1// SPDX-License-Identifier: GPL-2.0
  2/* Copyright(c) 2016-2019 Intel Corporation. All rights reserved. */
  3#include <linux/memremap.h>
  4#include <linux/pagemap.h>
  5#include <linux/memory.h>
  6#include <linux/module.h>
  7#include <linux/device.h>
  8#include <linux/pfn_t.h>
  9#include <linux/slab.h>
 10#include <linux/dax.h>
 11#include <linux/fs.h>
 12#include <linux/mm.h>
 13#include <linux/mman.h>
 14#include "dax-private.h"
 15#include "bus.h"
 16
 17/* Memory resource name used for add_memory_driver_managed(). */
 18static const char *kmem_name;
 19/* Set if any memory will remain added when the driver will be unloaded. */
 20static bool any_hotremove_failed;
 21
 22int dev_dax_kmem_probe(struct device *dev)
 23{
 24	struct dev_dax *dev_dax = to_dev_dax(dev);
 25	struct resource *res = &dev_dax->region->res;
 26	resource_size_t kmem_start;
 27	resource_size_t kmem_size;
 28	resource_size_t kmem_end;
 29	struct resource *new_res;
 30	const char *new_res_name;
 31	int numa_node;
 32	int rc;
 33
 34	/*
 35	 * Ensure good NUMA information for the persistent memory.
 36	 * Without this check, there is a risk that slow memory
 37	 * could be mixed in a node with faster memory, causing
 38	 * unavoidable performance issues.
 39	 */
 40	numa_node = dev_dax->target_node;
 41	if (numa_node < 0) {
 42		dev_warn(dev, "rejecting DAX region %pR with invalid node: %d\n",
 43			 res, numa_node);
 44		return -EINVAL;
 45	}
 46
 47	/* Hotplug starting at the beginning of the next block: */
 48	kmem_start = ALIGN(res->start, memory_block_size_bytes());
 49
 50	kmem_size = resource_size(res);
 51	/* Adjust the size down to compensate for moving up kmem_start: */
 52	kmem_size -= kmem_start - res->start;
 53	/* Align the size down to cover only complete blocks: */
 54	kmem_size &= ~(memory_block_size_bytes() - 1);
 55	kmem_end = kmem_start + kmem_size;
 56
 57	new_res_name = kstrdup(dev_name(dev), GFP_KERNEL);
 58	if (!new_res_name)
 59		return -ENOMEM;
 60
 61	/* Region is permanently reserved if hotremove fails. */
 62	new_res = request_mem_region(kmem_start, kmem_size, new_res_name);
 63	if (!new_res) {
 64		dev_warn(dev, "could not reserve region [%pa-%pa]\n",
 65			 &kmem_start, &kmem_end);
 66		kfree(new_res_name);
 67		return -EBUSY;
 68	}
 69
 70	/*
 71	 * Set flags appropriate for System RAM.  Leave ..._BUSY clear
 72	 * so that add_memory() can add a child resource.  Do not
 73	 * inherit flags from the parent since it may set new flags
 74	 * unknown to us that will break add_memory() below.
 75	 */
 76	new_res->flags = IORESOURCE_SYSTEM_RAM;
 77
 78	/*
 79	 * Ensure that future kexec'd kernels will not treat this as RAM
 80	 * automatically.
 81	 */
 82	rc = add_memory_driver_managed(numa_node, new_res->start,
 83				       resource_size(new_res), kmem_name);
 84	if (rc) {
 85		release_resource(new_res);
 86		kfree(new_res);
 87		kfree(new_res_name);
 88		return rc;
 89	}
 90	dev_dax->dax_kmem_res = new_res;
 91
 92	return 0;
 93}
 94
 95#ifdef CONFIG_MEMORY_HOTREMOVE
 96static int dev_dax_kmem_remove(struct device *dev)
 97{
 98	struct dev_dax *dev_dax = to_dev_dax(dev);
 99	struct resource *res = dev_dax->dax_kmem_res;
100	resource_size_t kmem_start = res->start;
101	resource_size_t kmem_size = resource_size(res);
102	const char *res_name = res->name;
103	int rc;
104
105	/*
106	 * We have one shot for removing memory, if some memory blocks were not
107	 * offline prior to calling this function remove_memory() will fail, and
108	 * there is no way to hotremove this memory until reboot because device
109	 * unbind will succeed even if we return failure.
110	 */
111	rc = remove_memory(dev_dax->target_node, kmem_start, kmem_size);
112	if (rc) {
113		any_hotremove_failed = true;
114		dev_err(dev,
115			"DAX region %pR cannot be hotremoved until the next reboot\n",
116			res);
117		return rc;
118	}
119
120	/* Release and free dax resources */
121	release_resource(res);
122	kfree(res);
123	kfree(res_name);
124	dev_dax->dax_kmem_res = NULL;
125
126	return 0;
127}
128#else
129static int dev_dax_kmem_remove(struct device *dev)
130{
131	/*
132	 * Without hotremove purposely leak the request_mem_region() for the
133	 * device-dax range and return '0' to ->remove() attempts. The removal
134	 * of the device from the driver always succeeds, but the region is
135	 * permanently pinned as reserved by the unreleased
136	 * request_mem_region().
137	 */
138	any_hotremove_failed = true;
139	return 0;
140}
141#endif /* CONFIG_MEMORY_HOTREMOVE */
142
143static struct dax_device_driver device_dax_kmem_driver = {
144	.drv = {
145		.probe = dev_dax_kmem_probe,
146		.remove = dev_dax_kmem_remove,
147	},
148};
149
150static int __init dax_kmem_init(void)
151{
152	int rc;
153
154	/* Resource name is permanently allocated if any hotremove fails. */
155	kmem_name = kstrdup_const("System RAM (kmem)", GFP_KERNEL);
156	if (!kmem_name)
157		return -ENOMEM;
158
159	rc = dax_driver_register(&device_dax_kmem_driver);
160	if (rc)
161		kfree_const(kmem_name);
162	return rc;
163}
164
165static void __exit dax_kmem_exit(void)
166{
167	dax_driver_unregister(&device_dax_kmem_driver);
168	if (!any_hotremove_failed)
169		kfree_const(kmem_name);
170}
171
172MODULE_AUTHOR("Intel Corporation");
173MODULE_LICENSE("GPL v2");
174module_init(dax_kmem_init);
175module_exit(dax_kmem_exit);
176MODULE_ALIAS_DAX_DEVICE(0);