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
 22static int dax_kmem_range(struct dev_dax *dev_dax, int i, struct range *r)
 23{
 24	struct dev_dax_range *dax_range = &dev_dax->ranges[i];
 25	struct range *range = &dax_range->range;
 26
 27	/* memory-block align the hotplug range */
 28	r->start = ALIGN(range->start, memory_block_size_bytes());
 29	r->end = ALIGN_DOWN(range->end + 1, memory_block_size_bytes()) - 1;
 30	if (r->start >= r->end) {
 31		r->start = range->start;
 32		r->end = range->end;
 33		return -ENOSPC;
 34	}
 35	return 0;
 36}
 37
 38struct dax_kmem_data {
 39	const char *res_name;
 40	struct resource *res[];
 41};
 42
 43static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
 44{
 45	struct device *dev = &dev_dax->dev;
 46	struct dax_kmem_data *data;
 47	int rc = -ENOMEM;
 48	int i, mapped = 0;
 49	int numa_node;
 50
 51	/*
 52	 * Ensure good NUMA information for the persistent memory.
 53	 * Without this check, there is a risk that slow memory
 54	 * could be mixed in a node with faster memory, causing
 55	 * unavoidable performance issues.
 56	 */
 57	numa_node = dev_dax->target_node;
 58	if (numa_node < 0) {
 59		dev_warn(dev, "rejecting DAX region with invalid node: %d\n",
 60				numa_node);
 61		return -EINVAL;
 62	}
 63
 64	data = kzalloc(struct_size(data, res, dev_dax->nr_range), GFP_KERNEL);
 65	if (!data)
 66		return -ENOMEM;
 67
 68	data->res_name = kstrdup(dev_name(dev), GFP_KERNEL);
 69	if (!data->res_name)
 70		goto err_res_name;
 71
 72	for (i = 0; i < dev_dax->nr_range; i++) {
 73		struct resource *res;
 74		struct range range;
 75
 76		rc = dax_kmem_range(dev_dax, i, &range);
 77		if (rc) {
 78			dev_info(dev, "mapping%d: %#llx-%#llx too small after alignment\n",
 79					i, range.start, range.end);
 80			continue;
 81		}
 82
 83		/* Region is permanently reserved if hotremove fails. */
 84		res = request_mem_region(range.start, range_len(&range), data->res_name);
 85		if (!res) {
 86			dev_warn(dev, "mapping%d: %#llx-%#llx could not reserve region\n",
 87					i, range.start, range.end);
 88			/*
 89			 * Once some memory has been onlined we can't
 90			 * assume that it can be un-onlined safely.
 91			 */
 92			if (mapped)
 93				continue;
 94			rc = -EBUSY;
 95			goto err_request_mem;
 96		}
 97		data->res[i] = res;
 98
 99		/*
100		 * Set flags appropriate for System RAM.  Leave ..._BUSY clear
101		 * so that add_memory() can add a child resource.  Do not
102		 * inherit flags from the parent since it may set new flags
103		 * unknown to us that will break add_memory() below.
104		 */
105		res->flags = IORESOURCE_SYSTEM_RAM;
106
107		/*
108		 * Ensure that future kexec'd kernels will not treat
109		 * this as RAM automatically.
110		 */
111		rc = add_memory_driver_managed(numa_node, range.start,
112				range_len(&range), kmem_name, MHP_NONE);
113
114		if (rc) {
115			dev_warn(dev, "mapping%d: %#llx-%#llx memory add failed\n",
116					i, range.start, range.end);
117			release_resource(res);
118			kfree(res);
119			data->res[i] = NULL;
120			if (mapped)
121				continue;
122			goto err_request_mem;
123		}
124		mapped++;
125	}
126
127	dev_set_drvdata(dev, data);
128
129	return 0;
130
131err_request_mem:
132	kfree(data->res_name);
133err_res_name:
134	kfree(data);
135	return rc;
136}
137
138#ifdef CONFIG_MEMORY_HOTREMOVE
139static void dev_dax_kmem_remove(struct dev_dax *dev_dax)
140{
141	int i, success = 0;
142	struct device *dev = &dev_dax->dev;
143	struct dax_kmem_data *data = dev_get_drvdata(dev);
144
145	/*
146	 * We have one shot for removing memory, if some memory blocks were not
147	 * offline prior to calling this function remove_memory() will fail, and
148	 * there is no way to hotremove this memory until reboot because device
149	 * unbind will succeed even if we return failure.
150	 */
151	for (i = 0; i < dev_dax->nr_range; i++) {
152		struct range range;
153		int rc;
154
155		rc = dax_kmem_range(dev_dax, i, &range);
156		if (rc)
157			continue;
158
159		rc = remove_memory(dev_dax->target_node, range.start,
160				range_len(&range));
161		if (rc == 0) {
162			release_resource(data->res[i]);
163			kfree(data->res[i]);
164			data->res[i] = NULL;
165			success++;
166			continue;
167		}
168		any_hotremove_failed = true;
169		dev_err(dev,
170			"mapping%d: %#llx-%#llx cannot be hotremoved until the next reboot\n",
171				i, range.start, range.end);
172	}
173
174	if (success >= dev_dax->nr_range) {
175		kfree(data->res_name);
176		kfree(data);
177		dev_set_drvdata(dev, NULL);
178	}
179}
180#else
181static void dev_dax_kmem_remove(struct dev_dax *dev_dax)
182{
183	/*
184	 * Without hotremove purposely leak the request_mem_region() for the
185	 * device-dax range and return '0' to ->remove() attempts. The removal
186	 * of the device from the driver always succeeds, but the region is
187	 * permanently pinned as reserved by the unreleased
188	 * request_mem_region().
189	 */
190	any_hotremove_failed = true;
191}
192#endif /* CONFIG_MEMORY_HOTREMOVE */
193
194static struct dax_device_driver device_dax_kmem_driver = {
195	.probe = dev_dax_kmem_probe,
196	.remove = dev_dax_kmem_remove,
197};
198
199static int __init dax_kmem_init(void)
200{
201	int rc;
202
203	/* Resource name is permanently allocated if any hotremove fails. */
204	kmem_name = kstrdup_const("System RAM (kmem)", GFP_KERNEL);
205	if (!kmem_name)
206		return -ENOMEM;
207
208	rc = dax_driver_register(&device_dax_kmem_driver);
209	if (rc)
210		kfree_const(kmem_name);
211	return rc;
212}
213
214static void __exit dax_kmem_exit(void)
215{
216	dax_driver_unregister(&device_dax_kmem_driver);
217	if (!any_hotremove_failed)
218		kfree_const(kmem_name);
219}
220
221MODULE_AUTHOR("Intel Corporation");
222MODULE_LICENSE("GPL v2");
223module_init(dax_kmem_init);
224module_exit(dax_kmem_exit);
225MODULE_ALIAS_DAX_DEVICE(0);