// SPDX-License-Identifier: GPL-2.0
/* Copyright(c) 2016-2019 Intel Corporation. All rights reserved. */
#include <linux/memremap.h>
#include <linux/pagemap.h>
#include <linux/memory.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/pfn_t.h>
#include <linux/slab.h>
#include <linux/dax.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include "dax-private.h"
#include "bus.h"

/* Memory resource name used for add_memory_driver_managed(). */
static const char *kmem_name;
/* Set if any memory will remain added when the driver will be unloaded. */
static bool any_hotremove_failed;

static int dax_kmem_range(struct dev_dax *dev_dax, int i, struct range *r)
{
        struct dev_dax_range *dax_range = &dev_dax->ranges[i];
        struct range *range = &dax_range->range;

        /* memory-block align the hotplug range */
        r->start = ALIGN(range->start, memory_block_size_bytes());
        r->end = ALIGN_DOWN(range->end + 1, memory_block_size_bytes()) - 1;
        if (r->start >= r->end) {
                r->start = range->start;
                r->end = range->end;
                return -ENOSPC;
        }
        return 0;
}

struct dax_kmem_data {
        const char *res_name;
        struct resource *res[];
};

static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
{
        struct device *dev = &dev_dax->dev;
        struct dax_kmem_data *data;
        int rc = -ENOMEM;
        int i, mapped = 0;
        int numa_node;

        /*
         * Ensure good NUMA information for the persistent memory.
         * Without this check, there is a risk that slow memory
         * could be mixed in a node with faster memory, causing
         * unavoidable performance issues.
         */
        numa_node = dev_dax->target_node;
        if (numa_node < 0) {
                dev_warn(dev, "rejecting DAX region with invalid node: %d\n",
                                numa_node);
                return -EINVAL;
        }

        data = kzalloc(struct_size(data, res, dev_dax->nr_range), GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        data->res_name = kstrdup(dev_name(dev), GFP_KERNEL);
        if (!data->res_name)
                goto err_res_name;

        for (i = 0; i < dev_dax->nr_range; i++) {
                struct resource *res;
                struct range range;

                rc = dax_kmem_range(dev_dax, i, &range);
                if (rc) {
                        dev_info(dev, "mapping%d: %#llx-%#llx too small after alignment\n",
                                        i, range.start, range.end);
                        continue;
                }

                /* Region is permanently reserved if hotremove fails. */
                res = request_mem_region(range.start, range_len(&range), data->res_name);
                if (!res) {
                        dev_warn(dev, "mapping%d: %#llx-%#llx could not reserve region\n",
                                        i, range.start, range.end);
                        /*
                         * Once some memory has been onlined we can't
                         * assume that it can be un-onlined safely.
                         */
                        if (mapped)
                                continue;
                        rc = -EBUSY;
                        goto err_request_mem;
                }
                data->res[i] = res;

                /*
                 * Set flags appropriate for System RAM.  Leave ..._BUSY clear
                 * so that add_memory() can add a child resource.  Do not
                 * inherit flags from the parent since it may set new flags
                 * unknown to us that will break add_memory() below.
                 */
                res->flags = IORESOURCE_SYSTEM_RAM;

                /*
                 * Ensure that future kexec'd kernels will not treat
                 * this as RAM automatically.
                 */
                rc = add_memory_driver_managed(numa_node, range.start,
                                range_len(&range), kmem_name, MHP_NONE);

                if (rc) {
                        dev_warn(dev, "mapping%d: %#llx-%#llx memory add failed\n",
                                        i, range.start, range.end);
                        release_resource(res);
                        kfree(res);
                        data->res[i] = NULL;
                        if (mapped)
                                continue;
                        goto err_request_mem;
                }
                mapped++;
        }

        dev_set_drvdata(dev, data);

        return 0;

err_request_mem:
        kfree(data->res_name);
err_res_name:
        kfree(data);
        return rc;
}

#ifdef CONFIG_MEMORY_HOTREMOVE
static void dev_dax_kmem_remove(struct dev_dax *dev_dax)
{
        int i, success = 0;
        struct device *dev = &dev_dax->dev;
        struct dax_kmem_data *data = dev_get_drvdata(dev);

        /*
         * We have one shot for removing memory, if some memory blocks were not
         * offline prior to calling this function remove_memory() will fail, and
         * there is no way to hotremove this memory until reboot because device
         * unbind will succeed even if we return failure.
         */
        for (i = 0; i < dev_dax->nr_range; i++) {
                struct range range;
                int rc;

                rc = dax_kmem_range(dev_dax, i, &range);
                if (rc)
                        continue;

                rc = remove_memory(dev_dax->target_node, range.start,
                                range_len(&range));
                if (rc == 0) {
                        release_resource(data->res[i]);
                        kfree(data->res[i]);
                        data->res[i] = NULL;
                        success++;
                        continue;
                }
                any_hotremove_failed = true;
                dev_err(dev,
                        "mapping%d: %#llx-%#llx cannot be hotremoved until the next reboot\n",
                                i, range.start, range.end);
        }

        if (success >= dev_dax->nr_range) {
                kfree(data->res_name);
                kfree(data);
                dev_set_drvdata(dev, NULL);
        }
}
#else
static void dev_dax_kmem_remove(struct dev_dax *dev_dax)
{
        /*
         * Without hotremove purposely leak the request_mem_region() for the
         * device-dax range and return '0' to ->remove() attempts. The removal
         * of the device from the driver always succeeds, but the region is
         * permanently pinned as reserved by the unreleased
         * request_mem_region().
         */
        any_hotremove_failed = true;
}
#endif /* CONFIG_MEMORY_HOTREMOVE */

static struct dax_device_driver device_dax_kmem_driver = {
        .probe = dev_dax_kmem_probe,
        .remove = dev_dax_kmem_remove,
};

static int __init dax_kmem_init(void)
{
        int rc;

        /* Resource name is permanently allocated if any hotremove fails. */
        kmem_name = kstrdup_const("System RAM (kmem)", GFP_KERNEL);
        if (!kmem_name)
                return -ENOMEM;

        rc = dax_driver_register(&device_dax_kmem_driver);
        if (rc)
                kfree_const(kmem_name);
        return rc;
}

static void __exit dax_kmem_exit(void)
{
        dax_driver_unregister(&device_dax_kmem_driver);
        if (!any_hotremove_failed)
                kfree_const(kmem_name);
}

MODULE_AUTHOR("Intel Corporation");
MODULE_LICENSE("GPL v2");
module_init(dax_kmem_init);
module_exit(dax_kmem_exit);
MODULE_ALIAS_DAX_DEVICE(0);