diff --git a/hypervisor/arch/x86/guest/instr_emul.c b/hypervisor/arch/x86/guest/instr_emul.c
index 4bb49eb2f..509da4573 100644
--- a/hypervisor/arch/x86/guest/instr_emul.c
+++ b/hypervisor/arch/x86/guest/instr_emul.c
@@ -271,50 +271,75 @@ static void encode_vmcs_seg_desc(enum cpu_reg_name seg,
  **/
 static uint32_t get_vmcs_field(enum cpu_reg_name ident)
 {
+	uint32_t ret;
+
 	switch (ident) {
 	case CPU_REG_CR0:
-		return VMX_GUEST_CR0;
+		ret = VMX_GUEST_CR0;
+		break;
 	case CPU_REG_CR3:
-		return VMX_GUEST_CR3;
+		ret = VMX_GUEST_CR3;
+		break;
 	case CPU_REG_CR4:
-		return VMX_GUEST_CR4;
+		ret = VMX_GUEST_CR4;
+		break;
 	case CPU_REG_DR7:
-		return VMX_GUEST_DR7;
+		ret = VMX_GUEST_DR7;
+		break;
 	case CPU_REG_RSP:
-		return VMX_GUEST_RSP;
+		ret = VMX_GUEST_RSP;
+		break;
 	case CPU_REG_RIP:
-		return VMX_GUEST_RIP;
+		ret = VMX_GUEST_RIP;
+		break;
 	case CPU_REG_RFLAGS:
-		return VMX_GUEST_RFLAGS;
+		ret = VMX_GUEST_RFLAGS;
+		break;
 	case CPU_REG_ES:
-		return VMX_GUEST_ES_SEL;
+		ret = VMX_GUEST_ES_SEL;
+		break;
 	case CPU_REG_CS:
-		return VMX_GUEST_CS_SEL;
+		ret = VMX_GUEST_CS_SEL;
+		break;
 	case CPU_REG_SS:
-		return VMX_GUEST_SS_SEL;
+		ret = VMX_GUEST_SS_SEL;
+		break;
 	case CPU_REG_DS:
-		return VMX_GUEST_DS_SEL;
+		ret = VMX_GUEST_DS_SEL;
+		break;
 	case CPU_REG_FS:
-		return VMX_GUEST_FS_SEL;
+		ret = VMX_GUEST_FS_SEL;
+		break;
 	case CPU_REG_GS:
-		return VMX_GUEST_GS_SEL;
+		ret = VMX_GUEST_GS_SEL;
+		break;
 	case CPU_REG_TR:
-		return VMX_GUEST_TR_SEL;
+		ret = VMX_GUEST_TR_SEL;
+		break;
 	case CPU_REG_LDTR:
-		return VMX_GUEST_LDTR_SEL;
+		ret = VMX_GUEST_LDTR_SEL;
+		break;
 	case CPU_REG_EFER:
-		return VMX_GUEST_IA32_EFER_FULL;
+		ret = VMX_GUEST_IA32_EFER_FULL;
+		break;
 	case CPU_REG_PDPTE0:
-		return VMX_GUEST_PDPTE0_FULL;
+		ret = VMX_GUEST_PDPTE0_FULL;
+		break;
 	case CPU_REG_PDPTE1:
-		return VMX_GUEST_PDPTE1_FULL;
+		ret = VMX_GUEST_PDPTE1_FULL;
+		break;
 	case CPU_REG_PDPTE2:
-		return VMX_GUEST_PDPTE2_FULL;
+		ret = VMX_GUEST_PDPTE2_FULL;
+		break;
 	case CPU_REG_PDPTE3:
-		return VMX_GUEST_PDPTE3_FULL;
+		ret = VMX_GUEST_PDPTE3_FULL;
+		break;
 	default: /* Never get here */
-		return VMX_INVALID_VMCS_FIELD;
+		ret = VMX_INVALID_VMCS_FIELD;
+		break;
 	}
+
+	return ret;
 }
 
 /**
diff --git a/hypervisor/common/io_request.c b/hypervisor/common/io_request.c
index 332ae8dad..0b12824b0 100644
--- a/hypervisor/common/io_request.c
+++ b/hypervisor/common/io_request.c
@@ -91,73 +91,76 @@ int32_t acrn_insert_request_wait(struct acrn_vcpu *vcpu, const struct io_request
 	union vhm_request_buffer *req_buf = NULL;
 	struct vhm_request *vhm_req;
 	bool is_polling = false;
+	int32_t ret;
 	uint16_t cur;
 
-	if (vcpu->vm->sw.io_shared_page == NULL) {
-		return -EINVAL;
-	}
+	if (vcpu->vm->sw.io_shared_page != NULL) {
+		ASSERT(get_vhm_req_state(vcpu->vm, vcpu->vcpu_id) == REQ_STATE_FREE,
+			"VHM request buffer is busy");
 
-	ASSERT(get_vhm_req_state(vcpu->vm, vcpu->vcpu_id) == REQ_STATE_FREE,
-		"VHM request buffer is busy");
+		req_buf = (union vhm_request_buffer *)(vcpu->vm->sw.io_shared_page);
+		cur = vcpu->vcpu_id;
 
-	req_buf = (union vhm_request_buffer *)(vcpu->vm->sw.io_shared_page);
-	cur = vcpu->vcpu_id;
+		stac();
+		vhm_req = &req_buf->req_queue[cur];
+		/* ACRN insert request to VHM and inject upcall */
+		vhm_req->type = io_req->type;
+		(void)memcpy_s(&vhm_req->reqs, sizeof(union vhm_io_request),
+			&io_req->reqs, sizeof(union vhm_io_request));
+		if (vcpu->vm->sw.is_completion_polling) {
+			vhm_req->completion_polling = 1U;
+			is_polling = true;
+		}
+		clac();
 
-	stac();
-	vhm_req = &req_buf->req_queue[cur];
-	/* ACRN insert request to VHM and inject upcall */
-	vhm_req->type = io_req->type;
-	(void)memcpy_s(&vhm_req->reqs, sizeof(union vhm_io_request),
-		&io_req->reqs, sizeof(union vhm_io_request));
-	if (vcpu->vm->sw.is_completion_polling) {
-		vhm_req->completion_polling = 1U;
-		is_polling = true;
-	}
-	clac();
+		/* pause vcpu in notification mode , wait for VHM to handle the MMIO request.
+		 * TODO: when pause_vcpu changed to switch vcpu out directlly, we
+		 * should fix the race issue between req.processed update and vcpu pause
+		 */
+		if (!is_polling) {
+			pause_vcpu(vcpu, VCPU_PAUSED);
+		}
 
-	/* pause vcpu in notification mode , wait for VHM to handle the MMIO request.
-	 * TODO: when pause_vcpu changed to switch vcpu out directlly, we
-	 * should fix the race issue between req.processed update and vcpu pause
-	 */
-	if (!is_polling) {
-		pause_vcpu(vcpu, VCPU_PAUSED);
-	}
-
-	/* Must clear the signal before we mark req as pending
-	 * Once we mark it pending, VHM may process req and signal us
-	 * before we perform upcall.
-	 * because VHM can work in pulling mode without wait for upcall
-	 */
-	set_vhm_req_state(vcpu->vm, vcpu->vcpu_id, REQ_STATE_PENDING);
+		/* Must clear the signal before we mark req as pending
+		 * Once we mark it pending, VHM may process req and signal us
+		 * before we perform upcall.
+		 * because VHM can work in pulling mode without wait for upcall
+		 */
+		set_vhm_req_state(vcpu->vm, vcpu->vcpu_id, REQ_STATE_PENDING);
 
 #if defined(HV_DEBUG)
-	stac();
-	acrn_print_request(vcpu->vcpu_id, vhm_req);
-	clac();
+		stac();
+		acrn_print_request(vcpu->vcpu_id, vhm_req);
+		clac();
 #endif
 
-	/* signal VHM */
-	fire_vhm_interrupt();
+		/* signal VHM */
+		fire_vhm_interrupt();
 
-	/* Polling completion of the request in polling mode */
-	if (is_polling) {
-		/*
-		 * Now, we only have one case that will schedule out this vcpu
-		 * from IO completion polling status, it's pause_vcpu to VCPU_ZOMBIE.
-		 * In this case, we cannot come back to polling status again. Currently,
-		 * it's OK as we needn't handle IO completion in zombie status.
-		 */
-		while (!need_reschedule(vcpu->pcpu_id)) {
-			if (has_complete_ioreq(vcpu)) {
-				/* we have completed ioreq pending */
-				emulate_io_post(vcpu);
-				break;
+		/* Polling completion of the request in polling mode */
+		if (is_polling) {
+			/*
+			 * Now, we only have one case that will schedule out this vcpu
+			 * from IO completion polling status, it's pause_vcpu to VCPU_ZOMBIE.
+			 * In this case, we cannot come back to polling status again. Currently,
+			 * it's OK as we needn't handle IO completion in zombie status.
+			 */
+			while (!need_reschedule(vcpu->pcpu_id)) {
+				if (has_complete_ioreq(vcpu)) {
+					/* we have completed ioreq pending */
+					emulate_io_post(vcpu);
+					break;
+				}
+				asm_pause();
 			}
-			asm_pause();
 		}
+		ret = 0;
+	} else {
+		ret = -EINVAL;
 	}
 
-	return 0;
+
+	return ret;
 }
 
 uint32_t get_vhm_req_state(struct acrn_vm *vm, uint16_t vhm_req_id)
diff --git a/hypervisor/common/schedule.c b/hypervisor/common/schedule.c
index eac7a7b4c..70b121475 100644
--- a/hypervisor/common/schedule.c
+++ b/hypervisor/common/schedule.c
@@ -186,7 +186,6 @@ void schedule(void)
 
 	if (prev == next) {
 		release_schedule_lock(pcpu_id);
-		return;
 	} else {
 		prepare_switch(prev, next);
 		release_schedule_lock(pcpu_id);