Documentation: Add documentation for Processor MMIO Stale Data

[mirror_ubuntu-jammy-kernel.git] / mm / memremap.c

// 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/mmzone.h>
#include <linux/swapops.h>
#include <linux/types.h>
#include <linux/wait_bit.h>
#include <linux/xarray.h>

static DEFINE_XARRAY(pgmap_array);

/*
 * The memremap() and memremap_pages() interfaces are alternately used
 * to map persistent memory namespaces. These interfaces place different
 * constraints on the alignment and size of the mapping (namespace).
 * memremap() can map individual PAGE_SIZE pages. memremap_pages() can
 * only map subsections (2MB), and at least one architecture (PowerPC)
 * the minimum mapping granularity of memremap_pages() is 16MB.
 *
 * The role of memremap_compat_align() is to communicate the minimum
 * arch supported alignment of a namespace such that it can freely
 * switch modes without violating the arch constraint. Namely, do not
 * allow a namespace to be PAGE_SIZE aligned since that namespace may be
 * reconfigured into a mode that requires SUBSECTION_SIZE alignment.
 */
#ifndef CONFIG_ARCH_HAS_MEMREMAP_COMPAT_ALIGN
unsigned long memremap_compat_align(void)
{
        return SUBSECTION_SIZE;
}
EXPORT_SYMBOL_GPL(memremap_compat_align);
#endif

#ifdef CONFIG_DEV_PAGEMAP_OPS
DEFINE_STATIC_KEY_FALSE(devmap_managed_key);
EXPORT_SYMBOL(devmap_managed_key);

static void devmap_managed_enable_put(struct dev_pagemap *pgmap)
{
        if (pgmap->type == MEMORY_DEVICE_PRIVATE ||
            pgmap->type == MEMORY_DEVICE_FS_DAX)
                static_branch_dec(&devmap_managed_key);
}

static void devmap_managed_enable_get(struct dev_pagemap *pgmap)
{
        if (pgmap->type == MEMORY_DEVICE_PRIVATE ||
            pgmap->type == MEMORY_DEVICE_FS_DAX)
                static_branch_inc(&devmap_managed_key);
}
#else
static void devmap_managed_enable_get(struct dev_pagemap *pgmap)
{
}
static void devmap_managed_enable_put(struct dev_pagemap *pgmap)
{
}
#endif /* CONFIG_DEV_PAGEMAP_OPS */

static void pgmap_array_delete(struct range *range)
{
        xa_store_range(&pgmap_array, PHYS_PFN(range->start), PHYS_PFN(range->end),
                        NULL, GFP_KERNEL);
        synchronize_rcu();
}

static unsigned long pfn_first(struct dev_pagemap *pgmap, int range_id)
{
        struct range *range = &pgmap->ranges[range_id];
        unsigned long pfn = PHYS_PFN(range->start);

        if (range_id)
                return pfn;
        return pfn + vmem_altmap_offset(pgmap_altmap(pgmap));
}

bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn)
{
        int i;

        for (i = 0; i < pgmap->nr_range; i++) {
                struct range *range = &pgmap->ranges[i];

                if (pfn >= PHYS_PFN(range->start) &&
                    pfn <= PHYS_PFN(range->end))
                        return pfn >= pfn_first(pgmap, i);
        }

        return false;
}

static unsigned long pfn_end(struct dev_pagemap *pgmap, int range_id)
{
        const struct range *range = &pgmap->ranges[range_id];

        return (range->start + range_len(range)) >> 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, i) \
        for (pfn = pfn_first(map, i); pfn < pfn_end(map, i); 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;
}

static void pageunmap_range(struct dev_pagemap *pgmap, int range_id)
{
        struct range *range = &pgmap->ranges[range_id];
        struct page *first_page;

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

        /* pages are dead and unused, undo the arch mapping */
        mem_hotplug_begin();
        remove_pfn_range_from_zone(page_zone(first_page), PHYS_PFN(range->start),
                                   PHYS_PFN(range_len(range)));
        if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
                __remove_pages(PHYS_PFN(range->start),
                               PHYS_PFN(range_len(range)), NULL);
        } else {
                arch_remove_memory(range->start, range_len(range),
                                pgmap_altmap(pgmap));
                kasan_remove_zero_shadow(__va(range->start), range_len(range));
        }
        mem_hotplug_done();

        untrack_pfn(NULL, PHYS_PFN(range->start), range_len(range));
        pgmap_array_delete(range);
}

void memunmap_pages(struct dev_pagemap *pgmap)
{
        unsigned long pfn;
        int i;

        dev_pagemap_kill(pgmap);
        for (i = 0; i < pgmap->nr_range; i++)
                for_each_device_pfn(pfn, pgmap, i)
                        put_page(pfn_to_page(pfn));
        dev_pagemap_cleanup(pgmap);

        for (i = 0; i < pgmap->nr_range; i++)
                pageunmap_range(pgmap, i);

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

static int pagemap_range(struct dev_pagemap *pgmap, struct mhp_params *params,
                int range_id, int nid)
{
        const bool is_private = pgmap->type == MEMORY_DEVICE_PRIVATE;
        struct range *range = &pgmap->ranges[range_id];
        struct dev_pagemap *conflict_pgmap;
        int error, is_ram;

        if (WARN_ONCE(pgmap_altmap(pgmap) && range_id > 0,
                                "altmap not supported for multiple ranges\n"))
                return -EINVAL;

        conflict_pgmap = get_dev_pagemap(PHYS_PFN(range->start), NULL);
        if (conflict_pgmap) {
                WARN(1, "Conflicting mapping in same section\n");
                put_dev_pagemap(conflict_pgmap);
                return -ENOMEM;
        }

        conflict_pgmap = get_dev_pagemap(PHYS_PFN(range->end), NULL);
        if (conflict_pgmap) {
                WARN(1, "Conflicting mapping in same section\n");
                put_dev_pagemap(conflict_pgmap);
                return -ENOMEM;
        }

        is_ram = region_intersects(range->start, range_len(range),
                IORESOURCE_SYSTEM_RAM, IORES_DESC_NONE);

        if (is_ram != REGION_DISJOINT) {
                WARN_ONCE(1, "attempted on %s region %#llx-%#llx\n",
                                is_ram == REGION_MIXED ? "mixed" : "ram",
                                range->start, range->end);
                return -ENXIO;
        }

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

        if (nid < 0)
                nid = numa_mem_id();

        error = track_pfn_remap(NULL, &params->pgprot, PHYS_PFN(range->start), 0,
                        range_len(range));
        if (error)
                goto err_pfn_remap;

        if (!mhp_range_allowed(range->start, range_len(range), !is_private)) {
                error = -EINVAL;
                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 (is_private) {
                error = add_pages(nid, PHYS_PFN(range->start),
                                PHYS_PFN(range_len(range)), params);
        } else {
                error = kasan_add_zero_shadow(__va(range->start), range_len(range));
                if (error) {
                        mem_hotplug_done();
                        goto err_kasan;
                }

                error = arch_add_memory(nid, range->start, range_len(range),
                                        params);
        }

        if (!error) {
                struct zone *zone;

                zone = &NODE_DATA(nid)->node_zones[ZONE_DEVICE];
                move_pfn_range_to_zone(zone, PHYS_PFN(range->start),
                                PHYS_PFN(range_len(range)), params->altmap,
                                MIGRATE_MOVABLE);
        }

        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(range->start),
                                PHYS_PFN(range_len(range)), pgmap);
        percpu_ref_get_many(pgmap->ref, pfn_end(pgmap, range_id)
                        - pfn_first(pgmap, range_id));
        return 0;

err_add_memory:
        kasan_remove_zero_shadow(__va(range->start), range_len(range));
err_kasan:
        untrack_pfn(NULL, PHYS_PFN(range->start), range_len(range));
err_pfn_remap:
        pgmap_array_delete(range);
        return error;
}


/*
 * 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 mhp_params params = {
                .altmap = pgmap_altmap(pgmap),
                .pgprot = PAGE_KERNEL,
        };
        const int nr_range = pgmap->nr_range;
        int error, i;

        if (WARN_ONCE(!nr_range, "nr_range must be specified\n"))
                return ERR_PTR(-EINVAL);

        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);
                }
                if (!pgmap->ops->page_free) {
                        WARN(1, "Missing page_free method\n");
                        return ERR_PTR(-EINVAL);
                }
                if (!pgmap->owner) {
                        WARN(1, "Missing owner\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_GENERIC:
                break;
        case MEMORY_DEVICE_PCI_P2PDMA:
                params.pgprot = pgprot_noncached(params.pgprot);
                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);
                }
        }

        devmap_managed_enable_get(pgmap);

        /*
         * Clear the pgmap nr_range as it will be incremented for each
         * successfully processed range. This communicates how many
         * regions to unwind in the abort case.
         */
        pgmap->nr_range = 0;
        error = 0;
        for (i = 0; i < nr_range; i++) {
                error = pagemap_range(pgmap, &params, i, nid);
                if (error)
                        break;
                pgmap->nr_range++;
        }

        if (i < nr_range) {
                memunmap_pages(pgmap);
                pgmap->nr_range = nr_range;
                return ERR_PTR(error);
        }

        return __va(pgmap->ranges[0].start);
}
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/ range 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->range.start && phys <= pgmap->range.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 free_devmap_managed_page(struct page *page)
{
        /* notify page idle for dax */
        if (!is_device_private_page(page)) {
                wake_up_var(&page->_refcount);
                return;
        }

        __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.
         */
        page->mapping = NULL;
        page->pgmap->ops->page_free(page);
}
#endif /* CONFIG_DEV_PAGEMAP_OPS */