summaryrefslogtreecommitdiffstats
path: root/drivers/iommu/iommufd/main.c
blob: fe98912bab0e022758f3fd8c720bf04ec7cf4291 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (C) 2021 Intel Corporation
 * Copyright (c) 2021-2022, NVIDIA CORPORATION & AFFILIATES
 *
 * iommufd provides control over the IOMMU HW objects created by IOMMU kernel
 * drivers. IOMMU HW objects revolve around IO page tables that map incoming DMA
 * addresses (IOVA) to CPU addresses.
 */
#define pr_fmt(fmt) "iommufd: " fmt

#include <linux/file.h>
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/miscdevice.h>
#include <linux/mutex.h>
#include <linux/bug.h>
#include <uapi/linux/iommufd.h>
#include <linux/iommufd.h>

#include "iommufd_private.h"

struct iommufd_object_ops {
	void (*destroy)(struct iommufd_object *obj);
};
static const struct iommufd_object_ops iommufd_object_ops[];

struct iommufd_object *_iommufd_object_alloc(struct iommufd_ctx *ictx,
					     size_t size,
					     enum iommufd_object_type type)
{
	struct iommufd_object *obj;
	int rc;

	obj = kzalloc(size, GFP_KERNEL_ACCOUNT);
	if (!obj)
		return ERR_PTR(-ENOMEM);
	obj->type = type;
	init_rwsem(&obj->destroy_rwsem);
	refcount_set(&obj->users, 1);

	/*
	 * Reserve an ID in the xarray but do not publish the pointer yet since
	 * the caller hasn't initialized it yet. Once the pointer is published
	 * in the xarray and visible to other threads we can't reliably destroy
	 * it anymore, so the caller must complete all errorable operations
	 * before calling iommufd_object_finalize().
	 */
	rc = xa_alloc(&ictx->objects, &obj->id, XA_ZERO_ENTRY,
		      xa_limit_32b, GFP_KERNEL_ACCOUNT);
	if (rc)
		goto out_free;
	return obj;
out_free:
	kfree(obj);
	return ERR_PTR(rc);
}

/*
 * Allow concurrent access to the object.
 *
 * Once another thread can see the object pointer it can prevent object
 * destruction. Expect for special kernel-only objects there is no in-kernel way
 * to reliably destroy a single object. Thus all APIs that are creating objects
 * must use iommufd_object_abort() to handle their errors and only call
 * iommufd_object_finalize() once object creation cannot fail.
 */
void iommufd_object_finalize(struct iommufd_ctx *ictx,
			     struct iommufd_object *obj)
{
	void *old;

	old = xa_store(&ictx->objects, obj->id, obj, GFP_KERNEL);
	/* obj->id was returned from xa_alloc() so the xa_store() cannot fail */
	WARN_ON(old);
}

/* Undo _iommufd_object_alloc() if iommufd_object_finalize() was not called */
void iommufd_object_abort(struct iommufd_ctx *ictx, struct iommufd_object *obj)
{
	void *old;

	old = xa_erase(&ictx->objects, obj->id);
	WARN_ON(old);
	kfree(obj);
}

/*
 * Abort an object that has been fully initialized and needs destroy, but has
 * not been finalized.
 */
void iommufd_object_abort_and_destroy(struct iommufd_ctx *ictx,
				      struct iommufd_object *obj)
{
	iommufd_object_ops[obj->type].destroy(obj);
	iommufd_object_abort(ictx, obj);
}

struct iommufd_object *iommufd_get_object(struct iommufd_ctx *ictx, u32 id,
					  enum iommufd_object_type type)
{
	struct iommufd_object *obj;

	xa_lock(&ictx->objects);
	obj = xa_load(&ictx->objects, id);
	if (!obj || (type != IOMMUFD_OBJ_ANY && obj->type != type) ||
	    !iommufd_lock_obj(obj))
		obj = ERR_PTR(-ENOENT);
	xa_unlock(&ictx->objects);
	return obj;
}

/*
 * The caller holds a users refcount and wants to destroy the object. Returns
 * true if the object was destroyed. In all cases the caller no longer has a
 * reference on obj.
 */
bool iommufd_object_destroy_user(struct iommufd_ctx *ictx,
				 struct iommufd_object *obj)
{
	/*
	 * The purpose of the destroy_rwsem is to ensure deterministic
	 * destruction of objects used by external drivers and destroyed by this
	 * function. Any temporary increment of the refcount must hold the read
	 * side of this, such as during ioctl execution.
	 */
	down_write(&obj->destroy_rwsem);
	xa_lock(&ictx->objects);
	refcount_dec(&obj->users);
	if (!refcount_dec_if_one(&obj->users)) {
		xa_unlock(&ictx->objects);
		up_write(&obj->destroy_rwsem);
		return false;
	}
	__xa_erase(&ictx->objects, obj->id);
	xa_unlock(&ictx->objects);
	up_write(&obj->destroy_rwsem);

	iommufd_object_ops[obj->type].destroy(obj);
	kfree(obj);
	return true;
}

static int iommufd_destroy(struct iommufd_ucmd *ucmd)
{
	struct iommu_destroy *cmd = ucmd->cmd;
	struct iommufd_object *obj;

	obj = iommufd_get_object(ucmd->ictx, cmd->id, IOMMUFD_OBJ_ANY);
	if (IS_ERR(obj))
		return PTR_ERR(obj);
	iommufd_ref_to_users(obj);
	/* See iommufd_ref_to_users() */
	if (!iommufd_object_destroy_user(ucmd->ictx, obj))
		return -EBUSY;
	return 0;
}

static int iommufd_fops_open(struct inode *inode, struct file *filp)
{
	struct iommufd_ctx *ictx;

	ictx = kzalloc(sizeof(*ictx), GFP_KERNEL_ACCOUNT);
	if (!ictx)
		return -ENOMEM;

	xa_init_flags(&ictx->objects, XA_FLAGS_ALLOC1 | XA_FLAGS_ACCOUNT);
	ictx->file = filp;
	filp->private_data = ictx;
	return 0;
}

static int iommufd_fops_release(struct inode *inode, struct file *filp)
{
	struct iommufd_ctx *ictx = filp->private_data;
	struct iommufd_object *obj;

	/*
	 * The objects in the xarray form a graph of "users" counts, and we have
	 * to destroy them in a depth first manner. Leaf objects will reduce the
	 * users count of interior objects when they are destroyed.
	 *
	 * Repeatedly destroying all the "1 users" leaf objects will progress
	 * until the entire list is destroyed. If this can't progress then there
	 * is some bug related to object refcounting.
	 */
	while (!xa_empty(&ictx->objects)) {
		unsigned int destroyed = 0;
		unsigned long index;

		xa_for_each(&ictx->objects, index, obj) {
			if (!refcount_dec_if_one(&obj->users))
				continue;
			destroyed++;
			xa_erase(&ictx->objects, index);
			iommufd_object_ops[obj->type].destroy(obj);
			kfree(obj);
		}
		/* Bug related to users refcount */
		if (WARN_ON(!destroyed))
			break;
	}
	kfree(ictx);
	return 0;
}

static int iommufd_option(struct iommufd_ucmd *ucmd)
{
	struct iommu_option *cmd = ucmd->cmd;
	int rc;

	if (cmd->__reserved)
		return -EOPNOTSUPP;

	switch (cmd->option_id) {
	case IOMMU_OPTION_RLIMIT_MODE:
		rc = iommufd_option_rlimit_mode(cmd, ucmd->ictx);
		break;
	case IOMMU_OPTION_HUGE_PAGES:
		rc = iommufd_ioas_option(ucmd);
		break;
	default:
		return -EOPNOTSUPP;
	}
	if (rc)
		return rc;
	if (copy_to_user(&((struct iommu_option __user *)ucmd->ubuffer)->val64,
			 &cmd->val64, sizeof(cmd->val64)))
		return -EFAULT;
	return 0;
}

union ucmd_buffer {
	struct iommu_destroy destroy;
	struct iommu_ioas_alloc alloc;
	struct iommu_ioas_allow_iovas allow_iovas;
	struct iommu_ioas_iova_ranges iova_ranges;
	struct iommu_ioas_map map;
	struct iommu_ioas_unmap unmap;
};

struct iommufd_ioctl_op {
	unsigned int size;
	unsigned int min_size;
	unsigned int ioctl_num;
	int (*execute)(struct iommufd_ucmd *ucmd);
};

#define IOCTL_OP(_ioctl, _fn, _struct, _last)                                  \
	[_IOC_NR(_ioctl) - IOMMUFD_CMD_BASE] = {                               \
		.size = sizeof(_struct) +                                      \
			BUILD_BUG_ON_ZERO(sizeof(union ucmd_buffer) <          \
					  sizeof(_struct)),                    \
		.min_size = offsetofend(_struct, _last),                       \
		.ioctl_num = _ioctl,                                           \
		.execute = _fn,                                                \
	}
static const struct iommufd_ioctl_op iommufd_ioctl_ops[] = {
	IOCTL_OP(IOMMU_DESTROY, iommufd_destroy, struct iommu_destroy, id),
	IOCTL_OP(IOMMU_IOAS_ALLOC, iommufd_ioas_alloc_ioctl,
		 struct iommu_ioas_alloc, out_ioas_id),
	IOCTL_OP(IOMMU_IOAS_ALLOW_IOVAS, iommufd_ioas_allow_iovas,
		 struct iommu_ioas_allow_iovas, allowed_iovas),
	IOCTL_OP(IOMMU_IOAS_COPY, iommufd_ioas_copy, struct iommu_ioas_copy,
		 src_iova),
	IOCTL_OP(IOMMU_IOAS_IOVA_RANGES, iommufd_ioas_iova_ranges,
		 struct iommu_ioas_iova_ranges, out_iova_alignment),
	IOCTL_OP(IOMMU_IOAS_MAP, iommufd_ioas_map, struct iommu_ioas_map,
		 iova),
	IOCTL_OP(IOMMU_IOAS_UNMAP, iommufd_ioas_unmap, struct iommu_ioas_unmap,
		 length),
	IOCTL_OP(IOMMU_OPTION, iommufd_option, struct iommu_option,
		 val64),
};

static long iommufd_fops_ioctl(struct file *filp, unsigned int cmd,
			       unsigned long arg)
{
	const struct iommufd_ioctl_op *op;
	struct iommufd_ucmd ucmd = {};
	union ucmd_buffer buf;
	unsigned int nr;
	int ret;

	ucmd.ictx = filp->private_data;
	ucmd.ubuffer = (void __user *)arg;
	ret = get_user(ucmd.user_size, (u32 __user *)ucmd.ubuffer);
	if (ret)
		return ret;

	nr = _IOC_NR(cmd);
	if (nr < IOMMUFD_CMD_BASE ||
	    (nr - IOMMUFD_CMD_BASE) >= ARRAY_SIZE(iommufd_ioctl_ops))
		return -ENOIOCTLCMD;
	op = &iommufd_ioctl_ops[nr - IOMMUFD_CMD_BASE];
	if (op->ioctl_num != cmd)
		return -ENOIOCTLCMD;
	if (ucmd.user_size < op->min_size)
		return -EINVAL;

	ucmd.cmd = &buf;
	ret = copy_struct_from_user(ucmd.cmd, op->size, ucmd.ubuffer,
				    ucmd.user_size);
	if (ret)
		return ret;
	ret = op->execute(&ucmd);
	return ret;
}

static const struct file_operations iommufd_fops = {
	.owner = THIS_MODULE,
	.open = iommufd_fops_open,
	.release = iommufd_fops_release,
	.unlocked_ioctl = iommufd_fops_ioctl,
};

/**
 * iommufd_ctx_get - Get a context reference
 * @ictx: Context to get
 *
 * The caller must already hold a valid reference to ictx.
 */
void iommufd_ctx_get(struct iommufd_ctx *ictx)
{
	get_file(ictx->file);
}
EXPORT_SYMBOL_NS_GPL(iommufd_ctx_get, IOMMUFD);

/**
 * iommufd_ctx_from_file - Acquires a reference to the iommufd context
 * @file: File to obtain the reference from
 *
 * Returns a pointer to the iommufd_ctx, otherwise ERR_PTR. The struct file
 * remains owned by the caller and the caller must still do fput. On success
 * the caller is responsible to call iommufd_ctx_put().
 */
struct iommufd_ctx *iommufd_ctx_from_file(struct file *file)
{
	struct iommufd_ctx *ictx;

	if (file->f_op != &iommufd_fops)
		return ERR_PTR(-EBADFD);
	ictx = file->private_data;
	iommufd_ctx_get(ictx);
	return ictx;
}
EXPORT_SYMBOL_NS_GPL(iommufd_ctx_from_file, IOMMUFD);

/**
 * iommufd_ctx_put - Put back a reference
 * @ictx: Context to put back
 */
void iommufd_ctx_put(struct iommufd_ctx *ictx)
{
	fput(ictx->file);
}
EXPORT_SYMBOL_NS_GPL(iommufd_ctx_put, IOMMUFD);

static const struct iommufd_object_ops iommufd_object_ops[] = {
	[IOMMUFD_OBJ_DEVICE] = {
		.destroy = iommufd_device_destroy,
	},
	[IOMMUFD_OBJ_IOAS] = {
		.destroy = iommufd_ioas_destroy,
	},
	[IOMMUFD_OBJ_HW_PAGETABLE] = {
		.destroy = iommufd_hw_pagetable_destroy,
	},
};

static struct miscdevice iommu_misc_dev = {
	.minor = MISC_DYNAMIC_MINOR,
	.name = "iommu",
	.fops = &iommufd_fops,
	.nodename = "iommu",
	.mode = 0660,
};

static int __init iommufd_init(void)
{
	int ret;

	ret = misc_register(&iommu_misc_dev);
	if (ret)
		return ret;
	return 0;
}

static void __exit iommufd_exit(void)
{
	misc_deregister(&iommu_misc_dev);
}

module_init(iommufd_init);
module_exit(iommufd_exit);

MODULE_DESCRIPTION("I/O Address Space Management for passthrough devices");
MODULE_LICENSE("GPL");