diff --git a/drivers/iommu/intel/debugfs.c b/drivers/iommu/intel/debugfs.c
index 21e4e465ca58..d87408ebb830 100644
--- a/drivers/iommu/intel/debugfs.c
+++ b/drivers/iommu/intel/debugfs.c
@@ -690,19 +690,11 @@ static ssize_t dmar_perf_latency_write(struct file *filp,
 {
 	struct dmar_drhd_unit *drhd;
 	struct intel_iommu *iommu;
-	int counting;
-	char buf[64];
+	int ret, counting;
 
-	if (cnt > 63)
-		cnt = 63;
-
-	if (copy_from_user(&buf, ubuf, cnt))
-		return -EFAULT;
-
-	buf[cnt] = 0;
-
-	if (kstrtoint(buf, 0, &counting))
-		return -EINVAL;
+	ret = kstrtoint_from_user(ubuf, cnt, 0, &counting);
+	if (ret)
+		return ret;
 
 	switch (counting) {
 	case 0: