diff --git a/hypervisor/arch/x86/ept.c b/hypervisor/arch/x86/ept.c
index 5bc46be26..dde409f5c 100644
--- a/hypervisor/arch/x86/ept.c
+++ b/hypervisor/arch/x86/ept.c
@@ -344,8 +344,9 @@ int dm_emulate_mmio_post(struct vcpu *vcpu)
 {
 	int ret = 0;
 	int cur = vcpu->vcpu_id;
-	struct vhm_request_buffer *req_buf =
-		(void *)HPA2HVA(vcpu->vm->sw.req_buf);
+	struct vhm_request_buffer *req_buf;
+
+	req_buf = (struct vhm_request_buffer *)(vcpu->vm->sw.req_buf);
 
 	vcpu->req.reqs.mmio_request.value =
 		req_buf->req_queue[cur].reqs.mmio_request.value;
diff --git a/hypervisor/arch/x86/guest/vm.c b/hypervisor/arch/x86/guest/vm.c
index 6c9435cfd..f15fcc9bf 100644
--- a/hypervisor/arch/x86/guest/vm.c
+++ b/hypervisor/arch/x86/guest/vm.c
@@ -170,7 +170,7 @@ int create_vm(struct vm_description *vm_desc, struct vm **rtn_vm)
 
 			/* Populate return VM handle */
 			*rtn_vm = vm;
-			vm->sw.req_buf = 0;
+			vm->sw.req_buf = NULL;
 
 			status = set_vcpuid_entries(vm);
 			if (status)
diff --git a/hypervisor/arch/x86/io.c b/hypervisor/arch/x86/io.c
index a9853240c..c93fc05ce 100644
--- a/hypervisor/arch/x86/io.c
+++ b/hypervisor/arch/x86/io.c
@@ -39,12 +39,13 @@ int dm_emulate_pio_post(struct vcpu *vcpu)
 {
 	int cur = vcpu->vcpu_id;
 	int cur_context = vcpu->arch_vcpu.cur_context;
-	struct vhm_request_buffer *req_buf =
-		(void *)HPA2HVA(vcpu->vm->sw.req_buf);
+	struct vhm_request_buffer *req_buf = NULL;
 	uint32_t mask =
 		0xFFFFFFFFul >> (32 - 8 * vcpu->req.reqs.pio_request.size);
 	uint64_t *rax;
 
+	req_buf = (struct vhm_request_buffer *)(vcpu->vm->sw.req_buf);
+
 	rax = &vcpu->arch_vcpu.contexts[cur_context].guest_cpu_regs.regs.rax;
 	vcpu->req.reqs.pio_request.value =
 		req_buf->req_queue[cur].reqs.pio_request.value;
diff --git a/hypervisor/common/hypercall.c b/hypervisor/common/hypercall.c
index 984e72989..64deb6ccb 100644
--- a/hypervisor/common/hypercall.c
+++ b/hypervisor/common/hypercall.c
@@ -213,7 +213,7 @@ int64_t hcall_resume_vm(uint64_t vmid)
 
 	if (target_vm == NULL)
 		return -1;
-	if (target_vm->sw.req_buf == 0)
+	if (target_vm->sw.req_buf == NULL)
 		ret = -1;
 	else
 		ret = start_vm(target_vm);
@@ -323,6 +323,7 @@ int64_t hcall_inject_msi(struct vm *vm, uint64_t vmid, uint64_t param)
 int64_t hcall_set_ioreq_buffer(struct vm *vm, uint64_t vmid, uint64_t param)
 {
 	int64_t ret = 0;
+	uint64_t hpa = 0;
 	struct acrn_set_ioreq_buffer iobuf;
 	struct vm *target_vm = get_vm_from_vmid(vmid);
 
@@ -336,11 +337,17 @@ int64_t hcall_set_ioreq_buffer(struct vm *vm, uint64_t vmid, uint64_t param)
 		return -1;
 	}
 
-	dev_dbg(ACRN_DBG_HYCALL, "[%d] SET BUFFER=0x%x",
+	dev_dbg(ACRN_DBG_HYCALL, "[%d] SET BUFFER=0x%p",
 			vmid, iobuf.req_buf);
 
-	/* store gpa of guest request_buffer */
-	target_vm->sw.req_buf = gpa2hpa(vm, iobuf.req_buf);
+	hpa = gpa2hpa(vm, iobuf.req_buf);
+	if (hpa == 0) {
+		pr_err("%s: invalid GPA.\n", __func__);
+		target_vm->sw.req_buf = NULL;
+		return -EINVAL;
+	}
+
+	target_vm->sw.req_buf = HPA2HVA(hpa);
 
 	return ret;
 }
@@ -386,8 +393,8 @@ int64_t hcall_notify_req_finish(uint64_t vmid, uint64_t vcpu_id)
 	struct vm *target_vm = get_vm_from_vmid(vmid);
 
 	/* make sure we have set req_buf */
-	if (!target_vm || target_vm->sw.req_buf == 0)
-		return -1;
+	if (!target_vm || target_vm->sw.req_buf == NULL)
+		return -EINVAL;
 
 	dev_dbg(ACRN_DBG_HYCALL, "[%d] NOTIFY_FINISH for vcpu %d",
 			vmid, vcpu_id);
@@ -779,16 +786,17 @@ static void acrn_print_request(int vcpu_id, struct vhm_request *req)
 
 int acrn_insert_request_wait(struct vcpu *vcpu, struct vhm_request *req)
 {
-	struct vhm_request_buffer *req_buf =
-		(void *)HPA2HVA(vcpu->vm->sw.req_buf);
+	struct vhm_request_buffer *req_buf = NULL;
 	long cur;
 
 	ASSERT(sizeof(*req) == (4096/VHM_REQUEST_MAX),
 			"vhm_request page broken!");
 
 
-	if (!vcpu || !req || vcpu->vm->sw.req_buf == 0)
-		return -1;
+	if (!vcpu || !req || vcpu->vm->sw.req_buf == NULL)
+		return -EINVAL;
+
+	req_buf = (struct vhm_request_buffer *)(vcpu->vm->sw.req_buf);
 
 	/* ACRN insert request to VHM and inject upcall */
 	cur = vcpu->vcpu_id;
@@ -820,9 +828,9 @@ int acrn_insert_request_nowait(struct vcpu *vcpu, struct vhm_request *req)
 	long cur;
 
 	if (!vcpu || !req || !vcpu->vm->sw.req_buf)
-		return -1;
+		return -EINVAL;
 
-	req_buf = (void *)gpa2hpa(vcpu->vm, vcpu->vm->sw.req_buf);
+	req_buf = (struct vhm_request_buffer *)(vcpu->vm->sw.req_buf);
 
 	/* ACRN insert request to VHM and inject upcall */
 	cur = vcpu->vcpu_id;
diff --git a/hypervisor/include/arch/x86/guest/vm.h b/hypervisor/include/arch/x86/guest/vm.h
index 0f2bc8b2d..b766cd6f3 100644
--- a/hypervisor/include/arch/x86/guest/vm.h
+++ b/hypervisor/include/arch/x86/guest/vm.h
@@ -76,8 +76,8 @@ struct vm_sw_info {
 	struct sw_kernel_info kernel_info;
 	/* Additional information specific to Linux guests */
 	struct sw_linux linux_info;
-	/* GPA Address of guest OS's request buffer */
-	uint64_t req_buf;
+	/* HVA to guest OS's request buffer */
+	void *req_buf;
 };
 
 struct vm_pm_info {