KVM: SVM: Return the local "r" variable from svm_set_msr()

Rename "r" to "ret" and actually return it from svm_set_msr() to reduce
the probability of repeating the mistake of commit 723d5fb ("kvm:
svm: Add IA32_FLUSH_CMD guest support"), which set "r" thinking that it
would be propagated to the caller.

Alternatively, the declaration of "r" could be moved into the handling of
MSR_TSC_AUX, but that risks variable shadowing in the future.  A wrapper
for kvm_set_user_return_msr() would allow eliding a local variable, but
that feels like delaying the inevitable.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20230322011440.2195485-7-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Author: sean-jc

arch/x86/kvm/svm/svm.c

@@ -2873,7 +2873,7 @@ static int svm_set_vm_cr(struct kvm_vcpu *vcpu, u64 data)
 static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
-	int r;
+	int ret = 0;
 
 	u32 ecx = msr->index;
 	u64 data = msr->data;
@@ -2995,10 +2995,10 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 		 * guest via direct_access_msrs, and switch it via user return.
 		 */
 		preempt_disable();
-		r = kvm_set_user_return_msr(tsc_aux_uret_slot, data, -1ull);
+		ret = kvm_set_user_return_msr(tsc_aux_uret_slot, data, -1ull);
 		preempt_enable();
-		if (r)
-			return 1;
+		if (ret)
+			break;
 
 		svm->tsc_aux = data;
 		break;
@@ -3056,7 +3056,7 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 	default:
 		return kvm_set_msr_common(vcpu, msr);
 	}
-	return 0;
+	return ret;
 }
 
 static int msr_interception(struct kvm_vcpu *vcpu)