/* 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\n");
                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(page_zone(first_page), 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\n");
        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\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(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\n");
                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\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;
        }

        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 */