1 // SPDX-License-Identifier: GPL-2.0
2 
3 /*
4  * Xen dma-buf functionality for gntdev.
5  *
6  * DMA buffer implementation is based on drivers/gpu/drm/drm_prime.c.
7  *
8  * Copyright (c) 2018 Oleksandr Andrushchenko, EPAM Systems Inc.
9  */
10 
11 #include <linux/kernel.h>
12 #include <linux/errno.h>
13 #include <linux/dma-buf.h>
14 #include <linux/dma-direct.h>
15 #include <linux/slab.h>
16 #include <linux/types.h>
17 #include <linux/uaccess.h>
18 #include <linux/module.h>
19 
20 #include <xen/xen.h>
21 #include <xen/grant_table.h>
22 
23 #include "gntdev-common.h"
24 #include "gntdev-dmabuf.h"
25 
26 MODULE_IMPORT_NS(DMA_BUF);
27 
28 struct gntdev_dmabuf {
29 	struct gntdev_dmabuf_priv *priv;
30 	struct dma_buf *dmabuf;
31 	struct list_head next;
32 	int fd;
33 
34 	union {
35 		struct {
36 			/* Exported buffers are reference counted. */
37 			struct kref refcount;
38 
39 			struct gntdev_priv *priv;
40 			struct gntdev_grant_map *map;
41 		} exp;
42 		struct {
43 			/* Granted references of the imported buffer. */
44 			grant_ref_t *refs;
45 			/* Scatter-gather table of the imported buffer. */
46 			struct sg_table *sgt;
47 			/* dma-buf attachment of the imported buffer. */
48 			struct dma_buf_attachment *attach;
49 		} imp;
50 	} u;
51 
52 	/* Number of pages this buffer has. */
53 	int nr_pages;
54 	/* Pages of this buffer (only for dma-buf export). */
55 	struct page **pages;
56 };
57 
58 struct gntdev_dmabuf_wait_obj {
59 	struct list_head next;
60 	struct gntdev_dmabuf *gntdev_dmabuf;
61 	struct completion completion;
62 };
63 
64 struct gntdev_dmabuf_attachment {
65 	struct sg_table *sgt;
66 	enum dma_data_direction dir;
67 };
68 
69 struct gntdev_dmabuf_priv {
70 	/* List of exported DMA buffers. */
71 	struct list_head exp_list;
72 	/* List of wait objects. */
73 	struct list_head exp_wait_list;
74 	/* List of imported DMA buffers. */
75 	struct list_head imp_list;
76 	/* This is the lock which protects dma_buf_xxx lists. */
77 	struct mutex lock;
78 	/*
79 	 * We reference this file while exporting dma-bufs, so
80 	 * the grant device context is not destroyed while there are
81 	 * external users alive.
82 	 */
83 	struct file *filp;
84 };
85 
86 /* DMA buffer export support. */
87 
88 /* Implementation of wait for exported DMA buffer to be released. */
89 
90 static void dmabuf_exp_release(struct kref *kref);
91 
92 static struct gntdev_dmabuf_wait_obj *
dmabuf_exp_wait_obj_new(struct gntdev_dmabuf_priv * priv,struct gntdev_dmabuf * gntdev_dmabuf)93 dmabuf_exp_wait_obj_new(struct gntdev_dmabuf_priv *priv,
94 			struct gntdev_dmabuf *gntdev_dmabuf)
95 {
96 	struct gntdev_dmabuf_wait_obj *obj;
97 
98 	obj = kzalloc(sizeof(*obj), GFP_KERNEL);
99 	if (!obj)
100 		return ERR_PTR(-ENOMEM);
101 
102 	init_completion(&obj->completion);
103 	obj->gntdev_dmabuf = gntdev_dmabuf;
104 
105 	mutex_lock(&priv->lock);
106 	list_add(&obj->next, &priv->exp_wait_list);
107 	/* Put our reference and wait for gntdev_dmabuf's release to fire. */
108 	kref_put(&gntdev_dmabuf->u.exp.refcount, dmabuf_exp_release);
109 	mutex_unlock(&priv->lock);
110 	return obj;
111 }
112 
dmabuf_exp_wait_obj_free(struct gntdev_dmabuf_priv * priv,struct gntdev_dmabuf_wait_obj * obj)113 static void dmabuf_exp_wait_obj_free(struct gntdev_dmabuf_priv *priv,
114 				     struct gntdev_dmabuf_wait_obj *obj)
115 {
116 	mutex_lock(&priv->lock);
117 	list_del(&obj->next);
118 	mutex_unlock(&priv->lock);
119 	kfree(obj);
120 }
121 
dmabuf_exp_wait_obj_wait(struct gntdev_dmabuf_wait_obj * obj,u32 wait_to_ms)122 static int dmabuf_exp_wait_obj_wait(struct gntdev_dmabuf_wait_obj *obj,
123 				    u32 wait_to_ms)
124 {
125 	if (wait_for_completion_timeout(&obj->completion,
126 			msecs_to_jiffies(wait_to_ms)) <= 0)
127 		return -ETIMEDOUT;
128 
129 	return 0;
130 }
131 
dmabuf_exp_wait_obj_signal(struct gntdev_dmabuf_priv * priv,struct gntdev_dmabuf * gntdev_dmabuf)132 static void dmabuf_exp_wait_obj_signal(struct gntdev_dmabuf_priv *priv,
133 				       struct gntdev_dmabuf *gntdev_dmabuf)
134 {
135 	struct gntdev_dmabuf_wait_obj *obj;
136 
137 	list_for_each_entry(obj, &priv->exp_wait_list, next)
138 		if (obj->gntdev_dmabuf == gntdev_dmabuf) {
139 			pr_debug("Found gntdev_dmabuf in the wait list, wake\n");
140 			complete_all(&obj->completion);
141 			break;
142 		}
143 }
144 
145 static struct gntdev_dmabuf *
dmabuf_exp_wait_obj_get_dmabuf(struct gntdev_dmabuf_priv * priv,int fd)146 dmabuf_exp_wait_obj_get_dmabuf(struct gntdev_dmabuf_priv *priv, int fd)
147 {
148 	struct gntdev_dmabuf *gntdev_dmabuf, *ret = ERR_PTR(-ENOENT);
149 
150 	mutex_lock(&priv->lock);
151 	list_for_each_entry(gntdev_dmabuf, &priv->exp_list, next)
152 		if (gntdev_dmabuf->fd == fd) {
153 			pr_debug("Found gntdev_dmabuf in the wait list\n");
154 			kref_get(&gntdev_dmabuf->u.exp.refcount);
155 			ret = gntdev_dmabuf;
156 			break;
157 		}
158 	mutex_unlock(&priv->lock);
159 	return ret;
160 }
161 
dmabuf_exp_wait_released(struct gntdev_dmabuf_priv * priv,int fd,int wait_to_ms)162 static int dmabuf_exp_wait_released(struct gntdev_dmabuf_priv *priv, int fd,
163 				    int wait_to_ms)
164 {
165 	struct gntdev_dmabuf *gntdev_dmabuf;
166 	struct gntdev_dmabuf_wait_obj *obj;
167 	int ret;
168 
169 	pr_debug("Will wait for dma-buf with fd %d\n", fd);
170 	/*
171 	 * Try to find the DMA buffer: if not found means that
172 	 * either the buffer has already been released or file descriptor
173 	 * provided is wrong.
174 	 */
175 	gntdev_dmabuf = dmabuf_exp_wait_obj_get_dmabuf(priv, fd);
176 	if (IS_ERR(gntdev_dmabuf))
177 		return PTR_ERR(gntdev_dmabuf);
178 
179 	/*
180 	 * gntdev_dmabuf still exists and is reference count locked by us now,
181 	 * so prepare to wait: allocate wait object and add it to the wait list,
182 	 * so we can find it on release.
183 	 */
184 	obj = dmabuf_exp_wait_obj_new(priv, gntdev_dmabuf);
185 	if (IS_ERR(obj))
186 		return PTR_ERR(obj);
187 
188 	ret = dmabuf_exp_wait_obj_wait(obj, wait_to_ms);
189 	dmabuf_exp_wait_obj_free(priv, obj);
190 	return ret;
191 }
192 
193 /* DMA buffer export support. */
194 
195 static struct sg_table *
dmabuf_pages_to_sgt(struct page ** pages,unsigned int nr_pages)196 dmabuf_pages_to_sgt(struct page **pages, unsigned int nr_pages)
197 {
198 	struct sg_table *sgt;
199 	int ret;
200 
201 	sgt = kmalloc(sizeof(*sgt), GFP_KERNEL);
202 	if (!sgt) {
203 		ret = -ENOMEM;
204 		goto out;
205 	}
206 
207 	ret = sg_alloc_table_from_pages(sgt, pages, nr_pages, 0,
208 					nr_pages << PAGE_SHIFT,
209 					GFP_KERNEL);
210 	if (ret)
211 		goto out;
212 
213 	return sgt;
214 
215 out:
216 	kfree(sgt);
217 	return ERR_PTR(ret);
218 }
219 
dmabuf_exp_ops_attach(struct dma_buf * dma_buf,struct dma_buf_attachment * attach)220 static int dmabuf_exp_ops_attach(struct dma_buf *dma_buf,
221 				 struct dma_buf_attachment *attach)
222 {
223 	struct gntdev_dmabuf_attachment *gntdev_dmabuf_attach;
224 
225 	gntdev_dmabuf_attach = kzalloc(sizeof(*gntdev_dmabuf_attach),
226 				       GFP_KERNEL);
227 	if (!gntdev_dmabuf_attach)
228 		return -ENOMEM;
229 
230 	gntdev_dmabuf_attach->dir = DMA_NONE;
231 	attach->priv = gntdev_dmabuf_attach;
232 	return 0;
233 }
234 
dmabuf_exp_ops_detach(struct dma_buf * dma_buf,struct dma_buf_attachment * attach)235 static void dmabuf_exp_ops_detach(struct dma_buf *dma_buf,
236 				  struct dma_buf_attachment *attach)
237 {
238 	struct gntdev_dmabuf_attachment *gntdev_dmabuf_attach = attach->priv;
239 
240 	if (gntdev_dmabuf_attach) {
241 		struct sg_table *sgt = gntdev_dmabuf_attach->sgt;
242 
243 		if (sgt) {
244 			if (gntdev_dmabuf_attach->dir != DMA_NONE)
245 				dma_unmap_sgtable(attach->dev, sgt,
246 						  gntdev_dmabuf_attach->dir,
247 						  DMA_ATTR_SKIP_CPU_SYNC);
248 			sg_free_table(sgt);
249 		}
250 
251 		kfree(sgt);
252 		kfree(gntdev_dmabuf_attach);
253 		attach->priv = NULL;
254 	}
255 }
256 
257 static struct sg_table *
dmabuf_exp_ops_map_dma_buf(struct dma_buf_attachment * attach,enum dma_data_direction dir)258 dmabuf_exp_ops_map_dma_buf(struct dma_buf_attachment *attach,
259 			   enum dma_data_direction dir)
260 {
261 	struct gntdev_dmabuf_attachment *gntdev_dmabuf_attach = attach->priv;
262 	struct gntdev_dmabuf *gntdev_dmabuf = attach->dmabuf->priv;
263 	struct sg_table *sgt;
264 
265 	pr_debug("Mapping %d pages for dev %p\n", gntdev_dmabuf->nr_pages,
266 		 attach->dev);
267 
268 	if (dir == DMA_NONE || !gntdev_dmabuf_attach)
269 		return ERR_PTR(-EINVAL);
270 
271 	/* Return the cached mapping when possible. */
272 	if (gntdev_dmabuf_attach->dir == dir)
273 		return gntdev_dmabuf_attach->sgt;
274 
275 	/*
276 	 * Two mappings with different directions for the same attachment are
277 	 * not allowed.
278 	 */
279 	if (gntdev_dmabuf_attach->dir != DMA_NONE)
280 		return ERR_PTR(-EBUSY);
281 
282 	sgt = dmabuf_pages_to_sgt(gntdev_dmabuf->pages,
283 				  gntdev_dmabuf->nr_pages);
284 	if (!IS_ERR(sgt)) {
285 		if (dma_map_sgtable(attach->dev, sgt, dir,
286 				    DMA_ATTR_SKIP_CPU_SYNC)) {
287 			sg_free_table(sgt);
288 			kfree(sgt);
289 			sgt = ERR_PTR(-ENOMEM);
290 		} else {
291 			gntdev_dmabuf_attach->sgt = sgt;
292 			gntdev_dmabuf_attach->dir = dir;
293 		}
294 	}
295 	if (IS_ERR(sgt))
296 		pr_debug("Failed to map sg table for dev %p\n", attach->dev);
297 	return sgt;
298 }
299 
dmabuf_exp_ops_unmap_dma_buf(struct dma_buf_attachment * attach,struct sg_table * sgt,enum dma_data_direction dir)300 static void dmabuf_exp_ops_unmap_dma_buf(struct dma_buf_attachment *attach,
301 					 struct sg_table *sgt,
302 					 enum dma_data_direction dir)
303 {
304 	/* Not implemented. The unmap is done at dmabuf_exp_ops_detach(). */
305 }
306 
dmabuf_exp_release(struct kref * kref)307 static void dmabuf_exp_release(struct kref *kref)
308 {
309 	struct gntdev_dmabuf *gntdev_dmabuf =
310 		container_of(kref, struct gntdev_dmabuf, u.exp.refcount);
311 
312 	dmabuf_exp_wait_obj_signal(gntdev_dmabuf->priv, gntdev_dmabuf);
313 	list_del(&gntdev_dmabuf->next);
314 	fput(gntdev_dmabuf->priv->filp);
315 	kfree(gntdev_dmabuf);
316 }
317 
dmabuf_exp_remove_map(struct gntdev_priv * priv,struct gntdev_grant_map * map)318 static void dmabuf_exp_remove_map(struct gntdev_priv *priv,
319 				  struct gntdev_grant_map *map)
320 {
321 	mutex_lock(&priv->lock);
322 	list_del(&map->next);
323 	gntdev_put_map(NULL /* already removed */, map);
324 	mutex_unlock(&priv->lock);
325 }
326 
dmabuf_exp_ops_release(struct dma_buf * dma_buf)327 static void dmabuf_exp_ops_release(struct dma_buf *dma_buf)
328 {
329 	struct gntdev_dmabuf *gntdev_dmabuf = dma_buf->priv;
330 	struct gntdev_dmabuf_priv *priv = gntdev_dmabuf->priv;
331 
332 	dmabuf_exp_remove_map(gntdev_dmabuf->u.exp.priv,
333 			      gntdev_dmabuf->u.exp.map);
334 	mutex_lock(&priv->lock);
335 	kref_put(&gntdev_dmabuf->u.exp.refcount, dmabuf_exp_release);
336 	mutex_unlock(&priv->lock);
337 }
338 
339 static const struct dma_buf_ops dmabuf_exp_ops =  {
340 	.attach = dmabuf_exp_ops_attach,
341 	.detach = dmabuf_exp_ops_detach,
342 	.map_dma_buf = dmabuf_exp_ops_map_dma_buf,
343 	.unmap_dma_buf = dmabuf_exp_ops_unmap_dma_buf,
344 	.release = dmabuf_exp_ops_release,
345 };
346 
347 struct gntdev_dmabuf_export_args {
348 	struct gntdev_priv *priv;
349 	struct gntdev_grant_map *map;
350 	struct gntdev_dmabuf_priv *dmabuf_priv;
351 	struct device *dev;
352 	int count;
353 	struct page **pages;
354 	u32 fd;
355 };
356 
dmabuf_exp_from_pages(struct gntdev_dmabuf_export_args * args)357 static int dmabuf_exp_from_pages(struct gntdev_dmabuf_export_args *args)
358 {
359 	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
360 	struct gntdev_dmabuf *gntdev_dmabuf;
361 	int ret;
362 
363 	gntdev_dmabuf = kzalloc(sizeof(*gntdev_dmabuf), GFP_KERNEL);
364 	if (!gntdev_dmabuf)
365 		return -ENOMEM;
366 
367 	kref_init(&gntdev_dmabuf->u.exp.refcount);
368 
369 	gntdev_dmabuf->priv = args->dmabuf_priv;
370 	gntdev_dmabuf->nr_pages = args->count;
371 	gntdev_dmabuf->pages = args->pages;
372 	gntdev_dmabuf->u.exp.priv = args->priv;
373 	gntdev_dmabuf->u.exp.map = args->map;
374 
375 	exp_info.exp_name = KBUILD_MODNAME;
376 	if (args->dev->driver && args->dev->driver->owner)
377 		exp_info.owner = args->dev->driver->owner;
378 	else
379 		exp_info.owner = THIS_MODULE;
380 	exp_info.ops = &dmabuf_exp_ops;
381 	exp_info.size = args->count << PAGE_SHIFT;
382 	exp_info.flags = O_RDWR;
383 	exp_info.priv = gntdev_dmabuf;
384 
385 	gntdev_dmabuf->dmabuf = dma_buf_export(&exp_info);
386 	if (IS_ERR(gntdev_dmabuf->dmabuf)) {
387 		ret = PTR_ERR(gntdev_dmabuf->dmabuf);
388 		gntdev_dmabuf->dmabuf = NULL;
389 		goto fail;
390 	}
391 
392 	ret = dma_buf_fd(gntdev_dmabuf->dmabuf, O_CLOEXEC);
393 	if (ret < 0)
394 		goto fail;
395 
396 	gntdev_dmabuf->fd = ret;
397 	args->fd = ret;
398 
399 	pr_debug("Exporting DMA buffer with fd %d\n", ret);
400 
401 	mutex_lock(&args->dmabuf_priv->lock);
402 	list_add(&gntdev_dmabuf->next, &args->dmabuf_priv->exp_list);
403 	mutex_unlock(&args->dmabuf_priv->lock);
404 	get_file(gntdev_dmabuf->priv->filp);
405 	return 0;
406 
407 fail:
408 	if (gntdev_dmabuf->dmabuf)
409 		dma_buf_put(gntdev_dmabuf->dmabuf);
410 	kfree(gntdev_dmabuf);
411 	return ret;
412 }
413 
414 static struct gntdev_grant_map *
dmabuf_exp_alloc_backing_storage(struct gntdev_priv * priv,int dmabuf_flags,int count)415 dmabuf_exp_alloc_backing_storage(struct gntdev_priv *priv, int dmabuf_flags,
416 				 int count)
417 {
418 	struct gntdev_grant_map *map;
419 
420 	if (unlikely(gntdev_test_page_count(count)))
421 		return ERR_PTR(-EINVAL);
422 
423 	if ((dmabuf_flags & GNTDEV_DMA_FLAG_WC) &&
424 	    (dmabuf_flags & GNTDEV_DMA_FLAG_COHERENT)) {
425 		pr_debug("Wrong dma-buf flags: 0x%x\n", dmabuf_flags);
426 		return ERR_PTR(-EINVAL);
427 	}
428 
429 	map = gntdev_alloc_map(priv, count, dmabuf_flags);
430 	if (!map)
431 		return ERR_PTR(-ENOMEM);
432 
433 	return map;
434 }
435 
dmabuf_exp_from_refs(struct gntdev_priv * priv,int flags,int count,u32 domid,u32 * refs,u32 * fd)436 static int dmabuf_exp_from_refs(struct gntdev_priv *priv, int flags,
437 				int count, u32 domid, u32 *refs, u32 *fd)
438 {
439 	struct gntdev_grant_map *map;
440 	struct gntdev_dmabuf_export_args args;
441 	int i, ret;
442 
443 	map = dmabuf_exp_alloc_backing_storage(priv, flags, count);
444 	if (IS_ERR(map))
445 		return PTR_ERR(map);
446 
447 	for (i = 0; i < count; i++) {
448 		map->grants[i].domid = domid;
449 		map->grants[i].ref = refs[i];
450 	}
451 
452 	mutex_lock(&priv->lock);
453 	gntdev_add_map(priv, map);
454 	mutex_unlock(&priv->lock);
455 
456 	map->flags |= GNTMAP_host_map;
457 #if defined(CONFIG_X86)
458 	map->flags |= GNTMAP_device_map;
459 #endif
460 
461 	ret = gntdev_map_grant_pages(map);
462 	if (ret < 0)
463 		goto out;
464 
465 	args.priv = priv;
466 	args.map = map;
467 	args.dev = priv->dma_dev;
468 	args.dmabuf_priv = priv->dmabuf_priv;
469 	args.count = map->count;
470 	args.pages = map->pages;
471 	args.fd = -1; /* Shut up unnecessary gcc warning for i386 */
472 
473 	ret = dmabuf_exp_from_pages(&args);
474 	if (ret < 0)
475 		goto out;
476 
477 	*fd = args.fd;
478 	return 0;
479 
480 out:
481 	dmabuf_exp_remove_map(priv, map);
482 	return ret;
483 }
484 
485 /* DMA buffer import support. */
486 
487 static int
dmabuf_imp_grant_foreign_access(unsigned long * gfns,u32 * refs,int count,int domid)488 dmabuf_imp_grant_foreign_access(unsigned long *gfns, u32 *refs,
489 				int count, int domid)
490 {
491 	grant_ref_t priv_gref_head;
492 	int i, ret;
493 
494 	ret = gnttab_alloc_grant_references(count, &priv_gref_head);
495 	if (ret < 0) {
496 		pr_debug("Cannot allocate grant references, ret %d\n", ret);
497 		return ret;
498 	}
499 
500 	for (i = 0; i < count; i++) {
501 		int cur_ref;
502 
503 		cur_ref = gnttab_claim_grant_reference(&priv_gref_head);
504 		if (cur_ref < 0) {
505 			ret = cur_ref;
506 			pr_debug("Cannot claim grant reference, ret %d\n", ret);
507 			goto out;
508 		}
509 
510 		gnttab_grant_foreign_access_ref(cur_ref, domid,
511 						gfns[i], 0);
512 		refs[i] = cur_ref;
513 	}
514 
515 	return 0;
516 
517 out:
518 	gnttab_free_grant_references(priv_gref_head);
519 	return ret;
520 }
521 
dmabuf_imp_end_foreign_access(u32 * refs,int count)522 static void dmabuf_imp_end_foreign_access(u32 *refs, int count)
523 {
524 	int i;
525 
526 	for (i = 0; i < count; i++)
527 		if (refs[i] != INVALID_GRANT_REF)
528 			gnttab_end_foreign_access(refs[i], NULL);
529 }
530 
dmabuf_imp_free_storage(struct gntdev_dmabuf * gntdev_dmabuf)531 static void dmabuf_imp_free_storage(struct gntdev_dmabuf *gntdev_dmabuf)
532 {
533 	kfree(gntdev_dmabuf->u.imp.refs);
534 	kfree(gntdev_dmabuf);
535 }
536 
dmabuf_imp_alloc_storage(int count)537 static struct gntdev_dmabuf *dmabuf_imp_alloc_storage(int count)
538 {
539 	struct gntdev_dmabuf *gntdev_dmabuf;
540 	int i;
541 
542 	gntdev_dmabuf = kzalloc(sizeof(*gntdev_dmabuf), GFP_KERNEL);
543 	if (!gntdev_dmabuf)
544 		goto fail_no_free;
545 
546 	gntdev_dmabuf->u.imp.refs = kcalloc(count,
547 					    sizeof(gntdev_dmabuf->u.imp.refs[0]),
548 					    GFP_KERNEL);
549 	if (!gntdev_dmabuf->u.imp.refs)
550 		goto fail;
551 
552 	gntdev_dmabuf->nr_pages = count;
553 
554 	for (i = 0; i < count; i++)
555 		gntdev_dmabuf->u.imp.refs[i] = INVALID_GRANT_REF;
556 
557 	return gntdev_dmabuf;
558 
559 fail:
560 	dmabuf_imp_free_storage(gntdev_dmabuf);
561 fail_no_free:
562 	return ERR_PTR(-ENOMEM);
563 }
564 
565 static struct gntdev_dmabuf *
dmabuf_imp_to_refs(struct gntdev_dmabuf_priv * priv,struct device * dev,int fd,int count,int domid)566 dmabuf_imp_to_refs(struct gntdev_dmabuf_priv *priv, struct device *dev,
567 		   int fd, int count, int domid)
568 {
569 	struct gntdev_dmabuf *gntdev_dmabuf, *ret;
570 	struct dma_buf *dma_buf;
571 	struct dma_buf_attachment *attach;
572 	struct sg_table *sgt;
573 	struct sg_dma_page_iter sg_iter;
574 	unsigned long *gfns;
575 	int i;
576 
577 	dma_buf = dma_buf_get(fd);
578 	if (IS_ERR(dma_buf))
579 		return ERR_CAST(dma_buf);
580 
581 	gntdev_dmabuf = dmabuf_imp_alloc_storage(count);
582 	if (IS_ERR(gntdev_dmabuf)) {
583 		ret = gntdev_dmabuf;
584 		goto fail_put;
585 	}
586 
587 	gntdev_dmabuf->priv = priv;
588 	gntdev_dmabuf->fd = fd;
589 
590 	attach = dma_buf_attach(dma_buf, dev);
591 	if (IS_ERR(attach)) {
592 		ret = ERR_CAST(attach);
593 		goto fail_free_obj;
594 	}
595 
596 	gntdev_dmabuf->u.imp.attach = attach;
597 
598 	sgt = dma_buf_map_attachment_unlocked(attach, DMA_BIDIRECTIONAL);
599 	if (IS_ERR(sgt)) {
600 		ret = ERR_CAST(sgt);
601 		goto fail_detach;
602 	}
603 
604 	/* Check that we have zero offset. */
605 	if (sgt->sgl->offset) {
606 		ret = ERR_PTR(-EINVAL);
607 		pr_debug("DMA buffer has %d bytes offset, user-space expects 0\n",
608 			 sgt->sgl->offset);
609 		goto fail_unmap;
610 	}
611 
612 	/* Check number of pages that imported buffer has. */
613 	if (attach->dmabuf->size != gntdev_dmabuf->nr_pages << PAGE_SHIFT) {
614 		ret = ERR_PTR(-EINVAL);
615 		pr_debug("DMA buffer has %zu pages, user-space expects %d\n",
616 			 attach->dmabuf->size, gntdev_dmabuf->nr_pages);
617 		goto fail_unmap;
618 	}
619 
620 	gntdev_dmabuf->u.imp.sgt = sgt;
621 
622 	gfns = kcalloc(count, sizeof(*gfns), GFP_KERNEL);
623 	if (!gfns) {
624 		ret = ERR_PTR(-ENOMEM);
625 		goto fail_unmap;
626 	}
627 
628 	/*
629 	 * Now convert sgt to array of gfns without accessing underlying pages.
630 	 * It is not allowed to access the underlying struct page of an sg table
631 	 * exported by DMA-buf, but since we deal with special Xen dma device here
632 	 * (not a normal physical one) look at the dma addresses in the sg table
633 	 * and then calculate gfns directly from them.
634 	 */
635 	i = 0;
636 	for_each_sgtable_dma_page(sgt, &sg_iter, 0) {
637 		dma_addr_t addr = sg_page_iter_dma_address(&sg_iter);
638 		unsigned long pfn = bfn_to_pfn(XEN_PFN_DOWN(dma_to_phys(dev, addr)));
639 
640 		gfns[i++] = pfn_to_gfn(pfn);
641 	}
642 
643 	ret = ERR_PTR(dmabuf_imp_grant_foreign_access(gfns,
644 						      gntdev_dmabuf->u.imp.refs,
645 						      count, domid));
646 	kfree(gfns);
647 	if (IS_ERR(ret))
648 		goto fail_end_access;
649 
650 	pr_debug("Imported DMA buffer with fd %d\n", fd);
651 
652 	mutex_lock(&priv->lock);
653 	list_add(&gntdev_dmabuf->next, &priv->imp_list);
654 	mutex_unlock(&priv->lock);
655 
656 	return gntdev_dmabuf;
657 
658 fail_end_access:
659 	dmabuf_imp_end_foreign_access(gntdev_dmabuf->u.imp.refs, count);
660 fail_unmap:
661 	dma_buf_unmap_attachment_unlocked(attach, sgt, DMA_BIDIRECTIONAL);
662 fail_detach:
663 	dma_buf_detach(dma_buf, attach);
664 fail_free_obj:
665 	dmabuf_imp_free_storage(gntdev_dmabuf);
666 fail_put:
667 	dma_buf_put(dma_buf);
668 	return ret;
669 }
670 
671 /*
672  * Find the hyper dma-buf by its file descriptor and remove
673  * it from the buffer's list.
674  */
675 static struct gntdev_dmabuf *
dmabuf_imp_find_unlink(struct gntdev_dmabuf_priv * priv,int fd)676 dmabuf_imp_find_unlink(struct gntdev_dmabuf_priv *priv, int fd)
677 {
678 	struct gntdev_dmabuf *q, *gntdev_dmabuf, *ret = ERR_PTR(-ENOENT);
679 
680 	mutex_lock(&priv->lock);
681 	list_for_each_entry_safe(gntdev_dmabuf, q, &priv->imp_list, next) {
682 		if (gntdev_dmabuf->fd == fd) {
683 			pr_debug("Found gntdev_dmabuf in the import list\n");
684 			ret = gntdev_dmabuf;
685 			list_del(&gntdev_dmabuf->next);
686 			break;
687 		}
688 	}
689 	mutex_unlock(&priv->lock);
690 	return ret;
691 }
692 
dmabuf_imp_release(struct gntdev_dmabuf_priv * priv,u32 fd)693 static int dmabuf_imp_release(struct gntdev_dmabuf_priv *priv, u32 fd)
694 {
695 	struct gntdev_dmabuf *gntdev_dmabuf;
696 	struct dma_buf_attachment *attach;
697 	struct dma_buf *dma_buf;
698 
699 	gntdev_dmabuf = dmabuf_imp_find_unlink(priv, fd);
700 	if (IS_ERR(gntdev_dmabuf))
701 		return PTR_ERR(gntdev_dmabuf);
702 
703 	pr_debug("Releasing DMA buffer with fd %d\n", fd);
704 
705 	dmabuf_imp_end_foreign_access(gntdev_dmabuf->u.imp.refs,
706 				      gntdev_dmabuf->nr_pages);
707 
708 	attach = gntdev_dmabuf->u.imp.attach;
709 
710 	if (gntdev_dmabuf->u.imp.sgt)
711 		dma_buf_unmap_attachment_unlocked(attach, gntdev_dmabuf->u.imp.sgt,
712 						  DMA_BIDIRECTIONAL);
713 	dma_buf = attach->dmabuf;
714 	dma_buf_detach(attach->dmabuf, attach);
715 	dma_buf_put(dma_buf);
716 
717 	dmabuf_imp_free_storage(gntdev_dmabuf);
718 	return 0;
719 }
720 
dmabuf_imp_release_all(struct gntdev_dmabuf_priv * priv)721 static void dmabuf_imp_release_all(struct gntdev_dmabuf_priv *priv)
722 {
723 	struct gntdev_dmabuf *q, *gntdev_dmabuf;
724 
725 	list_for_each_entry_safe(gntdev_dmabuf, q, &priv->imp_list, next)
726 		dmabuf_imp_release(priv, gntdev_dmabuf->fd);
727 }
728 
729 /* DMA buffer IOCTL support. */
730 
gntdev_ioctl_dmabuf_exp_from_refs(struct gntdev_priv * priv,int use_ptemod,struct ioctl_gntdev_dmabuf_exp_from_refs __user * u)731 long gntdev_ioctl_dmabuf_exp_from_refs(struct gntdev_priv *priv, int use_ptemod,
732 				       struct ioctl_gntdev_dmabuf_exp_from_refs __user *u)
733 {
734 	struct ioctl_gntdev_dmabuf_exp_from_refs op;
735 	u32 *refs;
736 	long ret;
737 
738 	if (use_ptemod) {
739 		pr_debug("Cannot provide dma-buf: use_ptemode %d\n",
740 			 use_ptemod);
741 		return -EINVAL;
742 	}
743 
744 	if (copy_from_user(&op, u, sizeof(op)) != 0)
745 		return -EFAULT;
746 
747 	if (unlikely(gntdev_test_page_count(op.count)))
748 		return -EINVAL;
749 
750 	refs = kcalloc(op.count, sizeof(*refs), GFP_KERNEL);
751 	if (!refs)
752 		return -ENOMEM;
753 
754 	if (copy_from_user(refs, u->refs, sizeof(*refs) * op.count) != 0) {
755 		ret = -EFAULT;
756 		goto out;
757 	}
758 
759 	ret = dmabuf_exp_from_refs(priv, op.flags, op.count,
760 				   op.domid, refs, &op.fd);
761 	if (ret)
762 		goto out;
763 
764 	if (copy_to_user(u, &op, sizeof(op)) != 0)
765 		ret = -EFAULT;
766 
767 out:
768 	kfree(refs);
769 	return ret;
770 }
771 
gntdev_ioctl_dmabuf_exp_wait_released(struct gntdev_priv * priv,struct ioctl_gntdev_dmabuf_exp_wait_released __user * u)772 long gntdev_ioctl_dmabuf_exp_wait_released(struct gntdev_priv *priv,
773 					   struct ioctl_gntdev_dmabuf_exp_wait_released __user *u)
774 {
775 	struct ioctl_gntdev_dmabuf_exp_wait_released op;
776 
777 	if (copy_from_user(&op, u, sizeof(op)) != 0)
778 		return -EFAULT;
779 
780 	return dmabuf_exp_wait_released(priv->dmabuf_priv, op.fd,
781 					op.wait_to_ms);
782 }
783 
gntdev_ioctl_dmabuf_imp_to_refs(struct gntdev_priv * priv,struct ioctl_gntdev_dmabuf_imp_to_refs __user * u)784 long gntdev_ioctl_dmabuf_imp_to_refs(struct gntdev_priv *priv,
785 				     struct ioctl_gntdev_dmabuf_imp_to_refs __user *u)
786 {
787 	struct ioctl_gntdev_dmabuf_imp_to_refs op;
788 	struct gntdev_dmabuf *gntdev_dmabuf;
789 	long ret;
790 
791 	if (copy_from_user(&op, u, sizeof(op)) != 0)
792 		return -EFAULT;
793 
794 	if (unlikely(gntdev_test_page_count(op.count)))
795 		return -EINVAL;
796 
797 	gntdev_dmabuf = dmabuf_imp_to_refs(priv->dmabuf_priv,
798 					   priv->dma_dev, op.fd,
799 					   op.count, op.domid);
800 	if (IS_ERR(gntdev_dmabuf))
801 		return PTR_ERR(gntdev_dmabuf);
802 
803 	if (copy_to_user(u->refs, gntdev_dmabuf->u.imp.refs,
804 			 sizeof(*u->refs) * op.count) != 0) {
805 		ret = -EFAULT;
806 		goto out_release;
807 	}
808 	return 0;
809 
810 out_release:
811 	dmabuf_imp_release(priv->dmabuf_priv, op.fd);
812 	return ret;
813 }
814 
gntdev_ioctl_dmabuf_imp_release(struct gntdev_priv * priv,struct ioctl_gntdev_dmabuf_imp_release __user * u)815 long gntdev_ioctl_dmabuf_imp_release(struct gntdev_priv *priv,
816 				     struct ioctl_gntdev_dmabuf_imp_release __user *u)
817 {
818 	struct ioctl_gntdev_dmabuf_imp_release op;
819 
820 	if (copy_from_user(&op, u, sizeof(op)) != 0)
821 		return -EFAULT;
822 
823 	return dmabuf_imp_release(priv->dmabuf_priv, op.fd);
824 }
825 
gntdev_dmabuf_init(struct file * filp)826 struct gntdev_dmabuf_priv *gntdev_dmabuf_init(struct file *filp)
827 {
828 	struct gntdev_dmabuf_priv *priv;
829 
830 	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
831 	if (!priv)
832 		return ERR_PTR(-ENOMEM);
833 
834 	mutex_init(&priv->lock);
835 	INIT_LIST_HEAD(&priv->exp_list);
836 	INIT_LIST_HEAD(&priv->exp_wait_list);
837 	INIT_LIST_HEAD(&priv->imp_list);
838 
839 	priv->filp = filp;
840 
841 	return priv;
842 }
843 
gntdev_dmabuf_fini(struct gntdev_dmabuf_priv * priv)844 void gntdev_dmabuf_fini(struct gntdev_dmabuf_priv *priv)
845 {
846 	dmabuf_imp_release_all(priv);
847 	kfree(priv);
848 }
849