[PATCH v6 19/25] KVM: VMX: Emulate read and write to CET MSRs

[Yang Weijiang]

Add emulation interface for CET MSR access. The emulation code is split
into common part and vendor specific part. The former does common check
for MSRs and reads/writes directly from/to XSAVE-managed MSRs via the
helpers while the latter accesses the MSRs linked to VMCS fields.

Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
---
 arch/x86/kvm/vmx/vmx.c | 18 +++++++++++
 arch/x86/kvm/x86.c     | 71 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 89 insertions(+)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index fd5893b3a2c8..9f4b56337251 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2111,6 +2111,15 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		else
 			msr_info->data = vmx->pt_desc.guest.addr_a[index / 2];
 		break;
+	case MSR_IA32_S_CET:
+		msr_info->data = vmcs_readl(GUEST_S_CET);
+		break;
+	case MSR_KVM_SSP:
+		msr_info->data = vmcs_readl(GUEST_SSP);
+		break;
+	case MSR_IA32_INT_SSP_TAB:
+		msr_info->data = vmcs_readl(GUEST_INTR_SSP_TABLE);
+		break;
 	case MSR_IA32_DEBUGCTLMSR:
 		msr_info->data = vmcs_read64(GUEST_IA32_DEBUGCTL);
 		break;
@@ -2420,6 +2429,15 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		else
 			vmx->pt_desc.guest.addr_a[index / 2] = data;
 		break;
+	case MSR_IA32_S_CET:
+		vmcs_writel(GUEST_S_CET, data);
+		break;
+	case MSR_KVM_SSP:
+		vmcs_writel(GUEST_SSP, data);
+		break;
+	case MSR_IA32_INT_SSP_TAB:
+		vmcs_writel(GUEST_INTR_SSP_TABLE, data);
+		break;
 	case MSR_IA32_PERF_CAPABILITIES:
 		if (data && !vcpu_to_pmu(vcpu)->version)
 			return 1;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 73b45351c0fc..c85ee42ab4f1 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1847,6 +1847,11 @@ bool kvm_msr_allowed(struct kvm_vcpu *vcpu, u32 index, u32 type)
 }
 EXPORT_SYMBOL_GPL(kvm_msr_allowed);
 
+#define CET_US_RESERVED_BITS		GENMASK(9, 6)
+#define CET_US_SHSTK_MASK_BITS		GENMASK(1, 0)
+#define CET_US_IBT_MASK_BITS		(GENMASK_ULL(5, 2) | GENMASK_ULL(63, 10))
+#define CET_US_LEGACY_BITMAP_BASE(data)	((data) >> 12)
+
 /*
  * Write @data into the MSR specified by @index.  Select MSR specific fault
  * checks are bypassed if @host_initiated is %true.
@@ -1856,6 +1861,7 @@ EXPORT_SYMBOL_GPL(kvm_msr_allowed);
 static int __kvm_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data,
 			 bool host_initiated)
 {
+	bool host_msr_reset = host_initiated && data == 0;
 	struct msr_data msr;
 
 	switch (index) {
@@ -1906,6 +1912,46 @@ static int __kvm_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data,
 
 		data = (u32)data;
 		break;
+	case MSR_IA32_U_CET:
+	case MSR_IA32_S_CET:
+		if (host_msr_reset && (kvm_cpu_cap_has(X86_FEATURE_SHSTK) ||
+				       kvm_cpu_cap_has(X86_FEATURE_IBT)))
+			break;
+		if (!guest_can_use(vcpu, X86_FEATURE_SHSTK) &&
+		    !guest_can_use(vcpu, X86_FEATURE_IBT))
+			return 1;
+		if (data & CET_US_RESERVED_BITS)
+			return 1;
+		if (!guest_can_use(vcpu, X86_FEATURE_SHSTK) &&
+		    (data & CET_US_SHSTK_MASK_BITS))
+			return 1;
+		if (!guest_can_use(vcpu, X86_FEATURE_IBT) &&
+		    (data & CET_US_IBT_MASK_BITS))
+			return 1;
+		if (!IS_ALIGNED(CET_US_LEGACY_BITMAP_BASE(data), 4))
+			return 1;
+
+		/* IBT can be suppressed iff the TRACKER isn't WAIT_ENDBR. */
+		if ((data & CET_SUPPRESS) && (data & CET_WAIT_ENDBR))
+			return 1;
+		break;
+	case MSR_IA32_INT_SSP_TAB:
+		if (!guest_cpuid_has(vcpu, X86_FEATURE_LM))
+			return 1;
+		fallthrough;
+	case MSR_IA32_PL0_SSP ... MSR_IA32_PL3_SSP:
+	case MSR_KVM_SSP:
+		if (host_msr_reset && kvm_cpu_cap_has(X86_FEATURE_SHSTK))
+			break;
+		if (!guest_can_use(vcpu, X86_FEATURE_SHSTK))
+			return 1;
+		if (index == MSR_KVM_SSP && !host_initiated)
+			return 1;
+		if (is_noncanonical_address(data, vcpu))
+			return 1;
+		if (index != MSR_IA32_INT_SSP_TAB && !IS_ALIGNED(data, 4))
+			return 1;
+		break;
 	}
 
 	msr.data = data;
@@ -1949,6 +1995,23 @@ static int __kvm_get_msr(struct kvm_vcpu *vcpu, u32 index, u64 *data,
 		    !guest_cpuid_has(vcpu, X86_FEATURE_RDPID))
 			return 1;
 		break;
+	case MSR_IA32_U_CET:
+	case MSR_IA32_S_CET:
+		if (!guest_can_use(vcpu, X86_FEATURE_IBT) &&
+		    !guest_can_use(vcpu, X86_FEATURE_SHSTK))
+			return 1;
+		break;
+	case MSR_IA32_INT_SSP_TAB:
+		if (!guest_cpuid_has(vcpu, X86_FEATURE_LM))
+			return 1;
+		fallthrough;
+	case MSR_IA32_PL0_SSP ... MSR_IA32_PL3_SSP:
+	case MSR_KVM_SSP:
+		if (!guest_can_use(vcpu, X86_FEATURE_SHSTK))
+			return 1;
+		if (index == MSR_KVM_SSP && !host_initiated)
+			return 1;
+		break;
 	}
 
 	msr.index = index;
@@ -4009,6 +4072,10 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		vcpu->arch.guest_fpu.xfd_err = data;
 		break;
 #endif
+	case MSR_IA32_U_CET:
+	case MSR_IA32_PL0_SSP ... MSR_IA32_PL3_SSP:
+		kvm_set_xstate_msr(vcpu, msr_info);
+		break;
 	default:
 		if (kvm_pmu_is_valid_msr(vcpu, msr))
 			return kvm_pmu_set_msr(vcpu, msr_info);
@@ -4365,6 +4432,10 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		msr_info->data = vcpu->arch.guest_fpu.xfd_err;
 		break;
 #endif
+	case MSR_IA32_U_CET:
+	case MSR_IA32_PL0_SSP ... MSR_IA32_PL3_SSP:
+		kvm_get_xstate_msr(vcpu, msr_info);
+		break;
 	default:
 		if (kvm_pmu_is_valid_msr(vcpu, msr_info->index))
 			return kvm_pmu_get_msr(vcpu, msr_info);
-- 
2.27.0