1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright (C) IBM Corporation, 2014, 2017
4 * Anton Blanchard, Rashmica Gupta.
5 */
6
7#define pr_fmt(fmt) "memtrace: " fmt
8
9#include <linux/bitops.h>
10#include <linux/string.h>
11#include <linux/memblock.h>
12#include <linux/init.h>
13#include <linux/moduleparam.h>
14#include <linux/fs.h>
15#include <linux/debugfs.h>
16#include <linux/slab.h>
17#include <linux/memory.h>
18#include <linux/memory_hotplug.h>
19#include <linux/numa.h>
20#include <asm/machdep.h>
21#include <asm/debugfs.h>
22
23/* This enables us to keep track of the memory removed from each node. */
24struct memtrace_entry {
25	void *mem;
26	u64 start;
27	u64 size;
28	u32 nid;
29	struct dentry *dir;
30	char name[16];
31};
32
33static DEFINE_MUTEX(memtrace_mutex);
34static u64 memtrace_size;
35
36static struct memtrace_entry *memtrace_array;
37static unsigned int memtrace_array_nr;
38
39
40static ssize_t memtrace_read(struct file *filp, char __user *ubuf,
41			     size_t count, loff_t *ppos)
42{
43	struct memtrace_entry *ent = filp->private_data;
44
45	return simple_read_from_buffer(ubuf, count, ppos, ent->mem, ent->size);
46}
47
48static const struct file_operations memtrace_fops = {
49	.llseek = default_llseek,
50	.read	= memtrace_read,
51	.open	= simple_open,
52};
53
54static int check_memblock_online(struct memory_block *mem, void *arg)
55{
56	if (mem->state != MEM_ONLINE)
57		return -1;
58
59	return 0;
60}
61
62static int change_memblock_state(struct memory_block *mem, void *arg)
63{
64	unsigned long state = (unsigned long)arg;
65
66	mem->state = state;
67
68	return 0;
69}
70
71static void memtrace_clear_range(unsigned long start_pfn,
72				 unsigned long nr_pages)
73{
74	unsigned long pfn;
75
76	/*
77	 * As pages are offline, we cannot trust the memmap anymore. As HIGHMEM
78	 * does not apply, avoid passing around "struct page" and use
79	 * clear_page() instead directly.
80	 */
81	for (pfn = start_pfn; pfn < start_pfn + nr_pages; pfn++) {
82		if (IS_ALIGNED(pfn, PAGES_PER_SECTION))
83			cond_resched();
84		clear_page(__va(PFN_PHYS(pfn)));
85	}
86}
87
88/* called with device_hotplug_lock held */
89static bool memtrace_offline_pages(u32 nid, u64 start_pfn, u64 nr_pages)
90{
91	const unsigned long start = PFN_PHYS(start_pfn);
92	const unsigned long size = PFN_PHYS(nr_pages);
93
94	if (walk_memory_blocks(start, size, NULL, check_memblock_online))
95		return false;
96
97	walk_memory_blocks(start, size, (void *)MEM_GOING_OFFLINE,
98			   change_memblock_state);
99
100	if (offline_pages(start_pfn, nr_pages)) {
101		walk_memory_blocks(start, size, (void *)MEM_ONLINE,
102				   change_memblock_state);
103		return false;
104	}
105
106	walk_memory_blocks(start, size, (void *)MEM_OFFLINE,
107			   change_memblock_state);
108
109
110	return true;
111}
112
113static u64 memtrace_alloc_node(u32 nid, u64 size)
114{
115	u64 start_pfn, end_pfn, nr_pages, pfn;
116	u64 base_pfn;
117	u64 bytes = memory_block_size_bytes();
118
119	if (!node_spanned_pages(nid))
120		return 0;
121
122	start_pfn = node_start_pfn(nid);
123	end_pfn = node_end_pfn(nid);
124	nr_pages = size >> PAGE_SHIFT;
125
126	/* Trace memory needs to be aligned to the size */
127	end_pfn = round_down(end_pfn - nr_pages, nr_pages);
128
129	lock_device_hotplug();
130	for (base_pfn = end_pfn; base_pfn > start_pfn; base_pfn -= nr_pages) {
131		if (memtrace_offline_pages(nid, base_pfn, nr_pages) == true) {
132			/*
133			 * Clear the range while we still have a linear
134			 * mapping.
135			 */
136			memtrace_clear_range(base_pfn, nr_pages);
137			/*
138			 * Remove memory in memory block size chunks so that
139			 * iomem resources are always split to the same size and
140			 * we never try to remove memory that spans two iomem
141			 * resources.
142			 */
143			end_pfn = base_pfn + nr_pages;
144			for (pfn = base_pfn; pfn < end_pfn; pfn += bytes>> PAGE_SHIFT) {
145				__remove_memory(nid, pfn << PAGE_SHIFT, bytes);
146			}
147			unlock_device_hotplug();
148			return base_pfn << PAGE_SHIFT;
149		}
150	}
151	unlock_device_hotplug();
152
153	return 0;
154}
155
156static int memtrace_init_regions_runtime(u64 size)
157{
158	u32 nid;
159	u64 m;
160
161	memtrace_array = kcalloc(num_online_nodes(),
162				sizeof(struct memtrace_entry), GFP_KERNEL);
163	if (!memtrace_array) {
164		pr_err("Failed to allocate memtrace_array\n");
165		return -EINVAL;
166	}
167
168	for_each_online_node(nid) {
169		m = memtrace_alloc_node(nid, size);
170
171		/*
172		 * A node might not have any local memory, so warn but
173		 * continue on.
174		 */
175		if (!m) {
176			pr_err("Failed to allocate trace memory on node %d\n", nid);
177			continue;
178		}
179
180		pr_info("Allocated trace memory on node %d at 0x%016llx\n", nid, m);
181
182		memtrace_array[memtrace_array_nr].start = m;
183		memtrace_array[memtrace_array_nr].size = size;
184		memtrace_array[memtrace_array_nr].nid = nid;
185		memtrace_array_nr++;
186	}
187
188	return 0;
189}
190
191static struct dentry *memtrace_debugfs_dir;
192
193static int memtrace_init_debugfs(void)
194{
195	int ret = 0;
196	int i;
197
198	for (i = 0; i < memtrace_array_nr; i++) {
199		struct dentry *dir;
200		struct memtrace_entry *ent = &memtrace_array[i];
201
202		ent->mem = ioremap(ent->start, ent->size);
203		/* Warn but continue on */
204		if (!ent->mem) {
205			pr_err("Failed to map trace memory at 0x%llx\n",
206				 ent->start);
207			ret = -1;
208			continue;
209		}
210
211		snprintf(ent->name, 16, "%08x", ent->nid);
212		dir = debugfs_create_dir(ent->name, memtrace_debugfs_dir);
213
214		ent->dir = dir;
215		debugfs_create_file("trace", 0400, dir, ent, &memtrace_fops);
216		debugfs_create_x64("start", 0400, dir, &ent->start);
217		debugfs_create_x64("size", 0400, dir, &ent->size);
218	}
219
220	return ret;
221}
222
223static int online_mem_block(struct memory_block *mem, void *arg)
224{
225	return device_online(&mem->dev);
226}
227
228/*
229 * Iterate through the chunks of memory we have removed from the kernel
230 * and attempt to add them back to the kernel.
231 */
232static int memtrace_online(void)
233{
234	int i, ret = 0;
235	struct memtrace_entry *ent;
236
237	for (i = memtrace_array_nr - 1; i >= 0; i--) {
238		ent = &memtrace_array[i];
239
240		/* We have onlined this chunk previously */
241		if (ent->nid == NUMA_NO_NODE)
242			continue;
243
244		/* Remove from io mappings */
245		if (ent->mem) {
246			iounmap(ent->mem);
247			ent->mem = 0;
248		}
249
250		if (add_memory(ent->nid, ent->start, ent->size, MHP_NONE)) {
251			pr_err("Failed to add trace memory to node %d\n",
252				ent->nid);
253			ret += 1;
254			continue;
255		}
256
257		lock_device_hotplug();
258		walk_memory_blocks(ent->start, ent->size, NULL,
259				   online_mem_block);
260		unlock_device_hotplug();
261
262		/*
263		 * Memory was added successfully so clean up references to it
264		 * so on reentry we can tell that this chunk was added.
265		 */
266		debugfs_remove_recursive(ent->dir);
267		pr_info("Added trace memory back to node %d\n", ent->nid);
268		ent->size = ent->start = ent->nid = NUMA_NO_NODE;
269	}
270	if (ret)
271		return ret;
272
273	/* If all chunks of memory were added successfully, reset globals */
274	kfree(memtrace_array);
275	memtrace_array = NULL;
276	memtrace_size = 0;
277	memtrace_array_nr = 0;
278	return 0;
279}
280
281static int memtrace_enable_set(void *data, u64 val)
282{
283	int rc = -EAGAIN;
284	u64 bytes;
285
286	/*
287	 * Don't attempt to do anything if size isn't aligned to a memory
288	 * block or equal to zero.
289	 */
290	bytes = memory_block_size_bytes();
291	if (val & (bytes - 1)) {
292		pr_err("Value must be aligned with 0x%llx\n", bytes);
293		return -EINVAL;
294	}
295
296	mutex_lock(&memtrace_mutex);
297
298	/* Re-add/online previously removed/offlined memory */
299	if (memtrace_size) {
300		if (memtrace_online())
301			goto out_unlock;
302	}
303
304	if (!val) {
305		rc = 0;
306		goto out_unlock;
307	}
308
309	/* Offline and remove memory */
310	if (memtrace_init_regions_runtime(val))
311		goto out_unlock;
312
313	if (memtrace_init_debugfs())
314		goto out_unlock;
315
316	memtrace_size = val;
317	rc = 0;
318out_unlock:
319	mutex_unlock(&memtrace_mutex);
320	return rc;
321}
322
323static int memtrace_enable_get(void *data, u64 *val)
324{
325	*val = memtrace_size;
326	return 0;
327}
328
329DEFINE_SIMPLE_ATTRIBUTE(memtrace_init_fops, memtrace_enable_get,
330					memtrace_enable_set, "0x%016llx\n");
331
332static int memtrace_init(void)
333{
334	memtrace_debugfs_dir = debugfs_create_dir("memtrace",
335						  powerpc_debugfs_root);
336
337	debugfs_create_file("enable", 0600, memtrace_debugfs_dir,
338			    NULL, &memtrace_init_fops);
339
340	return 0;
341}
342machine_device_initcall(powernv, memtrace_init);
343