diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
index 31d7a0a91f50..6285cf817347 100644
--- a/arch/x86/include/uapi/asm/hyperv.h
+++ b/arch/x86/include/uapi/asm/hyperv.h
@@ -320,6 +320,8 @@ typedef struct _HV_REFERENCE_TSC_PAGE {
 #define HV_SYNIC_SINT_COUNT		(16)
 /* Define the expected SynIC version. */
 #define HV_SYNIC_VERSION_1		(0x1)
+/* Valid SynIC vectors are 16-255. */
+#define HV_SYNIC_FIRST_VALID_VECTOR	(16)
 
 #define HV_SYNIC_CONTROL_ENABLE		(1ULL << 0)
 #define HV_SYNIC_SIMP_ENABLE		(1ULL << 0)
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 2cffb94565f6..93a22748c32b 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -75,22 +75,11 @@ static bool synic_has_vector_auto_eoi(struct kvm_vcpu_hv_synic *synic,
 	return false;
 }
 
-static int synic_set_sint(struct kvm_vcpu_hv_synic *synic, int sint,
-			  u64 data, bool host)
+static void synic_update_vector(struct kvm_vcpu_hv_synic *synic,
+				int vector)
 {
-	int vector;
-
-	vector = data & HV_SYNIC_SINT_VECTOR_MASK;
-	if (vector < 16 && !host)
-		return 1;
-	/*
-	 * Guest may configure multiple SINTs to use the same vector, so
-	 * we maintain a bitmap of vectors handled by synic, and a
-	 * bitmap of vectors with auto-eoi behavior.  The bitmaps are
-	 * updated here, and atomically queried on fast paths.
-	 */
-
-	atomic64_set(&synic->sint[sint], data);
+	if (vector < HV_SYNIC_FIRST_VALID_VECTOR)
+		return;
 
 	if (synic_has_vector_connected(synic, vector))
 		__set_bit(vector, synic->vec_bitmap);
@@ -101,6 +90,29 @@ static int synic_set_sint(struct kvm_vcpu_hv_synic *synic, int sint,
 		__set_bit(vector, synic->auto_eoi_bitmap);
 	else
 		__clear_bit(vector, synic->auto_eoi_bitmap);
+}
+
+static int synic_set_sint(struct kvm_vcpu_hv_synic *synic, int sint,
+			  u64 data, bool host)
+{
+	int vector, old_vector;
+
+	vector = data & HV_SYNIC_SINT_VECTOR_MASK;
+	if (vector < HV_SYNIC_FIRST_VALID_VECTOR && !host)
+		return 1;
+	/*
+	 * Guest may configure multiple SINTs to use the same vector, so
+	 * we maintain a bitmap of vectors handled by synic, and a
+	 * bitmap of vectors with auto-eoi behavior.  The bitmaps are
+	 * updated here, and atomically queried on fast paths.
+	 */
+	old_vector = synic_read_sint(synic, sint) & HV_SYNIC_SINT_VECTOR_MASK;
+
+	atomic64_set(&synic->sint[sint], data);
+
+	synic_update_vector(synic, old_vector);
+
+	synic_update_vector(synic, vector);
 
 	/* Load SynIC vectors into EOI exit bitmap */
 	kvm_make_request(KVM_REQ_SCAN_IOAPIC, synic_to_vcpu(synic));