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
  ...

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 */

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);
 }

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)

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);

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;

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

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 @@ nouveau_dmem_migrate_vma(struct nouveau_drm *drm,
 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;
 

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)) {

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;
 

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);

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 @@ static int pci_p2pdma_setup(struct pci_dev *pdev)
 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);

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)) {

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 */

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);

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);
 

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

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

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);

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);
 }

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"))

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
 

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

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;

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;
 

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 @@ static int mem_cgroup_move_account(struct page *page,
  *   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;

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;
 	}
 
 	/*

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 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
 		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 {

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);
 

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.

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 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
 				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.

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

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);

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);