[PATCH v2 6/8] KVM: selftests: Test consistency of CPUID with num of fixed counters

[Jinrong Liang <ljr.kernel@xxxxxxxxx>]

From: Jinrong Liang <cloudliang@xxxxxxxxxxx>

Add test to check if non-existent counters can be accessed in guest after
determining the number of Intel generic performance counters by CPUID.
Per SDM, fixed-function performance counter 'i' is supported if ECX[i] ||
(EDX[4:0] > i). KVM doesn't emulate more counters than it can support.

Co-developed-by: Like Xu <likexu@xxxxxxxxxxx>
Signed-off-by: Like Xu <likexu@xxxxxxxxxxx>
Signed-off-by: Jinrong Liang <cloudliang@xxxxxxxxxxx>
---
 .../kvm/x86_64/pmu_basic_functionality_test.c | 42 +++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/tools/testing/selftests/kvm/x86_64/pmu_basic_functionality_test.c b/tools/testing/selftests/kvm/x86_64/pmu_basic_functionality_test.c
index 116437ac2095..e19f8c2774c5 100644
--- a/tools/testing/selftests/kvm/x86_64/pmu_basic_functionality_test.c
+++ b/tools/testing/selftests/kvm/x86_64/pmu_basic_functionality_test.c
@@ -228,10 +228,46 @@ static void test_oob_gp_counter(uint8_t eax_gp_num, uint8_t offset,
 	kvm_vm_free(vm);
 }
 
+static void intel_test_oob_fixed_ctr(uint8_t edx_fix_num,
+				     uint32_t fixed_bitmask, uint64_t expected)
+{
+	struct kvm_vm *vm;
+	struct kvm_vcpu *vcpu;
+	struct kvm_cpuid_entry2 *entry;
+	uint8_t idx = edx_fix_num;
+	bool visible;
+	uint64_t msr_val;
+
+	vm = pmu_vm_create_with_one_vcpu(&vcpu, guest_wr_and_rd_msrs);
+
+	entry = vcpu_get_cpuid_entry(vcpu, 0xa);
+	entry->ecx = fixed_bitmask;
+	entry->edx = (entry->edx & ~FIXED_CTR_NUM_MASK) | edx_fix_num;
+	vcpu_set_cpuid(vcpu);
+
+	/* Per Intel SDM, FxCtr[i]_is_supported := ECX[i] || (EDX[4:0] > i). */
+	visible = (entry->ecx & BIT_ULL(idx) ||
+			((entry->edx & FIXED_CTR_NUM_MASK) > idx));
+
+	/* KVM doesn't emulate more fixed counters than it can support. */
+	if (idx >= X86_INTEL_MAX_FIXED_CTR_NUM)
+		visible = false;
+
+	vcpu_args_set(vcpu, 4, MSR_CORE_PERF_FIXED_CTR0, 0xffff, idx, 1);
+	if (!visible)
+		while (run_vcpu(vcpu, &msr_val) != UCALL_DONE)
+			TEST_ASSERT(msr_val == expected,
+				    "Unexpected when testing fixed counter num.");
+
+	kvm_vm_free(vm);
+}
+
 static void intel_test_counters_num(void)
 {
 	unsigned int i;
+	uint32_t ecx;
 	uint8_t kvm_gp_num = X86_INTEL_MAX_GP_CTR_NUM;
+	uint8_t kvm_fixed_num = X86_INTEL_MAX_FIXED_CTR_NUM;
 
 	TEST_REQUIRE(kvm_gp_num > 2);
 
@@ -254,6 +290,12 @@ static void intel_test_counters_num(void)
 		if (perf_caps[i] == 0)
 			test_oob_gp_counter(0, 2, perf_caps[i], 0);
 	}
+
+	for (ecx = 0; ecx <= X86_INTEL_FIXED_CTRS_BITMASK + 1; ecx++) {
+		intel_test_oob_fixed_ctr(0, ecx, GP_VECTOR);
+		intel_test_oob_fixed_ctr(kvm_fixed_num, ecx, GP_VECTOR);
+		intel_test_oob_fixed_ctr(kvm_fixed_num + 1, ecx, GP_VECTOR);
+	}
 }
 
 static void intel_test_pmu_cpuid(void)
-- 
2.31.1