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From:   John Allen <john.allen@amd.com>
To:     <kvm@vger.kernel.org>
CC:     <linux-kernel@vger.kernel.org>, <pbonzini@redhat.com>,
        <weijiang.yang@intel.com>, <rick.p.edgecombe@intel.com>,
        <seanjc@google.com>, <x86@kernel.org>, <thomas.lendacky@amd.com>,
        <bp@alien8.de>, John Allen <john.allen@amd.com>
Subject: [PATCH 1/9] KVM: x86: SVM: Emulate reads and writes to shadow stack MSRs
Date:   Tue, 10 Oct 2023 20:02:12 +0000
Message-ID: <20231010200220.897953-2-john.allen@amd.com>
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Set up interception of shadow stack MSRs. In the event that shadow stack
is unsupported on the host or the MSRs are otherwise inaccessible, the
interception code will return an error. In certain circumstances such as
host initiated MSR reads or writes, the interception code will get or
set the requested MSR value.

Signed-off-by: John Allen <john.allen@amd.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 f283eb47f6ac..6a0d225311bc 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2859,6 +2859,15 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		if (guest_cpuid_is_intel(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_SSP:
+		msr_info->data = svm->vmcb->save.ssp;
+		break;
 	case MSR_TSC_AUX:
 		msr_info->data = svm->tsc_aux;
 		break;
@@ -3085,6 +3094,15 @@ 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(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_SSP:
+		svm->vmcb->save.ssp = data;
+		break;
 	case MSR_TSC_AUX:
 		/*
 		 * TSC_AUX is usually changed only during boot and never read
-- 
2.40.1