blob: 275aa5f873991aff94cc5ebd62d17f77a87c6c8a [file] [log] [blame]
// 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;
int dev_dax_kmem_probe(struct device *dev)
struct dev_dax *dev_dax = to_dev_dax(dev);
struct resource *res = &dev_dax->region->res;
resource_size_t kmem_start;
resource_size_t kmem_size;
resource_size_t kmem_end;
struct resource *new_res;
const char *new_res_name;
int numa_node;
int rc;
* 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 %pR with invalid node: %d\n",
res, numa_node);
return -EINVAL;
/* Hotplug starting at the beginning of the next block: */
kmem_start = ALIGN(res->start, memory_block_size_bytes());
kmem_size = resource_size(res);
/* Adjust the size down to compensate for moving up kmem_start: */
kmem_size -= kmem_start - res->start;
/* Align the size down to cover only complete blocks: */
kmem_size &= ~(memory_block_size_bytes() - 1);
kmem_end = kmem_start + kmem_size;
new_res_name = kstrdup(dev_name(dev), GFP_KERNEL);
if (!new_res_name)
return -ENOMEM;
/* Region is permanently reserved if hotremove fails. */
new_res = request_mem_region(kmem_start, kmem_size, new_res_name);
if (!new_res) {
dev_warn(dev, "could not reserve region [%pa-%pa]\n",
&kmem_start, &kmem_end);
return -EBUSY;
* 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.
new_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, new_res->start,
resource_size(new_res), kmem_name);
if (rc) {
return rc;
dev_dax->dax_kmem_res = new_res;
return 0;
static int dev_dax_kmem_remove(struct device *dev)
struct dev_dax *dev_dax = to_dev_dax(dev);
struct resource *res = dev_dax->dax_kmem_res;
resource_size_t kmem_start = res->start;
resource_size_t kmem_size = resource_size(res);
const char *res_name = res->name;
int rc;
* 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.
rc = remove_memory(dev_dax->target_node, kmem_start, kmem_size);
if (rc) {
any_hotremove_failed = true;
"DAX region %pR cannot be hotremoved until the next reboot\n",
return rc;
/* Release and free dax resources */
dev_dax->dax_kmem_res = NULL;
return 0;
static int dev_dax_kmem_remove(struct device *dev)
* 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;
return 0;
static struct dax_device_driver device_dax_kmem_driver = {
.drv = {
.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)
return rc;
static void __exit dax_kmem_exit(void)
if (!any_hotremove_failed)
MODULE_AUTHOR("Intel Corporation");