1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  *  IOMMU helpers in MMU context.
4  *
5  *  Copyright (C) 2015 IBM Corp. <aik@ozlabs.ru>
6  */
7 
8 #include <linux/sched/signal.h>
9 #include <linux/slab.h>
10 #include <linux/rculist.h>
11 #include <linux/vmalloc.h>
12 #include <linux/mutex.h>
13 #include <linux/migrate.h>
14 #include <linux/hugetlb.h>
15 #include <linux/swap.h>
16 #include <linux/sizes.h>
17 #include <linux/mm.h>
18 #include <asm/mmu_context.h>
19 #include <asm/pte-walk.h>
20 #include <linux/mm_inline.h>
21 
22 static DEFINE_MUTEX(mem_list_mutex);
23 
24 #define MM_IOMMU_TABLE_GROUP_PAGE_DIRTY	0x1
25 #define MM_IOMMU_TABLE_GROUP_PAGE_MASK	~(SZ_4K - 1)
26 
27 struct mm_iommu_table_group_mem_t {
28 	struct list_head next;
29 	struct rcu_head rcu;
30 	unsigned long used;
31 	atomic64_t mapped;
32 	unsigned int pageshift;
33 	u64 ua;			/* userspace address */
34 	u64 entries;		/* number of entries in hpas/hpages[] */
35 	/*
36 	 * in mm_iommu_get we temporarily use this to store
37 	 * struct page address.
38 	 *
39 	 * We need to convert ua to hpa in real mode. Make it
40 	 * simpler by storing physical address.
41 	 */
42 	union {
43 		struct page **hpages;	/* vmalloc'ed */
44 		phys_addr_t *hpas;
45 	};
46 #define MM_IOMMU_TABLE_INVALID_HPA	((uint64_t)-1)
47 	u64 dev_hpa;		/* Device memory base address */
48 };
49 
50 bool mm_iommu_preregistered(struct mm_struct *mm)
51 {
52 	return !list_empty(&mm->context.iommu_group_mem_list);
53 }
54 EXPORT_SYMBOL_GPL(mm_iommu_preregistered);
55 
56 static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua,
57 			      unsigned long entries, unsigned long dev_hpa,
58 			      struct mm_iommu_table_group_mem_t **pmem)
59 {
60 	struct mm_iommu_table_group_mem_t *mem, *mem2;
61 	long i, ret, locked_entries = 0, pinned = 0;
62 	unsigned int pageshift;
63 	unsigned long entry, chunk;
64 
65 	if (dev_hpa == MM_IOMMU_TABLE_INVALID_HPA) {
66 		ret = account_locked_vm(mm, entries, true);
67 		if (ret)
68 			return ret;
69 
70 		locked_entries = entries;
71 	}
72 
73 	mem = kzalloc(sizeof(*mem), GFP_KERNEL);
74 	if (!mem) {
75 		ret = -ENOMEM;
76 		goto unlock_exit;
77 	}
78 
79 	if (dev_hpa != MM_IOMMU_TABLE_INVALID_HPA) {
80 		mem->pageshift = __ffs(dev_hpa | (entries << PAGE_SHIFT));
81 		mem->dev_hpa = dev_hpa;
82 		goto good_exit;
83 	}
84 	mem->dev_hpa = MM_IOMMU_TABLE_INVALID_HPA;
85 
86 	/*
87 	 * For a starting point for a maximum page size calculation
88 	 * we use @ua and @entries natural alignment to allow IOMMU pages
89 	 * smaller than huge pages but still bigger than PAGE_SIZE.
90 	 */
91 	mem->pageshift = __ffs(ua | (entries << PAGE_SHIFT));
92 	mem->hpas = vzalloc(array_size(entries, sizeof(mem->hpas[0])));
93 	if (!mem->hpas) {
94 		kfree(mem);
95 		ret = -ENOMEM;
96 		goto unlock_exit;
97 	}
98 
99 	mmap_read_lock(mm);
100 	chunk = (1UL << (PAGE_SHIFT + MAX_ORDER)) /
101 			sizeof(struct vm_area_struct *);
102 	chunk = min(chunk, entries);
103 	for (entry = 0; entry < entries; entry += chunk) {
104 		unsigned long n = min(entries - entry, chunk);
105 
106 		ret = pin_user_pages(ua + (entry << PAGE_SHIFT), n,
107 				FOLL_WRITE | FOLL_LONGTERM,
108 				mem->hpages + entry, NULL);
109 		if (ret == n) {
110 			pinned += n;
111 			continue;
112 		}
113 		if (ret > 0)
114 			pinned += ret;
115 		break;
116 	}
117 	mmap_read_unlock(mm);
118 	if (pinned != entries) {
119 		if (!ret)
120 			ret = -EFAULT;
121 		goto free_exit;
122 	}
123 
124 good_exit:
125 	atomic64_set(&mem->mapped, 1);
126 	mem->used = 1;
127 	mem->ua = ua;
128 	mem->entries = entries;
129 
130 	mutex_lock(&mem_list_mutex);
131 
132 	list_for_each_entry_rcu(mem2, &mm->context.iommu_group_mem_list, next,
133 				lockdep_is_held(&mem_list_mutex)) {
134 		/* Overlap? */
135 		if ((mem2->ua < (ua + (entries << PAGE_SHIFT))) &&
136 				(ua < (mem2->ua +
137 				       (mem2->entries << PAGE_SHIFT)))) {
138 			ret = -EINVAL;
139 			mutex_unlock(&mem_list_mutex);
140 			goto free_exit;
141 		}
142 	}
143 
144 	if (mem->dev_hpa == MM_IOMMU_TABLE_INVALID_HPA) {
145 		/*
146 		 * Allow to use larger than 64k IOMMU pages. Only do that
147 		 * if we are backed by hugetlb. Skip device memory as it is not
148 		 * backed with page structs.
149 		 */
150 		pageshift = PAGE_SHIFT;
151 		for (i = 0; i < entries; ++i) {
152 			struct page *page = mem->hpages[i];
153 
154 			if ((mem->pageshift > PAGE_SHIFT) && PageHuge(page))
155 				pageshift = page_shift(compound_head(page));
156 			mem->pageshift = min(mem->pageshift, pageshift);
157 			/*
158 			 * We don't need struct page reference any more, switch
159 			 * to physical address.
160 			 */
161 			mem->hpas[i] = page_to_pfn(page) << PAGE_SHIFT;
162 		}
163 	}
164 
165 	list_add_rcu(&mem->next, &mm->context.iommu_group_mem_list);
166 
167 	mutex_unlock(&mem_list_mutex);
168 
169 	*pmem = mem;
170 
171 	return 0;
172 
173 free_exit:
174 	/* free the references taken */
175 	unpin_user_pages(mem->hpages, pinned);
176 
177 	vfree(mem->hpas);
178 	kfree(mem);
179 
180 unlock_exit:
181 	account_locked_vm(mm, locked_entries, false);
182 
183 	return ret;
184 }
185 
186 long mm_iommu_new(struct mm_struct *mm, unsigned long ua, unsigned long entries,
187 		struct mm_iommu_table_group_mem_t **pmem)
188 {
189 	return mm_iommu_do_alloc(mm, ua, entries, MM_IOMMU_TABLE_INVALID_HPA,
190 			pmem);
191 }
192 EXPORT_SYMBOL_GPL(mm_iommu_new);
193 
194 long mm_iommu_newdev(struct mm_struct *mm, unsigned long ua,
195 		unsigned long entries, unsigned long dev_hpa,
196 		struct mm_iommu_table_group_mem_t **pmem)
197 {
198 	return mm_iommu_do_alloc(mm, ua, entries, dev_hpa, pmem);
199 }
200 EXPORT_SYMBOL_GPL(mm_iommu_newdev);
201 
202 static void mm_iommu_unpin(struct mm_iommu_table_group_mem_t *mem)
203 {
204 	long i;
205 	struct page *page = NULL;
206 
207 	if (!mem->hpas)
208 		return;
209 
210 	for (i = 0; i < mem->entries; ++i) {
211 		if (!mem->hpas[i])
212 			continue;
213 
214 		page = pfn_to_page(mem->hpas[i] >> PAGE_SHIFT);
215 		if (!page)
216 			continue;
217 
218 		if (mem->hpas[i] & MM_IOMMU_TABLE_GROUP_PAGE_DIRTY)
219 			SetPageDirty(page);
220 
221 		unpin_user_page(page);
222 
223 		mem->hpas[i] = 0;
224 	}
225 }
226 
227 static void mm_iommu_do_free(struct mm_iommu_table_group_mem_t *mem)
228 {
229 
230 	mm_iommu_unpin(mem);
231 	vfree(mem->hpas);
232 	kfree(mem);
233 }
234 
235 static void mm_iommu_free(struct rcu_head *head)
236 {
237 	struct mm_iommu_table_group_mem_t *mem = container_of(head,
238 			struct mm_iommu_table_group_mem_t, rcu);
239 
240 	mm_iommu_do_free(mem);
241 }
242 
243 static void mm_iommu_release(struct mm_iommu_table_group_mem_t *mem)
244 {
245 	list_del_rcu(&mem->next);
246 	call_rcu(&mem->rcu, mm_iommu_free);
247 }
248 
249 long mm_iommu_put(struct mm_struct *mm, struct mm_iommu_table_group_mem_t *mem)
250 {
251 	long ret = 0;
252 	unsigned long unlock_entries = 0;
253 
254 	mutex_lock(&mem_list_mutex);
255 
256 	if (mem->used == 0) {
257 		ret = -ENOENT;
258 		goto unlock_exit;
259 	}
260 
261 	--mem->used;
262 	/* There are still users, exit */
263 	if (mem->used)
264 		goto unlock_exit;
265 
266 	/* Are there still mappings? */
267 	if (atomic64_cmpxchg(&mem->mapped, 1, 0) != 1) {
268 		++mem->used;
269 		ret = -EBUSY;
270 		goto unlock_exit;
271 	}
272 
273 	if (mem->dev_hpa == MM_IOMMU_TABLE_INVALID_HPA)
274 		unlock_entries = mem->entries;
275 
276 	/* @mapped became 0 so now mappings are disabled, release the region */
277 	mm_iommu_release(mem);
278 
279 unlock_exit:
280 	mutex_unlock(&mem_list_mutex);
281 
282 	account_locked_vm(mm, unlock_entries, false);
283 
284 	return ret;
285 }
286 EXPORT_SYMBOL_GPL(mm_iommu_put);
287 
288 struct mm_iommu_table_group_mem_t *mm_iommu_lookup(struct mm_struct *mm,
289 		unsigned long ua, unsigned long size)
290 {
291 	struct mm_iommu_table_group_mem_t *mem, *ret = NULL;
292 
293 	rcu_read_lock();
294 	list_for_each_entry_rcu(mem, &mm->context.iommu_group_mem_list, next) {
295 		if ((mem->ua <= ua) &&
296 				(ua + size <= mem->ua +
297 				 (mem->entries << PAGE_SHIFT))) {
298 			ret = mem;
299 			break;
300 		}
301 	}
302 	rcu_read_unlock();
303 
304 	return ret;
305 }
306 EXPORT_SYMBOL_GPL(mm_iommu_lookup);
307 
308 struct mm_iommu_table_group_mem_t *mm_iommu_get(struct mm_struct *mm,
309 		unsigned long ua, unsigned long entries)
310 {
311 	struct mm_iommu_table_group_mem_t *mem, *ret = NULL;
312 
313 	mutex_lock(&mem_list_mutex);
314 
315 	list_for_each_entry_rcu(mem, &mm->context.iommu_group_mem_list, next,
316 				lockdep_is_held(&mem_list_mutex)) {
317 		if ((mem->ua == ua) && (mem->entries == entries)) {
318 			ret = mem;
319 			++mem->used;
320 			break;
321 		}
322 	}
323 
324 	mutex_unlock(&mem_list_mutex);
325 
326 	return ret;
327 }
328 EXPORT_SYMBOL_GPL(mm_iommu_get);
329 
330 long mm_iommu_ua_to_hpa(struct mm_iommu_table_group_mem_t *mem,
331 		unsigned long ua, unsigned int pageshift, unsigned long *hpa)
332 {
333 	const long entry = (ua - mem->ua) >> PAGE_SHIFT;
334 	u64 *va;
335 
336 	if (entry >= mem->entries)
337 		return -EFAULT;
338 
339 	if (pageshift > mem->pageshift)
340 		return -EFAULT;
341 
342 	if (!mem->hpas) {
343 		*hpa = mem->dev_hpa + (ua - mem->ua);
344 		return 0;
345 	}
346 
347 	va = &mem->hpas[entry];
348 	*hpa = (*va & MM_IOMMU_TABLE_GROUP_PAGE_MASK) | (ua & ~PAGE_MASK);
349 
350 	return 0;
351 }
352 EXPORT_SYMBOL_GPL(mm_iommu_ua_to_hpa);
353 
354 bool mm_iommu_is_devmem(struct mm_struct *mm, unsigned long hpa,
355 		unsigned int pageshift, unsigned long *size)
356 {
357 	struct mm_iommu_table_group_mem_t *mem;
358 	unsigned long end;
359 
360 	rcu_read_lock();
361 	list_for_each_entry_rcu(mem, &mm->context.iommu_group_mem_list, next) {
362 		if (mem->dev_hpa == MM_IOMMU_TABLE_INVALID_HPA)
363 			continue;
364 
365 		end = mem->dev_hpa + (mem->entries << PAGE_SHIFT);
366 		if ((mem->dev_hpa <= hpa) && (hpa < end)) {
367 			/*
368 			 * Since the IOMMU page size might be bigger than
369 			 * PAGE_SIZE, the amount of preregistered memory
370 			 * starting from @hpa might be smaller than 1<<pageshift
371 			 * and the caller needs to distinguish this situation.
372 			 */
373 			*size = min(1UL << pageshift, end - hpa);
374 			return true;
375 		}
376 	}
377 	rcu_read_unlock();
378 
379 	return false;
380 }
381 EXPORT_SYMBOL_GPL(mm_iommu_is_devmem);
382 
383 long mm_iommu_mapped_inc(struct mm_iommu_table_group_mem_t *mem)
384 {
385 	if (atomic64_inc_not_zero(&mem->mapped))
386 		return 0;
387 
388 	/* Last mm_iommu_put() has been called, no more mappings allowed() */
389 	return -ENXIO;
390 }
391 EXPORT_SYMBOL_GPL(mm_iommu_mapped_inc);
392 
393 void mm_iommu_mapped_dec(struct mm_iommu_table_group_mem_t *mem)
394 {
395 	atomic64_add_unless(&mem->mapped, -1, 1);
396 }
397 EXPORT_SYMBOL_GPL(mm_iommu_mapped_dec);
398 
399 void mm_iommu_init(struct mm_struct *mm)
400 {
401 	INIT_LIST_HEAD_RCU(&mm->context.iommu_group_mem_list);
402 }
403