATCH 3/5] perf/x86/amd/uncore: Detect available DF counters

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Date:   Thu, 19 May 2022 15:33:32 +0530
From:   Sandipan Das <sandipan.das@....com>
To:     <linux-kernel@...r.kernel.org>, <linux-perf-users@...r.kernel.org>,
        <x86@...nel.org>
CC:     <peterz@...radead.org>, <bp@...en8.de>, <acme@...nel.org>,
        <namhyung@...nel.org>, <jolsa@...nel.org>, <tglx@...utronix.de>,
        <mingo@...hat.com>, <pbonzini@...hat.com>, <jmattson@...gle.com>,
        <like.xu.linux@...il.com>, <eranian@...gle.com>,
        <ananth.narayan@....com>, <ravi.bangoria@....com>,
        <santosh.shukla@....com>, <sandipan.das@....com>
Subject: [PATCH 3/5] perf/x86/amd/uncore: Detect available DF counters

If AMD Performance Monitoring Version 2 (PerfMonV2) is
supported, use CPUID leaf 0x80000022 EBX to detect the
number of Data Fabric (DF) PMCs. This offers more
flexibility if the counts change in later processor
families.

Signed-off-by: Sandipan Das <sandipan.das@....com>
---
 arch/x86/events/amd/uncore.c      | 10 ++++++++++
 arch/x86/include/asm/perf_event.h |  3 +++
 2 files changed, 13 insertions(+)

diff --git a/arch/x86/events/amd/uncore.c b/arch/x86/events/amd/uncore.c
index c3e218dccf6e..233dd405dd06 100644
--- a/arch/x86/events/amd/uncore.c
+++ b/arch/x86/events/amd/uncore.c
@@ -30,6 +30,7 @@
 #undef pr_fmt
 #define pr_fmt(fmt)	"amd_uncore: " fmt
 
+static int pmu_version;
 static int num_counters_llc;
 static int num_counters_nb;
 static bool l3_mask;
@@ -629,6 +630,7 @@ static int __init amd_uncore_init(void)
 {
 	struct attribute **df_attr = amd_uncore_df_format_attr;
 	struct attribute **l3_attr = amd_uncore_l3_format_attr;
+	union cpuid_0x80000022_ebx ebx;
 	int ret = -ENODEV;
 
 	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
@@ -638,6 +640,9 @@ static int __init amd_uncore_init(void)
 	if (!boot_cpu_has(X86_FEATURE_TOPOEXT))
 		return -ENODEV;
 
+	if (boot_cpu_has(X86_FEATURE_PERFMON_V2))
+		pmu_version = 2;
+
 	num_counters_nb	= NUM_COUNTERS_NB;
 	num_counters_llc = NUM_COUNTERS_L2;
 	if (boot_cpu_data.x86 >= 0x17) {
@@ -666,6 +671,11 @@ static int __init amd_uncore_init(void)
 		if (ret)
 			goto fail_nb;
 
+		if (pmu_version >= 2) {
+			ebx.full = cpuid_ebx(EXT_PERFMON_DEBUG_FEATURES);
+			num_counters_nb = ebx.split.num_df_pmc;
+		}
+
 		pr_info("%d %s %s counters detected\n", num_counters_nb,
 			boot_cpu_data.x86_vendor == X86_VENDOR_HYGON ?  "HYGON" : "",
 			amd_nb_pmu.name);
diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
index 409725e86f42..af157aa74f4e 100644
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -194,6 +194,9 @@ union cpuid_0x80000022_ebx {
 	struct {
 		/* Number of Core Performance Counters */
 		unsigned int	num_core_pmc:4;
+		unsigned int	reserved:6;
+		/* Number of Data Fabric Counters */
+		unsigned int	num_df_pmc:6;
 	} split;
 	unsigned int		full;
 };
-- 
2.34.1