iommu: Make @handle mandatory in iommu_{attach|replace}_group_handle()

Caller of the two APIs always provide a valid handle, make @handle as
mandatory parameter. Take this chance incoporate the handle->domain
set under the protection of group->mutex in iommu_attach_group_handle().

Link: https://patch.msgid.link/r/20250226011849.5102-2-yi.l.liu@intel.com
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/iommu/iommu.c

@@ -3511,10 +3511,11 @@ int iommu_attach_group_handle(struct iommu_domain *domain,
 {
 	int ret;
 
-	if (handle)
-		handle->domain = domain;
+	if (!handle)
+		return -EINVAL;
 
 	mutex_lock(&group->mutex);
+	handle->domain = domain;
 	ret = xa_insert(&group->pasid_array, IOMMU_NO_PASID, handle, GFP_KERNEL);
 	if (ret)
 		goto err_unlock;
@@ -3568,16 +3569,14 @@ int iommu_replace_group_handle(struct iommu_group *group,
 	void *curr;
 	int ret;
 
-	if (!new_domain)
+	if (!new_domain || !handle)
 		return -EINVAL;
 
 	mutex_lock(&group->mutex);
-	if (handle) {
-		ret = xa_reserve(&group->pasid_array, IOMMU_NO_PASID, GFP_KERNEL);
-		if (ret)
-			goto err_unlock;
-		handle->domain = new_domain;
-	}
+	handle->domain = new_domain;
+	ret = xa_reserve(&group->pasid_array, IOMMU_NO_PASID, GFP_KERNEL);
+	if (ret)
+		goto err_unlock;
 
 	ret = __iommu_group_set_domain(group, new_domain);
 	if (ret)