[PATCH v8 23/26] KVM: selftests: Test PMC virtualization with forced emulation

[Sean Christopherson]

Extend the PMC counters test to use forced emulation to verify that KVM
emulates counter events for instructions retired and branches retired.
Force emulation for only a subset of the measured code to test that KVM
does the right thing when mixing perf events with emulated events.

Reviewed-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
 .../selftests/kvm/x86_64/pmu_counters_test.c  | 44 +++++++++++++------
 1 file changed, 30 insertions(+), 14 deletions(-)

diff --git a/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c b/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c
index 9e9dc4084c0d..cb808ac827ba 100644
--- a/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c
+++ b/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c
@@ -21,6 +21,7 @@
 
 static uint8_t kvm_pmu_version;
 static bool kvm_has_perf_caps;
+static bool is_forced_emulation_enabled;
 
 static struct kvm_vm *pmu_vm_create_with_one_vcpu(struct kvm_vcpu **vcpu,
 						  void *guest_code,
@@ -34,6 +35,7 @@ static struct kvm_vm *pmu_vm_create_with_one_vcpu(struct kvm_vcpu **vcpu,
 	vcpu_init_descriptor_tables(*vcpu);
 
 	sync_global_to_guest(vm, kvm_pmu_version);
+	sync_global_to_guest(vm, is_forced_emulation_enabled);
 
 	/*
 	 * Set PERF_CAPABILITIES before PMU version as KVM disallows enabling
@@ -138,37 +140,50 @@ static void guest_assert_event_count(uint8_t idx,
  * If CLFUSH{,OPT} is supported, flush the cacheline containing (at least) the
  * start of the loop to force LLC references and misses, i.e. to allow testing
  * that those events actually count.
+ *
+ * If forced emulation is enabled (and specified), force emulation on a subset
+ * of the measured code to verify that KVM correctly emulates instructions and
+ * branches retired events in conjunction with hardware also counting said
+ * events.
  */
-#define GUEST_MEASURE_EVENT(_msr, _value, clflush)				\
+#define GUEST_MEASURE_EVENT(_msr, _value, clflush, FEP)				\
 do {										\
 	__asm__ __volatile__("wrmsr\n\t"					\
 			     clflush "\n\t"					\
 			     "mfence\n\t"					\
 			     "1: mov $" __stringify(NUM_BRANCHES) ", %%ecx\n\t"	\
-			     "loop .\n\t"					\
-			     "mov %%edi, %%ecx\n\t"				\
-			     "xor %%eax, %%eax\n\t"				\
-			     "xor %%edx, %%edx\n\t"				\
+			     FEP "loop .\n\t"					\
+			     FEP "mov %%edi, %%ecx\n\t"				\
+			     FEP "xor %%eax, %%eax\n\t"				\
+			     FEP "xor %%edx, %%edx\n\t"				\
 			     "wrmsr\n\t"					\
 			     :: "a"((uint32_t)_value), "d"(_value >> 32),	\
 				"c"(_msr), "D"(_msr)				\
 	);									\
 } while (0)
 
+#define GUEST_TEST_EVENT(_idx, _event, _pmc, _pmc_msr, _ctrl_msr, _value, FEP)	\
+do {										\
+	wrmsr(pmc_msr, 0);							\
+										\
+	if (this_cpu_has(X86_FEATURE_CLFLUSHOPT))				\
+		GUEST_MEASURE_EVENT(_ctrl_msr, _value, "clflushopt 1f", FEP);	\
+	else if (this_cpu_has(X86_FEATURE_CLFLUSH))				\
+		GUEST_MEASURE_EVENT(_ctrl_msr, _value, "clflush 1f", FEP);	\
+	else									\
+		GUEST_MEASURE_EVENT(_ctrl_msr, _value, "nop", FEP);		\
+										\
+	guest_assert_event_count(_idx, _event, _pmc, _pmc_msr);			\
+} while (0)
+
 static void __guest_test_arch_event(uint8_t idx, struct kvm_x86_pmu_feature event,
 				    uint32_t pmc, uint32_t pmc_msr,
 				    uint32_t ctrl_msr, uint64_t ctrl_msr_value)
 {
-	wrmsr(pmc_msr, 0);
+	GUEST_TEST_EVENT(idx, event, pmc, pmc_msr, ctrl_msr, ctrl_msr_value, "");
 
-	if (this_cpu_has(X86_FEATURE_CLFLUSHOPT))
-		GUEST_MEASURE_EVENT(ctrl_msr, ctrl_msr_value, "clflushopt 1f");
-	else if (this_cpu_has(X86_FEATURE_CLFLUSH))
-		GUEST_MEASURE_EVENT(ctrl_msr, ctrl_msr_value, "clflush 1f");
-	else
-		GUEST_MEASURE_EVENT(ctrl_msr, ctrl_msr_value, "nop");
-
-	guest_assert_event_count(idx, event, pmc, pmc_msr);
+	if (is_forced_emulation_enabled)
+		GUEST_TEST_EVENT(idx, event, pmc, pmc_msr, ctrl_msr, ctrl_msr_value, KVM_FEP);
 }
 
 #define X86_PMU_FEATURE_NULL						\
@@ -553,6 +568,7 @@ int main(int argc, char *argv[])
 
 	kvm_pmu_version = kvm_cpu_property(X86_PROPERTY_PMU_VERSION);
 	kvm_has_perf_caps = kvm_cpu_has(X86_FEATURE_PDCM);
+	is_forced_emulation_enabled = kvm_is_forced_emulation_enabled();
 
 	test_intel_counters();
 
-- 
2.42.0.869.gea05f2083d-goog