linux-kernel - [PATCH v4 13/20] KVM:VMX: Emulate read and write to CET MSRs

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Message-Id: <20230721030352.72414-14-weijiang.yang@intel.com>
Date:   Thu, 20 Jul 2023 23:03:45 -0400
From:   Yang Weijiang <weijiang.yang@...el.com>
To:     seanjc@...gle.com, pbonzini@...hat.com, peterz@...radead.org,
        john.allen@....com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     rick.p.edgecombe@...el.com, chao.gao@...el.com,
        binbin.wu@...ux.intel.com, weijiang.yang@...el.com
Subject: [PATCH v4 13/20] KVM:VMX: Emulate read and write to CET MSRs

Add VMX specific emulation for CET MSR read and write.
IBT feature is only available on Intel platforms now and the
virtualization interface to the control fields is vensor
specific, so split this part from the common code.

Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
---
 arch/x86/kvm/vmx/vmx.c | 40 ++++++++++++++++++++++++++++++++++++++++
 arch/x86/kvm/x86.c     |  7 -------
 2 files changed, 40 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index c8d9870cfecb..b29817ec6f2e 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2093,6 +2093,21 @@ 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_U_CET:
+	case MSR_IA32_PL0_SSP ... MSR_IA32_PL3_SSP:
+		return kvm_get_msr_common(vcpu, msr_info);
+	case MSR_IA32_S_CET:
+	case MSR_KVM_GUEST_SSP:
+	case MSR_IA32_INT_SSP_TAB:
+		if (kvm_get_msr_common(vcpu, msr_info))
+			return 1;
+		if (msr_info->index == MSR_KVM_GUEST_SSP)
+			msr_info->data = vmcs_readl(GUEST_SSP);
+		else if (msr_info->index == MSR_IA32_S_CET)
+			msr_info->data = vmcs_readl(GUEST_S_CET);
+		else if (msr_info->index == 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;
@@ -2402,6 +2417,31 @@ 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;
+#define VMX_CET_CONTROL_MASK		(~GENMASK_ULL(9, 6))
+#define CET_LEG_BITMAP_BASE(data)	((data) >> 12)
+#define CET_EXCLUSIVE_BITS		(CET_SUPPRESS | CET_WAIT_ENDBR)
+	case MSR_IA32_PL0_SSP ... MSR_IA32_PL3_SSP:
+		return kvm_set_msr_common(vcpu, msr_info);
+		break;
+	case MSR_IA32_U_CET:
+	case MSR_IA32_S_CET:
+	case MSR_KVM_GUEST_SSP:
+	case MSR_IA32_INT_SSP_TAB:
+		if ((msr_index == MSR_IA32_U_CET ||
+		     msr_index == MSR_IA32_S_CET) &&
+		    ((data & ~VMX_CET_CONTROL_MASK) ||
+		     !IS_ALIGNED(CET_LEG_BITMAP_BASE(data), 4) ||
+		     (data & CET_EXCLUSIVE_BITS) == CET_EXCLUSIVE_BITS))
+			return 1;
+		if (kvm_set_msr_common(vcpu, msr_info))
+			return 1;
+		if (msr_index == MSR_KVM_GUEST_SSP)
+			vmcs_writel(GUEST_SSP, data);
+		else if (msr_index == MSR_IA32_S_CET)
+			vmcs_writel(GUEST_S_CET, data);
+		else if (msr_index == 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 70d7c80889d6..e200f22cdaad 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3642,13 +3642,6 @@ static inline bool is_shadow_stack_msr(struct kvm_vcpu *vcpu,
 static bool kvm_cet_is_msr_accessible(struct kvm_vcpu *vcpu,
 				      struct msr_data *msr)
 {
-
-	/*
-	 * This function cannot work without later CET MSR read/write
-	 * emulation patch.
-	 */
-	WARN_ON_ONCE(1);
-
 	if (is_shadow_stack_msr(vcpu, msr)) {
 		if (!kvm_cpu_cap_has(X86_FEATURE_SHSTK))
 			return false;
-- 
2.27.0