diff --git a/arch/powerpc/kernel/dma-iommu.c b/arch/powerpc/kernel/dma-iommu.c
index a1c744194018..9a2a3b95f72d 100644
--- a/arch/powerpc/kernel/dma-iommu.c
+++ b/arch/powerpc/kernel/dma-iommu.c
@@ -10,6 +10,16 @@
 #include <linux/pci.h>
 #include <asm/iommu.h>
 
+static inline bool can_map_direct(struct device *dev, phys_addr_t addr)
+{
+	return dev->bus_dma_limit >= phys_to_dma(dev, addr);
+}
+
+static inline bool dma_handle_direct(struct device *dev, dma_addr_t dma_handle)
+{
+	return dma_handle >= dev->archdata.dma_offset;
+}
+
 /*
  * Generic iommu implementation
  */
@@ -44,6 +54,12 @@ static dma_addr_t dma_iommu_map_page(struct device *dev, struct page *page,
 				     enum dma_data_direction direction,
 				     unsigned long attrs)
 {
+	if (dev->bus_dma_limit &&
+	    can_map_direct(dev, (phys_addr_t) page_to_phys(page) +
+			   offset + size))
+		return dma_direct_map_page(dev, page, offset, size, direction,
+					   attrs);
+
 	return iommu_map_page(dev, get_iommu_table_base(dev), page, offset,
 			      size, dma_get_mask(dev), direction, attrs);
 }
@@ -53,6 +69,12 @@ static void dma_iommu_unmap_page(struct device *dev, dma_addr_t dma_handle,
 				 size_t size, enum dma_data_direction direction,
 				 unsigned long attrs)
 {
+	if (dev->bus_dma_limit &&
+	    dma_handle_direct(dev, dma_handle + size)) {
+		dma_direct_unmap_page(dev, dma_handle, size, direction, attrs);
+		return;
+	}
+
 	iommu_unmap_page(get_iommu_table_base(dev), dma_handle, size, direction,
 			 attrs);
 }
@@ -62,6 +84,22 @@ static int dma_iommu_map_sg(struct device *dev, struct scatterlist *sglist,
 			    int nelems, enum dma_data_direction direction,
 			    unsigned long attrs)
 {
+	if (dev->bus_dma_limit) {
+		struct scatterlist *s;
+		bool direct = true;
+		int i;
+
+		for_each_sg(sglist, s, nelems, i) {
+			direct = can_map_direct(dev,
+					sg_phys(s) + s->offset + s->length);
+			if (!direct)
+				break;
+		}
+		if (direct)
+			return dma_direct_map_sg(dev, sglist, nelems, direction,
+						 attrs);
+	}
+
 	return ppc_iommu_map_sg(dev, get_iommu_table_base(dev), sglist, nelems,
 				dma_get_mask(dev), direction, attrs);
 }
@@ -70,6 +108,24 @@ static void dma_iommu_unmap_sg(struct device *dev, struct scatterlist *sglist,
 		int nelems, enum dma_data_direction direction,
 		unsigned long attrs)
 {
+	if (dev->bus_dma_limit) {
+		struct scatterlist *s;
+		bool direct = true;
+		int i;
+
+		for_each_sg(sglist, s, nelems, i) {
+			direct = dma_handle_direct(dev,
+						   s->dma_address + s->length);
+			if (!direct)
+				break;
+		}
+		if (direct) {
+			dma_direct_unmap_sg(dev, sglist, nelems, direction,
+					    attrs);
+			return;
+		}
+	}
+
 	ppc_iommu_unmap_sg(get_iommu_table_base(dev), sglist, nelems,
 			   direction, attrs);
 }
@@ -90,8 +146,16 @@ int dma_iommu_dma_supported(struct device *dev, u64 mask)
 	struct iommu_table *tbl = get_iommu_table_base(dev);
 
 	if (dev_is_pci(dev) && dma_iommu_bypass_supported(dev, mask)) {
-		dev->dma_ops_bypass = true;
-		dev_dbg(dev, "iommu: 64-bit OK, using fixed ops\n");
+		/*
+		 * dma_iommu_bypass_supported() sets dma_max when there is
+		 * 1:1 mapping but it is somehow limited.
+		 * ibm,pmemory is one example.
+		 */
+		dev->dma_ops_bypass = dev->bus_dma_limit == 0;
+		if (!dev->dma_ops_bypass)
+			dev_warn(dev, "iommu: 64-bit OK but using default ops\n");
+		else
+			dev_dbg(dev, "iommu: 64-bit OK, using fixed ops\n");
 		return 1;
 	}
 
diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index e4198700ed1a..e6aa6c923666 100644
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c
@@ -839,7 +839,7 @@ static void remove_ddw(struct device_node *np, bool remove_prop)
 			np, ret);
 }
 
-static u64 find_existing_ddw(struct device_node *pdn)
+static u64 find_existing_ddw(struct device_node *pdn, int *window_shift)
 {
 	struct direct_window *window;
 	const struct dynamic_dma_window_prop *direct64;
@@ -851,6 +851,7 @@ static u64 find_existing_ddw(struct device_node *pdn)
 		if (window->device == pdn) {
 			direct64 = window->prop;
 			dma_addr = be64_to_cpu(direct64->dma_base);
+			*window_shift = be32_to_cpu(direct64->window_shift);
 			break;
 		}
 	}
@@ -1111,11 +1112,13 @@ static void reset_dma_window(struct pci_dev *dev, struct device_node *par_dn)
  */
 static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 {
-	int len, ret;
+	int len = 0, ret;
+	bool pmem_present = of_find_node_by_type(NULL, "ibm,pmemory") != NULL;
+	int max_ram_len = order_base_2(ddw_memory_hotplug_max());
 	struct ddw_query_response query;
 	struct ddw_create_response create;
 	int page_shift;
-	u64 dma_addr, max_addr;
+	u64 dma_addr;
 	struct device_node *dn;
 	u32 ddw_avail[DDW_APPLICABLE_SIZE];
 	struct direct_window *window;
@@ -1126,7 +1129,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 
 	mutex_lock(&direct_window_init_mutex);
 
-	dma_addr = find_existing_ddw(pdn);
+	dma_addr = find_existing_ddw(pdn, &len);
 	if (dma_addr != 0)
 		goto out_unlock;
 
@@ -1212,14 +1215,27 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 	}
 	/* verify the window * number of ptes will map the partition */
 	/* check largest block * page size > max memory hotplug addr */
-	max_addr = ddw_memory_hotplug_max();
-	if (query.largest_available_block < (max_addr >> page_shift)) {
+	/*
+	 * The "ibm,pmemory" can appear anywhere in the address space.
+	 * Assuming it is still backed by page structs, try MAX_PHYSMEM_BITS
+	 * for the upper limit and fallback to max RAM otherwise but this
+	 * disables device::dma_ops_bypass.
+	 */
+	len = max_ram_len;
+	if (pmem_present) {
+		if (query.largest_available_block >=
+		    (1ULL << (MAX_PHYSMEM_BITS - page_shift)))
+			len = MAX_PHYSMEM_BITS - page_shift;
+		else
+			dev_info(&dev->dev, "Skipping ibm,pmemory");
+	}
+
+	if (query.largest_available_block < (1ULL << (len - page_shift))) {
 		dev_dbg(&dev->dev, "can't map partition max 0x%llx with %llu "
-			  "%llu-sized pages\n", max_addr,  query.largest_available_block,
+			  "%llu-sized pages\n", 1ULL << len, query.largest_available_block,
 			  1ULL << page_shift);
 		goto out_failed;
 	}
-	len = order_base_2(max_addr);
 	win64 = kzalloc(sizeof(struct property), GFP_KERNEL);
 	if (!win64) {
 		dev_info(&dev->dev,
@@ -1299,6 +1315,15 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 
 out_unlock:
 	mutex_unlock(&direct_window_init_mutex);
+
+	/*
+	 * If we have persistent memory and the window size is only as big
+	 * as RAM, then we failed to create a window to cover persistent
+	 * memory and need to set the DMA limit.
+	 */
+	if (pmem_present && dma_addr && (len == max_ram_len))
+		dev->dev.bus_dma_limit = dma_addr + (1ULL << len);
+
 	return dma_addr;
 }
 
