/* SPDX-License-Identifier: GPL-2.0 */
  /* Copyright(c) 2015 Intel Corporation. All rights reserved. */

  #include <linux/device.h>

  #include <linux/io.h>

  #include <linux/kasan.h>

  #include <linux/memory_hotplug.h>

  #include <linux/mm.h>
  #include <linux/pfn_t.h>

  #include <linux/swap.h>
  #include <linux/swapops.h>

  #include <linux/types.h>

  #include <linux/wait_bit.h>

  #include <linux/xarray.h>

  static DEFINE_XARRAY(pgmap_array);

  #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)

  {
  	if (atomic_dec_and_test(&devmap_managed_enable))
  		static_branch_disable(&devmap_managed_key);
  }

  static int devmap_managed_enable_get(struct dev_pagemap *pgmap)

  {

  	if (!pgmap->ops || !pgmap->ops->page_free) {

  		WARN(1, "Missing page_free method
  ");
  		return -EINVAL;
  	}
  
  	if (atomic_inc_return(&devmap_managed_enable) == 1)
  		static_branch_enable(&devmap_managed_key);

  	return 0;

  }
  #else

  static int devmap_managed_enable_get(struct dev_pagemap *pgmap)

  {
  	return -EINVAL;
  }

  static void devmap_managed_enable_put(void)
  {
  }

  #endif /* CONFIG_DEV_PAGEMAP_OPS */

  static void pgmap_array_delete(struct resource *res)

  {

  	xa_store_range(&pgmap_array, PHYS_PFN(res->start), PHYS_PFN(res->end),
  			NULL, GFP_KERNEL);

  	synchronize_rcu();

  }

  static unsigned long pfn_first(struct dev_pagemap *pgmap)

  {

  	return PHYS_PFN(pgmap->res.start) +

  		vmem_altmap_offset(pgmap_altmap(pgmap));

  }

  static unsigned long pfn_end(struct dev_pagemap *pgmap)

  {

  	const struct resource *res = &pgmap->res;

  
  	return (res->start + resource_size(res)) >> PAGE_SHIFT;
  }

  static unsigned long pfn_next(unsigned long pfn)
  {
  	if (pfn % 1024 == 0)
  		cond_resched();
  	return pfn + 1;
  }

  #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);
  	}

  	/*
  	 * Undo the pgmap ref assignment for the internal case as the
  	 * caller may re-enable the same pgmap.
  	 */
  	if (pgmap->ref == &pgmap->internal_ref)
  		pgmap->ref = NULL;

  }

  void memunmap_pages(struct dev_pagemap *pgmap)

  {

  	struct resource *res = &pgmap->res;

  	struct page *first_page;

  	unsigned long pfn;

  	int nid;

  	dev_pagemap_kill(pgmap);

  	for_each_device_pfn(pfn, pgmap)

  		put_page(pfn_to_page(pfn));

  	dev_pagemap_cleanup(pgmap);

  	/* make sure to access a memmap that was actually initialized */
  	first_page = pfn_to_page(pfn_first(pgmap));

  	/* pages are dead and unused, undo the arch mapping */

  	nid = page_to_nid(first_page);

  	mem_hotplug_begin();

  	if (pgmap->type == MEMORY_DEVICE_PRIVATE) {

  		__remove_pages(PHYS_PFN(res->start),

  			       PHYS_PFN(resource_size(res)), NULL);

  	} else {

  		arch_remove_memory(nid, res->start, resource_size(res),

  				pgmap_altmap(pgmap));

  		kasan_remove_zero_shadow(__va(res->start), resource_size(res));

  	}

  	mem_hotplug_done();

  	untrack_pfn(NULL, PHYS_PFN(res->start), resource_size(res));

  	pgmap_array_delete(res);

  	WARN_ONCE(pgmap->altmap.alloc, "failed to free all reserved pages
  ");

  	devmap_managed_enable_put();

  }

  EXPORT_SYMBOL_GPL(memunmap_pages);
  
  static void devm_memremap_pages_release(void *data)
  {
  	memunmap_pages(data);
  }

  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);
  }

  /*
   * Not device managed version of dev_memremap_pages, undone by
   * memunmap_pages().  Please use dev_memremap_pages if you have a struct
   * device available.

   */

  void *memremap_pages(struct dev_pagemap *pgmap, int nid)

  {

  	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 = pgmap_altmap(pgmap),

  	};

  	pgprot_t pgprot = PAGE_KERNEL;

  	int error, 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
  ");
  			return ERR_PTR(-EINVAL);
  		}

  		if (!pgmap->ops || !pgmap->ops->migrate_to_ram) {
  			WARN(1, "Missing migrate_to_ram method
  ");
  			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
  ");
  			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
  ", 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
  ");
  			return ERR_PTR(-EINVAL);
  		}

  	}

  	if (need_devmap_managed) {

  		error = devmap_managed_enable_get(pgmap);

  		if (error)
  			return ERR_PTR(error);
  	}

  	conflict_pgmap = get_dev_pagemap(PHYS_PFN(res->start), NULL);

  	if (conflict_pgmap) {

  		WARN(1, "Conflicting mapping in same section
  ");

  		put_dev_pagemap(conflict_pgmap);

  		error = -ENOMEM;
  		goto err_array;

  	}

  	conflict_pgmap = get_dev_pagemap(PHYS_PFN(res->end), NULL);

  	if (conflict_pgmap) {

  		WARN(1, "Conflicting mapping in same section
  ");

  		put_dev_pagemap(conflict_pgmap);

  		error = -ENOMEM;
  		goto err_array;

  	}

  	is_ram = region_intersects(res->start, resource_size(res),

  		IORESOURCE_SYSTEM_RAM, IORES_DESC_NONE);

  	if (is_ram != REGION_DISJOINT) {
  		WARN_ONCE(1, "%s attempted on %s region %pr
  ", __func__,
  				is_ram == REGION_MIXED ? "mixed" : "ram", res);

  		error = -ENXIO;
  		goto err_array;

  	}

  	error = xa_err(xa_store_range(&pgmap_array, PHYS_PFN(res->start),
  				PHYS_PFN(res->end), pgmap, GFP_KERNEL));

  	if (error)

  		goto err_array;

  	if (nid < 0)

  		nid = numa_mem_id();

  	error = track_pfn_remap(NULL, &pgprot, PHYS_PFN(res->start), 0,
  			resource_size(res));

  	if (error)
  		goto err_pfn_remap;

  	mem_hotplug_begin();

  
  	/*
  	 * For device private memory we call add_pages() as we only need to
  	 * allocate and initialize struct page for the device memory. More-
  	 * over the device memory is un-accessible thus we do not want to
  	 * create a linear mapping for the memory like arch_add_memory()
  	 * would do.
  	 *
  	 * For all other device memory types, which are accessible by
  	 * the CPU, we do want the linear mapping and thus use
  	 * arch_add_memory().
  	 */
  	if (pgmap->type == MEMORY_DEVICE_PRIVATE) {

  		error = add_pages(nid, PHYS_PFN(res->start),
  				PHYS_PFN(resource_size(res)), &restrictions);

  	} else {

  		error = kasan_add_zero_shadow(__va(res->start), resource_size(res));

  		if (error) {
  			mem_hotplug_done();
  			goto err_kasan;
  		}

  		error = arch_add_memory(nid, res->start, resource_size(res),

  					&restrictions);

  	}
  
  	if (!error) {
  		struct zone *zone;
  
  		zone = &NODE_DATA(nid)->node_zones[ZONE_DEVICE];

  		move_pfn_range_to_zone(zone, PHYS_PFN(res->start),
  				PHYS_PFN(resource_size(res)), restrictions.altmap);

  	}

  	mem_hotplug_done();

  	if (error)
  		goto err_add_memory;

  	/*
  	 * Initialization of the pages has been deferred until now in order
  	 * to allow us to do the work while not holding the hotplug lock.
  	 */
  	memmap_init_zone_device(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],

  				PHYS_PFN(res->start),
  				PHYS_PFN(resource_size(res)), pgmap);

  	percpu_ref_get_many(pgmap->ref, pfn_end(pgmap) - pfn_first(pgmap));

  	return __va(res->start);

  
   err_add_memory:

  	kasan_remove_zero_shadow(__va(res->start), resource_size(res));

   err_kasan:

  	untrack_pfn(NULL, PHYS_PFN(res->start), resource_size(res));

   err_pfn_remap:

  	pgmap_array_delete(res);
   err_array:

  	dev_pagemap_kill(pgmap);
  	dev_pagemap_cleanup(pgmap);

  	devmap_managed_enable_put();

  	return ERR_PTR(error);

  }

  EXPORT_SYMBOL_GPL(memremap_pages);
  
  /**
   * 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 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
   *    PGMAP_ALTMAP_VALID must be set in pgmap->flags.
   *
   * 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
   *    this is not enforced.
   */
  void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
  {
  	int error;
  	void *ret;
  
  	ret = memremap_pages(pgmap, dev_to_node(dev));
  	if (IS_ERR(ret))
  		return ret;
  
  	error = devm_add_action_or_reset(dev, devm_memremap_pages_release,
  			pgmap);
  	if (error)
  		return ERR_PTR(error);
  	return ret;
  }

  EXPORT_SYMBOL_GPL(devm_memremap_pages);

  void devm_memunmap_pages(struct device *dev, struct dev_pagemap *pgmap)
  {
  	devm_release_action(dev, devm_memremap_pages_release, pgmap);
  }
  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 */

  	if (altmap)
  		return altmap->reserve + altmap->free;
  	return 0;

  }
  
  void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns)
  {
  	altmap->alloc -= nr_pfns;
  }

  /**
   * get_dev_pagemap() - take a new live reference on the dev_pagemap for @pfn
   * @pfn: page frame number to lookup page_map
   * @pgmap: optional known pgmap that already has a reference
   *

   * If @pgmap is non-NULL and covers @pfn it will be returned as-is.  If @pgmap
   * is non-NULL but does not cover @pfn the reference to it will be released.

   */
  struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
  		struct dev_pagemap *pgmap)
  {

  	resource_size_t phys = PFN_PHYS(pfn);
  
  	/*

  	 * In the cached case we're already holding a live reference.

  	 */

  	if (pgmap) {

  		if (phys >= pgmap->res.start && phys <= pgmap->res.end)

  			return pgmap;
  		put_dev_pagemap(pgmap);

  	}
  
  	/* fall back to slow path lookup */
  	rcu_read_lock();

  	pgmap = xa_load(&pgmap_array, PHYS_PFN(phys));

  	if (pgmap && !percpu_ref_tryget_live(pgmap->ref))
  		pgmap = NULL;
  	rcu_read_unlock();
  
  	return pgmap;
  }

  EXPORT_SYMBOL_GPL(get_dev_pagemap);

  #ifdef CONFIG_DEV_PAGEMAP_OPS

  void __put_devmap_managed_page(struct page *page)

  {
  	int count = page_ref_dec_return(page);
  
  	/*
  	 * If refcount is 1 then page is freed and refcount is stable as nobody
  	 * holds a reference on the page.
  	 */
  	if (count == 1) {
  		/* Clear Active bit in case of parallel mark_page_accessed */
  		__ClearPageActive(page);
  		__ClearPageWaiters(page);

  		mem_cgroup_uncharge(page);

  		/*
  		 * When a device_private page is freed, the page->mapping field
  		 * may still contain a (stale) mapping value. For example, the
  		 * lower bits of page->mapping may still identify the page as
  		 * an anonymous page. Ultimately, this entire field is just
  		 * stale and wrong, and it will cause errors if not cleared.
  		 * One example is:
  		 *
  		 *  migrate_vma_pages()
  		 *    migrate_vma_insert_page()
  		 *      page_add_new_anon_rmap()
  		 *        __page_set_anon_rmap()
  		 *          ...checks page->mapping, via PageAnon(page) call,
  		 *            and incorrectly concludes that the page is an
  		 *            anonymous page. Therefore, it incorrectly,
  		 *            silently fails to set up the new anon rmap.
  		 *
  		 * For other types of ZONE_DEVICE pages, migration is either
  		 * handled differently or not done at all, so there is no need
  		 * to clear page->mapping.
  		 */
  		if (is_device_private_page(page))
  			page->mapping = NULL;

  		page->pgmap->ops->page_free(page);

  	} else if (!count)
  		__put_page(page);
  }

  EXPORT_SYMBOL(__put_devmap_managed_page);

  #endif /* CONFIG_DEV_PAGEMAP_OPS */