diff --git a/hypervisor/arch/x86/guest/guest.c b/hypervisor/arch/x86/guest/guest.c
index cd82463d6..3f2fb1432 100644
--- a/hypervisor/arch/x86/guest/guest.c
+++ b/hypervisor/arch/x86/guest/guest.c
@@ -75,11 +75,11 @@ inline struct vcpu *get_primary_vcpu(struct vm *vm)
 
 inline uint64_t vcpumask2pcpumask(struct vm *vm, uint64_t vdmask)
 {
-	int vcpu_id;
+	uint16_t vcpu_id;
 	uint64_t dmask = 0;
 	struct vcpu *vcpu;
 
-	while ((vcpu_id = ffs64(vdmask)) >= 0) {
+	while ((vcpu_id = ffs64(vdmask)) != INVALID_BIT_INDEX) {
 		bitmap_clear(vcpu_id, &vdmask);
 		vcpu = vcpu_from_vid(vm, vcpu_id);
 		ASSERT(vcpu != NULL, "vcpu_from_vid failed");
diff --git a/hypervisor/arch/x86/guest/vlapic.c b/hypervisor/arch/x86/guest/vlapic.c
index a729b9010..0306c8d2c 100644
--- a/hypervisor/arch/x86/guest/vlapic.c
+++ b/hypervisor/arch/x86/guest/vlapic.c
@@ -880,7 +880,7 @@ vlapic_calcdest(struct vm *vm, uint64_t *dmask, uint32_t dest,
 	uint32_t dfr, ldr, ldest, cluster;
 	uint32_t mda_flat_ldest, mda_cluster_ldest, mda_ldest, mda_cluster_id;
 	uint64_t amask;
-	int vcpu_id;
+	uint16_t vcpu_id;
 
 	if (dest == 0xff) {
 		/*
@@ -918,7 +918,7 @@ vlapic_calcdest(struct vm *vm, uint64_t *dmask, uint32_t dest,
 		 */
 		*dmask = 0;
 		amask = vm_active_cpus(vm);
-		while ((vcpu_id = ffs64(amask)) >= 0) {
+		while ((vcpu_id = ffs64(amask)) != INVALID_BIT_INDEX) {
 			bitmap_clear(vcpu_id, &amask);
 
 			vlapic = vm_lapic_from_vcpu_id(vm, vcpu_id);
@@ -1021,7 +1021,7 @@ vlapic_get_cr8(struct vlapic *vlapic)
 static int
 vlapic_icrlo_write_handler(struct vlapic *vlapic)
 {
-	int i;
+	uint16_t vcpu_id;
 	bool phys;
 	uint64_t dmask = 0;
 	uint64_t icrval;
@@ -1071,9 +1071,9 @@ vlapic_icrlo_write_handler(struct vlapic *vlapic)
 		break;
 	}
 
-	while ((i = ffs64(dmask)) >= 0) {
-		bitmap_clear(i, &dmask);
-		target_vcpu = vcpu_from_vid(vlapic->vm, i);
+	while ((vcpu_id = ffs64(dmask)) != INVALID_BIT_INDEX) {
+		bitmap_clear(vcpu_id, &dmask);
+		target_vcpu = vcpu_from_vid(vlapic->vm, vcpu_id);
 		if (target_vcpu == NULL)
 			continue;
 
@@ -1081,19 +1081,19 @@ vlapic_icrlo_write_handler(struct vlapic *vlapic)
 			vlapic_set_intr(target_vcpu, vec,
 				LAPIC_TRIG_EDGE);
 			dev_dbg(ACRN_DBG_LAPIC,
-				"vlapic sending ipi %d to vcpu_id %d",
-				vec, i);
+				"vlapic sending ipi %d to vcpu_id %hu",
+				vec, vcpu_id);
 		} else if (mode == APIC_DELMODE_NMI){
 			vcpu_inject_nmi(target_vcpu);
 			dev_dbg(ACRN_DBG_LAPIC,
-				"vlapic send ipi nmi to vcpu_id %d", i);
+				"vlapic send ipi nmi to vcpu_id %hu", vcpu_id);
 		} else if (mode == APIC_DELMODE_INIT) {
 			if ((icrval & APIC_LEVEL_MASK) == APIC_LEVEL_DEASSERT)
 				continue;
 
 			dev_dbg(ACRN_DBG_LAPIC,
-				"Sending INIT from VCPU %d to %d",
-				vlapic->vcpu->vcpu_id, i);
+				"Sending INIT from VCPU %d to %hu",
+				vlapic->vcpu->vcpu_id, vcpu_id);
 
 			/* put target vcpu to INIT state and wait for SIPI */
 			pause_vcpu(target_vcpu, VCPU_PAUSED);
@@ -1110,8 +1110,8 @@ vlapic_icrlo_write_handler(struct vlapic *vlapic)
 				continue;
 
 			dev_dbg(ACRN_DBG_LAPIC,
-				"Sending SIPI from VCPU %d to %d with vector %d",
-				vlapic->vcpu->vcpu_id, i, vec);
+				"Sending SIPI from VCPU %d to %hu with vector %d",
+				vlapic->vcpu->vcpu_id, vcpu_id, vec);
 
 			if (--target_vcpu->arch_vcpu.nr_sipi > 0)
 				continue;
@@ -1586,7 +1586,7 @@ vlapic_deliver_intr(struct vm *vm, bool level, uint32_t dest, bool phys,
 		int delmode, int vec)
 {
 	bool lowprio;
-	int vcpu_id;
+	uint16_t vcpu_id;
 	uint64_t dmask;
 	struct vcpu *target_vcpu;
 
@@ -1606,7 +1606,7 @@ vlapic_deliver_intr(struct vm *vm, bool level, uint32_t dest, bool phys,
 	 */
 	vlapic_calcdest(vm, &dmask, dest, phys, lowprio);
 
-	while ((vcpu_id = ffs64(dmask)) >= 0) {
+	while ((vcpu_id = ffs64(dmask)) != INVALID_BIT_INDEX) {
 		bitmap_clear(vcpu_id, &dmask);
 		target_vcpu = vcpu_from_vid(vm, vcpu_id);
 		if (target_vcpu == NULL)
@@ -1738,21 +1738,21 @@ vlapic_set_intr(struct vcpu *vcpu, uint32_t vector, bool level)
 }
 
 int
-vlapic_set_local_intr(struct vm *vm, int vcpu_id, uint32_t vector)
+vlapic_set_local_intr(struct vm *vm, uint16_t vcpu_id, uint32_t vector)
 {
 	struct vlapic *vlapic;
 	uint64_t dmask = 0;
 	int error;
 
-	if (vcpu_id < -1 || vcpu_id >= phys_cpu_num)
+	if ((vcpu_id != BROADCAST_CPU_ID) && (vcpu_id >= phys_cpu_num))
 		return -EINVAL;
 
-	if (vcpu_id == -1)
+	if (vcpu_id == BROADCAST_CPU_ID)
 		dmask = vm_active_cpus(vm);
 	else
 		bitmap_set(vcpu_id, &dmask);
 	error = 0;
-	while ((vcpu_id = ffs64(dmask)) >= 0) {
+	while ((vcpu_id = ffs64(dmask)) != INVALID_BIT_INDEX) {
 		bitmap_clear(vcpu_id, &dmask);
 		vlapic = vm_lapic_from_vcpu_id(vm, vcpu_id);
 		error = vlapic_trigger_lvt(vlapic, vector);
diff --git a/hypervisor/arch/x86/guest/vpic.c b/hypervisor/arch/x86/guest/vpic.c
index 2b4a2fcbe..f5ef577c8 100644
--- a/hypervisor/arch/x86/guest/vpic.c
+++ b/hypervisor/arch/x86/guest/vpic.c
@@ -231,7 +231,7 @@ static void vpic_notify_intr(struct vpic *vpic)
 			ASSERT(vcpu != NULL, "vm%d, vcpu0", vpic->vm->attr.id);
 			vcpu_inject_extint(vcpu);
 		} else {
-			vlapic_set_local_intr(vpic->vm, BROADCAST_PCPU_ID, APIC_LVT_LINT0);
+			vlapic_set_local_intr(vpic->vm, BROADCAST_CPU_ID, APIC_LVT_LINT0);
 			/* notify vioapic pin0 if existing
 			 * For vPIC + vIOAPIC mode, vpic master irq connected
 			 * to vioapic pin0 (irq2)
diff --git a/hypervisor/arch/x86/softirq.c b/hypervisor/arch/x86/softirq.c
index 13bebcfb2..c9b2076b1 100644
--- a/hypervisor/arch/x86/softirq.c
+++ b/hypervisor/arch/x86/softirq.c
@@ -42,7 +42,7 @@ void exec_softirq(void)
 	uint16_t cpu_id = get_cpu_id();
 	volatile uint64_t *bitmap = &per_cpu(softirq_pending, cpu_id);
 
-	int softirq_id;
+	uint16_t softirq_id;
 
 	if (cpu_id >= phys_cpu_num)
 		return;
@@ -61,7 +61,7 @@ again:
 
 	while (1) {
 		softirq_id = ffs64(*bitmap);
-		if ((softirq_id < 0) || (softirq_id >= SOFTIRQ_MAX))
+		if ((softirq_id == INVALID_BIT_INDEX) || (softirq_id >= SOFTIRQ_MAX))
 			break;
 
 		bitmap_clear(softirq_id, bitmap);
diff --git a/hypervisor/common/hypercall.c b/hypervisor/common/hypercall.c
index edeeedbbf..4aaacd6e9 100644
--- a/hypervisor/common/hypercall.c
+++ b/hypervisor/common/hypercall.c
@@ -220,7 +220,7 @@ int64_t hcall_create_vcpu(struct vm *vm, uint64_t vmid, uint64_t param)
 	}
 
 	pcpu_id = allocate_pcpu();
-	if (INVALID_PCPU_ID == pcpu_id) {
+	if (pcpu_id == INVALID_CPU_ID) {
 		pr_err("%s: No physical available\n", __func__);
 		return -1;
 	}
diff --git a/hypervisor/common/schedule.c b/hypervisor/common/schedule.c
index 01346bf38..27ec702e3 100644
--- a/hypervisor/common/schedule.c
+++ b/hypervisor/common/schedule.c
@@ -41,7 +41,7 @@ uint16_t allocate_pcpu(void)
 			return i;
 	}
 
-	return INVALID_PCPU_ID;
+	return INVALID_CPU_ID;
 }
 
 void set_pcpu_used(uint16_t pcpu_id)
diff --git a/hypervisor/include/arch/x86/cpu.h b/hypervisor/include/arch/x86/cpu.h
index b0bb475d1..b5d47fa7c 100644
--- a/hypervisor/include/arch/x86/cpu.h
+++ b/hypervisor/include/arch/x86/cpu.h
@@ -211,6 +211,20 @@ enum feature_word {
 	FEATURE_WORDS,
 };
 
+/**
+ *The invalid cpu_id (INVALID_CPU_ID) is error
+ *code for error handling, this means that
+ *caller can't find a valid physical cpu
+ *or virtual cpu.
+ */
+#define INVALID_CPU_ID 0xffffU
+/**
+ *The broadcast id (BROADCAST_CPU_ID)
+ *used to notify all valid phyiscal cpu
+ *or virtual cpu.
+ */
+#define BROADCAST_CPU_ID 0xfffeU
+
 /* CPU states defined */
 enum cpu_state {
 	CPU_STATE_RESET = 0,
diff --git a/hypervisor/include/arch/x86/cpuid.h b/hypervisor/include/arch/x86/cpuid.h
index 10477237a..a27e51265 100644
--- a/hypervisor/include/arch/x86/cpuid.h
+++ b/hypervisor/include/arch/x86/cpuid.h
@@ -96,15 +96,6 @@
 #define CPUID_EXTEND_FUNCTION_4      0x80000004
 #define CPUID_EXTEND_ADDRESS_SIZE    0x80000008
 
-/**pcpu id type is uint16_t,
-*The broadcast id (BROADCAST_PCPU_ID) 
-* used to notify all valid pcpu, 
-*the invalid pcpu id (INVALID_PCPU_ID) is error
-*code for error handling.
-*/
-#define INVALID_PCPU_ID 0xffffU
-#define BROADCAST_PCPU_ID 0xfffeU
-
 
 static inline void __cpuid(uint32_t *eax, uint32_t *ebx,
 				uint32_t *ecx, uint32_t *edx)
diff --git a/hypervisor/include/arch/x86/guest/vlapic.h b/hypervisor/include/arch/x86/guest/vlapic.h
index f179d31d5..5b2bf15c6 100644
--- a/hypervisor/include/arch/x86/guest/vlapic.h
+++ b/hypervisor/include/arch/x86/guest/vlapic.h
@@ -89,7 +89,7 @@ vlapic_intr_edge(struct vcpu *vcpu, uint32_t vector)
  * Triggers the LAPIC local interrupt (LVT) 'vector' on 'cpu'.  'cpu' can
  * be set to -1 to trigger the interrupt on all CPUs.
  */
-int vlapic_set_local_intr(struct vm *vm, int vcpu_id, uint32_t vector);
+int vlapic_set_local_intr(struct vm *vm, uint16_t vcpu_id, uint32_t vector);
 
 int vlapic_intr_msi(struct vm *vm, uint64_t addr, uint64_t msg);
 
diff --git a/hypervisor/include/arch/x86/softirq.h b/hypervisor/include/arch/x86/softirq.h
index 9d81987a4..0c768c025 100644
--- a/hypervisor/include/arch/x86/softirq.h
+++ b/hypervisor/include/arch/x86/softirq.h
@@ -7,9 +7,9 @@
 #ifndef SOFTIRQ_H
 #define SOFTIRQ_H
 
-#define SOFTIRQ_TIMER		0
-#define SOFTIRQ_DEV_ASSIGN	1
-#define SOFTIRQ_MAX		2
+#define SOFTIRQ_TIMER		0U
+#define SOFTIRQ_DEV_ASSIGN	1U
+#define SOFTIRQ_MAX		2U
 #define SOFTIRQ_MASK		((1UL<<SOFTIRQ_MAX)-1)
 
 /* used for atomic value for prevent recursive */
diff --git a/hypervisor/include/lib/bits.h b/hypervisor/include/lib/bits.h
index 7afc05ff4..17c8ac708 100644
--- a/hypervisor/include/lib/bits.h
+++ b/hypervisor/include/lib/bits.h
@@ -91,10 +91,11 @@ static inline uint16_t fls64(uint64_t value)
  * and return the index of that bit.
  *
  *  Bits are numbered starting at 0,the least significant bit.
- *  A return value of -1 means that the argument was zero.
+ *  A return value of INVALID_BIT_INDEX means that the return value is the inalid
+ *  bit index when the input argument was zero.
  *
  *  Examples:
- *	ffs64 (0x0) = -1
+ *	ffs64 (0x0) = INVALID_BIT_INDEX
  *	ffs64 (0x01) = 0
  *	ffs64 (0xf0) = 4
  *	ffs64 (0xf00) = 8
@@ -104,20 +105,24 @@ static inline uint16_t fls64(uint64_t value)
  *
  * @param value: 'unsigned long' type value
  *
- * @return value: zero-based bit index, -1 means 'value' was zero.
+ * @return value: zero-based bit index, INVALID_BIT_INDEX means
+ * when 'value' was zero, bit operations function can't find bit
+ * set and return the invalid bit index directly.
  *
  * **/
-static inline int ffs64(unsigned long value)
+static inline uint16_t ffs64(uint64_t value)
 {
-	int ret;
-	asm volatile("bsfq %1,%q0"
+	uint64_t ret = 0UL;
+	if (value == 0UL)
+		return (INVALID_BIT_INDEX);
+	asm volatile("bsfq %1,%0"
 			: "=r" (ret)
-			: "rm" (value), "0" (-1));
-	return ret;
+			: "rm" (value));
+	return (uint16_t)ret;
 }
 
 /*bit scan forward for the least significant bit '0'*/
-static inline int ffz64(unsigned long value)
+static inline uint16_t ffz64(uint64_t value)
 {
 	return ffs64(~value);
 }
diff --git a/hypervisor/include/lib/mem_mgt.h b/hypervisor/include/lib/mem_mgt.h
index fbd06cdfb..c176398b7 100644
--- a/hypervisor/include/lib/mem_mgt.h
+++ b/hypervisor/include/lib/mem_mgt.h
@@ -8,7 +8,7 @@
 #define __MEM_MGT_H__
 
 /* Macros */
-#define BITMAP_WORD_SIZE         32
+#define BITMAP_WORD_SIZE         32U
 
 struct mem_pool {
 	void *start_addr;	/* Start Address of Memory Pool */
diff --git a/hypervisor/lib/div.c b/hypervisor/lib/div.c
index 746924a15..103576eda 100644
--- a/hypervisor/lib/div.c
+++ b/hypervisor/lib/div.c
@@ -105,7 +105,7 @@ int udiv64(uint64_t dividend, uint64_t divisor, struct udiv_result *res)
 		}
 		divisor >>= 1;
 		mask >>= 1;
-	} while ((bits-- != 0) && (dividend != 0));
+	} while ((bits-- != 0UL) && (dividend != 0));
 
 	res->r.qword = dividend;
 	return 0;
diff --git a/hypervisor/lib/memory.c b/hypervisor/lib/memory.c
index d1450eda1..68a5df1ff 100644
--- a/hypervisor/lib/memory.c
+++ b/hypervisor/lib/memory.c
@@ -58,9 +58,10 @@ struct mem_pool Paging_Memory_Pool = {
 static void *allocate_mem(struct mem_pool *pool, unsigned int num_bytes)
 {
 
-        void *memory = NULL;
-        uint32_t idx, bit_idx;
-        uint32_t requested_buffs;
+         void *memory = NULL;
+         uint32_t idx; 
+         uint16_t bit_idx;
+         uint32_t requested_buffs;
 
         /* Check if provided memory pool exists */
         if (pool == NULL)
@@ -85,9 +86,9 @@ static void *allocate_mem(struct mem_pool *pool, unsigned int num_bytes)
                         /* Declare temporary variables to be used locally in
                          * this block
                          */
-                        uint32_t i;
-                        uint32_t tmp_bit_idx = bit_idx;
-                        uint32_t tmp_idx = idx;
+			uint32_t i;
+			uint16_t tmp_bit_idx = bit_idx;
+			uint32_t tmp_idx = idx;
 
                         /* Check requested_buffs number of buffers availability
                          * in memory-pool right after selected buffer
@@ -101,7 +102,7 @@ static void *allocate_mem(struct mem_pool *pool, unsigned int num_bytes)
                                         if (++tmp_idx == pool->bmp_size)
                                                 break;
                                         /* Reset tmp_bit_idx */
-                                        tmp_bit_idx = 0;
+                                        tmp_bit_idx = 0U;
                                 }
 
                                 /* Break if selected buffer is not free */