[PATCH v2 3/3] KVM: selftests: Test Hyper-V invariant TSC control

[Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>]

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/x86_64/hyperv_features.c    | 67 +++++++++++++++++++
 1 file changed, 67 insertions(+)

diff --git a/tools/testing/selftests/kvm/x86_64/hyperv_features.c b/tools/testing/selftests/kvm/x86_64/hyperv_features.c
index 4ec4776662a4..26e8c5f7677e 100644
--- a/tools/testing/selftests/kvm/x86_64/hyperv_features.c
+++ b/tools/testing/selftests/kvm/x86_64/hyperv_features.c
@@ -15,6 +15,9 @@
 
 #define LINUX_OS_ID ((u64)0x8100 << 48)
 
+/* CPUID.80000007H:EDX */
+#define X86_FEATURE_INVTSC (1 << 8)
+
 static inline uint8_t hypercall(u64 control, vm_vaddr_t input_address,
 				vm_vaddr_t output_address, uint64_t *hv_status)
 {
@@ -60,6 +63,24 @@ static void guest_msr(struct msr_data *msr)
 		GUEST_ASSERT_2(!vector, msr->idx, vector);
 	else
 		GUEST_ASSERT_2(vector == GP_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) {
+		u32 eax, ebx, ecx, edx;
+
+		cpuid(0x80000007, &eax, &ebx, &ecx, &edx);
+
+		/*
+		 * TSC invariant bit is present without the feature (legacy) or
+		 * when the feature is present and enabled.
+		 */
+		if ((!msr->should_not_gp && !msr->write) || (msr->write && msr->write_val == 1))
+			GUEST_ASSERT(edx & X86_FEATURE_INVTSC);
+		else
+			GUEST_ASSERT(!(edx & X86_FEATURE_INVTSC));
+	}
+
+
 	GUEST_DONE();
 }
 
@@ -104,6 +125,15 @@ static void vcpu_reset_hv_cpuid(struct kvm_vcpu *vcpu)
 	vcpu_clear_cpuid_entry(vcpu, HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES);
 }
 
+static bool guest_has_invtsc(void)
+{
+	const struct kvm_cpuid_entry2 *cpuid;
+
+	cpuid = kvm_get_supported_cpuid_entry(0x80000007);
+
+	return cpuid->edx & X86_FEATURE_INVTSC;
+}
+
 static void guest_test_msrs_access(void)
 {
 	struct kvm_cpuid2 *prev_cpuid = NULL;
@@ -115,6 +145,7 @@ static void guest_test_msrs_access(void)
 	int stage = 0;
 	vm_vaddr_t msr_gva;
 	struct msr_data *msr;
+	bool has_invtsc = guest_has_invtsc();
 
 	while (true) {
 		vm = vm_create_with_one_vcpu(&vcpu, guest_msr);
@@ -429,6 +460,42 @@ 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->should_not_gp = 0;
+			break;
+		case 45:
+			/* MSR is vailable when CPUID feature bit is set */
+			if (!has_invtsc)
+				continue;
+			feat->eax |= HV_ACCESS_TSC_INVARIANT;
+			msr->idx = HV_X64_MSR_TSC_INVARIANT_CONTROL;
+			msr->write = 0;
+			msr->should_not_gp = 1;
+			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->should_not_gp = 0;
+			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->should_not_gp = 1;
+			break;
+
+		default:
 			kvm_vm_free(vm);
 			return;
 		}
-- 
2.37.2