[PATCH 1/2] KVM: selftests: Test one random GP counter in PMU arch events testcase

[Sean Christopherson <seanjc@google.com>]

To significantly reduce the PMU counter test's runtime, without sacrificing
test coverage in the aggregate, test a random GP counter in the arch events
testcase instead of testing every possible GP counter.  Testing every PMC
in every run of the test significantly increases the runtime of the test,
without providing an equivalent increase in validation coverage, as the
odds of a KVM having a bug that only affected a subset of counters and only
when testing all other counters are extremely low.

Opportunistically clean up kvm_random_u64_in_range() to eliminate
unnecessary newlines.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 .../testing/selftests/kvm/include/test_util.h |  4 ++--
 tools/testing/selftests/kvm/lib/test_util.c   | 22 +++++++++++++++----
 .../selftests/kvm/x86/pmu_counters_test.c     | 18 +++++++--------
 3 files changed, 28 insertions(+), 16 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
index e8356ee54d7b..a6a3e1657895 100644
--- a/tools/testing/selftests/kvm/include/test_util.h
+++ b/tools/testing/selftests/kvm/include/test_util.h
@@ -135,8 +135,8 @@ static inline u64 kvm_random_u64(struct kvm_random_state *state)
 	return ((u64)kvm_random_u32(state) << 32) | kvm_random_u32(state);
 }
 
-u64 kvm_random_u64_in_range(struct kvm_random_state *state, u64 min,
-			    u64 max);
+u32 kvm_random_u32_in_range(struct kvm_random_state *state, u32 min, u32 max);
+u64 kvm_random_u64_in_range(struct kvm_random_state *state, u64 min, u64 max);
 
 enum vm_mem_backing_src_type {
 	VM_MEM_SRC_ANONYMOUS,
diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
index 6b00ab11f3c0..4dff72f6bd34 100644
--- a/tools/testing/selftests/kvm/lib/test_util.c
+++ b/tools/testing/selftests/kvm/lib/test_util.c
@@ -43,12 +43,26 @@ u32 kvm_random_u32(struct kvm_random_state *state)
 	return state->seed;
 }
 
+/* Returns a random u32 in the inclusive range [min, max] */
+u32 kvm_random_u32_in_range(struct kvm_random_state *state, u32 min, u32 max)
+{
+	u32 value, range;
+
+	TEST_ASSERT(min <= max, "PEBKAC, min = 0x%x, max = 0x%x", min, max);
+
+	value = kvm_random_u32(state);
+
+	range = max - min;
+	if (range == UINT_MAX)
+		return value;
+
+	return min + (value % (range + 1));
+}
+
 /* Returns a random u64 in the inclusive range [min, max] */
-u64 kvm_random_u64_in_range(struct kvm_random_state *state, u64 min,
-			    u64 max)
+u64 kvm_random_u64_in_range(struct kvm_random_state *state, u64 min, u64 max)
 {
-	u64 value;
-	u64 range;
+	u64 value, range;
 
 	TEST_ASSERT(min <= max, "PEBKAC, min = 0x%lx, max = 0x%lx", min, max);
 
diff --git a/tools/testing/selftests/kvm/x86/pmu_counters_test.c b/tools/testing/selftests/kvm/x86/pmu_counters_test.c
index dc6afac3aa91..8abf17cc9469 100644
--- a/tools/testing/selftests/kvm/x86/pmu_counters_test.c
+++ b/tools/testing/selftests/kvm/x86/pmu_counters_test.c
@@ -273,6 +273,7 @@ static void guest_test_arch_event(u8 idx)
 	struct kvm_x86_pmu_feature gp_event, fixed_event;
 	u32 base_pmc_msr;
 	unsigned int i;
+	u64 eventsel;
 
 	/* The host side shouldn't invoke this without a guest PMU. */
 	GUEST_ASSERT(pmu_version);
@@ -287,19 +288,16 @@ static void guest_test_arch_event(u8 idx)
 	GUEST_ASSERT_EQ(idx, gp_event.f.bit);
 
 	GUEST_ASSERT(nr_gp_counters);
+	i = kvm_random_u32_in_range(&kvm_rng, 0, nr_gp_counters - 1);
 
-	for (i = 0; i < nr_gp_counters; i++) {
-		u64 eventsel = ARCH_PERFMON_EVENTSEL_OS |
-				    ARCH_PERFMON_EVENTSEL_ENABLE |
-				    intel_pmu_arch_events[idx];
+	eventsel = ARCH_PERFMON_EVENTSEL_OS | ARCH_PERFMON_EVENTSEL_ENABLE |
+		   intel_pmu_arch_events[idx];
 
-		wrmsr(MSR_P6_EVNTSEL0 + i, 0);
-		if (guest_has_perf_global_ctrl)
-			wrmsr(MSR_CORE_PERF_GLOBAL_CTRL, BIT_ULL(i));
+	wrmsr(MSR_P6_EVNTSEL0 + i, 0);
+	if (guest_has_perf_global_ctrl)
+		wrmsr(MSR_CORE_PERF_GLOBAL_CTRL, BIT_ULL(i));
 
-		__guest_test_arch_event(idx, i, base_pmc_msr + i,
-					MSR_P6_EVNTSEL0 + i, eventsel);
-	}
+	__guest_test_arch_event(idx, i, base_pmc_msr + i, MSR_P6_EVNTSEL0 + i, eventsel);
 
 	if (!guest_has_perf_global_ctrl)
 		return;
-- 
2.55.0.571.g244d577d93-goog