[PATCH v8 7/7] KVM: X86: Add user-space access interface for CET MSRs

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There're two different places storing Guest CET states, 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 | 140 +++++++++++++++++++++++++++++++++++++++++
 arch/x86/kvm/x86.c     |   3 +
 2 files changed, 143 insertions(+)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index bfb1b922a9ac..71aba264b5d2 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1671,6 +1671,98 @@ static int vmx_get_msr_feature(struct kvm_msr_entry *msr)
 	return 0;
 }
 
+#define CET_MSR_RSVD_BITS_1    0x3
+#define CET_MSR_RSVD_BITS_2   (0xF << 6)
+
+static bool cet_msr_write_allowed(struct kvm_vcpu *vcpu, struct msr_data *msr)
+{
+	u32 index = msr->index;
+	u64 data = msr->data;
+	u32 high_word = data >> 32;
+
+	if ((index == MSR_IA32_U_CET || index == MSR_IA32_S_CET) &&
+	    (data & CET_MSR_RSVD_BITS_2))
+		return false;
+
+	if (is_64_bit_mode(vcpu)) {
+		if (is_noncanonical_address(data & PAGE_MASK, vcpu))
+			return false;
+		else if ((index == MSR_IA32_PL0_SSP ||
+			  index == MSR_IA32_PL1_SSP ||
+			  index == MSR_IA32_PL2_SSP ||
+			  index == MSR_IA32_PL3_SSP) &&
+			  (data & CET_MSR_RSVD_BITS_1))
+			return false;
+	} else {
+		if (msr->index == MSR_IA32_INT_SSP_TAB)
+			return false;
+		else if ((index == MSR_IA32_U_CET ||
+			  index == MSR_IA32_S_CET ||
+			  index == MSR_IA32_PL0_SSP ||
+			  index == MSR_IA32_PL1_SSP ||
+			  index == MSR_IA32_PL2_SSP ||
+			  index == MSR_IA32_PL3_SSP) &&
+			  (high_word & ~0ul))
+			return false;
+	}
+
+	return true;
+}
+
+static bool cet_msr_access_allowed(struct kvm_vcpu *vcpu, struct msr_data *msr)
+{
+	u64 kvm_xss;
+	u32 index = msr->index;
+
+	if (is_guest_mode(vcpu))
+		return false;
+
+	kvm_xss = kvm_supported_xss();
+
+	switch (index) {
+	case MSR_IA32_PL0_SSP ... MSR_IA32_PL3_SSP:
+		if (!boot_cpu_has(X86_FEATURE_SHSTK))
+			return false;
+		if (!msr->host_initiated) {
+			if (!guest_cpuid_has(vcpu, X86_FEATURE_SHSTK))
+				return false;
+		} else {
+			if (index == MSR_IA32_PL3_SSP) {
+				if (!(kvm_xss & XFEATURE_MASK_CET_USER))
+					return false;
+			} else {
+				if (!(kvm_xss & XFEATURE_MASK_CET_KERNEL))
+					return false;
+			}
+		}
+		break;
+	case MSR_IA32_U_CET:
+	case MSR_IA32_S_CET:
+		if (!boot_cpu_has(X86_FEATURE_SHSTK) &&
+		    !boot_cpu_has(X86_FEATURE_IBT))
+			return false;
+
+		if (!msr->host_initiated) {
+			if (!guest_cpuid_has(vcpu, X86_FEATURE_SHSTK) &&
+			    !guest_cpuid_has(vcpu, X86_FEATURE_IBT))
+				return false;
+		} else if (index == MSR_IA32_U_CET &&
+			   !(kvm_xss & XFEATURE_MASK_CET_USER))
+			return false;
+		break;
+	case MSR_IA32_INT_SSP_TAB:
+		if (!boot_cpu_has(X86_FEATURE_SHSTK))
+			return false;
+
+		if (!msr->host_initiated &&
+		    !guest_cpuid_has(vcpu, X86_FEATURE_SHSTK))
+			return false;
+		break;
+	default:
+		return false;
+	}
+	return true;
+}
 /*
  * Reads an msr value (of 'msr_index') into 'pdata'.
  * Returns 0 on success, non-0 otherwise.
@@ -1788,6 +1880,26 @@ 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 (!cet_msr_access_allowed(vcpu, msr_info))
+			return 1;
+		msr_info->data = vmcs_readl(GUEST_S_CET);
+		break;
+	case MSR_IA32_INT_SSP_TAB:
+		if (!cet_msr_access_allowed(vcpu, msr_info))
+			return 1;
+		msr_info->data = vmcs_readl(GUEST_INTR_SSP_TABLE);
+		break;
+	case MSR_IA32_U_CET:
+		if (!cet_msr_access_allowed(vcpu, msr_info))
+			return 1;
+		rdmsrl(MSR_IA32_U_CET, msr_info->data);
+		break;
+	case MSR_IA32_PL0_SSP ... MSR_IA32_PL3_SSP:
+		if (!cet_msr_access_allowed(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 +2151,34 @@ 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 (!cet_msr_access_allowed(vcpu, msr_info))
+			return 1;
+		if (!cet_msr_write_allowed(vcpu, msr_info))
+			return 1;
+		vmcs_writel(GUEST_S_CET, data);
+		break;
+	case MSR_IA32_INT_SSP_TAB:
+		if (!cet_msr_access_allowed(vcpu, msr_info))
+			return 1;
+		if (!cet_msr_write_allowed(vcpu, msr_info))
+			return 1;
+		vmcs_writel(GUEST_INTR_SSP_TABLE, data);
+		break;
+	case MSR_IA32_U_CET:
+		if (!cet_msr_access_allowed(vcpu, msr_info))
+			return 1;
+		if (!cet_msr_write_allowed(vcpu, msr_info))
+			return 1;
+		wrmsrl(MSR_IA32_U_CET, data);
+		break;
+	case MSR_IA32_PL0_SSP ... MSR_IA32_PL3_SSP:
+		if (!cet_msr_access_allowed(vcpu, msr_info))
+			return 1;
+		if (!cet_msr_write_allowed(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))
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 6275a75d5802..1bbe4550da90 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1143,6 +1143,9 @@ static u32 msrs_to_save[] = {
 	MSR_IA32_RTIT_ADDR1_A, MSR_IA32_RTIT_ADDR1_B,
 	MSR_IA32_RTIT_ADDR2_A, MSR_IA32_RTIT_ADDR2_B,
 	MSR_IA32_RTIT_ADDR3_A, MSR_IA32_RTIT_ADDR3_B,
+	MSR_IA32_XSS, MSR_IA32_U_CET, MSR_IA32_S_CET,
+	MSR_IA32_PL0_SSP, MSR_IA32_PL1_SSP, MSR_IA32_PL2_SSP,
+	MSR_IA32_PL3_SSP, MSR_IA32_INT_SSP_TAB,
 };
 
 static unsigned num_msrs_to_save;
-- 
2.17.2




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