Linux 4.20.17

[thirdparty/kernel/stable.git] / kernel / 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/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)

#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)
{
        struct page *page = device_private_entry_to_page(entry);

        /*
         * 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 page->pgmap->page_fault(vma, addr, page, flags, pmdp);
}
EXPORT_SYMBOL(device_private_entry_fault);
#endif /* CONFIG_DEVICE_PRIVATE */

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)
{
        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;
}

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 devm_memremap_pages_release(void *data)
{
        struct dev_pagemap *pgmap = data;
        struct device *dev = pgmap->dev;
        struct resource *res = &pgmap->res;
        resource_size_t align_start, align_size;
        unsigned long pfn;

        pgmap->kill(pgmap->ref);
        for_each_device_pfn(pfn, pgmap)
                put_page(pfn_to_page(pfn));

        /* pages are dead and unused, undo the arch mapping */
        align_start = res->start & ~(SECTION_SIZE - 1);
        align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
                - align_start;

        mem_hotplug_begin();
        if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
                pfn = align_start >> PAGE_SHIFT;
                __remove_pages(page_zone(pfn_to_page(pfn)), pfn,
                                align_size >> PAGE_SHIFT, NULL);
        } else {
                arch_remove_memory(align_start, align_size,
                                pgmap->altmap_valid ? &pgmap->altmap : NULL);
                kasan_remove_zero_shadow(__va(align_start), align_size);
        }
        mem_hotplug_done();

        untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
        pgmap_array_delete(res);
        dev_WARN_ONCE(dev, pgmap->altmap.alloc,
                      "%s: failed to free all reserved pages\n", __func__);
}

/**
 * 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
 *    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
 *
 * 3/ pgmap->ref must be 'live' on entry and will be killed 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)
{
        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;
        pgprot_t pgprot = PAGE_KERNEL;
        int error, nid, is_ram;

        if (!pgmap->ref || !pgmap->kill)
                return ERR_PTR(-EINVAL);

        align_start = res->start & ~(SECTION_SIZE - 1);
        align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
                - align_start;
        align_end = align_start + align_size - 1;

        conflict_pgmap = get_dev_pagemap(PHYS_PFN(align_start), NULL);
        if (conflict_pgmap) {
                dev_WARN(dev, "Conflicting mapping in same section\n");
                put_dev_pagemap(conflict_pgmap);
                return ERR_PTR(-ENOMEM);
        }

        conflict_pgmap = get_dev_pagemap(PHYS_PFN(align_end), NULL);
        if (conflict_pgmap) {
                dev_WARN(dev, "Conflicting mapping in same section\n");
                put_dev_pagemap(conflict_pgmap);
                return ERR_PTR(-ENOMEM);
        }

        is_ram = region_intersects(align_start, align_size,
                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(align_start), 0,
                        align_size);
        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, align_start >> PAGE_SHIFT,
                                align_size >> PAGE_SHIFT, NULL, false);
        } else {
                error = kasan_add_zero_shadow(__va(align_start), align_size);
                if (error) {
                        mem_hotplug_done();
                        goto err_kasan;
                }

                error = arch_add_memory(nid, align_start, align_size, altmap,
                                false);
        }

        if (!error) {
                struct zone *zone;

                zone = &NODE_DATA(nid)->node_zones[ZONE_DEVICE];
                move_pfn_range_to_zone(zone, align_start >> PAGE_SHIFT,
                                align_size >> PAGE_SHIFT, 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],
                                align_start >> PAGE_SHIFT,
                                align_size >> PAGE_SHIFT, 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(align_start), align_size);
 err_kasan:
        untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
 err_pfn_remap:
        pgmap_array_delete(res);
 err_array:
        pgmap->kill(pgmap->ref);
        return ERR_PTR(error);
}
EXPORT_SYMBOL_GPL(devm_memremap_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;
}

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
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);

        /*
         * 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->page_free(page, page->pgmap->data);
        } else if (!count)
                __put_page(page);
}
EXPORT_SYMBOL(__put_devmap_managed_page);
#endif /* CONFIG_DEV_PAGEMAP_OPS */