[PATCH 15/15] KVM: selftests: Support fixed counters bitmap in pmu_counters_test

[Zide Chen]

From: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>

On PerfMon v5, CPUID.0AH:ECX represents the fixed counter bitmask,
while EDX[4:0] represents the number of contiguous fixed counters
starting from 0.

pmu_counters_test does not correctly set up these two fixed counter
fields. For example, it may set EDX[4:0] to 0x0 while setting ECX to
0x1. It assumes that fixed counter 0 is available by checking:

FxCtr[i]_is_supported := ECX[i] || (EDX[4:0] > i).

However, this is an invalid setup because EDX[4:0] should not be zero
when the number of contiguous fixed counters is 1.

Correct the setting of EDX[4:0] when the fixed counter bitmask is
present, and also handle the non-contiguous fixed counter case.

Signed-off-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>
Co-developed-by: Zide Chen <zide.chen@xxxxxxxxx>
Signed-off-by: Zide Chen <zide.chen@xxxxxxxxx>
---
 .../selftests/kvm/x86/pmu_counters_test.c     | 25 ++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/kvm/x86/pmu_counters_test.c b/tools/testing/selftests/kvm/x86/pmu_counters_test.c
index 38057754e024..6f38a35a4ea7 100644
--- a/tools/testing/selftests/kvm/x86/pmu_counters_test.c
+++ b/tools/testing/selftests/kvm/x86/pmu_counters_test.c
@@ -3,6 +3,7 @@
  * Copyright (C) 2023, Tencent, Inc.
  */
 #include <x86intrin.h>
+#include <linux/bitmap.h>
 
 #include "pmu.h"
 #include "processor.h"
@@ -659,6 +660,8 @@ static void test_intel_counters(void)
 	u8 nr_gp_counters = kvm_cpu_property(X86_PROPERTY_PMU_NR_GP_COUNTERS);
 	u8 pmu_version = kvm_cpu_property(X86_PROPERTY_PMU_VERSION);
 	u64 advertised_perf_caps = kvm_get_feature_msr(MSR_IA32_PERF_CAPABILITIES);
+	unsigned long fixed_subset;
+	u32 fixed_bitmap = 0;
 	unsigned int i;
 	u8 v, j;
 	u32 k;
@@ -696,6 +699,12 @@ static void test_intel_counters(void)
 	 */
 	u8 max_pmu_version = max_t(typeof(pmu_version), pmu_version, 5);
 
+	if (nr_fixed_counters)
+		fixed_bitmap = GENMASK(nr_fixed_counters - 1, 0);
+
+	if (pmu_version > 4)
+		fixed_bitmap |= kvm_cpu_property(X86_PROPERTY_PMU_FIXED_COUNTERS_BITMASK);
+
 	/*
 	 * Detect the existence of events that aren't supported by selftests.
 	 * This will (obviously) fail any time hardware adds support for a new
@@ -750,9 +759,19 @@ static void test_intel_counters(void)
 
 			pr_info("Testing fixed counters, PMU version %u, perf_caps = %lx\n",
 				v, perf_caps[i]);
-			for (j = 0; j <= nr_fixed_counters; j++) {
-				for (k = 0; k <= (BIT(nr_fixed_counters) - 1); k++)
-					test_fixed_counters(v, perf_caps[i], j, k);
+			for (fixed_subset = 0; fixed_subset <= fixed_bitmap; fixed_subset++) {
+				u32 nr_contiguous;
+
+				/*
+				 * The loop walks all values from 0 to fixed_bitmap, so skip any
+				 * value that is not a true subset of fixed_bitmap.
+				 */
+				if (fixed_subset & ~fixed_bitmap)
+					continue;
+
+				nr_contiguous = find_first_zero_bit(&fixed_subset,
+								    MAX_NR_FIXED_COUNTERS);
+				test_fixed_counters(v, perf_caps[i], nr_contiguous, fixed_subset);
 			}
 
 			pr_info("Testing Perf Metrics, PMU version %u, perf_caps = %lx\n",
-- 
2.54.0