diff --git a/hypervisor/arch/x86/guest/assign.c b/hypervisor/arch/x86/guest/assign.c
index a21425eb2..8a9f5c602 100644
--- a/hypervisor/arch/x86/guest/assign.c
+++ b/hypervisor/arch/x86/guest/assign.c
@@ -358,6 +358,7 @@ static struct ptirq_remapping_info *add_intx_remapping(struct acrn_vm *vm, uint3
 		uint32_t phys_pin, bool pic_pin)
 {
 	struct ptirq_remapping_info *entry = NULL;
+	bool entry_is_updated = true;
 	uint32_t vpin_src = pic_pin ? PTDEV_VPIN_PIC : PTDEV_VPIN_IOAPIC;
 	DEFINE_IOAPIC_SID(phys_sid, phys_pin, 0U);
 	DEFINE_IOAPIC_SID(virt_sid, virt_pin, vpin_src);
@@ -398,9 +399,10 @@ static struct ptirq_remapping_info *add_intx_remapping(struct acrn_vm *vm, uint3
 		} else {
 			/* The mapping has already been added to the VM. No action
 			 * required. */
+			entry_is_updated = false;
 		}
 
-		if (entry != NULL) {
+		if (entry != NULL && entry_is_updated) {
 			if (pic_pin) {
 				vm->arch_vm.vpic.vpin_to_pt_entry[virt_pin] = entry;
 			} else {
diff --git a/hypervisor/arch/x86/vtd.c b/hypervisor/arch/x86/vtd.c
index 9b2d1e2e4..1a1a0aea2 100644
--- a/hypervisor/arch/x86/vtd.c
+++ b/hypervisor/arch/x86/vtd.c
@@ -1182,7 +1182,7 @@ static int32_t remove_iommu_device(const struct iommu_domain *domain, uint16_t s
 
 			context_entry = context + devfun;
 
-			if (context_entry == NULL) {
+			if (context == NULL || context_entry == NULL) {
 				pr_err("dmar context entry is invalid");
 				ret = -EINVAL;
 			} else if ((uint16_t)dmar_get_bitslice(context_entry->hi_64, CTX_ENTRY_UPPER_DID_MASK, CTX_ENTRY_UPPER_DID_POS) != vmid_to_domainid(domain->vm_id)) {