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

John Allen
2025-09-08T20:18:33Z

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

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 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