KVM: 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@amd.com>
[sean: mark VMCB_CET dirty/clean as appropriate]
Link: https://lore.kernel.org/r/20250919223258.1604852-36-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index ff4925a7bf96fd06fba289754f48c63808c6b78f..b977ea4a46e7a34e6b6b3cfb110f9d01a0caae45 100644 (file)
--- 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 +3008,18 @@ 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;
+               vmcb_mark_dirty(svm->vmcb01.ptr, VMCB_CET);
+               break;
+       case MSR_IA32_INT_SSP_TAB:
+               svm->vmcb->save.isst_addr = data;
+               vmcb_mark_dirty(svm->vmcb01.ptr, VMCB_CET);
+               break;
+       case MSR_KVM_INTERNAL_GUEST_SSP:
+               svm->vmcb->save.ssp = data;
+               vmcb_mark_dirty(svm->vmcb01.ptr, VMCB_CET);
+               break;
        case MSR_TSC_AUX:
                /*
                 * TSC_AUX is always virtualized for SEV-ES guests when the

diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 10d5cbc259e1ca82221f3a4007e64705713b824c..37de6a4a26656061fafef9eb6f09c83036b9d41c 100644 (file)
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -74,6 +74,7 @@ enum {
                          * AVIC PHYSICAL_TABLE pointer,
                          * AVIC LOGICAL_TABLE pointer
                          */
+       VMCB_CET,        /* S_CET, SSP, ISST_ADDR */
        VMCB_SW = 31,    /* Reserved for hypervisor/software use */
 };
 
@@ -82,7 +83,7 @@ enum {
        (1U << VMCB_ASID) | (1U << VMCB_INTR) |                 \
        (1U << VMCB_NPT) | (1U << VMCB_CR) | (1U << VMCB_DR) |  \
        (1U << VMCB_DT) | (1U << VMCB_SEG) | (1U << VMCB_CR2) | \
-       (1U << VMCB_LBR) | (1U << VMCB_AVIC) |                  \
+       (1U << VMCB_LBR) | (1U << VMCB_AVIC) | (1U << VMCB_CET) | \
        (1U << VMCB_SW))
 
 /* TPR and CR2 are always written before VMRUN */