kmem.c

  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/slab.h>
  9#include <linux/dax.h>
 10#include <linux/fs.h>
 11#include <linux/mm.h>
 12#include <linux/mman.h>
 13#include <linux/memory-tiers.h>
 14#include <linux/memory_hotplug.h>
 15#include <linux/string_helpers.h>
 16#include "dax-private.h"
 17#include "bus.h"
 18
 19/*
 20 * Default abstract distance assigned to the NUMA node onlined
 21 * by DAX/kmem if the low level platform driver didn't initialize
 22 * one for this NUMA node.
 23 */
 24#define MEMTIER_DEFAULT_DAX_ADISTANCE	(MEMTIER_ADISTANCE_DRAM * 5)
 25
 26/* Memory resource name used for add_memory_driver_managed(). */
 27static const char *kmem_name;
 28/* Set if any memory will remain added when the driver will be unloaded. */
 29static bool any_hotremove_failed;
 30
 31static int dax_kmem_range(struct dev_dax *dev_dax, int i, struct range *r)
 32{
 33	struct dev_dax_range *dax_range = &dev_dax->ranges[i];
 34	struct range *range = &dax_range->range;
 35
 36	/* memory-block align the hotplug range */
 37	r->start = ALIGN(range->start, memory_block_size_bytes());
 38	r->end = ALIGN_DOWN(range->end + 1, memory_block_size_bytes()) - 1;
 39	if (r->start >= r->end) {
 40		r->start = range->start;
 41		r->end = range->end;
 42		return -ENOSPC;
 43	}
 44	return 0;
 45}
 46
 47struct dax_kmem_data {
 48	const char *res_name;
 49	int mgid;
 50	struct resource *res[];
 51};
 52
 53static DEFINE_MUTEX(kmem_memory_type_lock);
 54static LIST_HEAD(kmem_memory_types);
 55
 56static struct memory_dev_type *kmem_find_alloc_memory_type(int adist)
 57{
 58	guard(mutex)(&kmem_memory_type_lock);
 59	return mt_find_alloc_memory_type(adist, &kmem_memory_types);
 60}
 61
 62static void kmem_put_memory_types(void)
 63{
 64	guard(mutex)(&kmem_memory_type_lock);
 65	mt_put_memory_types(&kmem_memory_types);
 66}
 67
 68static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
 69{
 70	struct device *dev = &dev_dax->dev;
 71	unsigned long total_len = 0, orig_len = 0;
 72	struct dax_kmem_data *data;
 73	struct memory_dev_type *mtype;
 74	int i, rc, mapped = 0;
 75	mhp_t mhp_flags;
 76	int numa_node;
 77	int adist = MEMTIER_DEFAULT_DAX_ADISTANCE;
 78
 79	/*
 80	 * Ensure good NUMA information for the persistent memory.
 81	 * Without this check, there is a risk that slow memory
 82	 * could be mixed in a node with faster memory, causing
 83	 * unavoidable performance issues.
 84	 */
 85	numa_node = dev_dax->target_node;
 86	if (numa_node < 0) {
 87		dev_warn(dev, "rejecting DAX region with invalid node: %d\n",
 88				numa_node);
 89		return -EINVAL;
 90	}
 91
 92	mt_calc_adistance(numa_node, &adist);
 93	mtype = kmem_find_alloc_memory_type(adist);
 94	if (IS_ERR(mtype))
 95		return PTR_ERR(mtype);
 96
 97	for (i = 0; i < dev_dax->nr_range; i++) {
 98		struct range range;
 99
100		orig_len += range_len(&dev_dax->ranges[i].range);
101		rc = dax_kmem_range(dev_dax, i, &range);
102		if (rc) {
103			dev_info(dev, "mapping%d: %#llx-%#llx too small after alignment\n",
104					i, range.start, range.end);
105			continue;
106		}
107		total_len += range_len(&range);
108	}
109
110	if (!total_len) {
111		dev_warn(dev, "rejecting DAX region without any memory after alignment\n");
112		return -EINVAL;
113	} else if (total_len != orig_len) {
114		char buf[16];
115
116		string_get_size(orig_len - total_len, 1, STRING_UNITS_2,
117				buf, sizeof(buf));
118		dev_warn(dev, "DAX region truncated by %s due to alignment\n", buf);
119	}
120
121	init_node_memory_type(numa_node, mtype);
122
123	rc = -ENOMEM;
124	data = kzalloc(struct_size(data, res, dev_dax->nr_range), GFP_KERNEL);
125	if (!data)
126		goto err_dax_kmem_data;
127
128	data->res_name = kstrdup(dev_name(dev), GFP_KERNEL);
129	if (!data->res_name)
130		goto err_res_name;
131
132	rc = memory_group_register_static(numa_node, PFN_UP(total_len));
133	if (rc < 0)
134		goto err_reg_mgid;
135	data->mgid = rc;
136
137	for (i = 0; i < dev_dax->nr_range; i++) {
138		struct resource *res;
139		struct range range;
140
141		rc = dax_kmem_range(dev_dax, i, &range);
142		if (rc)
143			continue;
144
145		/* Region is permanently reserved if hotremove fails. */
146		res = request_mem_region(range.start, range_len(&range), data->res_name);
147		if (!res) {
148			dev_warn(dev, "mapping%d: %#llx-%#llx could not reserve region\n",
149					i, range.start, range.end);
150			/*
151			 * Once some memory has been onlined we can't
152			 * assume that it can be un-onlined safely.
153			 */
154			if (mapped)
155				continue;
156			rc = -EBUSY;
157			goto err_request_mem;
158		}
159		data->res[i] = res;
160
161		/*
162		 * Set flags appropriate for System RAM.  Leave ..._BUSY clear
163		 * so that add_memory() can add a child resource.  Do not
164		 * inherit flags from the parent since it may set new flags
165		 * unknown to us that will break add_memory() below.
166		 */
167		res->flags = IORESOURCE_SYSTEM_RAM;
168
169		mhp_flags = MHP_NID_IS_MGID;
170		if (dev_dax->memmap_on_memory)
171			mhp_flags |= MHP_MEMMAP_ON_MEMORY;
172
173		/*
174		 * Ensure that future kexec'd kernels will not treat
175		 * this as RAM automatically.
176		 */
177		rc = add_memory_driver_managed(data->mgid, range.start,
178				range_len(&range), kmem_name, mhp_flags);
179
180		if (rc) {
181			dev_warn(dev, "mapping%d: %#llx-%#llx memory add failed\n",
182					i, range.start, range.end);
183			remove_resource(res);
184			kfree(res);
185			data->res[i] = NULL;
186			if (mapped)
187				continue;
188			goto err_request_mem;
189		}
190		mapped++;
191	}
192
193	dev_set_drvdata(dev, data);
194
195	return 0;
196
197err_request_mem:
198	memory_group_unregister(data->mgid);
199err_reg_mgid:
200	kfree(data->res_name);
201err_res_name:
202	kfree(data);
203err_dax_kmem_data:
204	clear_node_memory_type(numa_node, mtype);
205	return rc;
206}
207
208#ifdef CONFIG_MEMORY_HOTREMOVE
209static void dev_dax_kmem_remove(struct dev_dax *dev_dax)
210{
211	int i, success = 0;
212	int node = dev_dax->target_node;
213	struct device *dev = &dev_dax->dev;
214	struct dax_kmem_data *data = dev_get_drvdata(dev);
215
216	/*
217	 * We have one shot for removing memory, if some memory blocks were not
218	 * offline prior to calling this function remove_memory() will fail, and
219	 * there is no way to hotremove this memory until reboot because device
220	 * unbind will succeed even if we return failure.
221	 */
222	for (i = 0; i < dev_dax->nr_range; i++) {
223		struct range range;
224		int rc;
225
226		rc = dax_kmem_range(dev_dax, i, &range);
227		if (rc)
228			continue;
229
230		rc = remove_memory(range.start, range_len(&range));
231		if (rc == 0) {
232			remove_resource(data->res[i]);
233			kfree(data->res[i]);
234			data->res[i] = NULL;
235			success++;
236			continue;
237		}
238		any_hotremove_failed = true;
239		dev_err(dev,
240			"mapping%d: %#llx-%#llx cannot be hotremoved until the next reboot\n",
241				i, range.start, range.end);
242	}
243
244	if (success >= dev_dax->nr_range) {
245		memory_group_unregister(data->mgid);
246		kfree(data->res_name);
247		kfree(data);
248		dev_set_drvdata(dev, NULL);
249		/*
250		 * Clear the memtype association on successful unplug.
251		 * If not, we have memory blocks left which can be
252		 * offlined/onlined later. We need to keep memory_dev_type
253		 * for that. This implies this reference will be around
254		 * till next reboot.
255		 */
256		clear_node_memory_type(node, NULL);
257	}
258}
259#else
260static void dev_dax_kmem_remove(struct dev_dax *dev_dax)
261{
262	/*
263	 * Without hotremove purposely leak the request_mem_region() for the
264	 * device-dax range and return '0' to ->remove() attempts. The removal
265	 * of the device from the driver always succeeds, but the region is
266	 * permanently pinned as reserved by the unreleased
267	 * request_mem_region().
268	 */
269	any_hotremove_failed = true;
270}
271#endif /* CONFIG_MEMORY_HOTREMOVE */
272
273static struct dax_device_driver device_dax_kmem_driver = {
274	.probe = dev_dax_kmem_probe,
275	.remove = dev_dax_kmem_remove,
276	.type = DAXDRV_KMEM_TYPE,
277};
278
279static int __init dax_kmem_init(void)
280{
281	int rc;
282
283	/* Resource name is permanently allocated if any hotremove fails. */
284	kmem_name = kstrdup_const("System RAM (kmem)", GFP_KERNEL);
285	if (!kmem_name)
286		return -ENOMEM;
287
288	rc = dax_driver_register(&device_dax_kmem_driver);
289	if (rc)
290		goto error_dax_driver;
291
292	return rc;
293
294error_dax_driver:
295	kmem_put_memory_types();
296	kfree_const(kmem_name);
297	return rc;
298}
299
300static void __exit dax_kmem_exit(void)
301{
302	dax_driver_unregister(&device_dax_kmem_driver);
303	if (!any_hotremove_failed)
304		kfree_const(kmem_name);
305	kmem_put_memory_types();
306}
307
308MODULE_AUTHOR("Intel Corporation");
309MODULE_DESCRIPTION("KMEM DAX: map dax-devices as System-RAM");
310MODULE_LICENSE("GPL v2");
311module_init(dax_kmem_init);
312module_exit(dax_kmem_exit);
313MODULE_ALIAS_DAX_DEVICE(0);