[PATCH v7 7/7] KVM: x86: Add user-space access interface for CET MSRs

[Yang Weijiang]

There're two different places storing Guest CET states, the states
managed with XSAVES/XRSTORS, as restored/saved
in previous patch, can be read/write directly from/to the MSRs.
For those stored in VMCS fields, they're access via vmcs_read/
vmcs_write.

Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
---
 arch/x86/kvm/vmx/vmx.c | 83 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 44913e4ab558..5265db7cd2af 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1671,6 +1671,49 @@ static int vmx_get_msr_feature(struct kvm_msr_entry *msr)
 	return 0;
 }
 
+static int check_cet_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
+{
+	u64 kvm_xss = kvm_supported_xss();
+
+	switch (msr_info->index) {
+	case MSR_IA32_PL0_SSP ... MSR_IA32_PL2_SSP:
+		if (!(kvm_xss | XFEATURE_MASK_CET_KERNEL))
+			return 1;
+		if (!msr_info->host_initiated &&
+		    !guest_cpuid_has(vcpu, X86_FEATURE_SHSTK))
+			return 1;
+		break;
+	case MSR_IA32_PL3_SSP:
+		if (!(kvm_xss | XFEATURE_MASK_CET_USER))
+			return 1;
+		if (!msr_info->host_initiated &&
+		    !guest_cpuid_has(vcpu, X86_FEATURE_SHSTK))
+			return 1;
+		break;
+	case MSR_IA32_U_CET:
+		if (!(kvm_xss | XFEATURE_MASK_CET_USER))
+			return 1;
+		if (!msr_info->host_initiated &&
+		    !guest_cpuid_has(vcpu, X86_FEATURE_SHSTK) &&
+		    !guest_cpuid_has(vcpu, X86_FEATURE_IBT))
+			return 1;
+		break;
+	case MSR_IA32_S_CET:
+		if (!msr_info->host_initiated &&
+		    !guest_cpuid_has(vcpu, X86_FEATURE_SHSTK) &&
+		    !guest_cpuid_has(vcpu, X86_FEATURE_IBT))
+			return 1;
+		break;
+	case MSR_IA32_INT_SSP_TAB:
+		if (!msr_info->host_initiated &&
+		    !guest_cpuid_has(vcpu, X86_FEATURE_SHSTK))
+			return 1;
+		break;
+	default:
+		return 1;
+	}
+	return 0;
+}
 /*
  * Reads an msr value (of 'msr_index') into 'pdata'.
  * Returns 0 on success, non-0 otherwise.
@@ -1788,6 +1831,26 @@ 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:
+		if (check_cet_msr(vcpu, msr_info))
+			return 1;
+		msr_info->data = vmcs_readl(GUEST_S_CET);
+		break;
+	case MSR_IA32_INT_SSP_TAB:
+		if (check_cet_msr(vcpu, msr_info))
+			return 1;
+		msr_info->data = vmcs_readl(GUEST_INTR_SSP_TABLE);
+		break;
+	case MSR_IA32_U_CET:
+		if (check_cet_msr(vcpu, msr_info))
+			return 1;
+		rdmsrl(MSR_IA32_U_CET, msr_info->data);
+		break;
+	case MSR_IA32_PL0_SSP ... MSR_IA32_PL3_SSP:
+		if (check_cet_msr(vcpu, msr_info))
+			return 1;
+		rdmsrl(msr_info->index, msr_info->data);
+		break;
 	case MSR_TSC_AUX:
 		if (!msr_info->host_initiated &&
 		    !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP))
@@ -2039,6 +2102,26 @@ 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:
+		if (check_cet_msr(vcpu, msr_info))
+			return 1;
+		vmcs_writel(GUEST_S_CET, data);
+		break;
+	case MSR_IA32_INT_SSP_TAB:
+		if (check_cet_msr(vcpu, msr_info))
+			return 1;
+		vmcs_writel(GUEST_INTR_SSP_TABLE, data);
+		break;
+	case MSR_IA32_U_CET:
+		if (check_cet_msr(vcpu, msr_info))
+			return 1;
+		wrmsrl(MSR_IA32_U_CET, data);
+		break;
+	case MSR_IA32_PL0_SSP ... MSR_IA32_PL3_SSP:
+		if (check_cet_msr(vcpu, msr_info))
+			return 1;
+		wrmsrl(msr_info->index, data);
+		break;
 	case MSR_TSC_AUX:
 		if (!msr_info->host_initiated &&
 		    !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP))
-- 
2.17.2