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 <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Link: https://lore.kernel.org/r/bac7b2806561e03f2acc7fdc9db94f102df80e1d.1652954372.git.sandipan.das@amd.com

Author: sandip4n

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);

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;
 };