KVM: x86: nSVM: refactor svm_leave_smm and smm_enter_smm

Use return statements instead of nested if, and fix error
path to free all the maps that were allocated.
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210913140954.165665-2-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm/svm.c

@@ -4285,7 +4285,9 @@ static int svm_enter_smm(struct kvm_vcpu *vcpu, char *smstate)
 	struct kvm_host_map map_save;
 	int ret;
 
-	if (is_guest_mode(vcpu)) {
+	if (!is_guest_mode(vcpu))
+		return 0;
+
 	/* FED8h - SVM Guest */
 	put_smstate(u64, smstate, 0x7ed8, 1);
 	/* FEE0h - SVM Guest VMCB Physical Address */
@@ -4321,7 +4323,6 @@ static int svm_enter_smm(struct kvm_vcpu *vcpu, char *smstate)
 			     &svm->vmcb01.ptr->save);
 
 	kvm_vcpu_unmap(vcpu, &map_save, true);
-	}
 	return 0;
 }
 
@@ -4329,52 +4330,54 @@ static int svm_leave_smm(struct kvm_vcpu *vcpu, const char *smstate)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
 	struct kvm_host_map map, map_save;
-	int ret = 0;
-
-	if (guest_cpuid_has(vcpu, X86_FEATURE_LM)) {
-		u64 saved_efer = GET_SMSTATE(u64, smstate, 0x7ed0);
-		u64 guest = GET_SMSTATE(u64, smstate, 0x7ed8);
-		u64 vmcb12_gpa = GET_SMSTATE(u64, smstate, 0x7ee0);
+	u64 saved_efer, vmcb12_gpa;
 	struct vmcb *vmcb12;
+	int ret;
+
+	if (!guest_cpuid_has(vcpu, X86_FEATURE_LM))
+		return 0;
+
+	/* Non-zero if SMI arrived while vCPU was in guest mode. */
+	if (!GET_SMSTATE(u64, smstate, 0x7ed8))
+		return 0;
 
-		if (guest) {
 	if (!guest_cpuid_has(vcpu, X86_FEATURE_SVM))
 		return 1;
 
+	saved_efer = GET_SMSTATE(u64, smstate, 0x7ed0);
 	if (!(saved_efer & EFER_SVME))
 		return 1;
 
-			if (kvm_vcpu_map(vcpu,
-					 gpa_to_gfn(vmcb12_gpa), &map) == -EINVAL)
+	vmcb12_gpa = GET_SMSTATE(u64, smstate, 0x7ee0);
+	if (kvm_vcpu_map(vcpu, gpa_to_gfn(vmcb12_gpa), &map) == -EINVAL)
 		return 1;
 
-			if (svm_allocate_nested(svm))
-				return 1;
+	ret = 1;
+	if (kvm_vcpu_map(vcpu, gpa_to_gfn(svm->nested.hsave_msr), &map_save) == -EINVAL)
+		goto unmap_map;
 
-			kvm_vcpu_unmap(vcpu, &map, true);
+	if (svm_allocate_nested(svm))
+		goto unmap_save;
 
 	/*
 	 * Restore L1 host state from L1 HSAVE area as VMCB01 was
 	 * used during SMM (see svm_enter_smm())
 	 */
-			if (kvm_vcpu_map(vcpu, gpa_to_gfn(svm->nested.hsave_msr),
-					 &map_save) == -EINVAL)
-				return 1;
 
-			svm_copy_vmrun_state(&svm->vmcb01.ptr->save,
-					     map_save.hva + 0x400);
+	svm_copy_vmrun_state(&svm->vmcb01.ptr->save, map_save.hva + 0x400);
 
 	/*
 	 * Enter the nested guest now
 	 */
+
 	vmcb12 = map.hva;
 	nested_load_control_from_vmcb12(svm, &vmcb12->control);
 	ret = enter_svm_guest_mode(vcpu, vmcb12_gpa, vmcb12, false);
 
+unmap_save:
 	kvm_vcpu_unmap(vcpu, &map_save, true);
-		}
-	}
-
+unmap_map:
+	kvm_vcpu_unmap(vcpu, &map, true);
 	return ret;
 }