linux-kernel - [PATCH v4 1/5] KVM: x86: SVM: Emulate reads and writes to shadow stack MSRs

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Message-ID: <20250908201750.98824-2-john.allen@amd.com>
Date: Mon, 8 Sep 2025 20:17:46 +0000
From: John Allen <john.allen@....com>
To: <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <x86@...nel.org>,
	<seanjc@...gle.com>, <pbonzini@...hat.com>, <dave.hansen@...el.com>
CC: <rick.p.edgecombe@...el.com>, <mlevitsk@...hat.com>,
	<weijiang.yang@...el.com>, <chao.gao@...el.com>, <bp@...en8.de>,
	<dave.hansen@...ux.intel.com>, <hpa@...or.com>, <mingo@...hat.com>,
	<tglx@...utronix.de>, <thomas.lendacky@....com>, John Allen
	<john.allen@....com>
Subject: [PATCH v4 1/5] KVM: x86: SVM: Emulate reads and writes to shadow stack MSRs

Emulate shadow stack MSR access by reading and writing to the
corresponding fields in the VMCB.

Signed-off-by: John Allen <john.allen@....com>
---
 arch/x86/kvm/svm/svm.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index e4af4907c7d8..fee60f3378e1 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2767,6 +2767,15 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		if (guest_cpuid_is_intel_compatible(vcpu))
 			msr_info->data |= (u64)svm->sysenter_esp_hi << 32;
 		break;
+	case MSR_IA32_S_CET:
+		msr_info->data = svm->vmcb->save.s_cet;
+		break;
+	case MSR_IA32_INT_SSP_TAB:
+		msr_info->data = svm->vmcb->save.isst_addr;
+		break;
+	case MSR_KVM_INTERNAL_GUEST_SSP:
+		msr_info->data = svm->vmcb->save.ssp;
+		break;
 	case MSR_TSC_AUX:
 		msr_info->data = svm->tsc_aux;
 		break;
@@ -2999,6 +3008,15 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 		svm->vmcb01.ptr->save.sysenter_esp = (u32)data;
 		svm->sysenter_esp_hi = guest_cpuid_is_intel_compatible(vcpu) ? (data >> 32) : 0;
 		break;
+	case MSR_IA32_S_CET:
+		svm->vmcb->save.s_cet = data;
+		break;
+	case MSR_IA32_INT_SSP_TAB:
+		svm->vmcb->save.isst_addr = data;
+		break;
+	case MSR_KVM_INTERNAL_GUEST_SSP:
+		svm->vmcb->save.ssp = data;
+		break;
 	case MSR_TSC_AUX:
 		/*
 		 * TSC_AUX is always virtualized for SEV-ES guests when the
-- 
2.47.3