memremap: move from kernel/ to mm/

memremap.c implements MM functionality for ZONE_DEVICE, so it really
should be in the mm/ directory, not the kernel/ one.

Link: http://lkml.kernel.org/r/20190722094143.18387-1-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 406 insertions, 0 deletions

diff --git a/mm/Makefile b/mm/Makefile
index 338e528ad436..d0b295c3b764 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -102,5 +102,6 @@ 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-$(CONFIG_ZONE_DEVICE) += memremap.o
 obj-$(CONFIG_HMM_MIRROR) += hmm.o
 obj-$(CONFIG_MEMFD_CREATE) += memfd.o
diff --git a/mm/memremap.c b/mm/memremap.c
new file mode 100644
index 000000000000..6ee03a816d67
--- /dev/null
+++ b/mm/memremap.c
@@ -0,0 +1,405 @@
+/* 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);
+#define SECTION_MASK ~((1UL << PA_SECTION_SHIFT) - 1)
+#define SECTION_SIZE (1UL << PA_SECTION_SHIFT)
+
+#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)
+{
+	if (atomic_dec_and_test(&devmap_managed_enable))
+		static_branch_disable(&devmap_managed_key);
+}
+
+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;
+	}
+
+	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);
+}
+#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)
+{
+	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);
+	}
+}
+
+static void devm_memremap_pages_release(void *data)
+{
+	struct dev_pagemap *pgmap = data;
+	struct device *dev = pgmap->dev;
+	struct resource *res = &pgmap->res;
+	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);
+
+	/* pages are dead and unused, undo the arch mapping */
+	nid = page_to_nid(pfn_to_page(PHYS_PFN(res->start)));
+
+	mem_hotplug_begin();
+	if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
+		pfn = PHYS_PFN(res->start);
+		__remove_pages(page_zone(pfn_to_page(pfn)), pfn,
+				 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);
+	dev_WARN_ONCE(dev, pgmap->altmap.alloc,
+		      "%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 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)
+{
+	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, 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 (need_devmap_managed) {
+		error = devmap_managed_enable_get(dev, pgmap);
+		if (error)
+			return ERR_PTR(error);
+	}
+
+	conflict_pgmap = get_dev_pagemap(PHYS_PFN(res->start), NULL);
+	if (conflict_pgmap) {
+		dev_WARN(dev, "Conflicting mapping in same section\n");
+		put_dev_pagemap(conflict_pgmap);
+		error = -ENOMEM;
+		goto err_array;
+	}
+
+	conflict_pgmap = get_dev_pagemap(PHYS_PFN(res->end), NULL);
+	if (conflict_pgmap) {
+		dev_WARN(dev, "Conflicting mapping in same section\n");
+		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\n", __func__,
+				is_ram == REGION_MIXED ? "mixed" : "ram", res);
+		error = -ENXIO;
+		goto err_array;
+	}
+
+	pgmap->dev = dev;
+
+	error = xa_err(xa_store_range(&pgmap_array, PHYS_PFN(res->start),
+				PHYS_PFN(res->end), pgmap, GFP_KERNEL));
+	if (error)
+		goto err_array;
+
+	nid = dev_to_node(dev);
+	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));
+
+	error = devm_add_action_or_reset(dev, devm_memremap_pages_release,
+			pgmap);
+	if (error)
+		return ERR_PTR(error);
+
+	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);
+	return ERR_PTR(error);
+}
+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);
+
+		page->pgmap->ops->page_free(page);
+	} else if (!count)
+		__put_page(page);
+}
+EXPORT_SYMBOL(__put_devmap_managed_page);
+#endif /* CONFIG_DEV_PAGEMAP_OPS */