diff --git a/hypervisor/arch/x86/guest/guest.c b/hypervisor/arch/x86/guest/guest.c
index 8940ceef2..894469a62 100644
--- a/hypervisor/arch/x86/guest/guest.c
+++ b/hypervisor/arch/x86/guest/guest.c
@@ -286,7 +286,7 @@ int gva2gpa(struct vcpu *vcpu, uint64_t gva, uint64_t *gpa,
 	pw_info.level = pm;
 	pw_info.is_write_access = ((*err_code & PAGE_FAULT_WR_FLAG) != 0U);
 	pw_info.is_inst_fetch = ((*err_code & PAGE_FAULT_ID_FLAG) != 0U);
-	pw_info.is_user_mode = ((exec_vmread(VMX_GUEST_CS_SEL) & 0x3UL) == 3UL);
+	pw_info.is_user_mode = ((exec_vmread16(VMX_GUEST_CS_SEL) & 0x3U) == 3U);
 	pw_info.pse = true;
 	pw_info.nxe =
 		((cur_context->ia32_efer & MSR_IA32_EFER_NXE_BIT) != 0UL);
diff --git a/hypervisor/arch/x86/guest/instr_emul_wrapper.c b/hypervisor/arch/x86/guest/instr_emul_wrapper.c
index 889e189bd..4f835c527 100644
--- a/hypervisor/arch/x86/guest/instr_emul_wrapper.c
+++ b/hypervisor/arch/x86/guest/instr_emul_wrapper.c
@@ -44,7 +44,11 @@ int vm_get_register(struct vcpu *vcpu, enum cpu_reg_name reg, uint64_t *retval)
 		uint32_t field = get_vmcs_field(reg);
 
 		if (field != VMX_INVALID_VMCS_FIELD) {
-			*retval = exec_vmread(field);
+			if (reg < CPU_REG_64BIT_LAST) {
+				*retval = exec_vmread(field);
+			} else {
+				*retval = (uint64_t)exec_vmread16(field);
+			}
 		} else {
 			return -EINVAL;
 		}
@@ -73,7 +77,11 @@ int vm_set_register(struct vcpu *vcpu, enum cpu_reg_name reg, uint64_t val)
 		uint32_t field = get_vmcs_field(reg);
 
 		if (field != VMX_INVALID_VMCS_FIELD) {
-			exec_vmwrite(field, val);
+			if (reg < CPU_REG_64BIT_LAST) {
+				exec_vmwrite(field, val);
+			} else {
+				exec_vmwrite16(field, (uint16_t)val);
+			}
 		} else {
 			return -EINVAL;
 		}
@@ -223,7 +231,21 @@ encode_vmcs_seg_desc(enum cpu_reg_name seg,
 
 	return 0;
 }
-
+/**
+ *
+ *Description:
+ *This local function is to covert register names into
+ *the corresponding field index MACROs in VMCS.
+ *
+ *Post Condition:
+ *In the non-general register names group (CPU_REG_CR0~CPU_REG_LAST),
+ *for register names CPU_REG_CR2, CPU_REG_IDTR, CPU_REG_GDTR,
+ *CPU_REG_NATURAL_LAST, CPU_REG_64BIT_LAST and CPU_REG_LAST, 
+ *this function returns VMX_INVALID_VMCS_FIELD;
+ *for other register names, it returns correspoding field index MACROs
+ *in VMCS.
+ *
+ **/
 static uint32_t get_vmcs_field(enum cpu_reg_name ident)
 {
 	switch (ident) {
diff --git a/hypervisor/arch/x86/guest/vcpu.c b/hypervisor/arch/x86/guest/vcpu.c
index a1652986e..3ca8fe782 100644
--- a/hypervisor/arch/x86/guest/vcpu.c
+++ b/hypervisor/arch/x86/guest/vcpu.c
@@ -158,7 +158,7 @@ int start_vcpu(struct vcpu *vcpu)
 				vcpu->vm->attr.id, vcpu->vcpu_id);
 
 		if (vcpu->arch_vcpu.vpid)
-			exec_vmwrite(VMX_VPID, vcpu->arch_vcpu.vpid);
+			exec_vmwrite16(VMX_VPID, vcpu->arch_vcpu.vpid);
 
 		/*
 		 * A power-up or a reset invalidates all linear mappings,
diff --git a/hypervisor/arch/x86/guest/vlapic.c b/hypervisor/arch/x86/guest/vlapic.c
index 92474c120..77fd4b0d1 100644
--- a/hypervisor/arch/x86/guest/vlapic.c
+++ b/hypervisor/arch/x86/guest/vlapic.c
@@ -2340,13 +2340,12 @@ apicv_inject_pir(struct vlapic *vlapic)
 	if (pirval != 0UL) {
 		rvi = pirbase + fls64(pirval);
 
-		intr_status_old = (uint16_t)
-				(0xFFFFUL &
-				exec_vmread(VMX_GUEST_INTR_STATUS));
+		intr_status_old = 0xFFFFU & 
+				exec_vmread16(VMX_GUEST_INTR_STATUS);
 
 		intr_status_new = (intr_status_old & 0xFF00U) | rvi;
 		if (intr_status_new > intr_status_old) {
-			exec_vmwrite(VMX_GUEST_INTR_STATUS,
+			exec_vmwrite16(VMX_GUEST_INTR_STATUS,
 					intr_status_new);
 		}
 	}
diff --git a/hypervisor/arch/x86/trusty.c b/hypervisor/arch/x86/trusty.c
index 8608c7013..0a2370cc6 100644
--- a/hypervisor/arch/x86/trusty.c
+++ b/hypervisor/arch/x86/trusty.c
@@ -36,7 +36,7 @@ static struct key_info g_key_info = {
 
 #define save_segment(seg, SEG_NAME) \
 { \
-	seg.selector = exec_vmread(VMX_GUEST_##SEG_NAME##_SEL); \
+	seg.selector = exec_vmread16(VMX_GUEST_##SEG_NAME##_SEL); \
 	seg.base = exec_vmread(VMX_GUEST_##SEG_NAME##_BASE); \
 	seg.limit = exec_vmread(VMX_GUEST_##SEG_NAME##_LIMIT); \
 	seg.attr = exec_vmread(VMX_GUEST_##SEG_NAME##_ATTR); \
@@ -44,7 +44,7 @@ static struct key_info g_key_info = {
 
 #define load_segment(seg, SEG_NAME) \
 { \
-	exec_vmwrite(VMX_GUEST_##SEG_NAME##_SEL, seg.selector); \
+	exec_vmwrite16(VMX_GUEST_##SEG_NAME##_SEL, seg.selector); \
 	exec_vmwrite(VMX_GUEST_##SEG_NAME##_BASE, seg.base); \
 	exec_vmwrite(VMX_GUEST_##SEG_NAME##_LIMIT, seg.limit); \
 	exec_vmwrite(VMX_GUEST_##SEG_NAME##_ATTR, seg.attr); \
diff --git a/hypervisor/arch/x86/vmx.c b/hypervisor/arch/x86/vmx.c
index 2d6800408..806a810f6 100644
--- a/hypervisor/arch/x86/vmx.c
+++ b/hypervisor/arch/x86/vmx.c
@@ -220,6 +220,15 @@ uint64_t exec_vmread64(uint32_t field_full)
 	return low;
 }
 
+uint16_t exec_vmread16(uint32_t field)
+{
+        uint64_t value;
+
+        value = exec_vmread64(field);
+
+        return (uint16_t)value;
+}
+
 void exec_vmwrite(uint32_t field, uint64_t value)
 {
 	asm volatile (
@@ -241,6 +250,11 @@ void exec_vmwrite64(unsigned int field_full, uint64_t value)
 #endif
 }
 
+void exec_vmwrite16(uint32_t field, uint16_t value)
+{
+	exec_vmwrite64(field, (uint64_t)value);
+}
+
 #define HV_ARCH_VMX_GET_CS(SEL)				\
 {							\
 	asm volatile ("movw %%cs, %%ax" : "=a"(sel));	\
@@ -534,6 +548,7 @@ static void init_guest_state(struct vcpu *vcpu)
 {
 	uint32_t field;
 	uint64_t value;
+	uint16_t value16;
 	uint32_t value32;
 	uint64_t value64;
 	uint16_t sel;
@@ -646,7 +661,7 @@ static void init_guest_state(struct vcpu *vcpu)
 
 	/* Selector */
 	field = VMX_GUEST_CS_SEL;
-	exec_vmwrite(field, sel);
+	exec_vmwrite16(field, sel);
 	pr_dbg("VMX_GUEST_CS_SEL: 0x%x ", sel);
 
 	/* Limit */
@@ -812,23 +827,23 @@ static void init_guest_state(struct vcpu *vcpu)
 
 	/* Selector */
 	field = VMX_GUEST_ES_SEL;
-	exec_vmwrite(field, es);
+	exec_vmwrite16(field, es);
 	pr_dbg("VMX_GUEST_ES_SEL: 0x%x ", es);
 
 	field = VMX_GUEST_SS_SEL;
-	exec_vmwrite(field, ss);
+	exec_vmwrite16(field, ss);
 	pr_dbg("VMX_GUEST_SS_SEL: 0x%x ", ss);
 
 	field = VMX_GUEST_DS_SEL;
-	exec_vmwrite(field, ds);
+	exec_vmwrite16(field, ds);
 	pr_dbg("VMX_GUEST_DS_SEL: 0x%x ", ds);
 
 	field = VMX_GUEST_FS_SEL;
-	exec_vmwrite(field, fs);
+	exec_vmwrite16(field, fs);
 	pr_dbg("VMX_GUEST_FS_SEL: 0x%x ", fs);
 
 	field = VMX_GUEST_GS_SEL;
-	exec_vmwrite(field, gs);
+	exec_vmwrite16(field, gs);
 	pr_dbg("VMX_GUEST_GS_SEL: 0x%x ", gs);
 
 	/* Limit */
@@ -899,9 +914,9 @@ static void init_guest_state(struct vcpu *vcpu)
 	/* LDT and TR (dummy) */
 	/***************************************************/
 	field = VMX_GUEST_LDTR_SEL;
-	value32 = ldt_idx;
-	exec_vmwrite(field, value32);
-	pr_dbg("VMX_GUEST_LDTR_SEL: 0x%x ", value32);
+	value16 = ldt_idx;
+	exec_vmwrite16(field, value16);
+	pr_dbg("VMX_GUEST_LDTR_SEL: 0x%hu ", value16);
 
 	field = VMX_GUEST_LDTR_LIMIT;
 	value32 = 0xffffffffU;
@@ -920,9 +935,9 @@ static void init_guest_state(struct vcpu *vcpu)
 
 	/* Task Register */
 	field = VMX_GUEST_TR_SEL;
-	value32 = lssd32_idx;
-	exec_vmwrite(field, value32);
-	pr_dbg("VMX_GUEST_TR_SEL: 0x%x ", value32);
+	value16 = lssd32_idx;
+	exec_vmwrite16(field, value16);
+	pr_dbg("VMX_GUEST_TR_SEL: 0x%hu ", value16);
 
 	field = VMX_GUEST_TR_LIMIT;
 	value32 = 0xffU;
@@ -1023,37 +1038,37 @@ static void init_host_state(__unused struct vcpu *vcpu)
 	 ***************************************************/
 	field = VMX_HOST_ES_SEL;
 	asm volatile ("movw %%es, %%ax":"=a" (value16));
-	exec_vmwrite(field, value16);
-	pr_dbg("VMX_HOST_ES_SEL: 0x%x ", value16);
+	exec_vmwrite16(field, value16);
+	pr_dbg("VMX_HOST_ES_SEL: 0x%hu ", value16);
 
 	field = VMX_HOST_CS_SEL;
 	asm volatile ("movw %%cs, %%ax":"=a" (value16));
-	exec_vmwrite(field, value16);
-	pr_dbg("VMX_HOST_CS_SEL: 0x%x ", value16);
+	exec_vmwrite16(field, value16);
+	pr_dbg("VMX_HOST_CS_SEL: 0x%hu ", value16);
 
 	field = VMX_HOST_SS_SEL;
 	asm volatile ("movw %%ss, %%ax":"=a" (value16));
-	exec_vmwrite(field, value16);
-	pr_dbg("VMX_HOST_SS_SEL: 0x%x ", value16);
+	exec_vmwrite16(field, value16);
+	pr_dbg("VMX_HOST_SS_SEL: 0x%hu ", value16);
 
 	field = VMX_HOST_DS_SEL;
 	asm volatile ("movw %%ds, %%ax":"=a" (value16));
-	exec_vmwrite(field, value16);
-	pr_dbg("VMX_HOST_DS_SEL: 0x%x ", value16);
+	exec_vmwrite16(field, value16);
+	pr_dbg("VMX_HOST_DS_SEL: 0x%hu ", value16);
 
 	field = VMX_HOST_FS_SEL;
 	asm volatile ("movw %%fs, %%ax":"=a" (value16));
-	exec_vmwrite(field, value16);
-	pr_dbg("VMX_HOST_FS_SEL: 0x%x ", value16);
+	exec_vmwrite16(field, value16);
+	pr_dbg("VMX_HOST_FS_SEL: 0x%hu ", value16);
 
 	field = VMX_HOST_GS_SEL;
 	asm volatile ("movw %%gs, %%ax":"=a" (value16));
-	exec_vmwrite(field, value16);
-	pr_dbg("VMX_HOST_GS_SEL: 0x%x ", value16);
+	exec_vmwrite16(field, value16);
+	pr_dbg("VMX_HOST_GS_SEL: 0x%hu ", value16);
 
 	field = VMX_HOST_TR_SEL;
 	asm volatile ("str %%ax":"=a" (tr_sel));
-	exec_vmwrite(field, tr_sel);
+	exec_vmwrite16(field, tr_sel);
 	pr_dbg("VMX_HOST_TR_SEL: 0x%x ", tr_sel);
 
 	/******************************************************
@@ -1490,7 +1505,7 @@ static void override_uefi_vmcs(struct vcpu *vcpu)
 
 		/* Selector */
 		field = VMX_GUEST_CS_SEL;
-		exec_vmwrite(field, efi_ctx->cs_sel);
+		exec_vmwrite16(field, efi_ctx->cs_sel);
 		pr_dbg("VMX_GUEST_CS_SEL: 0x%x ", efi_ctx->cs_sel);
 
 		/* Access */
@@ -1499,23 +1514,23 @@ static void override_uefi_vmcs(struct vcpu *vcpu)
 		pr_dbg("VMX_GUEST_CS_ATTR: 0x%x ", efi_ctx->cs_ar);
 
 		field = VMX_GUEST_ES_SEL;
-		exec_vmwrite(field, efi_ctx->es_sel);
+		exec_vmwrite16(field, efi_ctx->es_sel);
 		pr_dbg("VMX_GUEST_ES_SEL: 0x%x ", efi_ctx->es_sel);
 
 		field = VMX_GUEST_SS_SEL;
-		exec_vmwrite(field, efi_ctx->ss_sel);
+		exec_vmwrite16(field, efi_ctx->ss_sel);
 		pr_dbg("VMX_GUEST_SS_SEL: 0x%x ", efi_ctx->ss_sel);
 
 		field = VMX_GUEST_DS_SEL;
-		exec_vmwrite(field, efi_ctx->ds_sel);
+		exec_vmwrite16(field, efi_ctx->ds_sel);
 		pr_dbg("VMX_GUEST_DS_SEL: 0x%x ", efi_ctx->ds_sel);
 
 		field = VMX_GUEST_FS_SEL;
-		exec_vmwrite(field, efi_ctx->fs_sel);
+		exec_vmwrite16(field, efi_ctx->fs_sel);
 		pr_dbg("VMX_GUEST_FS_SEL: 0x%x ", efi_ctx->fs_sel);
 
 		field = VMX_GUEST_GS_SEL;
-		exec_vmwrite(field, efi_ctx->gs_sel);
+		exec_vmwrite16(field, efi_ctx->gs_sel);
 		pr_dbg("VMX_GUEST_GS_SEL: 0x%x ", efi_ctx->gs_sel);
 
 		/* Base */
diff --git a/hypervisor/common/hypercall.c b/hypervisor/common/hypercall.c
index 9441b7ca5..4a0c4cd46 100644
--- a/hypervisor/common/hypercall.c
+++ b/hypervisor/common/hypercall.c
@@ -14,11 +14,11 @@
 
 bool is_hypercall_from_ring0(void)
 {
-	uint64_t cs_sel;
+	uint16_t cs_sel;
 
-	cs_sel = exec_vmread(VMX_GUEST_CS_SEL);
+	cs_sel = exec_vmread16(VMX_GUEST_CS_SEL);
 	/* cs_selector[1:0] is CPL */
-	if ((cs_sel & 0x3UL) == 0) {
+	if ((cs_sel & 0x3U) == 0U) {
 		return true;
 	}
 
diff --git a/hypervisor/include/arch/x86/vmx.h b/hypervisor/include/arch/x86/vmx.h
index 66a73c66c..69902305a 100644
--- a/hypervisor/include/arch/x86/vmx.h
+++ b/hypervisor/include/arch/x86/vmx.h
@@ -414,8 +414,10 @@ int exec_vmxon_instr(uint16_t pcpu_id);
  */
 uint64_t exec_vmread(uint32_t field);
 
+uint16_t exec_vmread16(uint32_t field);
 uint64_t exec_vmread64(uint32_t field_full);
 void exec_vmwrite(uint32_t field, uint64_t value);
+void exec_vmwrite16(uint32_t field, uint16_t value);
 void exec_vmwrite64(uint32_t field_full, uint64_t value);
 int init_vmcs(struct vcpu *vcpu);