[PATCH v3 6/6] KVM: selftests: Test Hyper-V invariant TSC control

[Vitaly Kuznetsov]

Add a test for the newly introduced Hyper-V invariant TSC control feature:
- HV_X64_MSR_TSC_INVARIANT_CONTROL is not available without
 HV_ACCESS_TSC_INVARIANT CPUID bit set and available with it.
- BIT(0) of HV_X64_MSR_TSC_INVARIANT_CONTROL controls the filtering of
architectural invariant TSC (CPUID.80000007H:EDX[8]) bit.

Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
 .../selftests/kvm/include/x86_64/hyperv.h     |  3 +
 .../selftests/kvm/include/x86_64/processor.h  |  1 +
 .../selftests/kvm/x86_64/hyperv_features.c    | 58 +++++++++++++++++--
 3 files changed, 58 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/x86_64/hyperv.h b/tools/testing/selftests/kvm/include/x86_64/hyperv.h
index 843748dde1ff..8368d65afbe4 100644
--- a/tools/testing/selftests/kvm/include/x86_64/hyperv.h
+++ b/tools/testing/selftests/kvm/include/x86_64/hyperv.h
@@ -232,4 +232,7 @@
 /* hypercall options */
 #define HV_HYPERCALL_FAST_BIT		BIT(16)
 
+/* HV_X64_MSR_TSC_INVARIANT_CONTROL bits */
+#define HV_INVARIANT_TSC_EXPOSED               BIT_ULL(0)
+
 #endif /* !SELFTEST_KVM_HYPERV_H */
diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h
index 0cbc71b7af50..8d106380b0af 100644
--- a/tools/testing/selftests/kvm/include/x86_64/processor.h
+++ b/tools/testing/selftests/kvm/include/x86_64/processor.h
@@ -128,6 +128,7 @@ struct kvm_x86_cpu_feature {
 #define	X86_FEATURE_GBPAGES		KVM_X86_CPU_FEATURE(0x80000001, 0, EDX, 26)
 #define	X86_FEATURE_RDTSCP		KVM_X86_CPU_FEATURE(0x80000001, 0, EDX, 27)
 #define	X86_FEATURE_LM			KVM_X86_CPU_FEATURE(0x80000001, 0, EDX, 29)
+#define	X86_FEATURE_INVTSC		KVM_X86_CPU_FEATURE(0x80000007, 0, EDX, 8)
 #define	X86_FEATURE_RDPRU		KVM_X86_CPU_FEATURE(0x80000008, 0, EBX, 4)
 #define	X86_FEATURE_AMD_IBPB		KVM_X86_CPU_FEATURE(0x80000008, 0, EBX, 12)
 #define	X86_FEATURE_NPT			KVM_X86_CPU_FEATURE(0x8000000A, 0, EDX, 0)
diff --git a/tools/testing/selftests/kvm/x86_64/hyperv_features.c b/tools/testing/selftests/kvm/x86_64/hyperv_features.c
index d4bd18bc580d..18b44450dfb8 100644
--- a/tools/testing/selftests/kvm/x86_64/hyperv_features.c
+++ b/tools/testing/selftests/kvm/x86_64/hyperv_features.c
@@ -46,20 +46,33 @@ struct hcall_data {
 
 static void guest_msr(struct msr_data *msr)
 {
-	uint64_t ignored;
+	uint64_t msr_val = 0;
 	uint8_t vector;
 
 	GUEST_ASSERT(msr->idx);
 
-	if (!msr->write)
-		vector = rdmsr_safe(msr->idx, &ignored);
-	else
+	if (!msr->write) {
+		vector = rdmsr_safe(msr->idx, &msr_val);
+	} else {
 		vector = wrmsr_safe(msr->idx, msr->write_val);
+		if (!vector)
+			msr_val = msr->write_val;
+	}
 
 	if (msr->fault_expected)
 		GUEST_ASSERT_2(vector == GP_VECTOR, msr->idx, vector);
 	else
 		GUEST_ASSERT_2(!vector, msr->idx, vector);
+
+	/* Invariant TSC bit appears when TSC invariant control MSR is written to */
+	if (msr->idx == HV_X64_MSR_TSC_INVARIANT_CONTROL) {
+		if (!this_cpu_has(HV_ACCESS_TSC_INVARIANT))
+			GUEST_ASSERT(this_cpu_has(X86_FEATURE_INVTSC));
+		else
+			GUEST_ASSERT(this_cpu_has(X86_FEATURE_INVTSC) ==
+				     !!(msr_val & HV_INVARIANT_TSC_EXPOSED));
+	}
+
 	GUEST_DONE();
 }
 
@@ -114,6 +127,7 @@ static void guest_test_msrs_access(void)
 	int stage = 0;
 	vm_vaddr_t msr_gva;
 	struct msr_data *msr;
+	bool has_invtsc = kvm_cpu_has(X86_FEATURE_INVTSC);
 
 	while (true) {
 		vm = vm_create_with_one_vcpu(&vcpu, guest_msr);
@@ -425,6 +439,42 @@ static void guest_test_msrs_access(void)
 			break;
 
 		case 44:
+			/* MSR is not available when CPUID feature bit is unset */
+			if (!has_invtsc)
+				continue;
+			msr->idx = HV_X64_MSR_TSC_INVARIANT_CONTROL;
+			msr->write = 0;
+			msr->fault_expected = 1;
+			break;
+		case 45:
+			/* MSR is vailable when CPUID feature bit is set */
+			if (!has_invtsc)
+				continue;
+			vcpu_set_cpuid_feature(vcpu, HV_ACCESS_TSC_INVARIANT);
+			msr->idx = HV_X64_MSR_TSC_INVARIANT_CONTROL;
+			msr->write = 0;
+			msr->fault_expected = 0;
+			break;
+		case 46:
+			/* Writing bits other than 0 is forbidden */
+			if (!has_invtsc)
+				continue;
+			msr->idx = HV_X64_MSR_TSC_INVARIANT_CONTROL;
+			msr->write = 1;
+			msr->write_val = 0xdeadbeef;
+			msr->fault_expected = 1;
+			break;
+		case 47:
+			/* Setting bit 0 enables the feature */
+			if (!has_invtsc)
+				continue;
+			msr->idx = HV_X64_MSR_TSC_INVARIANT_CONTROL;
+			msr->write = 1;
+			msr->write_val = 1;
+			msr->fault_expected = 0;
+			break;
+
+		default:
 			kvm_vm_free(vm);
 			return;
 		}
-- 
2.37.2