KVM: selftests: Add functional test for Intel's fixed PMU counters

Extend the fixed counters test to verify that supported counters can
actually be enabled in the control MSRs, that unsupported counters cannot,
and that enabled counters actually count.

Co-developed-by: Like Xu <likexu@tencent.com>
Signed-off-by: Like Xu <likexu@tencent.com>
Signed-off-by: Jinrong Liang <cloudliang@tencent.com>
[sean: fold into the rd/wr access test, massage changelog]
Reviewed-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Tested-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://lore.kernel.org/r/20240109230250.424295-21-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

tools/testing/selftests/kvm/x86_64/pmu_counters_test.c

@@ -332,7 +332,6 @@ static void guest_rd_wr_counters(uint32_t base_msr, uint8_t nr_possible_counters
 		vector = wrmsr_safe(msr, 0);
 		GUEST_ASSERT_PMC_MSR_ACCESS(WRMSR, msr, expect_gp, vector);
 	}
-	GUEST_DONE();
 }
 
 static void guest_test_gp_counters(void)
@@ -350,6 +349,7 @@ static void guest_test_gp_counters(void)
 		base_msr = MSR_IA32_PERFCTR0;
 
 	guest_rd_wr_counters(base_msr, MAX_NR_GP_COUNTERS, nr_gp_counters, 0);
+	GUEST_DONE();
 }
 
 static void test_gp_counters(uint8_t pmu_version, uint64_t perf_capabilities,
@@ -373,6 +373,7 @@ static void guest_test_fixed_counters(void)
 {
 	uint64_t supported_bitmask = 0;
 	uint8_t nr_fixed_counters = 0;
+	uint8_t i;
 
 	/* Fixed counters require Architectural vPMU Version 2+. */
 	if (guest_get_pmu_version() >= 2)
@@ -387,6 +388,34 @@ static void guest_test_fixed_counters(void)
 
 	guest_rd_wr_counters(MSR_CORE_PERF_FIXED_CTR0, MAX_NR_FIXED_COUNTERS,
 			     nr_fixed_counters, supported_bitmask);
+
+	for (i = 0; i < MAX_NR_FIXED_COUNTERS; i++) {
+		uint8_t vector;
+		uint64_t val;
+
+		if (i >= nr_fixed_counters && !(supported_bitmask & BIT_ULL(i))) {
+			vector = wrmsr_safe(MSR_CORE_PERF_FIXED_CTR_CTRL,
+					    FIXED_PMC_CTRL(i, FIXED_PMC_KERNEL));
+			__GUEST_ASSERT(vector == GP_VECTOR,
+				       "Expected #GP for counter %u in FIXED_CTR_CTRL", i);
+
+			vector = wrmsr_safe(MSR_CORE_PERF_GLOBAL_CTRL,
+					    FIXED_PMC_GLOBAL_CTRL_ENABLE(i));
+			__GUEST_ASSERT(vector == GP_VECTOR,
+				       "Expected #GP for counter %u in PERF_GLOBAL_CTRL", i);
+			continue;
+		}
+
+		wrmsr(MSR_CORE_PERF_FIXED_CTR0 + i, 0);
+		wrmsr(MSR_CORE_PERF_FIXED_CTR_CTRL, FIXED_PMC_CTRL(i, FIXED_PMC_KERNEL));
+		wrmsr(MSR_CORE_PERF_GLOBAL_CTRL, FIXED_PMC_GLOBAL_CTRL_ENABLE(i));
+		__asm__ __volatile__("loop ." : "+c"((int){NUM_BRANCHES}));
+		wrmsr(MSR_CORE_PERF_GLOBAL_CTRL, 0);
+		val = rdmsr(MSR_CORE_PERF_FIXED_CTR0 + i);
+
+		GUEST_ASSERT_NE(val, 0);
+	}
+	GUEST_DONE();
 }
 
 static void test_fixed_counters(uint8_t pmu_version, uint64_t perf_capabilities,