Merge tag 'for-linus-hmm' of git://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma

Pull HMM updates from Jason Gunthorpe:
 "Improvements and bug fixes for the hmm interface in the kernel:

   - Improve clarity, locking and APIs related to the 'hmm mirror'
     feature merged last cycle. In linux-next we now see AMDGPU and
     nouveau to be using this API.

   - Remove old or transitional hmm APIs. These are hold overs from the
     past with no users, or APIs that existed only to manage cross tree
     conflicts. There are still a few more of these cleanups that didn't
     make the merge window cut off.

   - Improve some core mm APIs:
       - export alloc_pages_vma() for driver use
       - refactor into devm_request_free_mem_region() to manage
         DEVICE_PRIVATE resource reservations
       - refactor duplicative driver code into the core dev_pagemap
         struct

   - Remove hmm wrappers of improved core mm APIs, instead have drivers
     use the simplified API directly

   - Remove DEVICE_PUBLIC

   - Simplify the kconfig flow for the hmm users and core code"

* tag 'for-linus-hmm' of git://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma: (42 commits)
  mm: don't select MIGRATE_VMA_HELPER from HMM_MIRROR
  mm: remove the HMM config option
  mm: sort out the DEVICE_PRIVATE Kconfig mess
  mm: simplify ZONE_DEVICE page private data
  mm: remove hmm_devmem_add
  mm: remove hmm_vma_alloc_locked_page
  nouveau: use devm_memremap_pages directly
  nouveau: use alloc_page_vma directly
  PCI/P2PDMA: use the dev_pagemap internal refcount
  device-dax: use the dev_pagemap internal refcount
  memremap: provide an optional internal refcount in struct dev_pagemap
  memremap: replace the altmap_valid field with a PGMAP_ALTMAP_VALID flag
  memremap: remove the data field in struct dev_pagemap
  memremap: add a migrate_to_ram method to struct dev_pagemap_ops
  memremap: lift the devmap_enable manipulation into devm_memremap_pages
  memremap: pass a struct dev_pagemap to ->kill and ->cleanup
  memremap: move dev_pagemap callbacks into a separate structure
  memremap: validate the pagemap type passed to devm_memremap_pages
  mm: factor out a devm_request_free_mem_region helper
  mm: export alloc_pages_vma
  ...

36 files changed, 620 insertions, 1327 deletions

diff --git a/Documentation/vm/hmm.rst b/Documentation/vm/hmm.rst
index 7cdf7282e022..7d90964abbb0 100644
--- a/Documentation/vm/hmm.rst
+++ b/Documentation/vm/hmm.rst
@@ -10,7 +10,7 @@ of this being specialized struct page for such memory (see sections 5 to 7 of
 this document).
 
 HMM also provides optional helpers for SVM (Share Virtual Memory), i.e.,
-allowing a device to transparently access program address coherently with
+allowing a device to transparently access program addresses coherently with
 the CPU meaning that any valid pointer on the CPU is also a valid pointer
 for the device. This is becoming mandatory to simplify the use of advanced
 heterogeneous computing where GPU, DSP, or FPGA are used to perform various
@@ -22,8 +22,8 @@ expose the hardware limitations that are inherent to many platforms. The third
 section gives an overview of the HMM design. The fourth section explains how
 CPU page-table mirroring works and the purpose of HMM in this context. The
 fifth section deals with how device memory is represented inside the kernel.
-Finally, the last section presents a new migration helper that allows lever-
-aging the device DMA engine.
+Finally, the last section presents a new migration helper that allows
+leveraging the device DMA engine.
 
 .. contents:: :local:
 
@@ -39,20 +39,20 @@ address space. I use shared address space to refer to the opposite situation:
 i.e., one in which any application memory region can be used by a device
 transparently.
 
-Split address space happens because device can only access memory allocated
-through device specific API. This implies that all memory objects in a program
+Split address space happens because devices can only access memory allocated
+through a device specific API. This implies that all memory objects in a program
 are not equal from the device point of view which complicates large programs
 that rely on a wide set of libraries.
 
-Concretely this means that code that wants to leverage devices like GPUs needs
-to copy object between generically allocated memory (malloc, mmap private, mmap
+Concretely, this means that code that wants to leverage devices like GPUs needs
+to copy objects between generically allocated memory (malloc, mmap private, mmap
 share) and memory allocated through the device driver API (this still ends up
 with an mmap but of the device file).
 
 For flat data sets (array, grid, image, ...) this isn't too hard to achieve but
-complex data sets (list, tree, ...) are hard to get right. Duplicating a
+for complex data sets (list, tree, ...) it's hard to get right. Duplicating a
 complex data set needs to re-map all the pointer relations between each of its
-elements. This is error prone and program gets harder to debug because of the
+elements. This is error prone and programs get harder to debug because of the
 duplicate data set and addresses.
 
 Split address space also means that libraries cannot transparently use data
@@ -77,12 +77,12 @@ I/O bus, device memory characteristics
 
 I/O buses cripple shared address spaces due to a few limitations. Most I/O
 buses only allow basic memory access from device to main memory; even cache
-coherency is often optional. Access to device memory from CPU is even more
+coherency is often optional. Access to device memory from a CPU is even more
 limited. More often than not, it is not cache coherent.
 
 If we only consider the PCIE bus, then a device can access main memory (often
 through an IOMMU) and be cache coherent with the CPUs. However, it only allows
-a limited set of atomic operations from device on main memory. This is worse
+a limited set of atomic operations from the device on main memory. This is worse
 in the other direction: the CPU can only access a limited range of the device
 memory and cannot perform atomic operations on it. Thus device memory cannot
 be considered the same as regular memory from the kernel point of view.
@@ -93,20 +93,20 @@ The final limitation is latency. Access to main memory from the device has an
 order of magnitude higher latency than when the device accesses its own memory.
 
 Some platforms are developing new I/O buses or additions/modifications to PCIE
-to address some of these limitations (OpenCAPI, CCIX). They mainly allow two-
-way cache coherency between CPU and device and allow all atomic operations the
+to address some of these limitations (OpenCAPI, CCIX). They mainly allow
+two-way cache coherency between CPU and device and allow all atomic operations the
 architecture supports. Sadly, not all platforms are following this trend and
 some major architectures are left without hardware solutions to these problems.
 
 So for shared address space to make sense, not only must we allow devices to
 access any memory but we must also permit any memory to be migrated to device
-memory while device is using it (blocking CPU access while it happens).
+memory while the device is using it (blocking CPU access while it happens).
 
 
 Shared address space and migration
 ==================================
 
-HMM intends to provide two main features. First one is to share the address
+HMM intends to provide two main features. The first one is to share the address
 space by duplicating the CPU page table in the device page table so the same
 address points to the same physical memory for any valid main memory address in
 the process address space.
@@ -121,14 +121,14 @@ why HMM provides helpers to factor out everything that can be while leaving the
 hardware specific details to the device driver.
 
 The second mechanism HMM provides is a new kind of ZONE_DEVICE memory that
-allows allocating a struct page for each page of the device memory. Those pages
+allows allocating a struct page for each page of device memory. Those pages
 are special because the CPU cannot map them. However, they allow migrating
 main memory to device memory using existing migration mechanisms and everything
-looks like a page is swapped out to disk from the CPU point of view. Using a
-struct page gives the easiest and cleanest integration with existing mm mech-
-anisms. Here again, HMM only provides helpers, first to hotplug new ZONE_DEVICE
+looks like a page that is swapped out to disk from the CPU point of view. Using a
+struct page gives the easiest and cleanest integration with existing mm
+mechanisms. Here again, HMM only provides helpers, first to hotplug new ZONE_DEVICE
 memory for the device memory and second to perform migration. Policy decisions
-of what and when to migrate things is left to the device driver.
+of what and when to migrate is left to the device driver.
 
 Note that any CPU access to a device page triggers a page fault and a migration
 back to main memory. For example, when a page backing a given CPU address A is
@@ -136,8 +136,8 @@ migrated from a main memory page to a device page, then any CPU access to
 address A triggers a page fault and initiates a migration back to main memory.
 
 With these two features, HMM not only allows a device to mirror process address
-space and keeping both CPU and device page table synchronized, but also lever-
-ages device memory by migrating the part of the data set that is actively being
+space and keeps both CPU and device page tables synchronized, but also
+leverages device memory by migrating the part of the data set that is actively being
 used by the device.
 
 
@@ -151,21 +151,28 @@ registration of an hmm_mirror struct::
 
  int hmm_mirror_register(struct hmm_mirror *mirror,
                          struct mm_struct *mm);
- int hmm_mirror_register_locked(struct hmm_mirror *mirror,
-                                struct mm_struct *mm);
 
-
-The locked variant is to be used when the driver is already holding mmap_sem
-of the mm in write mode. The mirror struct has a set of callbacks that are used
+The mirror struct has a set of callbacks that are used
 to propagate CPU page tables::
 
  struct hmm_mirror_ops {
+     /* release() - release hmm_mirror
+      *
+      * @mirror: pointer to struct hmm_mirror
+      *
+      * This is called when the mm_struct is being released.  The callback
+      * must ensure that all access to any pages obtained from this mirror
+      * is halted before the callback returns. All future access should
+      * fault.
+      */
+     void (*release)(struct hmm_mirror *mirror);
+
      /* sync_cpu_device_pagetables() - synchronize page tables
       *
       * @mirror: pointer to struct hmm_mirror
-      * @update_type: type of update that occurred to the CPU page table
-      * @start: virtual start address of the range to update
-      * @end: virtual end address of the range to update
+      * @update: update information (see struct mmu_notifier_range)
+      * Return: -EAGAIN if update.blockable false and callback need to
+      *         block, 0 otherwise.
       *
       * This callback ultimately originates from mmu_notifiers when the CPU
       * page table is updated. The device driver must update its page table
@@ -176,14 +183,12 @@ to propagate CPU page tables::
       * page tables are completely updated (TLBs flushed, etc); this is a
       * synchronous call.
       */
-      void (*update)(struct hmm_mirror *mirror,
-                     enum hmm_update action,
-                     unsigned long start,
-                     unsigned long end);
+     int (*sync_cpu_device_pagetables)(struct hmm_mirror *mirror,
+                                       const struct hmm_update *update);
  };
 
 The device driver must perform the update action to the range (mark range
-read only, or fully unmap, ...). The device must be done with the update before
+read only, or fully unmap, etc.). The device must complete the update before
 the driver callback returns.
 
 When the device driver wants to populate a range of virtual addresses, it can
@@ -194,17 +199,18 @@ use either::
 
 The first one (hmm_range_snapshot()) will only fetch present CPU page table
 entries and will not trigger a page fault on missing or non-present entries.
-The second one does trigger a page fault on missing or read-only entry if the
-write parameter is true. Page faults use the generic mm page fault code path
-just like a CPU page fault.
+The second one does trigger a page fault on missing or read-only entries if
+write access is requested (see below). Page faults use the generic mm page
+fault code path just like a CPU page fault.
 
 Both functions copy CPU page table entries into their pfns array argument. Each
 entry in that array corresponds to an address in the virtual range. HMM
 provides a set of flags to help the driver identify special CPU page table
 entries.
 
-Locking with the update() callback is the most important aspect the driver must
-respect in order to keep things properly synchronized. The usage pattern is::
+Locking within the sync_cpu_device_pagetables() callback is the most important
+aspect the driver must respect in order to keep things properly synchronized.
+The usage pattern is::
 
  int driver_populate_range(...)
  {
@@ -239,11 +245,11 @@ respect in order to keep things properly synchronized. The usage pattern is::
             hmm_range_wait_until_valid(&range, TIMEOUT_IN_MSEC);
             goto again;
           }
-          hmm_mirror_unregister(&range);
+          hmm_range_unregister(&range);
           return ret;
       }
       take_lock(driver->update);
-      if (!range.valid) {
+      if (!hmm_range_valid(&range)) {
           release_lock(driver->update);
           up_read(&mm->mmap_sem);
           goto again;
@@ -251,15 +257,15 @@ respect in order to keep things properly synchronized. The usage pattern is::
 
       // Use pfns array content to update device page table
 
-      hmm_mirror_unregister(&range);
+      hmm_range_unregister(&range);
       release_lock(driver->update);
       up_read(&mm->mmap_sem);
       return 0;
  }
 
 The driver->update lock is the same lock that the driver takes inside its
-update() callback. That lock must be held before checking the range.valid
-field to avoid any race with a concurrent CPU page table update.
+sync_cpu_device_pagetables() callback. That lock must be held before calling
+hmm_range_valid() to avoid any race with a concurrent CPU page table update.
 
 HMM implements all this on top of the mmu_notifier API because we wanted a
 simpler API and also to be able to perform optimizations latter on like doing
@@ -279,46 +285,47 @@ concurrently).
 Leverage default_flags and pfn_flags_mask
 =========================================
 
-The hmm_range struct has 2 fields default_flags and pfn_flags_mask that allows
-to set fault or snapshot policy for a whole range instead of having to set them
-for each entries in the range.
+The hmm_range struct has 2 fields, default_flags and pfn_flags_mask, that specify
+fault or snapshot policy for the whole range instead of having to set them
+for each entry in the pfns array.
+
+For instance, if the device flags for range.flags are::
 
-For instance if the device flags for device entries are:
-    VALID (1 << 63)
-    WRITE (1 << 62)
+    range.flags[HMM_PFN_VALID] = (1 << 63);
+    range.flags[HMM_PFN_WRITE] = (1 << 62);
 
-Now let say that device driver wants to fault with at least read a range then
-it does set::
+and the device driver wants pages for a range with at least read permission,
+it sets::
 
     range->default_flags = (1 << 63);
     range->pfn_flags_mask = 0;
 
-and calls hmm_range_fault() as described above. This will fill fault all page
+and calls hmm_range_fault() as described above. This will fill fault all pages
 in the range with at least read permission.
 
-Now let say driver wants to do the same except for one page in the range for
-which its want to have write. Now driver set::
+Now let's say the driver wants to do the same except for one page in the range for
+which it wants to have write permission. Now driver set::
 
     range->default_flags = (1 << 63);
     range->pfn_flags_mask = (1 << 62);
     range->pfns[index_of_write] = (1 << 62);
 
-With this HMM will fault in all page with at least read (ie valid) and for the
+With this, HMM will fault in all pages with at least read (i.e., valid) and for the
 address == range->start + (index_of_write << PAGE_SHIFT) it will fault with
-write permission ie if the CPU pte does not have write permission set then HMM
+write permission i.e., if the CPU pte does not have write permission set then HMM
 will call handle_mm_fault().
 
-Note that HMM will populate the pfns array with write permission for any entry
-that have write permission within the CPU pte no matter what are the values set
+Note that HMM will populate the pfns array with write permission for any page
+that is mapped with CPU write permission no matter what values are set
 in default_flags or pfn_flags_mask.
 
 
 Represent and manage device memory from core kernel point of view
 =================================================================
 
-Several different designs were tried to support device memory. First one used
-a device specific data structure to keep information about migrated memory and
-HMM hooked itself in various places of mm code to handle any access to
+Several different designs were tried to support device memory. The first one
+used a device specific data structure to keep information about migrated memory
+and HMM hooked itself in various places of mm code to handle any access to
 addresses that were backed by device memory. It turns out that this ended up
 replicating most of the fields of struct page and also needed many kernel code
 paths to be updated to understand this new kind of memory.
@@ -329,33 +336,6 @@ directly using struct page for device memory which left most kernel code paths
 unaware of the difference. We only need to make sure that no one ever tries to
 map those pages from the CPU side.
 
-HMM provides a set of helpers to register and hotplug device memory as a new
-region needing a struct page. This is offered through a very simple API::
-
- struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
-                                   struct device *device,
-                                   unsigned long size);
- void hmm_devmem_remove(struct hmm_devmem *devmem);
-
-The hmm_devmem_ops is where most of the important things are::
-
- struct hmm_devmem_ops {
-     void (*free)(struct hmm_devmem *devmem, struct page *page);
-     int (*fault)(struct hmm_devmem *devmem,
-                  struct vm_area_struct *vma,
-                  unsigned long addr,
-                  struct page *page,
-                  unsigned flags,
-                  pmd_t *pmdp);
- };
-
-The first callback (free()) happens when the last reference on a device page is
-dropped. This means the device page is now free and no longer used by anyone.
-The second callback happens whenever the CPU tries to access a device page
-which it cannot do. This second callback must trigger a migration back to
-system memory.
-
-
 Migration to and from device memory
 ===================================
 
@@ -417,9 +397,9 @@ willing to pay to keep all the code simpler.
 Memory cgroup (memcg) and rss accounting
 ========================================
 
-For now device memory is accounted as any regular page in rss counters (either
+For now, device memory is accounted as any regular page in rss counters (either
 anonymous if device page is used for anonymous, file if device page is used for
-file backed page or shmem if device page is used for shared memory). This is a
+file backed page, or shmem if device page is used for shared memory). This is a
 deliberate choice to keep existing applications, that might start using device
 memory without knowing about it, running unimpacted.
 
@@ -439,6 +419,6 @@ get more experience in how device memory is used and its impact on memory
 resource control.
 
 
-Note that device memory can never be pinned by device driver nor through GUP
+Note that device memory can never be pinned by a device driver nor through GUP
 and thus such memory is always free upon process exit. Or when last reference
 is dropped in case of shared memory or file backed memory.
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 6d5f0fc76666..26a8da3723bb 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -131,17 +131,9 @@ void __ref arch_remove_memory(int nid, u64 start, u64 size,
 {
 	unsigned long start_pfn = start >> PAGE_SHIFT;
 	unsigned long nr_pages = size >> PAGE_SHIFT;
-	struct page *page;
+	struct page *page = pfn_to_page(start_pfn) + vmem_altmap_offset(altmap);
 	int ret;
 
-	/*
-	 * If we have an altmap then we need to skip over any reserved PFNs
-	 * when querying the zone.
-	 */
-	page = pfn_to_page(start_pfn);
-	if (altmap)
-		page += vmem_altmap_offset(altmap);
-
 	__remove_pages(page_zone(page), start_pfn, nr_pages, altmap);
 
 	/* Remove htab bolted mappings for this section of memory */
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 0f01c7b1d217..08bbf648827b 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1213,13 +1213,9 @@ void __ref arch_remove_memory(int nid, u64 start, u64 size,
 {
 	unsigned long start_pfn = start >> PAGE_SHIFT;
 	unsigned long nr_pages = size >> PAGE_SHIFT;
-	struct page *page = pfn_to_page(start_pfn);
-	struct zone *zone;
+	struct page *page = pfn_to_page(start_pfn) + vmem_altmap_offset(altmap);
+	struct zone *zone = page_zone(page);
 
-	/* With altmap the first mapped page is offset from @start */
-	if (altmap)
-		page += vmem_altmap_offset(altmap);
-	zone = page_zone(page);
 	__remove_pages(zone, start_pfn, nr_pages, altmap);
 	kernel_physical_mapping_remove(start, start + size);
 }
diff --git a/drivers/dax/dax-private.h b/drivers/dax/dax-private.h
index b4177aafbbd1..c915889d1769 100644
--- a/drivers/dax/dax-private.h
+++ b/drivers/dax/dax-private.h
@@ -43,8 +43,6 @@ struct dax_region {
  * @target_node: effective numa node if dev_dax memory range is onlined
  * @dev - device core
  * @pgmap - pgmap for memmap setup / lifetime (driver owned)
- * @ref: pgmap reference count (driver owned)
- * @cmp: @ref final put completion (driver owned)
  */
 struct dev_dax {
 	struct dax_region *region;
@@ -52,8 +50,6 @@ struct dev_dax {
 	int target_node;
 	struct device dev;
 	struct dev_pagemap pgmap;
-	struct percpu_ref ref;
-	struct completion cmp;
 };
 
 static inline struct dev_dax *to_dev_dax(struct device *dev)
diff --git a/drivers/dax/device.c b/drivers/dax/device.c
index 8465d12fecba..1af823b2fe6b 100644
--- a/drivers/dax/device.c
+++ b/drivers/dax/device.c
@@ -14,37 +14,6 @@
 #include "dax-private.h"
 #include "bus.h"
 
-static struct dev_dax *ref_to_dev_dax(struct percpu_ref *ref)
-{
-	return container_of(ref, struct dev_dax, ref);
-}
-
-static void dev_dax_percpu_release(struct percpu_ref *ref)
-{
-	struct dev_dax *dev_dax = ref_to_dev_dax(ref);
-
-	dev_dbg(&dev_dax->dev, "%s\n", __func__);
-	complete(&dev_dax->cmp);
-}
-
-static void dev_dax_percpu_exit(struct percpu_ref *ref)
-{
-	struct dev_dax *dev_dax = ref_to_dev_dax(ref);
-
-	dev_dbg(&dev_dax->dev, "%s\n", __func__);
-	wait_for_completion(&dev_dax->cmp);
-	percpu_ref_exit(ref);
-}
-
-static void dev_dax_percpu_kill(struct percpu_ref *data)
-{
-	struct percpu_ref *ref = data;
-	struct dev_dax *dev_dax = ref_to_dev_dax(ref);
-
-	dev_dbg(&dev_dax->dev, "%s\n", __func__);
-	percpu_ref_kill(ref);
-}
-
 static int check_vma(struct dev_dax *dev_dax, struct vm_area_struct *vma,
 		const char *func)
 {
@@ -459,15 +428,7 @@ int dev_dax_probe(struct device *dev)
 		return -EBUSY;
 	}
 
-	init_completion(&dev_dax->cmp);
-	rc = percpu_ref_init(&dev_dax->ref, dev_dax_percpu_release, 0,
-			GFP_KERNEL);
-	if (rc)
-		return rc;
-
-	dev_dax->pgmap.ref = &dev_dax->ref;
-	dev_dax->pgmap.kill = dev_dax_percpu_kill;
-	dev_dax->pgmap.cleanup = dev_dax_percpu_exit;
+	dev_dax->pgmap.type = MEMORY_DEVICE_DEVDAX;
 	addr = devm_memremap_pages(dev, &dev_dax->pgmap);
 	if (IS_ERR(addr))
 		return PTR_ERR(addr);
diff --git a/drivers/dax/pmem/core.c b/drivers/dax/pmem/core.c
index f9f51786d556..6eb6dfdf19bf 100644
--- a/drivers/dax/pmem/core.c
+++ b/drivers/dax/pmem/core.c
@@ -16,7 +16,7 @@ struct dev_dax *__dax_pmem_probe(struct device *dev, enum dev_dax_subsys subsys)
 	struct dev_dax *dev_dax;
 	struct nd_namespace_io *nsio;
 	struct dax_region *dax_region;
-	struct dev_pagemap pgmap = { 0 };
+	struct dev_pagemap pgmap = { };
 	struct nd_namespace_common *ndns;
 	struct nd_dax *nd_dax = to_nd_dax(dev);
 	struct nd_pfn *nd_pfn = &nd_dax->nd_pfn;
diff --git a/drivers/gpu/drm/nouveau/Kconfig b/drivers/gpu/drm/nouveau/Kconfig
index dba2613f7180..96b9814e6d06 100644
--- a/drivers/gpu/drm/nouveau/Kconfig
+++ b/drivers/gpu/drm/nouveau/Kconfig
@@ -84,11 +84,11 @@ config DRM_NOUVEAU_BACKLIGHT
 
 config DRM_NOUVEAU_SVM
 	bool "(EXPERIMENTAL) Enable SVM (Shared Virtual Memory) support"
-	depends on ARCH_HAS_HMM
+	depends on DEVICE_PRIVATE
 	depends on DRM_NOUVEAU
+	depends on HMM_MIRROR
 	depends on STAGING
-	select HMM_MIRROR
-	select DEVICE_PRIVATE
+	select MIGRATE_VMA_HELPER
 	default n
 	help
 	  Say Y here if you want to enable experimental support for
diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c b/drivers/gpu/drm/nouveau/nouveau_dmem.c
index 40c47d6a7d78..42c026010938 100644
--- a/drivers/gpu/drm/nouveau/nouveau_dmem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c
@@ -72,7 +72,8 @@ struct nouveau_dmem_migrate {
 };
 
 struct nouveau_dmem {
-	struct hmm_devmem *devmem;
+	struct nouveau_drm *drm;
+	struct dev_pagemap pagemap;
 	struct nouveau_dmem_migrate migrate;
 	struct list_head chunk_free;
 	struct list_head chunk_full;
@@ -80,6 +81,11 @@ struct nouveau_dmem {
 	struct mutex mutex;
 };
 
+static inline struct nouveau_dmem *page_to_dmem(struct page *page)
+{
+	return container_of(page->pgmap, struct nouveau_dmem, pagemap);
+}
+
 struct nouveau_dmem_fault {
 	struct nouveau_drm *drm;
 	struct nouveau_fence *fence;
@@ -96,14 +102,10 @@ struct nouveau_migrate {
 	unsigned long dma_nr;
 };
 
-static void
-nouveau_dmem_free(struct hmm_devmem *devmem, struct page *page)
+static void nouveau_dmem_page_free(struct page *page)
 {
-	struct nouveau_dmem_chunk *chunk;
-	unsigned long idx;
-
-	chunk = (void *)hmm_devmem_page_get_drvdata(page);
-	idx = page_to_pfn(page) - chunk->pfn_first;
+	struct nouveau_dmem_chunk *chunk = page->zone_device_data;
+	unsigned long idx = page_to_pfn(page) - chunk->pfn_first;
 
 	/*
 	 * FIXME:
@@ -148,11 +150,12 @@ nouveau_dmem_fault_alloc_and_copy(struct vm_area_struct *vma,
 		if (!spage || !(src_pfns[i] & MIGRATE_PFN_MIGRATE))
 			continue;
 
-		dpage = hmm_vma_alloc_locked_page(vma, addr);
+		dpage = alloc_page_vma(GFP_HIGHUSER, vma, addr);
 		if (!dpage) {
 			dst_pfns[i] = MIGRATE_PFN_ERROR;
 			continue;
 		}
+		lock_page(dpage);
 
 		dst_pfns[i] = migrate_pfn(page_to_pfn(dpage)) |
 			      MIGRATE_PFN_LOCKED;
@@ -194,7 +197,7 @@ nouveau_dmem_fault_alloc_and_copy(struct vm_area_struct *vma,
 
 		dst_addr = fault->dma[fault->npages++];
 
-		chunk = (void *)hmm_devmem_page_get_drvdata(spage);
+		chunk = spage->zone_device_data;
 		src_addr = page_to_pfn(spage) - chunk->pfn_first;
 		src_addr = (src_addr << PAGE_SHIFT) + chunk->bo->bo.offset;
 
@@ -259,29 +262,21 @@ static const struct migrate_vma_ops nouveau_dmem_fault_migrate_ops = {
 	.finalize_and_map	= nouveau_dmem_fault_finalize_and_map,
 };
 
-static vm_fault_t
-nouveau_dmem_fault(struct hmm_devmem *devmem,
-		   struct vm_area_struct *vma,
-		   unsigned long addr,
-		   const struct page *page,
-		   unsigned int flags,
-		   pmd_t *pmdp)
+static vm_fault_t nouveau_dmem_migrate_to_ram(struct vm_fault *vmf)
 {
-	struct drm_device *drm_dev = dev_get_drvdata(devmem->device);
+	struct nouveau_dmem *dmem = page_to_dmem(vmf->page);
 	unsigned long src[1] = {0}, dst[1] = {0};
-	struct nouveau_dmem_fault fault = {0};
+	struct nouveau_dmem_fault fault = { .drm = dmem->drm };
 	int ret;
 
-
-
 	/*
 	 * FIXME what we really want is to find some heuristic to migrate more
 	 * than just one page on CPU fault. When such fault happens it is very
 	 * likely that more surrounding page will CPU fault too.
 	 */
-	fault.drm = nouveau_drm(drm_dev);
-	ret = migrate_vma(&nouveau_dmem_fault_migrate_ops, vma, addr,
-			  addr + PAGE_SIZE, src, dst, &fault);
+	ret = migrate_vma(&nouveau_dmem_fault_migrate_ops, vmf->vma,
+			vmf->address, vmf->address + PAGE_SIZE,
+			src, dst, &fault);
 	if (ret)
 		return VM_FAULT_SIGBUS;
 
@@ -291,10 +286,9 @@ nouveau_dmem_fault(struct hmm_devmem *devmem,
 	return 0;
 }
 
-static const struct hmm_devmem_ops
-nouveau_dmem_devmem_ops = {
-	.free = nouveau_dmem_free,
-	.fault = nouveau_dmem_fault,
+static const struct dev_pagemap_ops nouveau_dmem_pagemap_ops = {
+	.page_free		= nouveau_dmem_page_free,
+	.migrate_to_ram		= nouveau_dmem_migrate_to_ram,
 };
 
 static int
@@ -580,7 +574,8 @@ void
 nouveau_dmem_init(struct nouveau_drm *drm)
 {
 	struct device *device = drm->dev->dev;
-	unsigned long i, size;
+	struct resource *res;
+	unsigned long i, size, pfn_first;
 	int ret;
 
 	/* This only make sense on PASCAL or newer */
@@ -590,6 +585,7 @@ nouveau_dmem_init(struct nouveau_drm *drm)
 	if (!(drm->dmem = kzalloc(sizeof(*drm->dmem), GFP_KERNEL)))
 		return;
 
+	drm->dmem->drm = drm;
 	mutex_init(&drm->dmem->mutex);
 	INIT_LIST_HEAD(&drm->dmem->chunk_free);
 	INIT_LIST_HEAD(&drm->dmem->chunk_full);
@@ -599,11 +595,8 @@ nouveau_dmem_init(struct nouveau_drm *drm)
 
 	/* Initialize migration dma helpers before registering memory */
 	ret = nouveau_dmem_migrate_init(drm);
-	if (ret) {
-		kfree(drm->dmem);
-		drm->dmem = NULL;
-		return;
-	}
+	if (ret)
+		goto out_free;
 
 	/*
 	 * FIXME we need some kind of policy to decide how much VRAM we
@@ -611,14 +604,16 @@ nouveau_dmem_init(struct nouveau_drm *drm)
 	 * and latter if we want to do thing like over commit then we
 	 * could revisit this.
 	 */
-	drm->dmem->devmem = hmm_devmem_add(&nouveau_dmem_devmem_ops,
-					   device, size);
-	if (IS_ERR(drm->dmem->devmem)) {
-		kfree(drm->dmem);
-		drm->dmem = NULL;
-		return;
-	}
-
+	res = devm_request_free_mem_region(device, &iomem_resource, size);
+	if (IS_ERR(res))
+		goto out_free;
+	drm->dmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
+	drm->dmem->pagemap.res = *res;
+	drm->dmem->pagemap.ops = &nouveau_dmem_pagemap_ops;
+	if (IS_ERR(devm_memremap_pages(device, &drm->dmem->pagemap)))
+		goto out_free;
+
+	pfn_first = res->start >> PAGE_SHIFT;
 	for (i = 0; i < (size / DMEM_CHUNK_SIZE); ++i) {
 		struct nouveau_dmem_chunk *chunk;
 		struct page *page;
@@ -631,17 +626,19 @@ nouveau_dmem_init(struct nouveau_drm *drm)
 		}
 
 		chunk->drm = drm;
-		chunk->pfn_first = drm->dmem->devmem->pfn_first;
-		chunk->pfn_first += (i * DMEM_CHUNK_NPAGES);
+		chunk->pfn_first = pfn_first + (i * DMEM_CHUNK_NPAGES);
 		list_add_tail(&chunk->list, &drm->dmem->chunk_empty);
 
 		page = pfn_to_page(chunk->pfn_first);
-		for (j = 0; j < DMEM_CHUNK_NPAGES; ++j, ++page) {
-			hmm_devmem_page_set_drvdata(page, (long)chunk);
-		}
+		for (j = 0; j < DMEM_CHUNK_NPAGES; ++j, ++page)
+			page->zone_device_data = chunk;
 	}
 
 	NV_INFO(drm, "DMEM: registered %ldMB of device memory\n", size >> 20);
+	return;
+out_free:
+	kfree(drm->dmem);
+	drm->dmem = NULL;
 }
 
 static void
@@ -697,7 +694,7 @@ nouveau_dmem_migrate_alloc_and_copy(struct vm_area_struct *vma,
 		if (!dpage || dst_pfns[i] == MIGRATE_PFN_ERROR)
 			continue;
 
-		chunk = (void *)hmm_devmem_page_get_drvdata(dpage);
+		chunk = dpage->zone_device_data;
 		dst_addr = page_to_pfn(dpage) - chunk->pfn_first;
 		dst_addr = (dst_addr << PAGE_SHIFT) + chunk->bo->bo.offset;
 
@@ -832,13 +829,7 @@ out:
 static inline bool
 nouveau_dmem_page(struct nouveau_drm *drm, struct page *page)
 {
-	if (!is_device_private_page(page))
-		return false;
-
-	if (drm->dmem->devmem != page->pgmap->data)
-		return false;
-
-	return true;
+	return is_device_private_page(page) && drm->dmem == page_to_dmem(page);
 }
 
 void
@@ -867,7 +858,7 @@ nouveau_dmem_convert_pfn(struct nouveau_drm *drm,
 			continue;
 		}
 
-		chunk = (void *)hmm_devmem_page_get_drvdata(page);
+		chunk = page->zone_device_data;
 		addr = page_to_pfn(page) - chunk->pfn_first;
 		addr = (addr + chunk->bo->bo.mem.start) << PAGE_SHIFT;
 
diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c
index 93ed43c413f0..8c92374afcf2 100644
--- a/drivers/gpu/drm/nouveau/nouveau_svm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_svm.c
@@ -649,7 +649,7 @@ nouveau_svm_fault(struct nvif_notify *notify)
 		range.values = nouveau_svm_pfn_values;
 		range.pfn_shift = NVIF_VMM_PFNMAP_V0_ADDR_SHIFT;
 again:
-		ret = hmm_vma_fault(&range, true);
+		ret = hmm_vma_fault(&svmm->mirror, &range, true);
 		if (ret == 0) {
 			mutex_lock(&svmm->mutex);
 			if (!hmm_vma_range_done(&range)) {
diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
index 0f81fc56bbfd..55fb6b7433ed 100644
--- a/drivers/nvdimm/pfn_devs.c
+++ b/drivers/nvdimm/pfn_devs.c
@@ -622,7 +622,6 @@ static int __nvdimm_setup_pfn(struct nd_pfn *nd_pfn, struct dev_pagemap *pgmap)
 		if (offset < reserve)
 			return -EINVAL;
 		nd_pfn->npfns = le64_to_cpu(pfn_sb->npfns);
-		pgmap->altmap_valid = false;
 	} else if (nd_pfn->mode == PFN_MODE_PMEM) {
 		nd_pfn->npfns = PFN_SECTION_ALIGN_UP((resource_size(res)
 					- offset) / PAGE_SIZE);
@@ -634,7 +633,7 @@ static int __nvdimm_setup_pfn(struct nd_pfn *nd_pfn, struct dev_pagemap *pgmap)
 		memcpy(altmap, &__altmap, sizeof(*altmap));
 		altmap->free = PHYS_PFN(offset - reserve);
 		altmap->alloc = 0;
-		pgmap->altmap_valid = true;
+		pgmap->flags |= PGMAP_ALTMAP_VALID;
 	} else
 		return -ENXIO;
 
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 24d7fe7c74ed..e7d8cc9f41e8 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -303,24 +303,24 @@ static const struct attribute_group *pmem_attribute_groups[] = {
 	NULL,
 };
 
-static void __pmem_release_queue(struct percpu_ref *ref)
+static void pmem_pagemap_cleanup(struct dev_pagemap *pgmap)
 {
-	struct request_queue *q;
+	struct request_queue *q =
+		container_of(pgmap->ref, struct request_queue, q_usage_counter);
 
-	q = container_of(ref, typeof(*q), q_usage_counter);
 	blk_cleanup_queue(q);
 }
 
-static void pmem_release_queue(void *ref)
+static void pmem_release_queue(void *pgmap)
 {
-	__pmem_release_queue(ref);
+	pmem_pagemap_cleanup(pgmap);
 }
 
-static void pmem_freeze_queue(struct percpu_ref *ref)
+static void pmem_pagemap_kill(struct dev_pagemap *pgmap)
 {
-	struct request_queue *q;
+	struct request_queue *q =
+		container_of(pgmap->ref, struct request_queue, q_usage_counter);
 
-	q = container_of(ref, typeof(*q), q_usage_counter);
 	blk_freeze_queue_start(q);
 }
 
@@ -334,26 +334,16 @@ static void pmem_release_disk(void *__pmem)
 	put_disk(pmem->disk);
 }
 
-static void pmem_release_pgmap_ops(void *__pgmap)
-{
-	dev_pagemap_put_ops();
-}
-
-static void fsdax_pagefree(struct page *page, void *data)
+static void pmem_pagemap_page_free(struct page *page)
 {
 	wake_up_var(&page->_refcount);
 }
 
-static int setup_pagemap_fsdax(struct device *dev, struct dev_pagemap *pgmap)
-{
-	dev_pagemap_get_ops();
-	if (devm_add_action_or_reset(dev, pmem_release_pgmap_ops, pgmap))
-		return -ENOMEM;
-	pgmap->type = MEMORY_DEVICE_FS_DAX;
-	pgmap->page_free = fsdax_pagefree;
-
-	return 0;
-}
+static const struct dev_pagemap_ops fsdax_pagemap_ops = {
+	.page_free		= pmem_pagemap_page_free,
+	.kill			= pmem_pagemap_kill,
+	.cleanup		= pmem_pagemap_cleanup,
+};
 
 static int pmem_attach_disk(struct device *dev,
 		struct nd_namespace_common *ndns)
@@ -409,11 +399,9 @@ static int pmem_attach_disk(struct device *dev,
 
 	pmem->pfn_flags = PFN_DEV;
 	pmem->pgmap.ref = &q->q_usage_counter;
-	pmem->pgmap.kill = pmem_freeze_queue;
-	pmem->pgmap.cleanup = __pmem_release_queue;
 	if (is_nd_pfn(dev)) {
-		if (setup_pagemap_fsdax(dev, &pmem->pgmap))
-			return -ENOMEM;
+		pmem->pgmap.type = MEMORY_DEVICE_FS_DAX;
+		pmem->pgmap.ops = &fsdax_pagemap_ops;
 		addr = devm_memremap_pages(dev, &pmem->pgmap);
 		pfn_sb = nd_pfn->pfn_sb;
 		pmem->data_offset = le64_to_cpu(pfn_sb->dataoff);
@@ -424,15 +412,14 @@ static int pmem_attach_disk(struct device *dev,
 		bb_res.start += pmem->data_offset;
 	} else if (pmem_should_map_pages(dev)) {
 		memcpy(&pmem->pgmap.res, &nsio->res, sizeof(pmem->pgmap.res));
-		pmem->pgmap.altmap_valid = false;
-		if (setup_pagemap_fsdax(dev, &pmem->pgmap))
-			return -ENOMEM;
+		pmem->pgmap.type = MEMORY_DEVICE_FS_DAX;
+		pmem->pgmap.ops = &fsdax_pagemap_ops;
 		addr = devm_memremap_pages(dev, &pmem->pgmap);
 		pmem->pfn_flags |= PFN_MAP;
 		memcpy(&bb_res, &pmem->pgmap.res, sizeof(bb_res));
 	} else {
 		if (devm_add_action_or_reset(dev, pmem_release_queue,
-					&q->q_usage_counter))
+					&pmem->pgmap))
 			return -ENOMEM;
 		addr = devm_memremap(dev, pmem->phys_addr,
 				pmem->size, ARCH_MEMREMAP_PMEM);
diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index a4994aa3acc0..a3073ce16520 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -25,12 +25,6 @@ struct pci_p2pdma {
 	bool p2pmem_published;
 };
 
-struct p2pdma_pagemap {
-	struct dev_pagemap pgmap;
-	struct percpu_ref ref;
-	struct completion ref_done;
-};
-
 static ssize_t size_show(struct device *dev, struct device_attribute *attr,
 			 char *buf)
 {
@@ -79,31 +73,6 @@ static const struct attribute_group p2pmem_group = {
 	.name = "p2pmem",
 };
 
-static struct p2pdma_pagemap *to_p2p_pgmap(struct percpu_ref *ref)
-{
-	return container_of(ref, struct p2pdma_pagemap, ref);
-}
-
-static void pci_p2pdma_percpu_release(struct percpu_ref *ref)
-{
-	struct p2pdma_pagemap *p2p_pgmap = to_p2p_pgmap(ref);
-
-	complete(&p2p_pgmap->ref_done);
-}
-
-static void pci_p2pdma_percpu_kill(struct percpu_ref *ref)
-{
-	percpu_ref_kill(ref);
-}
-
-static void pci_p2pdma_percpu_cleanup(struct percpu_ref *ref)
-{
-	struct p2pdma_pagemap *p2p_pgmap = to_p2p_pgmap(ref);
-
-	wait_for_completion(&p2p_pgmap->ref_done);
-	percpu_ref_exit(&p2p_pgmap->ref);
-}
-
 static void pci_p2pdma_release(void *data)
 {
 	struct pci_dev *pdev = data;
@@ -166,7 +135,6 @@ out:
 int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size,
 			    u64 offset)
 {
-	struct p2pdma_pagemap *p2p_pgmap;
 	struct dev_pagemap *pgmap;
 	void *addr;
 	int error;
@@ -189,27 +157,15 @@ int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size,
 			return error;
 	}
 
-	p2p_pgmap = devm_kzalloc(&pdev->dev, sizeof(*p2p_pgmap), GFP_KERNEL);
-	if (!p2p_pgmap)
+	pgmap = devm_kzalloc(&pdev->dev, sizeof(*pgmap), GFP_KERNEL);
+	if (!pgmap)
 		return -ENOMEM;
-
-	init_completion(&p2p_pgmap->ref_done);
-	error = percpu_ref_init(&p2p_pgmap->ref,
-			pci_p2pdma_percpu_release, 0, GFP_KERNEL);
-	if (error)
-		goto pgmap_free;
-
-	pgmap = &p2p_pgmap->pgmap;
-
 	pgmap->res.start = pci_resource_start(pdev, bar) + offset;
 	pgmap->res.end = pgmap->res.start + size - 1;
 	pgmap->res.flags = pci_resource_flags(pdev, bar);
-	pgmap->ref = &p2p_pgmap->ref;
 	pgmap->type = MEMORY_DEVICE_PCI_P2PDMA;
 	pgmap->pci_p2pdma_bus_offset = pci_bus_address(pdev, bar) -
 		pci_resource_start(pdev, bar);
-	pgmap->kill = pci_p2pdma_percpu_kill;
-	pgmap->cleanup = pci_p2pdma_percpu_cleanup;
 
 	addr = devm_memremap_pages(&pdev->dev, pgmap);
 	if (IS_ERR(addr)) {
@@ -220,7 +176,7 @@ int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size,
 	error = gen_pool_add_owner(pdev->p2pdma->pool, (unsigned long)addr,
 			pci_bus_address(pdev, bar) + offset,
 			resource_size(&pgmap->res), dev_to_node(&pdev->dev),
-			&p2p_pgmap->ref);
+			pgmap->ref);
 	if (error)
 		goto pages_free;
 
@@ -232,7 +188,7 @@ int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size,
 pages_free:
 	devm_memunmap_pages(&pdev->dev, pgmap);
 pgmap_free:
-	devm_kfree(&pdev->dev, p2p_pgmap);
+	devm_kfree(&pdev->dev, pgmap);
 	return error;
 }
 EXPORT_SYMBOL_GPL(pci_p2pdma_add_resource);
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index dedca3da428a..818cedbed95f 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1322,7 +1322,7 @@ static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm,
 		if (pm->show_pfn)
 			frame = pte_pfn(pte);
 		flags |= PM_PRESENT;
-		page = _vm_normal_page(vma, addr, pte, true);
+		page = vm_normal_page(vma, addr, pte);
 		if (pte_soft_dirty(pte))
 			flags |= PM_SOFT_DIRTY;
 	} else if (is_swap_pte(pte)) {
diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index 044a36d7c3f8..b8a08b2a10ca 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -21,8 +21,8 @@
  *
  * HMM address space mirroring API:
  *
- * Use HMM address space mirroring if you want to mirror range of the CPU page
- * table of a process into a device page table. Here, "mirror" means "keep
+ * Use HMM address space mirroring if you want to mirror a range of the CPU
+ * page tables of a process into a device page table. Here, "mirror" means "keep
  * synchronized". Prerequisites: the device must provide the ability to write-
  * protect its page tables (at PAGE_SIZE granularity), and must be able to
  * recover from the resulting potential page faults.
@@ -62,7 +62,7 @@
 #include <linux/kconfig.h>
 #include <asm/pgtable.h>
 
-#if IS_ENABLED(CONFIG_HMM)
+#ifdef CONFIG_HMM_MIRROR
 
 #include <linux/device.h>
 #include <linux/migrate.h>
@@ -82,19 +82,18 @@
  * @mirrors_sem: read/write semaphore protecting the mirrors list
  * @wq: wait queue for user waiting on a range invalidation
  * @notifiers: count of active mmu notifiers
- * @dead: is the mm dead ?
  */
 struct hmm {
 	struct mm_struct	*mm;
 	struct kref		kref;
-	struct mutex		lock;
+	spinlock_t		ranges_lock;
 	struct list_head	ranges;
 	struct list_head	mirrors;
 	struct mmu_notifier	mmu_notifier;
 	struct rw_semaphore	mirrors_sem;
 	wait_queue_head_t	wq;
+	struct rcu_head		rcu;
 	long			notifiers;
-	bool			dead;
 };
 
 /*
@@ -105,10 +104,11 @@ struct hmm {
  * HMM_PFN_WRITE: CPU page table has write permission set
  * HMM_PFN_DEVICE_PRIVATE: private device memory (ZONE_DEVICE)
  *
- * The driver provide a flags array, if driver valid bit for an entry is bit
- * 3 ie (entry & (1 << 3)) is true if entry is valid then driver must provide
+ * The driver provides a flags array for mapping page protections to device
+ * PTE bits. If the driver valid bit for an entry is bit 3,
+ * i.e., (entry & (1 << 3)), then the driver must provide
  * an array in hmm_range.flags with hmm_range.flags[HMM_PFN_VALID] == 1 << 3.
- * Same logic apply to all flags. This is same idea as vm_page_prot in vma
+ * Same logic apply to all flags. This is the same idea as vm_page_prot in vma
  * except that this is per device driver rather than per architecture.
  */
 enum hmm_pfn_flag_e {
@@ -129,13 +129,13 @@ enum hmm_pfn_flag_e {
  *      be mirrored by a device, because the entry will never have HMM_PFN_VALID
  *      set and the pfn value is undefined.
  *
- * Driver provide entry value for none entry, error entry and special entry,
- * driver can alias (ie use same value for error and special for instance). It
- * should not alias none and error or special.
+ * Driver provides values for none entry, error entry, and special entry.
+ * Driver can alias (i.e., use same value) error and special, but
+ * it should not alias none with error or special.
  *
  * HMM pfn value returned by hmm_vma_get_pfns() or hmm_vma_fault() will be:
  * hmm_range.values[HMM_PFN_ERROR] if CPU page table entry is poisonous,
- * hmm_range.values[HMM_PFN_NONE] if there is no CPU page table
+ * hmm_range.values[HMM_PFN_NONE] if there is no CPU page table entry,
  * hmm_range.values[HMM_PFN_SPECIAL] if CPU page table entry is a special one
  */
 enum hmm_pfn_value_e {
@@ -158,6 +158,7 @@ enum hmm_pfn_value_e {
  * @values: pfn value for some special case (none, special, error, ...)
  * @default_flags: default flags for the range (write, read, ... see hmm doc)
  * @pfn_flags_mask: allows to mask pfn flags so that only default_flags matter
+ * @page_shift: device virtual address shift value (should be >= PAGE_SHIFT)
  * @pfn_shifts: pfn shift value (should be <= PAGE_SHIFT)
  * @valid: pfns array did not change since it has been fill by an HMM function
  */
@@ -180,7 +181,7 @@ struct hmm_range {
 /*
  * hmm_range_page_shift() - return the page shift for the range
  * @range: range being queried
- * Returns: page shift (page size = 1 << page shift) for the range
+ * Return: page shift (page size = 1 << page shift) for the range
  */
 static inline unsigned hmm_range_page_shift(const struct hmm_range *range)
 {
@@ -190,7 +191,7 @@ static inline unsigned hmm_range_page_shift(const struct hmm_range *range)
 /*
  * hmm_range_page_size() - return the page size for the range
  * @range: range being queried
- * Returns: page size for the range in bytes
+ * Return: page size for the range in bytes
  */
 static inline unsigned long hmm_range_page_size(const struct hmm_range *range)
 {
@@ -201,28 +202,19 @@ static inline unsigned long hmm_range_page_size(const struct hmm_range *range)
  * hmm_range_wait_until_valid() - wait for range to be valid
  * @range: range affected by invalidation to wait on
  * @timeout: time out for wait in ms (ie abort wait after that period of time)
- * Returns: true if the range is valid, false otherwise.
+ * Return: true if the range is valid, false otherwise.
  */
 static inline bool hmm_range_wait_until_valid(struct hmm_range *range,
 					      unsigned long timeout)
 {
-	/* Check if mm is dead ? */
-	if (range->hmm == NULL || range->hmm->dead || range->hmm->mm == NULL) {
-		range->valid = false;
-		return false;
-	}
-	if (range->valid)
-		return true;
-	wait_event_timeout(range->hmm->wq, range->valid || range->hmm->dead,
-			   msecs_to_jiffies(timeout));
-	/* Return current valid status just in case we get lucky */
-	return range->valid;
+	return wait_event_timeout(range->hmm->wq, range->valid,
+				  msecs_to_jiffies(timeout)) != 0;
 }
 
 /*
  * hmm_range_valid() - test if a range is valid or not
  * @range: range
- * Returns: true if the range is valid, false otherwise.
+ * Return: true if the range is valid, false otherwise.
  */
 static inline bool hmm_range_valid(struct hmm_range *range)
 {
@@ -233,7 +225,7 @@ static inline bool hmm_range_valid(struct hmm_range *range)
  * hmm_device_entry_to_page() - return struct page pointed to by a device entry
  * @range: range use to decode device entry value
  * @entry: device entry value to get corresponding struct page from
- * Returns: struct page pointer if entry is a valid, NULL otherwise
+ * Return: struct page pointer if entry is a valid, NULL otherwise
  *
  * If the device entry is valid (ie valid flag set) then return the struct page
  * matching the entry value. Otherwise return NULL.
@@ -256,7 +248,7 @@ static inline struct page *hmm_device_entry_to_page(const struct hmm_range *rang
  * hmm_device_entry_to_pfn() - return pfn value store in a device entry
  * @range: range use to decode device entry value
  * @entry: device entry to extract pfn from
- * Returns: pfn value if device entry is valid, -1UL otherwise
+ * Return: pfn value if device entry is valid, -1UL otherwise
  */
 static inline unsigned long
 hmm_device_entry_to_pfn(const struct hmm_range *range, uint64_t pfn)
@@ -276,7 +268,7 @@ hmm_device_entry_to_pfn(const struct hmm_range *range, uint64_t pfn)
  * hmm_device_entry_from_page() - create a valid device entry for a page
  * @range: range use to encode HMM pfn value
  * @page: page for which to create the device entry
- * Returns: valid device entry for the page
+ * Return: valid device entry for the page
  */
 static inline uint64_t hmm_device_entry_from_page(const struct hmm_range *range,
 						  struct page *page)
@@ -289,7 +281,7 @@ static inline uint64_t hmm_device_entry_from_page(const struct hmm_range *range,
  * hmm_device_entry_from_pfn() - create a valid device entry value from pfn
  * @range: range use to encode HMM pfn value
  * @pfn: pfn value for which to create the device entry
- * Returns: valid device entry for the pfn
+ * Return: valid device entry for the pfn
  */
 static inline uint64_t hmm_device_entry_from_pfn(const struct hmm_range *range,
 						 unsigned long pfn)
@@ -332,9 +324,6 @@ static inline uint64_t hmm_pfn_from_pfn(const struct hmm_range *range,
 	return hmm_device_entry_from_pfn(range, pfn);
 }
 
-
-
-#if IS_ENABLED(CONFIG_HMM_MIRROR)
 /*
  * Mirroring: how to synchronize device page table with CPU page table.
  *
@@ -394,7 +383,7 @@ enum hmm_update_event {
 };
 
 /*
- * struct hmm_update - HMM update informations for callback
+ * struct hmm_update - HMM update information for callback
  *
  * @start: virtual start address of the range to update
  * @end: virtual end address of the range to update
@@ -418,17 +407,18 @@ struct hmm_mirror_ops {
 	 *
 	 * @mirror: pointer to struct hmm_mirror
 	 *
-	 * This is called when the mm_struct is being released.
-	 * The callback should make sure no references to the mirror occur
-	 * after the callback returns.
+	 * This is called when the mm_struct is being released.  The callback
+	 * must ensure that all access to any pages obtained from this mirror
+	 * is halted before the callback returns. All future access should
+	 * fault.
 	 */
 	void (*release)(struct hmm_mirror *mirror);
 
 	/* sync_cpu_device_pagetables() - synchronize page tables
 	 *
 	 * @mirror: pointer to struct hmm_mirror
-	 * @update: update informations (see struct hmm_update)
-	 * Returns: -EAGAIN if update.blockable false and callback need to
+	 * @update: update information (see struct hmm_update)
+	 * Return: -EAGAIN if update.blockable false and callback need to
 	 *          block, 0 otherwise.
 	 *
 	 * This callback ultimately originates from mmu_notifiers when the CPU
@@ -465,35 +455,10 @@ int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm);
 void hmm_mirror_unregister(struct hmm_mirror *mirror);
 
 /*
- * hmm_mirror_mm_is_alive() - test if mm is still alive
- * @mirror: the HMM mm mirror for which we want to lock the mmap_sem
- * Returns: false if the mm is dead, true otherwise
- *
- * This is an optimization it will not accurately always return -EINVAL if the
- * mm is dead ie there can be false negative (process is being kill but HMM is
- * not yet inform of that). It is only intented to be use to optimize out case
- * where driver is about to do something time consuming and it would be better
- * to skip it if the mm is dead.
- */
-static inline bool hmm_mirror_mm_is_alive(struct hmm_mirror *mirror)
-{
-	struct mm_struct *mm;
-
-	if (!mirror || !mirror->hmm)
-		return false;
-	mm = READ_ONCE(mirror->hmm->mm);
-	if (mirror->hmm->dead || !mm)
-		return false;
-
-	return true;
-}
-
-
-/*
  * Please see Documentation/vm/hmm.rst for how to use the range API.
  */
 int hmm_range_register(struct hmm_range *range,
-		       struct mm_struct *mm,
+		       struct hmm_mirror *mirror,
 		       unsigned long start,
 		       unsigned long end,
 		       unsigned page_shift);
@@ -529,7 +494,8 @@ static inline bool hmm_vma_range_done(struct hmm_range *range)
 }
 
 /* This is a temporary helper to avoid merge conflict between trees. */
-static inline int hmm_vma_fault(struct hmm_range *range, bool block)
+static inline int hmm_vma_fault(struct hmm_mirror *mirror,
+				struct hmm_range *range, bool block)
 {
 	long ret;
 
@@ -542,7 +508,7 @@ static inline int hmm_vma_fault(struct hmm_range *range, bool block)
 	range->default_flags = 0;
 	range->pfn_flags_mask = -1UL;
 
-	ret = hmm_range_register(range, range->vma->vm_mm,
+	ret = hmm_range_register(range, mirror,
 				 range->start, range->end,
 				 PAGE_SHIFT);
 	if (ret)
@@ -561,7 +527,7 @@ static inline int hmm_vma_fault(struct hmm_range *range, bool block)
 	ret = hmm_range_fault(range, block);
 	if (ret <= 0) {
 		if (ret == -EBUSY || !ret) {
-			/* Same as above  drop mmap_sem to match old API. */
+			/* Same as above, drop mmap_sem to match old API. */
 			up_read(&range->vma->vm_mm->mmap_sem);
 			ret = -EBUSY;
 		} else if (ret == -EAGAIN)
@@ -573,208 +539,12 @@ static inline int hmm_vma_fault(struct hmm_range *range, bool block)
 }
 
 /* Below are for HMM internal use only! Not to be used by device driver! */
-void hmm_mm_destroy(struct mm_struct *mm);
-
 static inline void hmm_mm_init(struct mm_struct *mm)
 {
 	mm->hmm = NULL;
 }
 #else /* IS_ENABLED(CONFIG_HMM_MIRROR) */
-static inline void hmm_mm_destroy(struct mm_struct *mm) {}
 static inline void hmm_mm_init(struct mm_struct *mm) {}
 #endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */
 
-#if IS_ENABLED(CONFIG_DEVICE_PRIVATE) ||  IS_ENABLED(CONFIG_DEVICE_PUBLIC)
-struct hmm_devmem;
-
-struct page *hmm_vma_alloc_locked_page(struct vm_area_struct *vma,
-				       unsigned long addr);
-
-/*
- * struct hmm_devmem_ops - callback for ZONE_DEVICE memory events
- *
- * @free: call when refcount on page reach 1 and thus is no longer use
- * @fault: call when there is a page fault to unaddressable memory
- *
- * Both callback happens from page_free() and page_fault() callback of struct
- * dev_pagemap respectively. See include/linux/memremap.h for more details on
- * those.
- *
- * The hmm_devmem_ops callback are just here to provide a coherent and
- * uniq API to device driver and device driver should not register their
- * own page_free() or page_fault() but rely on the hmm_devmem_ops call-
- * back.
- */
-struct hmm_devmem_ops {
-	/*
-	 * free() - free a device page
-	 * @devmem: device memory structure (see struct hmm_devmem)
-	 * @page: pointer to struct page being freed
-	 *
-	 * Call back occurs whenever a device page refcount reach 1 which
-	 * means that no one is holding any reference on the page anymore
-	 * (ZONE_DEVICE page have an elevated refcount of 1 as default so
-	 * that they are not release to the general page allocator).
-	 *
-	 * Note that callback has exclusive ownership of the page (as no
-	 * one is holding any reference).
-	 */
-	void (*free)(struct hmm_devmem *devmem, struct page *page);
-	/*
-	 * fault() - CPU page fault or get user page (GUP)
-	 * @devmem: device memory structure (see struct hmm_devmem)
-	 * @vma: virtual memory area containing the virtual address
-	 * @addr: virtual address that faulted or for which there is a GUP
-	 * @page: pointer to struct page backing virtual address (unreliable)
-	 * @flags: FAULT_FLAG_* (see include/linux/mm.h)
-	 * @pmdp: page middle directory
-	 * Returns: VM_FAULT_MINOR/MAJOR on success or one of VM_FAULT_ERROR
-	 *   on error
-	 *
-	 * The callback occurs whenever there is a CPU page fault or GUP on a
-	 * virtual address. This means that the device driver must migrate the
-	 * page back to regular memory (CPU accessible).
-	 *
-	 * The device driver is free to migrate more than one page from the
-	 * fault() callback as an optimization. However if device decide to
-	 * migrate more than one page it must always priotirize the faulting
-	 * address over the others.
-	 *
-	 * The struct page pointer is only given as an hint to allow quick
-	 * lookup of internal device driver data. A concurrent migration
-	 * might have already free that page and the virtual address might
-	 * not longer be back by it. So it should not be modified by the
-	 * callback.
-	 *
-	 * Note that mmap semaphore is held in read mode at least when this
-	 * callback occurs, hence the vma is valid upon callback entry.
-	 */
-	vm_fault_t (*fault)(struct hmm_devmem *devmem,
-		     struct vm_area_struct *vma,
-		     unsigned long addr,
-		     const struct page *page,
-		     unsigned int flags,
-		     pmd_t *pmdp);
-};
-
-/*
- * struct hmm_devmem - track device memory
- *
- * @completion: completion object for device memory
- * @pfn_first: first pfn for this resource (set by hmm_devmem_add())
- * @pfn_last: last pfn for this resource (set by hmm_devmem_add())
- * @resource: IO resource reserved for this chunk of memory
- * @pagemap: device page map for that chunk
- * @device: device to bind resource to
- * @ops: memory operations callback
- * @ref: per CPU refcount
- * @page_fault: callback when CPU fault on an unaddressable device page
- *
- * This an helper structure for device drivers that do not wish to implement
- * the gory details related to hotplugging new memoy and allocating struct
- * pages.
- *
- * Device drivers can directly use ZONE_DEVICE memory on their own if they
- * wish to do so.
- *
- * The page_fault() callback must migrate page back, from device memory to
- * system memory, so that the CPU can access it. This might fail for various
- * reasons (device issues,  device have been unplugged, ...). When such error
- * conditions happen, the page_fault() callback must return VM_FAULT_SIGBUS and
- * set the CPU page table entry to "poisoned".
- *
- * Note that because memory cgroup charges are transferred to the device memory,
- * this should never fail due to memory restrictions. However, allocation
- * of a regular system page might still fail because we are out of memory. If
- * that happens, the page_fault() callback must return VM_FAULT_OOM.
- *
- * The page_fault() callback can also try to migrate back multiple pages in one
- * chunk, as an optimization. It must, however, prioritize the faulting address
- * over all the others.
- */
-typedef vm_fault_t (*dev_page_fault_t)(struct vm_area_struct *vma,
-				unsigned long addr,
-				const struct page *page,
-				unsigned int flags,
-				pmd_t *pmdp);
-
-struct hmm_devmem {
-	struct completion		completion;
-	unsigned long			pfn_first;
-	unsigned long			pfn_last;
-	struct resource			*resource;
-	struct device			*device;
-	struct dev_pagemap		pagemap;
-	const struct hmm_devmem_ops	*ops;
-	struct percpu_ref		ref;
-	dev_page_fault_t		page_fault;
-};
-
-/*
- * To add (hotplug) device memory, HMM assumes that there is no real resource
- * that reserves a range in the physical address space (this is intended to be
- * use by unaddressable device memory). It will reserve a physical range big
- * enough and allocate struct page for it.
- *
- * The device driver can wrap the hmm_devmem struct inside a private device
- * driver struct.
- */
-struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
-				  struct device *device,
-				  unsigned long size);
-struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
-					   struct device *device,
-					   struct resource *res);
-
-/*
- * hmm_devmem_page_set_drvdata - set per-page driver data field
- *
- * @page: pointer to struct page
- * @data: driver data value to set
- *
- * Because page can not be on lru we have an unsigned long that driver can use
- * to store a per page field. This just a simple helper to do that.
- */
-static inline void hmm_devmem_page_set_drvdata(struct page *page,
-					       unsigned long data)
-{
-	page->hmm_data = data;
-}
-
-/*
- * hmm_devmem_page_get_drvdata - get per page driver data field
- *
- * @page: pointer to struct page
- * Return: driver data value
- */
-static inline unsigned long hmm_devmem_page_get_drvdata(const struct page *page)
-{
-	return page->hmm_data;
-}
-
-
-/*
- * struct hmm_device - fake device to hang device memory onto
- *
- * @device: device struct
- * @minor: device minor number
- */
-struct hmm_device {
-	struct device		device;
-	unsigned int		minor;
-};
-
-/*
- * A device driver that wants to handle multiple devices memory through a
- * single fake device can use hmm_device to do so. This is purely a helper and
- * it is not strictly needed, in order to make use of any HMM functionality.
- */
-struct hmm_device *hmm_device_new(void *drvdata);
-void hmm_device_put(struct hmm_device *hmm_device);
-#endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */
-#else /* IS_ENABLED(CONFIG_HMM) */
-static inline void hmm_mm_destroy(struct mm_struct *mm) {}
-static inline void hmm_mm_init(struct mm_struct *mm) {}
-#endif /* IS_ENABLED(CONFIG_HMM) */
-
 #endif /* LINUX_HMM_H */
diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index 5db386cfc2d4..5b6a7121c9f0 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -133,8 +133,7 @@ enum {
 	IORES_DESC_PERSISTENT_MEMORY		= 4,
 	IORES_DESC_PERSISTENT_MEMORY_LEGACY	= 5,
 	IORES_DESC_DEVICE_PRIVATE_MEMORY	= 6,
-	IORES_DESC_DEVICE_PUBLIC_MEMORY		= 7,
-	IORES_DESC_RESERVED			= 8,
+	IORES_DESC_RESERVED			= 7,
 };
 
 /*
@@ -296,6 +295,8 @@ static inline bool resource_overlaps(struct resource *r1, struct resource *r2)
        return (r1->start <= r2->end && r1->end >= r2->start);
 }
 
+struct resource *devm_request_free_mem_region(struct device *dev,
+		struct resource *base, unsigned long size);
 
 #endif /* __ASSEMBLY__ */
 #endif	/* _LINUX_IOPORT_H */
diff --git a/include/linux/memremap.h b/include/linux/memremap.h
index 1732dea030b2..f8a5b2a19945 100644
--- a/include/linux/memremap.h
+++ b/include/linux/memremap.h
@@ -37,13 +37,6 @@ struct vmem_altmap {
  * A more complete discussion of unaddressable memory may be found in
  * include/linux/hmm.h and Documentation/vm/hmm.rst.
  *
- * MEMORY_DEVICE_PUBLIC:
- * Device memory that is cache coherent from device and CPU point of view. This
- * is use on platform that have an advance system bus (like CAPI or CCIX). A
- * driver can hotplug the device memory using ZONE_DEVICE and with that memory
- * type. Any page of a process can be migrated to such memory. However no one
- * should be allow to pin such memory so that it can always be evicted.
- *
  * MEMORY_DEVICE_FS_DAX:
  * Host memory that has similar access semantics as System RAM i.e. DMA
  * coherent and supports page pinning. In support of coordinating page
@@ -52,54 +45,84 @@ struct vmem_altmap {
  * wakeup is used to coordinate physical address space management (ex:
  * fs truncate/hole punch) vs pinned pages (ex: device dma).
  *
+ * MEMORY_DEVICE_DEVDAX:
+ * Host memory that has similar access semantics as System RAM i.e. DMA
+ * coherent and supports page pinning. In contrast to
+ * MEMORY_DEVICE_FS_DAX, this memory is access via a device-dax
+ * character device.
+ *
  * MEMORY_DEVICE_PCI_P2PDMA:
  * Device memory residing in a PCI BAR intended for use with Peer-to-Peer
  * transactions.
  */
 enum memory_type {
+	/* 0 is reserved to catch uninitialized type fields */
 	MEMORY_DEVICE_PRIVATE = 1,
-	MEMORY_DEVICE_PUBLIC,
 	MEMORY_DEVICE_FS_DAX,
+	MEMORY_DEVICE_DEVDAX,
 	MEMORY_DEVICE_PCI_P2PDMA,
 };
 
-/*
- * Additional notes about MEMORY_DEVICE_PRIVATE may be found in
- * include/linux/hmm.h and Documentation/vm/hmm.rst. There is also a brief
- * explanation in include/linux/memory_hotplug.h.
- *
- * The page_free() callback is called once the page refcount reaches 1
- * (ZONE_DEVICE pages never reach 0 refcount unless there is a refcount bug.
- * This allows the device driver to implement its own memory management.)
- */
-typedef void (*dev_page_free_t)(struct page *page, void *data);
+struct dev_pagemap_ops {
+	/*
+	 * Called once the page refcount reaches 1.  (ZONE_DEVICE pages never
+	 * reach 0 refcount unless there is a refcount bug. This allows the
+	 * device driver to implement its own memory management.)
+	 */
+	void (*page_free)(struct page *page);
+
+	/*
+	 * Transition the refcount in struct dev_pagemap to the dead state.
+	 */
+	void (*kill)(struct dev_pagemap *pgmap);
+
+	/*
+	 * Wait for refcount in struct dev_pagemap to be idle and reap it.
+	 */
+	void (*cleanup)(struct dev_pagemap *pgmap);
+
+	/*
+	 * Used for private (un-addressable) device memory only.  Must migrate
+	 * the page back to a CPU accessible page.
+	 */
+	vm_fault_t (*migrate_to_ram)(struct vm_fault *vmf);
+};
+
+#define PGMAP_ALTMAP_VALID	(1 << 0)
 
 /**
  * struct dev_pagemap - metadata for ZONE_DEVICE mappings
- * @page_free: free page callback when page refcount reaches 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
- * @kill: callback to transition @ref to the dead state
- * @cleanup: callback to wait for @ref to be idle and reap it
+ * @internal_ref: internal reference if @ref is not provided by the caller
+ * @done: completion for @internal_ref
  * @dev: host device of the mapping for debug
  * @data: private data pointer for page_free()
  * @type: memory type: see MEMORY_* in memory_hotplug.h
+ * @flags: PGMAP_* flags to specify defailed behavior
+ * @ops: method table
  */
 struct dev_pagemap {
-	dev_page_free_t page_free;
 	struct vmem_altmap altmap;
-	bool altmap_valid;
 	struct resource res;
 	struct percpu_ref *ref;
-	void (*kill)(struct percpu_ref *ref);
-	void (*cleanup)(struct percpu_ref *ref);
+	struct percpu_ref internal_ref;
+	struct completion done;
 	struct device *dev;
-	void *data;
 	enum memory_type type;
+	unsigned int flags;
 	u64 pci_p2pdma_bus_offset;
+	const struct dev_pagemap_ops *ops;
 };
 
+static inline struct vmem_altmap *pgmap_altmap(struct dev_pagemap *pgmap)
+{
+	if (pgmap->flags & PGMAP_ALTMAP_VALID)
+		return &pgmap->altmap;
+	return NULL;
+}
+
 #ifdef CONFIG_ZONE_DEVICE
 void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap);
 void devm_memunmap_pages(struct device *dev, struct dev_pagemap *pgmap);
diff --git a/include/linux/mm.h b/include/linux/mm.h
index f88f0eabcc5e..0389c34ac529 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -937,8 +937,6 @@ static inline bool is_zone_device_page(const struct page *page)
 #endif
 
 #ifdef CONFIG_DEV_PAGEMAP_OPS
-void dev_pagemap_get_ops(void);
-void dev_pagemap_put_ops(void);
 void __put_devmap_managed_page(struct page *page);
 DECLARE_STATIC_KEY_FALSE(devmap_managed_key);
 static inline bool put_devmap_managed_page(struct page *page)
@@ -949,7 +947,6 @@ static inline bool put_devmap_managed_page(struct page *page)
 		return false;
 	switch (page->pgmap->type) {
 	case MEMORY_DEVICE_PRIVATE:
-	case MEMORY_DEVICE_PUBLIC:
 	case MEMORY_DEVICE_FS_DAX:
 		__put_devmap_managed_page(page);
 		return true;
@@ -965,12 +962,6 @@ static inline bool is_device_private_page(const struct page *page)
 		page->pgmap->type == MEMORY_DEVICE_PRIVATE;
 }
 
-static inline bool is_device_public_page(const struct page *page)
-{
-	return is_zone_device_page(page) &&
-		page->pgmap->type == MEMORY_DEVICE_PUBLIC;
-}
-
 #ifdef CONFIG_PCI_P2PDMA
 static inline bool is_pci_p2pdma_page(const struct page *page)
 {
@@ -985,14 +976,6 @@ static inline bool is_pci_p2pdma_page(const struct page *page)
 #endif /* CONFIG_PCI_P2PDMA */
 
 #else /* CONFIG_DEV_PAGEMAP_OPS */
-static inline void dev_pagemap_get_ops(void)
-{
-}
-
-static inline void dev_pagemap_put_ops(void)
-{
-}
-
 static inline bool put_devmap_managed_page(struct page *page)
 {
 	return false;
@@ -1003,11 +986,6 @@ static inline bool is_device_private_page(const struct page *page)
 	return false;
 }
 
-static inline bool is_device_public_page(const struct page *page)
-{
-	return false;
-}
-
 static inline bool is_pci_p2pdma_page(const struct page *page)
 {
 	return false;
@@ -1436,10 +1414,8 @@ struct zap_details {
 	pgoff_t last_index;			/* Highest page->index to unmap */
 };
 
-struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
-			     pte_t pte, bool with_public_device);
-#define vm_normal_page(vma, addr, pte) _vm_normal_page(vma, addr, pte, false)
-
+struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
+			     pte_t pte);
 struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,
 				pmd_t pmd);
 
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 1d1093474c1a..3a37a89eb7a7 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -158,7 +158,7 @@ struct page {
 		struct {	/* ZONE_DEVICE pages */
 			/** @pgmap: Points to the hosting device page map. */
 			struct dev_pagemap *pgmap;
-			unsigned long hmm_data;
+			void *zone_device_data;
 			unsigned long _zd_pad_1;	/* uses mapping */
 		};
 
@@ -503,7 +503,7 @@ struct mm_struct {
 #endif
 		struct work_struct async_put_work;
 
-#if IS_ENABLED(CONFIG_HMM)
+#ifdef CONFIG_HMM_MIRROR
 		/* HMM needs to track a few things per mm */
 		struct hmm *hmm;
 #endif
diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index 4d961668e5fc..15bdb6fe71e5 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -129,12 +129,6 @@ static inline struct page *device_private_entry_to_page(swp_entry_t entry)
 {
 	return pfn_to_page(swp_offset(entry));
 }
-
-vm_fault_t device_private_entry_fault(struct vm_area_struct *vma,
-		       unsigned long addr,
-		       swp_entry_t entry,
-		       unsigned int flags,
-		       pmd_t *pmdp);
 #else /* CONFIG_DEVICE_PRIVATE */
 static inline swp_entry_t make_device_private_entry(struct page *page, bool write)
 {
@@ -164,15 +158,6 @@ static inline struct page *device_private_entry_to_page(swp_entry_t entry)
 {
 	return NULL;
 }
-
-static inline vm_fault_t device_private_entry_fault(struct vm_area_struct *vma,
-				     unsigned long addr,
-				     swp_entry_t entry,
-				     unsigned int flags,
-				     pmd_t *pmdp)
-{
-	return VM_FAULT_SIGBUS;
-}
 #endif /* CONFIG_DEVICE_PRIVATE */
 
 #ifdef CONFIG_MIGRATION
diff --git a/kernel/fork.c b/kernel/fork.c
index 8f3e2d97d771..dfa78985a6fd 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -677,7 +677,6 @@ void __mmdrop(struct mm_struct *mm)
 	WARN_ON_ONCE(mm == current->active_mm);
 	mm_free_pgd(mm);
 	destroy_context(mm);
-	hmm_mm_destroy(mm);
 	mmu_notifier_mm_destroy(mm);
 	check_mm(mm);
 	put_user_ns(mm->user_ns);
diff --git a/kernel/memremap.c b/kernel/memremap.c
index 6e1970719dc2..bea6f887adad 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -11,41 +11,39 @@
 #include <linux/types.h>
 #include <linux/wait_bit.h>
 #include <linux/xarray.h>
-#include <linux/hmm.h>
 
 static DEFINE_XARRAY(pgmap_array);
 #define SECTION_MASK ~((1UL << PA_SECTION_SHIFT) - 1)
 #define SECTION_SIZE (1UL << PA_SECTION_SHIFT)
 
-#if IS_ENABLED(CONFIG_DEVICE_PRIVATE)
-vm_fault_t device_private_entry_fault(struct vm_area_struct *vma,
-		       unsigned long addr,
-		       swp_entry_t entry,
-		       unsigned int flags,
-		       pmd_t *pmdp)
+#ifdef CONFIG_DEV_PAGEMAP_OPS
+DEFINE_STATIC_KEY_FALSE(devmap_managed_key);
+EXPORT_SYMBOL(devmap_managed_key);
+static atomic_t devmap_managed_enable;
+
+static void devmap_managed_enable_put(void *data)
 {
-	struct page *page = device_private_entry_to_page(entry);
-	struct hmm_devmem *devmem;
+	if (atomic_dec_and_test(&devmap_managed_enable))
+		static_branch_disable(&devmap_managed_key);
+}
 
-	devmem = container_of(page->pgmap, typeof(*devmem), pagemap);
+static int devmap_managed_enable_get(struct device *dev, struct dev_pagemap *pgmap)
+{
+	if (!pgmap->ops || !pgmap->ops->page_free) {
+		WARN(1, "Missing page_free method\n");
+		return -EINVAL;
+	}
 
-	/*
-	 * The page_fault() callback must migrate page back to system memory
-	 * so that CPU can access it. This might fail for various reasons
-	 * (device issue, device was unsafely unplugged, ...). When such
-	 * error conditions happen, the callback must return VM_FAULT_SIGBUS.
-	 *
-	 * Note that because memory cgroup charges are accounted to the device
-	 * memory, this should never fail because of memory restrictions (but
-	 * allocation of regular system page might still fail because we are
-	 * out of memory).
-	 *
-	 * There is a more in-depth description of what that callback can and
-	 * cannot do, in include/linux/memremap.h
-	 */
-	return devmem->page_fault(vma, addr, page, flags, pmdp);
+	if (atomic_inc_return(&devmap_managed_enable) == 1)
+		static_branch_enable(&devmap_managed_key);
+	return devm_add_action_or_reset(dev, devmap_managed_enable_put, NULL);
 }
-#endif /* CONFIG_DEVICE_PRIVATE */
+#else
+static int devmap_managed_enable_get(struct device *dev, struct dev_pagemap *pgmap)
+{
+	return -EINVAL;
+}
+#endif /* CONFIG_DEV_PAGEMAP_OPS */
 
 static void pgmap_array_delete(struct resource *res)
 {
@@ -56,14 +54,8 @@ static void pgmap_array_delete(struct resource *res)
 
 static unsigned long pfn_first(struct dev_pagemap *pgmap)
 {
-	const struct resource *res = &pgmap->res;
-	struct vmem_altmap *altmap = &pgmap->altmap;
-	unsigned long pfn;
-
-	pfn = res->start >> PAGE_SHIFT;
-	if (pgmap->altmap_valid)
-		pfn += vmem_altmap_offset(altmap);
-	return pfn;
+	return (pgmap->res.start >> PAGE_SHIFT) +
+		vmem_altmap_offset(pgmap_altmap(pgmap));
 }
 
 static unsigned long pfn_end(struct dev_pagemap *pgmap)
@@ -83,6 +75,24 @@ static unsigned long pfn_next(unsigned long pfn)
 #define for_each_device_pfn(pfn, map) \
 	for (pfn = pfn_first(map); pfn < pfn_end(map); pfn = pfn_next(pfn))
 
+static void dev_pagemap_kill(struct dev_pagemap *pgmap)
+{
+	if (pgmap->ops && pgmap->ops->kill)
+		pgmap->ops->kill(pgmap);
+	else
+		percpu_ref_kill(pgmap->ref);
+}
+
+static void dev_pagemap_cleanup(struct dev_pagemap *pgmap)
+{
+	if (pgmap->ops && pgmap->ops->cleanup) {
+		pgmap->ops->cleanup(pgmap);
+	} else {
+		wait_for_completion(&pgmap->done);
+		percpu_ref_exit(pgmap->ref);
+	}
+}
+
 static void devm_memremap_pages_release(void *data)
 {
 	struct dev_pagemap *pgmap = data;
@@ -92,10 +102,10 @@ static void devm_memremap_pages_release(void *data)
 	unsigned long pfn;
 	int nid;
 
-	pgmap->kill(pgmap->ref);
+	dev_pagemap_kill(pgmap);
 	for_each_device_pfn(pfn, pgmap)
 		put_page(pfn_to_page(pfn));
-	pgmap->cleanup(pgmap->ref);
+	dev_pagemap_cleanup(pgmap);
 
 	/* pages are dead and unused, undo the arch mapping */
 	align_start = res->start & ~(SECTION_SIZE - 1);
@@ -111,7 +121,7 @@ static void devm_memremap_pages_release(void *data)
 				align_size >> PAGE_SHIFT, NULL);
 	} else {
 		arch_remove_memory(nid, align_start, align_size,
-				pgmap->altmap_valid ? &pgmap->altmap : NULL);
+				pgmap_altmap(pgmap));
 		kasan_remove_zero_shadow(__va(align_start), align_size);
 	}
 	mem_hotplug_done();
@@ -122,20 +132,29 @@ static void devm_memremap_pages_release(void *data)
 		      "%s: failed to free all reserved pages\n", __func__);
 }
 
+static void dev_pagemap_percpu_release(struct percpu_ref *ref)
+{
+	struct dev_pagemap *pgmap =
+		container_of(ref, struct dev_pagemap, internal_ref);
+
+	complete(&pgmap->done);
+}
+
 /**
  * devm_memremap_pages - remap and provide memmap backing for the given resource
  * @dev: hosting device for @res
  * @pgmap: pointer to a struct dev_pagemap
  *
  * Notes:
- * 1/ At a minimum the res, ref and type members of @pgmap must be initialized
+ * 1/ At a minimum the res and type members of @pgmap must be initialized
  *    by the caller before passing it to this function
  *
- * 2/ The altmap field may optionally be initialized, in which case altmap_valid
- *    must be set to true
+ * 2/ The altmap field may optionally be initialized, in which case
+ *    PGMAP_ALTMAP_VALID must be set in pgmap->flags.
  *
- * 3/ pgmap->ref must be 'live' on entry and will be killed and reaped
- *    at devm_memremap_pages_release() time, or if this routine fails.
+ * 3/ The ref field may optionally be provided, in which pgmap->ref must be
+ *    'live' on entry and will be killed and reaped at
+ *    devm_memremap_pages_release() time, or if this routine fails.
  *
  * 4/ res is expected to be a host memory range that could feasibly be
  *    treated as a "System RAM" range, i.e. not a device mmio range, but
@@ -144,22 +163,66 @@ static void devm_memremap_pages_release(void *data)
 void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
 {
 	resource_size_t align_start, align_size, align_end;
-	struct vmem_altmap *altmap = pgmap->altmap_valid ?
-			&pgmap->altmap : NULL;
 	struct resource *res = &pgmap->res;
 	struct dev_pagemap *conflict_pgmap;
 	struct mhp_restrictions restrictions = {
 		/*
 		 * We do not want any optional features only our own memmap
 		*/
-		.altmap = altmap,
+		.altmap = pgmap_altmap(pgmap),
 	};
 	pgprot_t pgprot = PAGE_KERNEL;
 	int error, nid, is_ram;
+	bool need_devmap_managed = true;
+
+	switch (pgmap->type) {
+	case MEMORY_DEVICE_PRIVATE:
+		if (!IS_ENABLED(CONFIG_DEVICE_PRIVATE)) {
+			WARN(1, "Device private memory not supported\n");
+			return ERR_PTR(-EINVAL);
+		}
+		if (!pgmap->ops || !pgmap->ops->migrate_to_ram) {
+			WARN(1, "Missing migrate_to_ram method\n");
+			return ERR_PTR(-EINVAL);
+		}
+		break;
+	case MEMORY_DEVICE_FS_DAX:
+		if (!IS_ENABLED(CONFIG_ZONE_DEVICE) ||
+		    IS_ENABLED(CONFIG_FS_DAX_LIMITED)) {
+			WARN(1, "File system DAX not supported\n");
+			return ERR_PTR(-EINVAL);
+		}
+		break;
+	case MEMORY_DEVICE_DEVDAX:
+	case MEMORY_DEVICE_PCI_P2PDMA:
+		need_devmap_managed = false;
+		break;
+	default:
+		WARN(1, "Invalid pgmap type %d\n", pgmap->type);
+		break;
+	}
+
+	if (!pgmap->ref) {
+		if (pgmap->ops && (pgmap->ops->kill || pgmap->ops->cleanup))
+			return ERR_PTR(-EINVAL);
+
+		init_completion(&pgmap->done);
+		error = percpu_ref_init(&pgmap->internal_ref,
+				dev_pagemap_percpu_release, 0, GFP_KERNEL);
+		if (error)
+			return ERR_PTR(error);
+		pgmap->ref = &pgmap->internal_ref;
+	} else {
+		if (!pgmap->ops || !pgmap->ops->kill || !pgmap->ops->cleanup) {
+			WARN(1, "Missing reference count teardown definition\n");
+			return ERR_PTR(-EINVAL);
+		}
+	}
 
-	if (!pgmap->ref || !pgmap->kill || !pgmap->cleanup) {
-		WARN(1, "Missing reference count teardown definition\n");
-		return ERR_PTR(-EINVAL);
+	if (need_devmap_managed) {
+		error = devmap_managed_enable_get(dev, pgmap);
+		if (error)
+			return ERR_PTR(error);
 	}
 
 	align_start = res->start & ~(SECTION_SIZE - 1);
@@ -241,7 +304,7 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
 
 		zone = &NODE_DATA(nid)->node_zones[ZONE_DEVICE];
 		move_pfn_range_to_zone(zone, align_start >> PAGE_SHIFT,
-				align_size >> PAGE_SHIFT, altmap);
+				align_size >> PAGE_SHIFT, pgmap_altmap(pgmap));
 	}
 
 	mem_hotplug_done();
@@ -271,9 +334,8 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
  err_pfn_remap:
 	pgmap_array_delete(res);
  err_array:
-	pgmap->kill(pgmap->ref);
-	pgmap->cleanup(pgmap->ref);
-
+	dev_pagemap_kill(pgmap);
+	dev_pagemap_cleanup(pgmap);
 	return ERR_PTR(error);
 }
 EXPORT_SYMBOL_GPL(devm_memremap_pages);
@@ -287,7 +349,9 @@ EXPORT_SYMBOL_GPL(devm_memunmap_pages);
 unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
 {
 	/* number of pfns from base where pfn_to_page() is valid */
-	return altmap->reserve + altmap->free;
+	if (altmap)
+		return altmap->reserve + altmap->free;
+	return 0;
 }
 
 void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns)
@@ -329,28 +393,6 @@ struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
 EXPORT_SYMBOL_GPL(get_dev_pagemap);
 
 #ifdef CONFIG_DEV_PAGEMAP_OPS
-DEFINE_STATIC_KEY_FALSE(devmap_managed_key);
-EXPORT_SYMBOL(devmap_managed_key);
-static atomic_t devmap_enable;
-
-/*
- * Toggle the static key for ->page_free() callbacks when dev_pagemap
- * pages go idle.
- */
-void dev_pagemap_get_ops(void)
-{
-	if (atomic_inc_return(&devmap_enable) == 1)
-		static_branch_enable(&devmap_managed_key);
-}
-EXPORT_SYMBOL_GPL(dev_pagemap_get_ops);
-
-void dev_pagemap_put_ops(void)
-{
-	if (atomic_dec_and_test(&devmap_enable))
-		static_branch_disable(&devmap_managed_key);
-}
-EXPORT_SYMBOL_GPL(dev_pagemap_put_ops);
-
 void __put_devmap_managed_page(struct page *page)
 {
 	int count = page_ref_dec_return(page);
@@ -366,7 +408,7 @@ void __put_devmap_managed_page(struct page *page)
 
 		mem_cgroup_uncharge(page);
 
-		page->pgmap->page_free(page, page->pgmap->data);
+		page->pgmap->ops->page_free(page);
 	} else if (!count)
 		__put_page(page);
 }
diff --git a/kernel/resource.c b/kernel/resource.c
index 158f04ec1d4f..d22423e85cf8 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -1628,6 +1628,45 @@ void resource_list_free(struct list_head *head)
 }
 EXPORT_SYMBOL(resource_list_free);
 
+#ifdef CONFIG_DEVICE_PRIVATE
+/**
+ * devm_request_free_mem_region - find free region for device private memory
+ *
+ * @dev: device struct to bind the resource to
+ * @size: size in bytes of the device memory to add
+ * @base: resource tree to look in
+ *
+ * This function tries to find an empty range of physical address big enough to
+ * contain the new resource, so that it can later be hotplugged as ZONE_DEVICE
+ * memory, which in turn allocates struct pages.
+ */
+struct resource *devm_request_free_mem_region(struct device *dev,
+		struct resource *base, unsigned long size)
+{
+	resource_size_t end, addr;
+	struct resource *res;
+
+	size = ALIGN(size, 1UL << PA_SECTION_SHIFT);
+	end = min_t(unsigned long, base->end, (1UL << MAX_PHYSMEM_BITS) - 1);
+	addr = end - size + 1UL;
+
+	for (; addr > size && addr >= base->start; addr -= size) {
+		if (region_intersects(addr, size, 0, IORES_DESC_NONE) !=
+				REGION_DISJOINT)
+			continue;
+
+		res = devm_request_mem_region(dev, addr, size, dev_name(dev));
+		if (!res)
+			return ERR_PTR(-ENOMEM);
+		res->desc = IORES_DESC_DEVICE_PRIVATE_MEMORY;
+		return res;
+	}
+
+	return ERR_PTR(-ERANGE);
+}
+EXPORT_SYMBOL_GPL(devm_request_free_mem_region);
+#endif /* CONFIG_DEVICE_PRIVATE */
+
 static int __init strict_iomem(char *str)
 {
 	if (strstr(str, "relaxed"))
diff --git a/mm/Kconfig b/mm/Kconfig
index 0b4352557dd5..495d7368ced8 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -670,47 +670,17 @@ config ZONE_DEVICE
 
 	  If FS_DAX is enabled, then say Y.
 
-config ARCH_HAS_HMM_MIRROR
-	bool
-	default y
-	depends on (X86_64 || PPC64)
-	depends on MMU && 64BIT
-
-config ARCH_HAS_HMM_DEVICE
-	bool
-	default y
-	depends on (X86_64 || PPC64)
-	depends on MEMORY_HOTPLUG
-	depends on MEMORY_HOTREMOVE
-	depends on SPARSEMEM_VMEMMAP
-	depends on ARCH_HAS_ZONE_DEVICE
-	select XARRAY_MULTI
-
-config ARCH_HAS_HMM
-	bool
-	default y
-	depends on (X86_64 || PPC64)
-	depends on ZONE_DEVICE
-	depends on MMU && 64BIT
-	depends on MEMORY_HOTPLUG
-	depends on MEMORY_HOTREMOVE
-	depends on SPARSEMEM_VMEMMAP
-
 config MIGRATE_VMA_HELPER
 	bool
 
 config DEV_PAGEMAP_OPS
 	bool
 
-config HMM
-	bool
-	select MMU_NOTIFIER
-	select MIGRATE_VMA_HELPER
-
 config HMM_MIRROR
 	bool "HMM mirror CPU page table into a device page table"
-	depends on ARCH_HAS_HMM
-	select HMM
+	depends on (X86_64 || PPC64)
+	depends on MMU && 64BIT
+	select MMU_NOTIFIER
 	help
 	  Select HMM_MIRROR if you want to mirror range of the CPU page table of a
 	  process into a device page table. Here, mirror means "keep synchronized".
@@ -720,8 +690,7 @@ config HMM_MIRROR
 
 config DEVICE_PRIVATE
 	bool "Unaddressable device memory (GPU memory, ...)"
-	depends on ARCH_HAS_HMM
-	select HMM
+	depends on ZONE_DEVICE
 	select DEV_PAGEMAP_OPS
 
 	help
@@ -729,17 +698,6 @@ config DEVICE_PRIVATE
 	  memory; i.e., memory that is only accessible from the device (or
 	  group of devices). You likely also want to select HMM_MIRROR.
 
-config DEVICE_PUBLIC
-	bool "Addressable device memory (like GPU memory)"
-	depends on ARCH_HAS_HMM
-	select HMM
-	select DEV_PAGEMAP_OPS
-
-	help
-	  Allows creation of struct pages to represent addressable device
-	  memory; i.e., memory that is accessible from both the device and
-	  the CPU
-
 config FRAME_VECTOR
 	bool
 
diff --git a/mm/Makefile b/mm/Makefile
index dc0746ca1109..338e528ad436 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -102,5 +102,5 @@ obj-$(CONFIG_FRAME_VECTOR) += frame_vector.o
 obj-$(CONFIG_DEBUG_PAGE_REF) += debug_page_ref.o
 obj-$(CONFIG_HARDENED_USERCOPY) += usercopy.o
 obj-$(CONFIG_PERCPU_STATS) += percpu-stats.o
-obj-$(CONFIG_HMM) += hmm.o
+obj-$(CONFIG_HMM_MIRROR) += hmm.o
 obj-$(CONFIG_MEMFD_CREATE) += memfd.o
diff --git a/mm/gup.c b/mm/gup.c
index 43b7d875de37..8bbaa5523116 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -609,13 +609,6 @@ static int get_gate_page(struct mm_struct *mm, unsigned long address,
 		if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte)))
 			goto unmap;
 		*page = pte_page(*pte);
-
-		/*
-		 * This should never happen (a device public page in the gate
-		 * area).
-		 */
-		if (is_device_public_page(*page))
-			goto unmap;
 	}
 	if (unlikely(!try_get_page(*page))) {
 		ret = -ENOMEM;
diff --git a/mm/hmm.c b/mm/hmm.c
index f702a3895d05..e1eedef129cf 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -20,26 +20,14 @@
 #include <linux/swapops.h>
 #include <linux/hugetlb.h>
 #include <linux/memremap.h>
+#include <linux/sched/mm.h>
 #include <linux/jump_label.h>
 #include <linux/dma-mapping.h>
 #include <linux/mmu_notifier.h>
 #include <linux/memory_hotplug.h>
 
-#define PA_SECTION_SIZE (1UL << PA_SECTION_SHIFT)
-
-#if IS_ENABLED(CONFIG_HMM_MIRROR)
 static const struct mmu_notifier_ops hmm_mmu_notifier_ops;
 
-static inline struct hmm *mm_get_hmm(struct mm_struct *mm)
-{
-	struct hmm *hmm = READ_ONCE(mm->hmm);
-
-	if (hmm && kref_get_unless_zero(&hmm->kref))
-		return hmm;
-
-	return NULL;
-}
-
 /**
  * hmm_get_or_create - register HMM against an mm (HMM internal)
  *
@@ -54,11 +42,16 @@ static inline struct hmm *mm_get_hmm(struct mm_struct *mm)
  */
 static struct hmm *hmm_get_or_create(struct mm_struct *mm)
 {
-	struct hmm *hmm = mm_get_hmm(mm);
-	bool cleanup = false;
+	struct hmm *hmm;
 
-	if (hmm)
-		return hmm;
+	lockdep_assert_held_write(&mm->mmap_sem);
+
+	/* Abuse the page_table_lock to also protect mm->hmm. */
+	spin_lock(&mm->page_table_lock);
+	hmm = mm->hmm;
+	if (mm->hmm && kref_get_unless_zero(&mm->hmm->kref))
+		goto out_unlock;
+	spin_unlock(&mm->page_table_lock);
 
 	hmm = kmalloc(sizeof(*hmm), GFP_KERNEL);
 	if (!hmm)
@@ -68,55 +61,50 @@ static struct hmm *hmm_get_or_create(struct mm_struct *mm)
 	init_rwsem(&hmm->mirrors_sem);
 	hmm->mmu_notifier.ops = NULL;
 	INIT_LIST_HEAD(&hmm->ranges);
-	mutex_init(&hmm->lock);
+	spin_lock_init(&hmm->ranges_lock);
 	kref_init(&hmm->kref);
 	hmm->notifiers = 0;
-	hmm->dead = false;
 	hmm->mm = mm;
 
-	spin_lock(&mm->page_table_lock);
-	if (!mm->hmm)
-		mm->hmm = hmm;
-	else
-		cleanup = true;
-	spin_unlock(&mm->page_table_lock);
+	hmm->mmu_notifier.ops = &hmm_mmu_notifier_ops;
+	if (__mmu_notifier_register(&hmm->mmu_notifier, mm)) {
+		kfree(hmm);
+		return NULL;
+	}
 
-	if (cleanup)
-		goto error;
+	mmgrab(hmm->mm);
 
 	/*
-	 * We should only get here if hold the mmap_sem in write mode ie on
-	 * registration of first mirror through hmm_mirror_register()
+	 * We hold the exclusive mmap_sem here so we know that mm->hmm is
+	 * still NULL or 0 kref, and is safe to update.
 	 */
-	hmm->mmu_notifier.ops = &hmm_mmu_notifier_ops;
-	if (__mmu_notifier_register(&hmm->mmu_notifier, mm))
-		goto error_mm;
+	spin_lock(&mm->page_table_lock);
+	mm->hmm = hmm;
 
+out_unlock:
+	spin_unlock(&mm->page_table_lock);
 	return hmm;
+}
 
-error_mm:
-	spin_lock(&mm->page_table_lock);
-	if (mm->hmm == hmm)
-		mm->hmm = NULL;
-	spin_unlock(&mm->page_table_lock);
-error:
+static void hmm_free_rcu(struct rcu_head *rcu)
+{
+	struct hmm *hmm = container_of(rcu, struct hmm, rcu);
+
+	mmdrop(hmm->mm);
 	kfree(hmm);
-	return NULL;
 }
 
 static void hmm_free(struct kref *kref)
 {
 	struct hmm *hmm = container_of(kref, struct hmm, kref);
-	struct mm_struct *mm = hmm->mm;
 
-	mmu_notifier_unregister_no_release(&hmm->mmu_notifier, mm);
+	spin_lock(&hmm->mm->page_table_lock);
+	if (hmm->mm->hmm == hmm)
+		hmm->mm->hmm = NULL;
+	spin_unlock(&hmm->mm->page_table_lock);
 
-	spin_lock(&mm->page_table_lock);
-	if (mm->hmm == hmm)
-		mm->hmm = NULL;
-	spin_unlock(&mm->page_table_lock);
-
-	kfree(hmm);
+	mmu_notifier_unregister_no_release(&hmm->mmu_notifier, hmm->mm);
+	mmu_notifier_call_srcu(&hmm->rcu, hmm_free_rcu);
 }
 
 static inline void hmm_put(struct hmm *hmm)
@@ -124,86 +112,73 @@ static inline void hmm_put(struct hmm *hmm)
 	kref_put(&hmm->kref, hmm_free);
 }
 
-void hmm_mm_destroy(struct mm_struct *mm)
+static void hmm_release(struct mmu_notifier *mn, struct mm_struct *mm)
 {
-	struct hmm *hmm;
+	struct hmm *hmm = container_of(mn, struct hmm, mmu_notifier);
+	struct hmm_mirror *mirror;
 
-	spin_lock(&mm->page_table_lock);
-	hmm = mm_get_hmm(mm);
-	mm->hmm = NULL;
-	if (hmm) {
-		hmm->mm = NULL;
-		hmm->dead = true;
-		spin_unlock(&mm->page_table_lock);
-		hmm_put(hmm);
+	/* Bail out if hmm is in the process of being freed */
+	if (!kref_get_unless_zero(&hmm->kref))
 		return;
+
+	/*
+	 * Since hmm_range_register() holds the mmget() lock hmm_release() is
+	 * prevented as long as a range exists.
+	 */
+	WARN_ON(!list_empty_careful(&hmm->ranges));
+
+	down_read(&hmm->mirrors_sem);
+	list_for_each_entry(mirror, &hmm->mirrors, list) {
+		/*
+		 * Note: The driver is not allowed to trigger
+		 * hmm_mirror_unregister() from this thread.
+		 */
+		if (mirror->ops->release)
+			mirror->ops->release(mirror);
 	}
+	up_read(&hmm->mirrors_sem);
 
-	spin_unlock(&mm->page_table_lock);
+	hmm_put(hmm);
 }
 
-static void hmm_release(struct mmu_notifier *mn, struct mm_struct *mm)
+static void notifiers_decrement(struct hmm *hmm)
 {
-	struct hmm *hmm = mm_get_hmm(mm);
-	struct hmm_mirror *mirror;
-	struct hmm_range *range;
-
-	/* Report this HMM as dying. */
-	hmm->dead = true;
+	unsigned long flags;
 
-	/* Wake-up everyone waiting on any range. */
-	mutex_lock(&hmm->lock);
-	list_for_each_entry(range, &hmm->ranges, list) {
-		range->valid = false;
-	}
-	wake_up_all(&hmm->wq);
-	mutex_unlock(&hmm->lock);
+	spin_lock_irqsave(&hmm->ranges_lock, flags);
+	hmm->notifiers--;
+	if (!hmm->notifiers) {
+		struct hmm_range *range;
 
-	down_write(&hmm->mirrors_sem);
-	mirror = list_first_entry_or_null(&hmm->mirrors, struct hmm_mirror,
-					  list);
-	while (mirror) {
-		list_del_init(&mirror->list);
-		if (mirror->ops->release) {
-			/*
-			 * Drop mirrors_sem so callback can wait on any pending
-			 * work that might itself trigger mmu_notifier callback
-			 * and thus would deadlock with us.
-			 */
-			up_write(&hmm->mirrors_sem);
-			mirror->ops->release(mirror);
-			down_write(&hmm->mirrors_sem);
+		list_for_each_entry(range, &hmm->ranges, list) {
+			if (range->valid)
+				continue;
+			range->valid = true;
 		}
-		mirror = list_first_entry_or_null(&hmm->mirrors,
-						  struct hmm_mirror, list);
+		wake_up_all(&hmm->wq);
 	}
-	up_write(&hmm->mirrors_sem);
-
-	hmm_put(hmm);
+	spin_unlock_irqrestore(&hmm->ranges_lock, flags);
 }
 
 static int hmm_invalidate_range_start(struct mmu_notifier *mn,
 			const struct mmu_notifier_range *nrange)
 {
-	struct hmm *hmm = mm_get_hmm(nrange->mm);
+	struct hmm *hmm = container_of(mn, struct hmm, mmu_notifier);
 	struct hmm_mirror *mirror;
 	struct hmm_update update;
 	struct hmm_range *range;
+	unsigned long flags;
 	int ret = 0;
 
-	VM_BUG_ON(!hmm);
+	if (!kref_get_unless_zero(&hmm->kref))
+		return 0;
 
 	update.start = nrange->start;
 	update.end = nrange->end;
 	update.event = HMM_UPDATE_INVALIDATE;
 	update.blockable = mmu_notifier_range_blockable(nrange);
 
-	if (mmu_notifier_range_blockable(nrange))
-		mutex_lock(&hmm->lock);
-	else if (!mutex_trylock(&hmm->lock)) {
-		ret = -EAGAIN;
-		goto out;
-	}
+	spin_lock_irqsave(&hmm->ranges_lock, flags);
 	hmm->notifiers++;
 	list_for_each_entry(range, &hmm->ranges, list) {
 		if (update.end < range->start || update.start >= range->end)
@@ -211,7 +186,7 @@ static int hmm_invalidate_range_start(struct mmu_notifier *mn,
 
 		range->valid = false;
 	}
-	mutex_unlock(&hmm->lock);
+	spin_unlock_irqrestore(&hmm->ranges_lock, flags);
 
 	if (mmu_notifier_range_blockable(nrange))
 		down_read(&hmm->mirrors_sem);
@@ -219,19 +194,23 @@ static int hmm_invalidate_range_start(struct mmu_notifier *mn,
 		ret = -EAGAIN;
 		goto out;
 	}
+
 	list_for_each_entry(mirror, &hmm->mirrors, list) {
-		int ret;
+		int rc;
 
-		ret = mirror->ops->sync_cpu_device_pagetables(mirror, &update);
-		if (!update.blockable && ret == -EAGAIN) {
-			up_read(&hmm->mirrors_sem);
+		rc = mirror->ops->sync_cpu_device_pagetables(mirror, &update);
+		if (rc) {
+			if (WARN_ON(update.blockable || rc != -EAGAIN))
+				continue;
 			ret = -EAGAIN;
-			goto out;
+			break;
 		}
 	}
 	up_read(&hmm->mirrors_sem);
 
 out:
+	if (ret)
+		notifiers_decrement(hmm);
 	hmm_put(hmm);
 	return ret;
 }
@@ -239,24 +218,12 @@ out:
 static void hmm_invalidate_range_end(struct mmu_notifier *mn,
 			const struct mmu_notifier_range *nrange)
 {
-	struct hmm *hmm = mm_get_hmm(nrange->mm);
-
-	VM_BUG_ON(!hmm);
+	struct hmm *hmm = container_of(mn, struct hmm, mmu_notifier);
 
-	mutex_lock(&hmm->lock);
-	hmm->notifiers--;
-	if (!hmm->notifiers) {
-		struct hmm_range *range;
-
-		list_for_each_entry(range, &hmm->ranges, list) {
-			if (range->valid)
-				continue;
-			range->valid = true;
-		}
-		wake_up_all(&hmm->wq);
-	}
-	mutex_unlock(&hmm->lock);
+	if (!kref_get_unless_zero(&hmm->kref))
+		return;
 
+	notifiers_decrement(hmm);
 	hmm_put(hmm);
 }
 
@@ -271,14 +238,15 @@ static const struct mmu_notifier_ops hmm_mmu_notifier_ops = {
  *
  * @mirror: new mirror struct to register
  * @mm: mm to register against
+ * Return: 0 on success, -ENOMEM if no memory, -EINVAL if invalid arguments
  *
  * To start mirroring a process address space, the device driver must register
  * an HMM mirror struct.
- *
- * THE mm->mmap_sem MUST BE HELD IN WRITE MODE !
  */
 int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm)
 {
+	lockdep_assert_held_write(&mm->mmap_sem);
+
 	/* Sanity check */
 	if (!mm || !mirror || !mirror->ops)
 		return -EINVAL;
@@ -298,23 +266,17 @@ EXPORT_SYMBOL(hmm_mirror_register);
 /*
  * hmm_mirror_unregister() - unregister a mirror
  *
- * @mirror: new mirror struct to register
+ * @mirror: mirror struct to unregister
  *
  * Stop mirroring a process address space, and cleanup.
  */
 void hmm_mirror_unregister(struct hmm_mirror *mirror)
 {
-	struct hmm *hmm = READ_ONCE(mirror->hmm);
-
-	if (hmm == NULL)
-		return;
+	struct hmm *hmm = mirror->hmm;
 
 	down_write(&hmm->mirrors_sem);
-	list_del_init(&mirror->list);
-	/* To protect us against double unregister ... */
-	mirror->hmm = NULL;
+	list_del(&mirror->list);
 	up_write(&hmm->mirrors_sem);
-
 	hmm_put(hmm);
 }
 EXPORT_SYMBOL(hmm_mirror_unregister);
@@ -330,7 +292,7 @@ struct hmm_vma_walk {
 static int hmm_vma_do_fault(struct mm_walk *walk, unsigned long addr,
 			    bool write_fault, uint64_t *pfn)
 {
-	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_REMOTE;
+	unsigned int flags = FAULT_FLAG_REMOTE;
 	struct hmm_vma_walk *hmm_vma_walk = walk->private;
 	struct hmm_range *range = hmm_vma_walk->range;
 	struct vm_area_struct *vma = walk->vma;
@@ -372,7 +334,7 @@ static int hmm_pfns_bad(unsigned long addr,
  * @fault: should we fault or not ?
  * @write_fault: write fault ?
  * @walk: mm_walk structure
- * Returns: 0 on success, -EBUSY after page fault, or page fault error
+ * Return: 0 on success, -EBUSY after page fault, or page fault error
  *
  * This function will be called whenever pmd_none() or pte_none() returns true,
  * or whenever there is no page directory covering the virtual address range.
@@ -550,7 +512,7 @@ static int hmm_vma_handle_pmd(struct mm_walk *walk,
 
 static inline uint64_t pte_to_hmm_pfn_flags(struct hmm_range *range, pte_t pte)
 {
-	if (pte_none(pte) || !pte_present(pte))
+	if (pte_none(pte) || !pte_present(pte) || pte_protnone(pte))
 		return 0;
 	return pte_write(pte) ? range->flags[HMM_PFN_VALID] |
 				range->flags[HMM_PFN_WRITE] :
@@ -788,7 +750,6 @@ again:
 			return hmm_vma_walk_hole_(addr, end, fault,
 						write_fault, walk);
 
-#ifdef CONFIG_HUGETLB_PAGE
 		pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
 		for (i = 0; i < npages; ++i, ++pfn) {
 			hmm_vma_walk->pgmap = get_dev_pagemap(pfn,
@@ -804,9 +765,6 @@ again:
 		}
 		hmm_vma_walk->last = end;
 		return 0;
-#else
-		return -EINVAL;
-#endif
 	}
 
 	split_huge_pud(walk->vma, pudp, addr);
@@ -909,12 +867,14 @@ static void hmm_pfns_clear(struct hmm_range *range,
  * Track updates to the CPU page table see include/linux/hmm.h
  */
 int hmm_range_register(struct hmm_range *range,
-		       struct mm_struct *mm,
+		       struct hmm_mirror *mirror,
 		       unsigned long start,
 		       unsigned long end,
 		       unsigned page_shift)
 {
 	unsigned long mask = ((1UL << page_shift) - 1UL);
+	struct hmm *hmm = mirror->hmm;
+	unsigned long flags;
 
 	range->valid = false;
 	range->hmm = NULL;
@@ -928,28 +888,24 @@ int hmm_range_register(struct hmm_range *range,
 	range->start = start;
 	range->end = end;
 
-	range->hmm = hmm_get_or_create(mm);
-	if (!range->hmm)
-		return -EFAULT;
-
-	/* Check if hmm_mm_destroy() was call. */
-	if (range->hmm->mm == NULL || range->hmm->dead) {
-		hmm_put(range->hmm);
+	/* Prevent hmm_release() from running while the range is valid */
+	if (!mmget_not_zero(hmm->mm))
 		return -EFAULT;
-	}
 
-	/* Initialize range to track CPU page table update */
-	mutex_lock(&range->hmm->lock);
+	/* Initialize range to track CPU page table updates. */
+	spin_lock_irqsave(&hmm->ranges_lock, flags);
 
-	list_add_rcu(&range->list, &range->hmm->ranges);
+	range->hmm = hmm;
+	kref_get(&hmm->kref);
+	list_add(&range->list, &hmm->ranges);
 
 	/*
 	 * If there are any concurrent notifiers we have to wait for them for
 	 * the range to be valid (see hmm_range_wait_until_valid()).
 	 */
-	if (!range->hmm->notifiers)
+	if (!hmm->notifiers)
 		range->valid = true;
-	mutex_unlock(&range->hmm->lock);
+	spin_unlock_irqrestore(&hmm->ranges_lock, flags);
 
 	return 0;
 }
@@ -964,25 +920,31 @@ EXPORT_SYMBOL(hmm_range_register);
  */
 void hmm_range_unregister(struct hmm_range *range)
 {
-	/* Sanity check this really should not happen. */
-	if (range->hmm == NULL || range->end <= range->start)
-		return;
+	struct hmm *hmm = range->hmm;
+	unsigned long flags;
 
-	mutex_lock(&range->hmm->lock);
-	list_del_rcu(&range->list);
-	mutex_unlock(&range->hmm->lock);
+	spin_lock_irqsave(&hmm->ranges_lock, flags);
+	list_del_init(&range->list);
+	spin_unlock_irqrestore(&hmm->ranges_lock, flags);
 
 	/* Drop reference taken by hmm_range_register() */
+	mmput(hmm->mm);
+	hmm_put(hmm);
+
+	/*
+	 * The range is now invalid and the ref on the hmm is dropped, so
+	 * poison the pointer.  Leave other fields in place, for the caller's
+	 * use.
+	 */
 	range->valid = false;
-	hmm_put(range->hmm);
-	range->hmm = NULL;
+	memset(&range->hmm, POISON_INUSE, sizeof(range->hmm));
 }
 EXPORT_SYMBOL(hmm_range_unregister);
 
 /*
  * hmm_range_snapshot() - snapshot CPU page table for a range
  * @range: range
- * Returns: -EINVAL if invalid argument, -ENOMEM out of memory, -EPERM invalid
+ * Return: -EINVAL if invalid argument, -ENOMEM out of memory, -EPERM invalid
  *          permission (for instance asking for write and range is read only),
  *          -EAGAIN if you need to retry, -EFAULT invalid (ie either no valid
  *          vma or it is illegal to access that range), number of valid pages
@@ -1001,10 +963,7 @@ long hmm_range_snapshot(struct hmm_range *range)
 	struct vm_area_struct *vma;
 	struct mm_walk mm_walk;
 
-	/* Check if hmm_mm_destroy() was call. */
-	if (hmm->mm == NULL || hmm->dead)
-		return -EFAULT;
-
+	lockdep_assert_held(&hmm->mm->mmap_sem);
 	do {
 		/* If range is no longer valid force retry. */
 		if (!range->valid)
@@ -1015,9 +974,8 @@ long hmm_range_snapshot(struct hmm_range *range)
 			return -EFAULT;
 
 		if (is_vm_hugetlb_page(vma)) {
-			struct hstate *h = hstate_vma(vma);
-
-			if (huge_page_shift(h) != range->page_shift &&
+			if (huge_page_shift(hstate_vma(vma)) !=
+				    range->page_shift &&
 			    range->page_shift != PAGE_SHIFT)
 				return -EINVAL;
 		} else {
@@ -1066,7 +1024,7 @@ EXPORT_SYMBOL(hmm_range_snapshot);
  * hmm_range_fault() - try to fault some address in a virtual address range
  * @range: range being faulted
  * @block: allow blocking on fault (if true it sleeps and do not drop mmap_sem)
- * Returns: number of valid pages in range->pfns[] (from range start
+ * Return: number of valid pages in range->pfns[] (from range start
  *          address). This may be zero. If the return value is negative,
  *          then one of the following values may be returned:
  *
@@ -1100,9 +1058,7 @@ long hmm_range_fault(struct hmm_range *range, bool block)
 	struct mm_walk mm_walk;
 	int ret;
 
-	/* Check if hmm_mm_destroy() was call. */
-	if (hmm->mm == NULL || hmm->dead)
-		return -EFAULT;
+	lockdep_assert_held(&hmm->mm->mmap_sem);
 
 	do {
 		/* If range is no longer valid force retry. */
@@ -1184,7 +1140,7 @@ EXPORT_SYMBOL(hmm_range_fault);
  * @device: device against to dma map page to
  * @daddrs: dma address of mapped pages
  * @block: allow blocking on fault (if true it sleeps and do not drop mmap_sem)
- * Returns: number of pages mapped on success, -EAGAIN if mmap_sem have been
+ * Return: number of pages mapped on success, -EAGAIN if mmap_sem have been
  *          drop and you need to try again, some other error value otherwise
  *
  * Note same usage pattern as hmm_range_fault().
@@ -1272,7 +1228,7 @@ EXPORT_SYMBOL(hmm_range_dma_map);
  * @device: device against which dma map was done
  * @daddrs: dma address of mapped pages
  * @dirty: dirty page if it had the write flag set
- * Returns: number of page unmapped on success, -EINVAL otherwise
+ * Return: number of page unmapped on success, -EINVAL otherwise
  *
  * Note that caller MUST abide by mmu notifier or use HMM mirror and abide
  * to the sync_cpu_device_pagetables() callback so that it is safe here to
@@ -1328,284 +1284,3 @@ long hmm_range_dma_unmap(struct hmm_range *range,
 	return cpages;
 }
 EXPORT_SYMBOL(hmm_range_dma_unmap);
-#endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */
-
-
-#if IS_ENABLED(CONFIG_DEVICE_PRIVATE) ||  IS_ENABLED(CONFIG_DEVICE_PUBLIC)
-struct page *hmm_vma_alloc_locked_page(struct vm_area_struct *vma,
-				       unsigned long addr)
-{
-	struct page *page;
-
-	page = alloc_page_vma(GFP_HIGHUSER, vma, addr);
-	if (!page)
-		return NULL;
-	lock_page(page);
-	return page;
-}
-EXPORT_SYMBOL(hmm_vma_alloc_locked_page);
-
-
-static void hmm_devmem_ref_release(struct percpu_ref *ref)
-{
-	struct hmm_devmem *devmem;
-
-	devmem = container_of(ref, struct hmm_devmem, ref);
-	complete(&devmem->completion);
-}
-
-static void hmm_devmem_ref_exit(struct percpu_ref *ref)
-{
-	struct hmm_devmem *devmem;
-
-	devmem = container_of(ref, struct hmm_devmem, ref);
-	wait_for_completion(&devmem->completion);
-	percpu_ref_exit(ref);
-}
-
-static void hmm_devmem_ref_kill(struct percpu_ref *ref)
-{
-	percpu_ref_kill(ref);
-}
-
-static vm_fault_t hmm_devmem_fault(struct vm_area_struct *vma,
-			    unsigned long addr,
-			    const struct page *page,
-			    unsigned int flags,
-			    pmd_t *pmdp)
-{
-	struct hmm_devmem *devmem = page->pgmap->data;
-
-	return devmem->ops->fault(devmem, vma, addr, page, flags, pmdp);
-}
-
-static void hmm_devmem_free(struct page *page, void *data)
-{
-	struct hmm_devmem *devmem = data;
-
-	page->mapping = NULL;
-
-	devmem->ops->free(devmem, page);
-}
-
-/*
- * hmm_devmem_add() - hotplug ZONE_DEVICE memory for device memory
- *
- * @ops: memory event device driver callback (see struct hmm_devmem_ops)
- * @device: device struct to bind the resource too
- * @size: size in bytes of the device memory to add
- * Returns: pointer to new hmm_devmem struct ERR_PTR otherwise
- *
- * This function first finds an empty range of physical address big enough to
- * contain the new resource, and then hotplugs it as ZONE_DEVICE memory, which
- * in turn allocates struct pages. It does not do anything beyond that; all
- * events affecting the memory will go through the various callbacks provided
- * by hmm_devmem_ops struct.
- *
- * Device driver should call this function during device initialization and
- * is then responsible of memory management. HMM only provides helpers.
- */
-struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
-				  struct device *device,
-				  unsigned long size)
-{
-	struct hmm_devmem *devmem;
-	resource_size_t addr;
-	void *result;
-	int ret;
-
-	dev_pagemap_get_ops();
-
-	devmem = devm_kzalloc(device, sizeof(*devmem), GFP_KERNEL);
-	if (!devmem)
-		return ERR_PTR(-ENOMEM);
-
-	init_completion(&devmem->completion);
-	devmem->pfn_first = -1UL;
-	devmem->pfn_last = -1UL;
-	devmem->resource = NULL;
-	devmem->device = device;
-	devmem->ops = ops;
-
-	ret = percpu_ref_init(&devmem->ref, &hmm_devmem_ref_release,
-			      0, GFP_KERNEL);
-	if (ret)
-		return ERR_PTR(ret);
-
-	size = ALIGN(size, PA_SECTION_SIZE);
-	addr = min((unsigned long)iomem_resource.end,
-		   (1UL << MAX_PHYSMEM_BITS) - 1);
-	addr = addr - size + 1UL;
-
-	/*
-	 * FIXME add a new helper to quickly walk resource tree and find free
-	 * range
-	 *
-	 * FIXME what about ioport_resource resource ?
-	 */
-	for (; addr > size && addr >= iomem_resource.start; addr -= size) {
-		ret = region_intersects(addr, size, 0, IORES_DESC_NONE);
-		if (ret != REGION_DISJOINT)
-			continue;
-
-		devmem->resource = devm_request_mem_region(device, addr, size,
-							   dev_name(device));
-		if (!devmem->resource)
-			return ERR_PTR(-ENOMEM);
-		break;
-	}
-	if (!devmem->resource)
-		return ERR_PTR(-ERANGE);
-
-	devmem->resource->desc = IORES_DESC_DEVICE_PRIVATE_MEMORY;
-	devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT;
-	devmem->pfn_last = devmem->pfn_first +
-			   (resource_size(devmem->resource) >> PAGE_SHIFT);
-	devmem->page_fault = hmm_devmem_fault;
-
-	devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
-	devmem->pagemap.res = *devmem->resource;
-	devmem->pagemap.page_free = hmm_devmem_free;
-	devmem->pagemap.altmap_valid = false;
-	devmem->pagemap.ref = &devmem->ref;
-	devmem->pagemap.data = devmem;
-	devmem->pagemap.kill = hmm_devmem_ref_kill;
-	devmem->pagemap.cleanup = hmm_devmem_ref_exit;
-
-	result = devm_memremap_pages(devmem->device, &devmem->pagemap);
-	if (IS_ERR(result))
-		return result;
-	return devmem;
-}
-EXPORT_SYMBOL_GPL(hmm_devmem_add);
-
-struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
-					   struct device *device,
-					   struct resource *res)
-{
-	struct hmm_devmem *devmem;
-	void *result;
-	int ret;
-
-	if (res->desc != IORES_DESC_DEVICE_PUBLIC_MEMORY)
-		return ERR_PTR(-EINVAL);
-
-	dev_pagemap_get_ops();
-
-	devmem = devm_kzalloc(device, sizeof(*devmem), GFP_KERNEL);
-	if (!devmem)
-		return ERR_PTR(-ENOMEM);
-
-	init_completion(&devmem->completion);
-	devmem->pfn_first = -1UL;
-	devmem->pfn_last = -1UL;
-	devmem->resource = res;
-	devmem->device = device;
-	devmem->ops = ops;
-
-	ret = percpu_ref_init(&devmem->ref, &hmm_devmem_ref_release,
-			      0, GFP_KERNEL);
-	if (ret)
-		return ERR_PTR(ret);
-
-	devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT;
-	devmem->pfn_last = devmem->pfn_first +
-			   (resource_size(devmem->resource) >> PAGE_SHIFT);
-	devmem->page_fault = hmm_devmem_fault;
-
-	devmem->pagemap.type = MEMORY_DEVICE_PUBLIC;
-	devmem->pagemap.res = *devmem->resource;
-	devmem->pagemap.page_free = hmm_devmem_free;
-	devmem->pagemap.altmap_valid = false;
-	devmem->pagemap.ref = &devmem->ref;
-	devmem->pagemap.data = devmem;
-	devmem->pagemap.kill = hmm_devmem_ref_kill;
-	devmem->pagemap.cleanup = hmm_devmem_ref_exit;
-
-	result = devm_memremap_pages(devmem->device, &devmem->pagemap);
-	if (IS_ERR(result))
-		return result;
-	return devmem;
-}
-EXPORT_SYMBOL_GPL(hmm_devmem_add_resource);
-
-/*
- * A device driver that wants to handle multiple devices memory through a
- * single fake device can use hmm_device to do so. This is purely a helper
- * and it is not needed to make use of any HMM functionality.
- */
-#define HMM_DEVICE_MAX 256
-
-static DECLARE_BITMAP(hmm_device_mask, HMM_DEVICE_MAX);
-static DEFINE_SPINLOCK(hmm_device_lock);
-static struct class *hmm_device_class;
-static dev_t hmm_device_devt;
-
-static void hmm_device_release(struct device *device)
-{
-	struct hmm_device *hmm_device;
-
-	hmm_device = container_of(device, struct hmm_device, device);
-	spin_lock(&hmm_device_lock);
-	clear_bit(hmm_device->minor, hmm_device_mask);
-	spin_unlock(&hmm_device_lock);
-
-	kfree(hmm_device);
-}
-
-struct hmm_device *hmm_device_new(void *drvdata)
-{
-	struct hmm_device *hmm_device;
-
-	hmm_device = kzalloc(sizeof(*hmm_device), GFP_KERNEL);
-	if (!hmm_device)
-		return ERR_PTR(-ENOMEM);
-
-	spin_lock(&hmm_device_lock);
-	hmm_device->minor = find_first_zero_bit(hmm_device_mask, HMM_DEVICE_MAX);
-	if (hmm_device->minor >= HMM_DEVICE_MAX) {
-		spin_unlock(&hmm_device_lock);
-		kfree(hmm_device);
-		return ERR_PTR(-EBUSY);
-	}
-	set_bit(hmm_device->minor, hmm_device_mask);
-	spin_unlock(&hmm_device_lock);
-
-	dev_set_name(&hmm_device->device, "hmm_device%d", hmm_device->minor);
-	hmm_device->device.devt = MKDEV(MAJOR(hmm_device_devt),
-					hmm_device->minor);
-	hmm_device->device.release = hmm_device_release;
-	dev_set_drvdata(&hmm_device->device, drvdata);
-	hmm_device->device.class = hmm_device_class;
-	device_initialize(&hmm_device->device);
-
-	return hmm_device;
-}
-EXPORT_SYMBOL(hmm_device_new);
-
-void hmm_device_put(struct hmm_device *hmm_device)
-{
-	put_device(&hmm_device->device);
-}
-EXPORT_SYMBOL(hmm_device_put);
-
-static int __init hmm_init(void)
-{
-	int ret;
-
-	ret = alloc_chrdev_region(&hmm_device_devt, 0,
-				  HMM_DEVICE_MAX,
-				  "hmm_device");
-	if (ret)
-		return ret;
-
-	hmm_device_class = class_create(THIS_MODULE, "hmm_device");
-	if (IS_ERR(hmm_device_class)) {
-		unregister_chrdev_region(hmm_device_devt, HMM_DEVICE_MAX);
-		return PTR_ERR(hmm_device_class);
-	}
-	return 0;
-}
-
-device_initcall(hmm_init);
-#endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */
diff --git a/mm/madvise.c b/mm/madvise.c
index 628022e674a7..968df3aa069f 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -354,7 +354,7 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
 			continue;
 		}
 
-		page = _vm_normal_page(vma, addr, ptent, true);
+		page = vm_normal_page(vma, addr, ptent);
 		if (!page)
 			continue;
 
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 4f05735b02d3..249671873aa9 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4908,7 +4908,7 @@ enum mc_target_type {
 static struct page *mc_handle_present_pte(struct vm_area_struct *vma,
 						unsigned long addr, pte_t ptent)
 {
-	struct page *page = _vm_normal_page(vma, addr, ptent, true);
+	struct page *page = vm_normal_page(vma, addr, ptent);
 
 	if (!page || !page_mapped(page))
 		return NULL;
@@ -5109,8 +5109,8 @@ out:
  *   2(MC_TARGET_SWAP): if the swap entry corresponding to this pte is a
  *     target for charge migration. if @target is not NULL, the entry is stored
  *     in target->ent.
- *   3(MC_TARGET_DEVICE): like MC_TARGET_PAGE  but page is MEMORY_DEVICE_PUBLIC
- *     or MEMORY_DEVICE_PRIVATE (so ZONE_DEVICE page and thus not on the lru).
+ *   3(MC_TARGET_DEVICE): like MC_TARGET_PAGE  but page is MEMORY_DEVICE_PRIVATE
+ *     (so ZONE_DEVICE page and thus not on the lru).
  *     For now we such page is charge like a regular page would be as for all
  *     intent and purposes it is just special memory taking the place of a
  *     regular page.
@@ -5144,8 +5144,7 @@ static enum mc_target_type get_mctgt_type(struct vm_area_struct *vma,
 		 */
 		if (page->mem_cgroup == mc.from) {
 			ret = MC_TARGET_PAGE;
-			if (is_device_private_page(page) ||
-			    is_device_public_page(page))
+			if (is_device_private_page(page))
 				ret = MC_TARGET_DEVICE;
 			if (target)
 				target->page = page;
@@ -5216,8 +5215,8 @@ static int mem_cgroup_count_precharge_pte_range(pmd_t *pmd,
 	if (ptl) {
 		/*
 		 * Note their can not be MC_TARGET_DEVICE for now as we do not
-		 * support transparent huge page with MEMORY_DEVICE_PUBLIC or
-		 * MEMORY_DEVICE_PRIVATE but this might change.
+		 * support transparent huge page with MEMORY_DEVICE_PRIVATE but
+		 * this might change.
 		 */
 		if (get_mctgt_type_thp(vma, addr, *pmd, NULL) == MC_TARGET_PAGE)
 			mc.precharge += HPAGE_PMD_NR;
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 7e08cbf3ba49..7ef849da8278 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1177,16 +1177,12 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
 		goto unlock;
 	}
 
-	switch (pgmap->type) {
-	case MEMORY_DEVICE_PRIVATE:
-	case MEMORY_DEVICE_PUBLIC:
+	if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
 		/*
 		 * TODO: Handle HMM pages which may need coordination
 		 * with device-side memory.
 		 */
 		goto unlock;
-	default:
-		break;
 	}
 
 	/*
diff --git a/mm/memory.c b/mm/memory.c
index 53bd59579861..89325f9c6173 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -571,8 +571,8 @@ static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
  * PFNMAP mappings in order to support COWable mappings.
  *
  */
-struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
-			     pte_t pte, bool with_public_device)
+struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
+			    pte_t pte)
 {
 	unsigned long pfn = pte_pfn(pte);
 
@@ -585,29 +585,6 @@ struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
 			return NULL;
 		if (is_zero_pfn(pfn))
 			return NULL;
-
-		/*
-		 * Device public pages are special pages (they are ZONE_DEVICE
-		 * pages but different from persistent memory). They behave
-		 * allmost like normal pages. The difference is that they are
-		 * not on the lru and thus should never be involve with any-
-		 * thing that involve lru manipulation (mlock, numa balancing,
-		 * ...).
-		 *
-		 * This is why we still want to return NULL for such page from
-		 * vm_normal_page() so that we do not have to special case all
-		 * call site of vm_normal_page().
-		 */
-		if (likely(pfn <= highest_memmap_pfn)) {
-			struct page *page = pfn_to_page(pfn);
-
-			if (is_device_public_page(page)) {
-				if (with_public_device)
-					return page;
-				return NULL;
-			}
-		}
-
 		if (pte_devmap(pte))
 			return NULL;
 
@@ -797,17 +774,6 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 		rss[mm_counter(page)]++;
 	} else if (pte_devmap(pte)) {
 		page = pte_page(pte);
-
-		/*
-		 * Cache coherent device memory behave like regular page and
-		 * not like persistent memory page. For more informations see
-		 * MEMORY_DEVICE_CACHE_COHERENT in memory_hotplug.h
-		 */
-		if (is_device_public_page(page)) {
-			get_page(page);
-			page_dup_rmap(page, false);
-			rss[mm_counter(page)]++;
-		}
 	}
 
 out_set_pte:
@@ -1063,7 +1029,7 @@ again:
 		if (pte_present(ptent)) {
 			struct page *page;
 
-			page = _vm_normal_page(vma, addr, ptent, true);
+			page = vm_normal_page(vma, addr, ptent);
 			if (unlikely(details) && page) {
 				/*
 				 * unmap_shared_mapping_pages() wants to
@@ -2777,13 +2743,8 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 			migration_entry_wait(vma->vm_mm, vmf->pmd,
 					     vmf->address);
 		} else if (is_device_private_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_private_entry_fault(vma, vmf->address, entry,
-						 vmf->flags, vmf->pmd);
+			vmf->page = device_private_entry_to_page(entry);
+			ret = vmf->page->pgmap->ops->migrate_to_ram(vmf);
 		} else if (is_hwpoison_entry(entry)) {
 			ret = VM_FAULT_HWPOISON;
 		} else {
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index e096c987d261..6166ba5a15f3 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -557,10 +557,8 @@ void __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
 	int sections_to_remove;
 
 	/* In the ZONE_DEVICE case device driver owns the memory region */
-	if (is_dev_zone(zone)) {
-		if (altmap)
-			map_offset = vmem_altmap_offset(altmap);
-	}
+	if (is_dev_zone(zone))
+		map_offset = vmem_altmap_offset(altmap);
 
 	clear_zone_contiguous(zone);
 
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index fdcb73536319..f48693f75b37 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2098,6 +2098,7 @@ alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
 out:
 	return page;
 }
+EXPORT_SYMBOL(alloc_pages_vma);
 
 /**
  * 	alloc_pages_current - Allocate pages.
diff --git a/mm/migrate.c b/mm/migrate.c
index e9594bc0d406..3445747e229d 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -246,8 +246,6 @@ static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma,
 			if (is_device_private_page(new)) {
 				entry = make_device_private_entry(new, pte_write(pte));
 				pte = swp_entry_to_pte(entry);
-			} else if (is_device_public_page(new)) {
-				pte = pte_mkdevmap(pte);
 			}
 		}
 
@@ -381,7 +379,6 @@ static int expected_page_refs(struct address_space *mapping, struct page *page)
 	 * ZONE_DEVICE pages.
 	 */
 	expected_count += is_device_private_page(page);
-	expected_count += is_device_public_page(page);
 	if (mapping)
 		expected_count += hpage_nr_pages(page) + page_has_private(page);
 
@@ -994,10 +991,7 @@ static int move_to_new_page(struct page *newpage, struct page *page,
 		if (!PageMappingFlags(page))
 			page->mapping = NULL;
 
-		if (unlikely(is_zone_device_page(newpage))) {
-			if (is_device_public_page(newpage))
-				flush_dcache_page(newpage);
-		} else
+		if (likely(!is_zone_device_page(newpage)))
 			flush_dcache_page(newpage);
 
 	}
@@ -2265,7 +2259,7 @@ again:
 				pfn = 0;
 				goto next;
 			}
-			page = _vm_normal_page(migrate->vma, addr, pte, true);
+			page = vm_normal_page(migrate->vma, addr, pte);
 			mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
 			mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
 		}
@@ -2406,16 +2400,7 @@ static bool migrate_vma_check_page(struct page *page)
 		 * FIXME proper solution is to rework migration_entry_wait() so
 		 * it does not need to take a reference on page.
 		 */
-		if (is_device_private_page(page))
-			return true;
-
-		/*
-		 * Only allow device public page to be migrated and account for
-		 * the extra reference count imply by ZONE_DEVICE pages.
-		 */
-		if (!is_device_public_page(page))
-			return false;
-		extra++;
+		return is_device_private_page(page);
 	}
 
 	/* For file back page */
@@ -2665,11 +2650,6 @@ static void migrate_vma_insert_page(struct migrate_vma *migrate,
 
 			swp_entry = make_device_private_entry(page, vma->vm_flags & VM_WRITE);
 			entry = swp_entry_to_pte(swp_entry);
-		} else if (is_device_public_page(page)) {
-			entry = pte_mkold(mk_pte(page, READ_ONCE(vma->vm_page_prot)));
-			if (vma->vm_flags & VM_WRITE)
-				entry = pte_mkwrite(pte_mkdirty(entry));
-			entry = pte_mkdevmap(entry);
 		}
 	} else {
 		entry = mk_pte(page, vma->vm_page_prot);
@@ -2789,7 +2769,7 @@ static void migrate_vma_pages(struct migrate_vma *migrate)
 					migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
 					continue;
 				}
-			} else if (!is_device_public_page(newpage)) {
+			} else {
 				/*
 				 * Other types of ZONE_DEVICE page are not
 				 * supported.
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index dbd0d5cbbcbb..8fd7f45a04eb 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5925,6 +5925,7 @@ void __ref memmap_init_zone_device(struct zone *zone,
 {
 	unsigned long pfn, end_pfn = start_pfn + size;
 	struct pglist_data *pgdat = zone->zone_pgdat;
+	struct vmem_altmap *altmap = pgmap_altmap(pgmap);
 	unsigned long zone_idx = zone_idx(zone);
 	unsigned long start = jiffies;
 	int nid = pgdat->node_id;
@@ -5937,9 +5938,7 @@ void __ref memmap_init_zone_device(struct zone *zone,
 	 * of the pages reserved for the memmap, so we can just jump to
 	 * the end of that region and start processing the device pages.
 	 */
-	if (pgmap->altmap_valid) {
-		struct vmem_altmap *altmap = &pgmap->altmap;
-
+	if (altmap) {
 		start_pfn = altmap->base_pfn + vmem_altmap_offset(altmap);
 		size = end_pfn - start_pfn;
 	}
@@ -5959,12 +5958,12 @@ void __ref memmap_init_zone_device(struct zone *zone,
 		__SetPageReserved(page);
 
 		/*
-		 * ZONE_DEVICE pages union ->lru with a ->pgmap back
-		 * pointer and hmm_data.  It is a bug if a ZONE_DEVICE
-		 * page is ever freed or placed on a driver-private list.
+		 * ZONE_DEVICE pages union ->lru with a ->pgmap back pointer
+		 * and zone_device_data.  It is a bug if a ZONE_DEVICE page is
+		 * ever freed or placed on a driver-private list.
 		 */
 		page->pgmap = pgmap;
-		page->hmm_data = 0;
+		page->zone_device_data = NULL;
 
 		/*
 		 * Mark the block movable so that blocks are reserved for
diff --git a/mm/swap.c b/mm/swap.c
index 7ede3eddc12a..607c48229a1d 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -740,15 +740,20 @@ void release_pages(struct page **pages, int nr)
 		if (is_huge_zero_page(page))
 			continue;
 
-		/* Device public page can not be huge page */
-		if (is_device_public_page(page)) {
+		if (is_zone_device_page(page)) {
 			if (locked_pgdat) {
 				spin_unlock_irqrestore(&locked_pgdat->lru_lock,
 						       flags);
 				locked_pgdat = NULL;
 			}
-			put_devmap_managed_page(page);
-			continue;
+			/*
+			 * ZONE_DEVICE pages that return 'false' from
+			 * put_devmap_managed_page() do not require special
+			 * processing, and instead, expect a call to
+			 * put_page_testzero().
+			 */
+			if (put_devmap_managed_page(page))
+				continue;
 		}
 
 		page = compound_head(page);
diff --git a/tools/testing/nvdimm/test/iomap.c b/tools/testing/nvdimm/test/iomap.c
index 076df22e4bda..cd040b5abffe 100644
--- a/tools/testing/nvdimm/test/iomap.c
+++ b/tools/testing/nvdimm/test/iomap.c
@@ -100,25 +100,60 @@ static void nfit_test_kill(void *_pgmap)
 {
 	struct dev_pagemap *pgmap = _pgmap;
 
-	WARN_ON(!pgmap || !pgmap->ref || !pgmap->kill || !pgmap->cleanup);
-	pgmap->kill(pgmap->ref);
-	pgmap->cleanup(pgmap->ref);
+	WARN_ON(!pgmap || !pgmap->ref);
+
+	if (pgmap->ops && pgmap->ops->kill)
+		pgmap->ops->kill(pgmap);
+	else
+		percpu_ref_kill(pgmap->ref);
+
+	if (pgmap->ops && pgmap->ops->cleanup) {
+		pgmap->ops->cleanup(pgmap);
+	} else {
+		wait_for_completion(&pgmap->done);
+		percpu_ref_exit(pgmap->ref);
+	}
+}
+
+static void dev_pagemap_percpu_release(struct percpu_ref *ref)
+{
+	struct dev_pagemap *pgmap =
+		container_of(ref, struct dev_pagemap, internal_ref);
+
+	complete(&pgmap->done);
 }
 
 void *__wrap_devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
 {
+	int error;
 	resource_size_t offset = pgmap->res.start;
 	struct nfit_test_resource *nfit_res = get_nfit_res(offset);
 
-	if (nfit_res) {
-		int rc;
-
-		rc = devm_add_action_or_reset(dev, nfit_test_kill, pgmap);
-		if (rc)
-			return ERR_PTR(rc);
-		return nfit_res->buf + offset - nfit_res->res.start;
+	if (!nfit_res)
+		return devm_memremap_pages(dev, pgmap);
+
+	pgmap->dev = dev;
+	if (!pgmap->ref) {
+		if (pgmap->ops && (pgmap->ops->kill || pgmap->ops->cleanup))
+			return ERR_PTR(-EINVAL);
+
+		init_completion(&pgmap->done);
+		error = percpu_ref_init(&pgmap->internal_ref,
+				dev_pagemap_percpu_release, 0, GFP_KERNEL);
+		if (error)
+			return ERR_PTR(error);
+		pgmap->ref = &pgmap->internal_ref;
+	} else {
+		if (!pgmap->ops || !pgmap->ops->kill || !pgmap->ops->cleanup) {
+			WARN(1, "Missing reference count teardown definition\n");
+			return ERR_PTR(-EINVAL);
+		}
 	}
-	return devm_memremap_pages(dev, pgmap);
+
+	error = devm_add_action_or_reset(dev, nfit_test_kill, pgmap);
+	if (error)
+		return ERR_PTR(error);
+	return nfit_res->buf + offset - nfit_res->res.start;
 }
 EXPORT_SYMBOL_GPL(__wrap_devm_memremap_pages);