KVM: SVM: Add a helper to get LBR field pointer to dedup MSR accesses

Add a helper to get a pointer to the corresponding VMCB field given an LBR
MSR index, and use it to dedup the handling in svm_{g,s}et_msr().

No functional change intended.

Suggested-by: Yosry Ahmed <yosry@kernel.org>
Reviewed-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260310220414.2569208-1-seanjc@google.com
[sean: use KVM_BUG_ON() instead of BUILD_BUG(), clang ain't smart enough]
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 4bf0f5d7167faa3a98b1f8dc3590b971d33d6f44..5e6bd7fca2982f78b9b76f1d47b7c2e0a30178bd 100644 (file)
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2751,6 +2751,24 @@ static int svm_get_feature_msr(u32 msr, u64 *data)
        return 0;
 }
 
+static u64 *svm_vmcb_lbr(struct vcpu_svm *svm, u32 msr)
+{
+       switch (msr) {
+       case MSR_IA32_LASTBRANCHFROMIP:
+               return &svm->vmcb->save.br_from;
+       case MSR_IA32_LASTBRANCHTOIP:
+               return &svm->vmcb->save.br_to;
+       case MSR_IA32_LASTINTFROMIP:
+               return &svm->vmcb->save.last_excp_from;
+       case MSR_IA32_LASTINTTOIP:
+               return &svm->vmcb->save.last_excp_to;
+       default:
+               break;
+       }
+       KVM_BUG_ON(1, svm->vcpu.kvm);
+       return &svm->vmcb->save.br_from;
+}
+
 static bool sev_es_prevent_msr_access(struct kvm_vcpu *vcpu,
                                      struct msr_data *msr_info)
 {
@@ -2827,16 +2845,10 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
                msr_info->data = lbrv ? svm->vmcb->save.dbgctl : 0;
                break;
        case MSR_IA32_LASTBRANCHFROMIP:
-               msr_info->data = lbrv ? svm->vmcb->save.br_from : 0;
-               break;
        case MSR_IA32_LASTBRANCHTOIP:
-               msr_info->data = lbrv ? svm->vmcb->save.br_to : 0;
-               break;
        case MSR_IA32_LASTINTFROMIP:
-               msr_info->data = lbrv ? svm->vmcb->save.last_excp_from : 0;
-               break;
        case MSR_IA32_LASTINTTOIP:
-               msr_info->data = lbrv ? svm->vmcb->save.last_excp_to : 0;
+               msr_info->data = lbrv ? *svm_vmcb_lbr(svm, msr_info->index) : 0;
                break;
        case MSR_VM_HSAVE_PA:
                msr_info->data = svm->nested.hsave_msr;
@@ -3112,35 +3124,14 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
                svm_update_lbrv(vcpu);
                break;
        case MSR_IA32_LASTBRANCHFROMIP:
-               if (!lbrv)
-                       return KVM_MSR_RET_UNSUPPORTED;
-               if (!msr->host_initiated)
-                       return 1;
-               svm->vmcb->save.br_from = data;
-               vmcb_mark_dirty(svm->vmcb, VMCB_LBR);
-               break;
        case MSR_IA32_LASTBRANCHTOIP:
-               if (!lbrv)
-                       return KVM_MSR_RET_UNSUPPORTED;
-               if (!msr->host_initiated)
-                       return 1;
-               svm->vmcb->save.br_to = data;
-               vmcb_mark_dirty(svm->vmcb, VMCB_LBR);
-               break;
        case MSR_IA32_LASTINTFROMIP:
-               if (!lbrv)
-                       return KVM_MSR_RET_UNSUPPORTED;
-               if (!msr->host_initiated)
-                       return 1;
-               svm->vmcb->save.last_excp_from = data;
-               vmcb_mark_dirty(svm->vmcb, VMCB_LBR);
-               break;
        case MSR_IA32_LASTINTTOIP:
                if (!lbrv)
                        return KVM_MSR_RET_UNSUPPORTED;
                if (!msr->host_initiated)
                        return 1;
-               svm->vmcb->save.last_excp_to = data;
+               *svm_vmcb_lbr(svm, ecx) = data;
                vmcb_mark_dirty(svm->vmcb, VMCB_LBR);
                break;
        case MSR_VM_HSAVE_PA: