Message-Id: <1481215184-18551-6-git-send-email-jglisse@redhat.com>
Date:   Thu,  8 Dec 2016 11:39:33 -0500
From:   Jérôme Glisse <jglisse@...hat.com>
To:     akpm@...ux-foundation.org, <linux-kernel@...r.kernel.org>,
        linux-mm@...ck.org
Cc:     John Hubbard <jhubbard@...dia.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>
Subject: [HMM v14 05/16] mm/ZONE_DEVICE/unaddressable: add support for un-addressable device memory

This add support for un-addressable device memory. Such memory is hotpluged
only so we can have struct page but we should never map them as such memory
can not be accessed by CPU. For that reason it uses a special swap entry for
CPU page table entry.

This patch implement all the logic from special swap type to handling CPU
page fault through a callback specified in the ZONE_DEVICE pgmap struct.

Architecture that wish to support un-addressable device memory should make
sure to never populate the kernel linar mapping for the physical range.

Signed-off-by: Jérôme Glisse <jglisse@...hat.com>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Ross Zwisler <ross.zwisler@...ux.intel.com>
---
 drivers/dax/pmem.c                |  4 +--
 drivers/nvdimm/pmem.c             |  6 ++--
 fs/proc/task_mmu.c                | 10 +++++-
 include/linux/memory_hotplug.h    |  7 ++++
 include/linux/memremap.h          | 29 +++++++++++++++--
 include/linux/swap.h              | 18 +++++++++--
 include/linux/swapops.h           | 67 +++++++++++++++++++++++++++++++++++++++
 kernel/memremap.c                 | 43 +++++++++++++++++++++++--
 mm/Kconfig                        | 12 +++++++
 mm/memory.c                       | 62 ++++++++++++++++++++++++++++++++++++
 mm/mprotect.c                     | 12 +++++++
 tools/testing/nvdimm/test/iomap.c |  3 +-
 12 files changed, 259 insertions(+), 14 deletions(-)

diff --git a/drivers/dax/pmem.c b/drivers/dax/pmem.c
index 52ff674..f65a68a 100644
--- a/drivers/dax/pmem.c
+++ b/drivers/dax/pmem.c
@@ -107,8 +107,8 @@ static int dax_pmem_probe(struct device *dev)
 	if (rc)
 		return rc;
 
-	addr = devm_memremap_pages(dev, &res, &dax_pmem->ref,
-				   altmap, NULL, NULL);
+	addr = devm_memremap_pages(dev, &res, &dax_pmem->ref, altmap,
+				   NULL, NULL, NULL, NULL, MEMORY_DEVICE);
 	if (IS_ERR(addr))
 		return PTR_ERR(addr);
 
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index c261d12..dcad86f 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -260,7 +260,8 @@ static int pmem_attach_disk(struct device *dev,
 	pmem->pfn_flags = PFN_DEV;
 	if (is_nd_pfn(dev)) {
 		addr = devm_memremap_pages(dev, &pfn_res, &q->q_usage_counter,
-					   altmap, NULL, NULL);
+					   altmap, NULL, NULL, NULL,
+					   NULL, MEMORY_DEVICE);
 		pfn_sb = nd_pfn->pfn_sb;
 		pmem->data_offset = le64_to_cpu(pfn_sb->dataoff);
 		pmem->pfn_pad = resource_size(res) - resource_size(&pfn_res);
@@ -270,7 +271,8 @@ static int pmem_attach_disk(struct device *dev,
 	} else if (pmem_should_map_pages(dev)) {
 		addr = devm_memremap_pages(dev, &nsio->res,
 					   &q->q_usage_counter,
-					   NULL, NULL, NULL);
+					   NULL, NULL, NULL, NULL,
+					   NULL, MEMORY_DEVICE);
 		pmem->pfn_flags |= PFN_MAP;
 	} else
 		addr = devm_memremap(dev, pmem->phys_addr,
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 6909582..0726d39 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -544,8 +544,11 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
 			} else {
 				mss->swap_pss += (u64)PAGE_SIZE << PSS_SHIFT;
 			}
-		} else if (is_migration_entry(swpent))
+		} else if (is_migration_entry(swpent)) {
 			page = migration_entry_to_page(swpent);
+		} else if (is_device_entry(swpent)) {
+			page = device_entry_to_page(swpent);
+		}
 	} else if (unlikely(IS_ENABLED(CONFIG_SHMEM) && mss->check_shmem_swap
 							&& pte_none(*pte))) {
 		page = find_get_entry(vma->vm_file->f_mapping,
@@ -708,6 +711,8 @@ static int smaps_hugetlb_range(pte_t *pte, unsigned long hmask,
 
 		if (is_migration_entry(swpent))
 			page = migration_entry_to_page(swpent);
+		if (is_device_entry(swpent))
+			page = device_entry_to_page(swpent);
 	}
 	if (page) {
 		int mapcount = page_mapcount(page);
@@ -1191,6 +1196,9 @@ static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm,
 		flags |= PM_SWAP;
 		if (is_migration_entry(entry))
 			page = migration_entry_to_page(entry);
+
+		if (is_device_entry(entry))
+			page = device_entry_to_page(entry);
 	}
 
 	if (page && !PageAnon(page))
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 3f50eb8..e7c5dc6 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -285,15 +285,22 @@ extern int zone_for_memory(int nid, u64 start, u64 size, int zone_default,
  * never relied on struct page migration so far and new user of might also
  * prefer avoiding struct page migration.
  *
+ * For device memory (which use ZONE_DEVICE) we want differentiate between CPU
+ * accessible memory (persitent memory, device memory on an architecture with a
+ * system bus that allow transparent access to device memory) and unaddressable
+ * memory (device memory that can not be accessed by CPU directly).
+ *
  * New non device memory specific flags can be added if ever needed.
  *
  * MEMORY_REGULAR: regular system memory
  * DEVICE_MEMORY: device memory create a ZONE_DEVICE zone for it
  * DEVICE_MEMORY_ALLOW_MIGRATE: page in that device memory ca be migrated
+ * MEMORY_DEVICE_UNADDRESSABLE: un-addressable memory (CPU can not access it)
  */
 #define MEMORY_NORMAL 0
 #define MEMORY_DEVICE (1 << 0)
 #define MEMORY_DEVICE_ALLOW_MIGRATE (1 << 1)
+#define MEMORY_DEVICE_UNADDRESSABLE (1 << 2)
 
 extern int arch_add_memory(int nid, u64 start, u64 size, int flags);
 extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages);
diff --git a/include/linux/memremap.h b/include/linux/memremap.h
index 7845f2e..a646c47 100644
--- a/include/linux/memremap.h
+++ b/include/linux/memremap.h
@@ -35,31 +35,42 @@ static inline struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start)
 }
 #endif
 
+typedef int (*dev_page_fault_t)(struct vm_area_struct *vma,
+				unsigned long addr,
+				struct page *page,
+				unsigned flags,
+				pmd_t *pmdp);
 typedef void (*dev_page_free_t)(struct page *page, void *data);
 
 /**
  * struct dev_pagemap - metadata for ZONE_DEVICE mappings
+ * @page_fault: callback when CPU fault on an un-addressable device page
  * @page_free: free page callback when page refcount reach 1
  * @altmap: pre-allocated/reserved memory for vmemmap allocations
  * @res: physical address range covered by @ref
  * @ref: reference count that pins the devm_memremap_pages() mapping
  * @dev: host device of the mapping for debug
  * @data: privata data pointer for page_free
+ * @flags: device memory flags (look for MEMORY_DEVICE_* memory_hotplug.h)
  */
 struct dev_pagemap {
+	dev_page_fault_t page_fault;
 	dev_page_free_t page_free;
 	struct vmem_altmap *altmap;
 	const struct resource *res;
 	struct percpu_ref *ref;
 	struct device *dev;
 	void *data;
+	int flags;
 };
 
 #ifdef CONFIG_ZONE_DEVICE
 void *devm_memremap_pages(struct device *dev, struct resource *res,
 			  struct percpu_ref *ref, struct vmem_altmap *altmap,
+			  struct dev_pagemap **ppgmap,
+			  dev_page_fault_t page_fault,
 			  dev_page_free_t page_free,
-			  void *data);
+			  void *data, int flags);
 struct dev_pagemap *find_dev_pagemap(resource_size_t phys);
 int devm_memremap_pages_remove(struct device *dev, struct dev_pagemap *pgmap);
 
@@ -68,13 +79,22 @@ static inline bool dev_page_allow_migrate(const struct page *page)
 	return ((page_zonenum(page) == ZONE_DEVICE) &&
 		(page->pgmap->flags & MEMORY_DEVICE_ALLOW_MIGRATE));
 }
+
+static inline bool is_addressable_page(const struct page *page)
+{
+	return ((page_zonenum(page) != ZONE_DEVICE) ||
+		!(page->pgmap->flags & MEMORY_DEVICE_UNADDRESSABLE));
+}
 #else
 static inline void *devm_memremap_pages(struct device *dev,
 					struct resource *res,
 					struct percpu_ref *ref,
 					struct vmem_altmap *altmap,
+					struct dev_pagemap **ppgmap,
+					dev_page_fault_t page_fault,
 					dev_page_free_t page_free,
-					void *data)
+					void *data,
+					int flags)
 {
 	/*
 	 * Fail attempts to call devm_memremap_pages() without
@@ -100,6 +120,11 @@ static inline bool dev_page_allow_migrate(const struct page *page)
 {
 	return false;
 }
+
+static inline bool is_addressable_page(const struct page *page)
+{
+	return true;
+}
 #endif
 
 /**
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 7e553e1..599cb54 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -50,6 +50,17 @@ static inline int current_is_kswapd(void)
  */
 
 /*
+ * Un-addressable device memory support
+ */
+#ifdef CONFIG_DEVICE_UNADDRESSABLE
+#define SWP_DEVICE_NUM 2
+#define SWP_DEVICE_WRITE (MAX_SWAPFILES + SWP_HWPOISON_NUM + SWP_MIGRATION_NUM)
+#define SWP_DEVICE (MAX_SWAPFILES + SWP_HWPOISON_NUM + SWP_MIGRATION_NUM + 1)
+#else
+#define SWP_DEVICE_NUM 0
+#endif
+
+/*
  * NUMA node memory migration support
  */
 #ifdef CONFIG_MIGRATION
@@ -71,7 +82,8 @@ static inline int current_is_kswapd(void)
 #endif
 
 #define MAX_SWAPFILES \
-	((1 << MAX_SWAPFILES_SHIFT) - SWP_MIGRATION_NUM - SWP_HWPOISON_NUM)
+	((1 << MAX_SWAPFILES_SHIFT) - SWP_DEVICE_NUM - \
+	SWP_MIGRATION_NUM - SWP_HWPOISON_NUM)
 
 /*
  * Magic header for a swap area. The first part of the union is
@@ -442,8 +454,8 @@ static inline void show_swap_cache_info(void)
 {
 }
 
-#define free_swap_and_cache(swp)	is_migration_entry(swp)
-#define swapcache_prepare(swp)		is_migration_entry(swp)
+#define free_swap_and_cache(e) (is_migration_entry(e) || is_device_entry(e))
+#define swapcache_prepare(e) (is_migration_entry(e) || is_device_entry(e))
 
 static inline int add_swap_count_continuation(swp_entry_t swp, gfp_t gfp_mask)
 {
diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index 5c3a5f3..0e339f0 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -100,6 +100,73 @@ static inline void *swp_to_radix_entry(swp_entry_t entry)
 	return (void *)(value | RADIX_TREE_EXCEPTIONAL_ENTRY);
 }
 
+#if IS_ENABLED(CONFIG_DEVICE_UNADDRESSABLE)
+static inline swp_entry_t make_device_entry(struct page *page, bool write)
+{
+	return swp_entry(write?SWP_DEVICE_WRITE:SWP_DEVICE, page_to_pfn(page));
+}
+
+static inline bool is_device_entry(swp_entry_t entry)
+{
+	int type = swp_type(entry);
+	return type == SWP_DEVICE || type == SWP_DEVICE_WRITE;
+}
+
+static inline void make_device_entry_read(swp_entry_t *entry)
+{
+	*entry = swp_entry(SWP_DEVICE, swp_offset(*entry));
+}
+
+static inline bool is_write_device_entry(swp_entry_t entry)
+{
+	return unlikely(swp_type(entry) == SWP_DEVICE_WRITE);
+}
+
+static inline struct page *device_entry_to_page(swp_entry_t entry)
+{
+	return pfn_to_page(swp_offset(entry));
+}
+
+int device_entry_fault(struct vm_area_struct *vma,
+		       unsigned long addr,
+		       swp_entry_t entry,
+		       unsigned flags,
+		       pmd_t *pmdp);
+#else /* CONFIG_DEVICE_UNADDRESSABLE */
+static inline swp_entry_t make_device_entry(struct page *page, bool write)
+{
+	return swp_entry(0, 0);
+}
+
+static inline void make_device_entry_read(swp_entry_t *entry)
+{
+}
+
+static inline bool is_device_entry(swp_entry_t entry)
+{
+	return false;
+}
+
+static inline bool is_write_device_entry(swp_entry_t entry)
+{
+	return false;
+}
+
+static inline struct page *device_entry_to_page(swp_entry_t entry)
+{
+	return NULL;
+}
+
+static inline int device_entry_fault(struct vm_area_struct *vma,
+				     unsigned long addr,
+				     swp_entry_t entry,
+				     unsigned flags,
+				     pmd_t *pmdp)
+{
+	return VM_FAULT_SIGBUS;
+}
+#endif /* CONFIG_DEVICE_UNADDRESSABLE */
+
 #ifdef CONFIG_MIGRATION
 static inline swp_entry_t make_migration_entry(struct page *page, int write)
 {
diff --git a/kernel/memremap.c b/kernel/memremap.c
index bc1e400..3df08f4 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -18,6 +18,8 @@
 #include <linux/io.h>
 #include <linux/mm.h>
 #include <linux/memory_hotplug.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
 
 #ifndef ioremap_cache
 /* temporary while we convert existing ioremap_cache users to memremap */
@@ -200,6 +202,21 @@ void put_zone_device_page(struct page *page)
 }
 EXPORT_SYMBOL(put_zone_device_page);
 
+#if IS_ENABLED(CONFIG_DEVICE_UNADDRESSABLE)
+int device_entry_fault(struct vm_area_struct *vma,
+		       unsigned long addr,
+		       swp_entry_t entry,
+		       unsigned flags,
+		       pmd_t *pmdp)
+{
+	struct page *page = device_entry_to_page(entry);
+
+	BUG_ON(!page->pgmap->page_fault);
+	return page->pgmap->page_fault(vma, addr, page, flags, pmdp);
+}
+EXPORT_SYMBOL(device_entry_fault);
+#endif /* CONFIG_DEVICE_UNADDRESSABLE */
+
 static void pgmap_radix_release(struct resource *res)
 {
 	resource_size_t key, align_start, align_size, align_end;
@@ -252,7 +269,7 @@ static void devm_memremap_pages_release(struct device *dev, void *data)
 	/* pages are dead and unused, undo the arch mapping */
 	align_start = res->start & ~(SECTION_SIZE - 1);
 	align_size = ALIGN(resource_size(res), SECTION_SIZE);
-	arch_remove_memory(align_start, align_size, MEMORY_DEVICE);
+	arch_remove_memory(align_start, align_size, pgmap->flags);
 	untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
 	pgmap_radix_release(res);
 	dev_WARN_ONCE(dev, pgmap->altmap && pgmap->altmap->alloc,
@@ -276,8 +293,11 @@ struct dev_pagemap *find_dev_pagemap(resource_size_t phys)
  * @res: "host memory" address range
  * @ref: a live per-cpu reference count
  * @altmap: optional descriptor for allocating the memmap from @res
+ * @ppgmap: pointer set to new page dev_pagemap on success
+ * @page_fault: callback for CPU page fault on un-addressable memory
  * @page_free: callback call when page refcount reach 1 ie it is free
  * @data: privata data pointer for page_free
+ * @flags: device memory flags (look for MEMORY_DEVICE_* memory_hotplug.h)
  *
  * Notes:
  * 1/ @ref must be 'live' on entry and 'dead' before devm_memunmap_pages() time
@@ -289,8 +309,10 @@ struct dev_pagemap *find_dev_pagemap(resource_size_t phys)
  */
 void *devm_memremap_pages(struct device *dev, struct resource *res,
 			  struct percpu_ref *ref, struct vmem_altmap *altmap,
+			  struct dev_pagemap **ppgmap,
+			  dev_page_fault_t page_fault,
 			  dev_page_free_t page_free,
-			  void *data)
+			  void *data, int flags)
 {
 	resource_size_t key, align_start, align_size, align_end;
 	pgprot_t pgprot = PAGE_KERNEL;
@@ -299,6 +321,17 @@ void *devm_memremap_pages(struct device *dev, struct resource *res,
 	int error, nid, is_ram;
 	unsigned long pfn;
 
+	if (!(flags & MEMORY_DEVICE)) {
+		WARN_ONCE(1, "%s attempted on non device memory\n", __func__);
+		return ERR_PTR(-EINVAL);
+	}
+
+	if (altmap && (flags & MEMORY_DEVICE_UNADDRESSABLE)) {
+		WARN_ONCE(1, "%s with altmap for un-addressable "
+			  "device memory\n", __func__);
+		return ERR_PTR(-EINVAL);
+	}
+
 	align_start = res->start & ~(SECTION_SIZE - 1);
 	align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
 		- align_start;
@@ -332,8 +365,10 @@ void *devm_memremap_pages(struct device *dev, struct resource *res,
 	}
 	pgmap->ref = ref;
 	pgmap->res = &page_map->res;
+	pgmap->page_fault = page_fault;
 	pgmap->page_free = page_free;
 	pgmap->data = data;
+	pgmap->flags = flags;
 
 	mutex_lock(&pgmap_lock);
 	error = 0;
@@ -370,7 +405,7 @@ void *devm_memremap_pages(struct device *dev, struct resource *res,
 	if (error)
 		goto err_pfn_remap;
 
-	error = arch_add_memory(nid, align_start, align_size, MEMORY_DEVICE);
+	error = arch_add_memory(nid, align_start, align_size, pgmap->flags);
 	if (error)
 		goto err_add_memory;
 
@@ -387,6 +422,8 @@ void *devm_memremap_pages(struct device *dev, struct resource *res,
 		page->pgmap = pgmap;
 	}
 	devres_add(dev, page_map);
+	if (ppgmap)
+		*ppgmap = pgmap;
 	return __va(res->start);
 
  err_add_memory:
diff --git a/mm/Kconfig b/mm/Kconfig
index be0ee11..8564a5f 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -704,6 +704,18 @@ config ZONE_DEVICE
 
 	  If FS_DAX is enabled, then say Y.
 
+config DEVICE_UNADDRESSABLE
+	bool "Un-addressable device memory (GPU memory, ...)"
+	depends on ZONE_DEVICE
+
+	help
+	  Allow to create struct page for un-addressable device memory
+	  ie memory that is only accessible by the device (or group of
+	  devices).
+
+	  Having struct page is necessary for process memory migration
+	  to device memory.
+
 config FRAME_VECTOR
 	bool
 
diff --git a/mm/memory.c b/mm/memory.c
index 840adc6..03306cf 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -45,6 +45,7 @@
 #include <linux/swap.h>
 #include <linux/highmem.h>
 #include <linux/pagemap.h>
+#include <linux/memremap.h>
 #include <linux/ksm.h>
 #include <linux/rmap.h>
 #include <linux/export.h>
@@ -888,6 +889,25 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 					pte = pte_swp_mksoft_dirty(pte);
 				set_pte_at(src_mm, addr, src_pte, pte);
 			}
+		} else if (is_device_entry(entry)) {
+			page = device_entry_to_page(entry);
+
+			/*
+			 * Update rss count even for un-addressable page as
+			 * they should be consider just like any other page.
+			 */
+			get_page(page);
+			rss[mm_counter(page)]++;
+			page_dup_rmap(page, false);
+
+			if (is_write_device_entry(entry) &&
+			    is_cow_mapping(vm_flags)) {
+				make_device_entry_read(&entry);
+				pte = swp_entry_to_pte(entry);
+				if (pte_swp_soft_dirty(*src_pte))
+					pte = pte_swp_mksoft_dirty(pte);
+				set_pte_at(src_mm, addr, src_pte, pte);
+			}
 		}
 		goto out_set_pte;
 	}
@@ -1178,6 +1198,32 @@ again:
 			}
 			continue;
 		}
+
+		/*
+		 * Un-addressable page must always be check that are not like
+		 * other swap entries and thus should be check no matter what
+		 * details->check_swap_entries value is.
+		 */
+		entry = pte_to_swp_entry(ptent);
+		if (non_swap_entry(entry) && is_device_entry(entry)) {
+			struct page *page = device_entry_to_page(entry);
+
+			if (unlikely(details)) {
+				/*
+				 * unmap_shared_mapping_pages() wants to
+				 * invalidate cache without truncating:
+				 * unmap shared but keep private pages.
+				 */
+				if (details->check_mapping &&
+				    details->check_mapping != page_rmapping(page))
+					continue;
+			}
+
+			rss[mm_counter(page)]--;
+			page_remove_rmap(page, false);
+			put_page(page);
+		}
+
 		/* only check swap_entries if explicitly asked for in details */
 		if (unlikely(details && !details->check_swap_entries))
 			continue;
@@ -2535,6 +2581,14 @@ int do_swap_page(struct fault_env *fe, pte_t orig_pte)
 	if (unlikely(non_swap_entry(entry))) {
 		if (is_migration_entry(entry)) {
 			migration_entry_wait(vma->vm_mm, fe->pmd, fe->address);
+		} else if (is_device_entry(entry)) {
+			/*
+			 * For un-addressable device memory we call the pgmap
+			 * fault handler callback. The callback must migrate
+			 * the page back to some CPU accessible page.
+			 */
+			ret = device_entry_fault(vma, fe->address, entry,
+						 fe->flags, fe->pmd);
 		} else if (is_hwpoison_entry(entry)) {
 			ret = VM_FAULT_HWPOISON;
 		} else {
@@ -3482,6 +3536,7 @@ static inline bool vma_is_accessible(struct vm_area_struct *vma)
 static int handle_pte_fault(struct fault_env *fe)
 {
 	pte_t entry;
+	struct page *page;
 
 	if (unlikely(pmd_none(*fe->pmd))) {
 		/*
@@ -3533,6 +3588,13 @@ static int handle_pte_fault(struct fault_env *fe)
 	if (pte_protnone(entry) && vma_is_accessible(fe->vma))
 		return do_numa_page(fe, entry);
 
+	/* Catch mapping of un-addressable memory this should never happen */
+	page = pfn_to_page(pte_pfn(entry));
+	if (!is_addressable_page(page)) {
+		print_bad_pte(fe->vma, fe->address, entry, page);
+		return VM_FAULT_SIGBUS;
+	}
+
 	fe->ptl = pte_lockptr(fe->vma->vm_mm, fe->pmd);
 	spin_lock(fe->ptl);
 	if (unlikely(!pte_same(*fe->pte, entry)))
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 1bc1eb3..70aff3a 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -139,6 +139,18 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 
 				pages++;
 			}
+
+			if (is_write_device_entry(entry)) {
+				pte_t newpte;
+
+				make_device_entry_read(&entry);
+				newpte = swp_entry_to_pte(entry);
+				if (pte_swp_soft_dirty(oldpte))
+					newpte = pte_swp_mksoft_dirty(newpte);
+				set_pte_at(mm, addr, pte, newpte);
+
+				pages++;
+			}
 		}
 	} while (pte++, addr += PAGE_SIZE, addr != end);
 	arch_leave_lazy_mmu_mode();
diff --git a/tools/testing/nvdimm/test/iomap.c b/tools/testing/nvdimm/test/iomap.c
index 6505a87..0c8696c 100644
--- a/tools/testing/nvdimm/test/iomap.c
+++ b/tools/testing/nvdimm/test/iomap.c
@@ -108,7 +108,8 @@ void *__wrap_devm_memremap_pages(struct device *dev, struct resource *res,
 
 	if (nfit_res)
 		return nfit_res->buf + offset - nfit_res->res->start;
-	return devm_memremap_pages(dev, res, ref, altmap, NULL, NULL);
+	return devm_memremap_pages(dev, res, ref, altmap, NULL,
+				   NULL, NULL, NULL, MEMORY_DEVICE);
 }
 EXPORT_SYMBOL(__wrap_devm_memremap_pages);
 
-- 
2.4.3

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