diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c
index 568c52317757ca2924598b69c7329dcfad940356..483f7bc379fa84beace777cb5acef14de4f0cc73 100644
--- a/drivers/iommu/amd_iommu_init.c
+++ b/drivers/iommu/amd_iommu_init.c
@@ -1655,27 +1655,39 @@ static int iommu_pc_get_set_reg(struct amd_iommu *iommu, u8 bank, u8 cntr,
 static void init_iommu_perf_ctr(struct amd_iommu *iommu)
 {
 	struct pci_dev *pdev = iommu->dev;
-	u64 val = 0xabcd, val2 = 0;
+	u64 val = 0xabcd, val2 = 0, save_reg = 0;
 
 	if (!iommu_feature(iommu, FEATURE_PC))
 		return;
 
 	amd_iommu_pc_present = true;
 
+	/* save the value to restore, if writable */
+	if (iommu_pc_get_set_reg(iommu, 0, 0, 0, &save_reg, false))
+		goto pc_false;
+
 	/* Check if the performance counters can be written to */
 	if ((iommu_pc_get_set_reg(iommu, 0, 0, 0, &val, true)) ||
 	    (iommu_pc_get_set_reg(iommu, 0, 0, 0, &val2, false)) ||
-	    (val != val2)) {
-		pci_err(pdev, "Unable to write to IOMMU perf counter.\n");
-		amd_iommu_pc_present = false;
-		return;
-	}
+	    (val != val2))
+		goto pc_false;
+
+	/* restore */
+	if (iommu_pc_get_set_reg(iommu, 0, 0, 0, &save_reg, true))
+		goto pc_false;
 
 	pci_info(pdev, "IOMMU performance counters supported\n");
 
 	val = readl(iommu->mmio_base + MMIO_CNTR_CONF_OFFSET);
 	iommu->max_banks = (u8) ((val >> 12) & 0x3f);
 	iommu->max_counters = (u8) ((val >> 7) & 0xf);
+
+	return;
+
+pc_false:
+	pci_err(pdev, "Unable to read/write to IOMMU perf counter.\n");
+	amd_iommu_pc_present = false;
+	return;
 }
 
 static ssize_t amd_iommu_show_cap(struct device *dev,
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 1801f0aaf01327337b888b796474d8748621655c..932267f49f9a8c6529c120c938262a1d15f1f11f 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -5163,7 +5163,8 @@ static void dmar_remove_one_dev_info(struct device *dev)
 
 	spin_lock_irqsave(&device_domain_lock, flags);
 	info = dev->archdata.iommu;
-	if (info)
+	if (info && info != DEFER_DEVICE_DOMAIN_INFO
+	    && info != DUMMY_DEVICE_DOMAIN_INFO)
 		__dmar_remove_one_dev_info(info);
 	spin_unlock_irqrestore(&device_domain_lock, flags);
 }