summaryrefslogtreecommitdiffstats
path: root/drivers/lguest/io.c
blob: d2f02f0653cab1fb86bd1d9a71f8e47c2ce60c11 (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
399
400
401
402
403
/*P:300 The I/O mechanism in lguest is simple yet flexible, allowing the Guest
 * to talk to the Launcher or directly to another Guest.  It uses familiar
 * concepts of DMA and interrupts, plus some neat code stolen from
 * futexes... :*/

/* Copyright (C) 2006 Rusty Russell IBM Corporation
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 */
#include <linux/types.h>
#include <linux/futex.h>
#include <linux/jhash.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/uaccess.h>
#include "lg.h"

static struct list_head dma_hash[61];

void lguest_io_init(void)
{
	unsigned int i;

	for (i = 0; i < ARRAY_SIZE(dma_hash); i++)
		INIT_LIST_HEAD(&dma_hash[i]);
}

/* FIXME: allow multi-page lengths. */
static int check_dma_list(struct lguest *lg, const struct lguest_dma *dma)
{
	unsigned int i;

	for (i = 0; i < LGUEST_MAX_DMA_SECTIONS; i++) {
		if (!dma->len[i])
			return 1;
		if (!lguest_address_ok(lg, dma->addr[i], dma->len[i]))
			goto kill;
		if (dma->len[i] > PAGE_SIZE)
			goto kill;
		/* We could do over a page, but is it worth it? */
		if ((dma->addr[i] % PAGE_SIZE) + dma->len[i] > PAGE_SIZE)
			goto kill;
	}
	return 1;

kill:
	kill_guest(lg, "bad DMA entry: %u@%#lx", dma->len[i], dma->addr[i]);
	return 0;
}

static unsigned int hash(const union futex_key *key)
{
	return jhash2((u32*)&key->both.word,
		      (sizeof(key->both.word)+sizeof(key->both.ptr))/4,
		      key->both.offset)
		% ARRAY_SIZE(dma_hash);
}

static inline int key_eq(const union futex_key *a, const union futex_key *b)
{
	return (a->both.word == b->both.word
		&& a->both.ptr == b->both.ptr
		&& a->both.offset == b->both.offset);
}

/* Must hold read lock on dmainfo owner's current->mm->mmap_sem */
static void unlink_dma(struct lguest_dma_info *dmainfo)
{
	BUG_ON(!mutex_is_locked(&lguest_lock));
	dmainfo->interrupt = 0;
	list_del(&dmainfo->list);
	drop_futex_key_refs(&dmainfo->key);
}

static int unbind_dma(struct lguest *lg,
		      const union futex_key *key,
		      unsigned long dmas)
{
	int i, ret = 0;

	for (i = 0; i < LGUEST_MAX_DMA; i++) {
		if (key_eq(key, &lg->dma[i].key) && dmas == lg->dma[i].dmas) {
			unlink_dma(&lg->dma[i]);
			ret = 1;
			break;
		}
	}
	return ret;
}

int bind_dma(struct lguest *lg,
	     unsigned long ukey, unsigned long dmas, u16 numdmas, u8 interrupt)
{
	unsigned int i;
	int ret = 0;
	union futex_key key;
	struct rw_semaphore *fshared = &current->mm->mmap_sem;

	if (interrupt >= LGUEST_IRQS)
		return 0;

	mutex_lock(&lguest_lock);
	down_read(fshared);
	if (get_futex_key((u32 __user *)ukey, fshared, &key) != 0) {
		kill_guest(lg, "bad dma key %#lx", ukey);
		goto unlock;
	}
	get_futex_key_refs(&key);

	if (interrupt == 0)
		ret = unbind_dma(lg, &key, dmas);
	else {
		for (i = 0; i < LGUEST_MAX_DMA; i++) {
			if (lg->dma[i].interrupt)
				continue;

			lg->dma[i].dmas = dmas;
			lg->dma[i].num_dmas = numdmas;
			lg->dma[i].next_dma = 0;
			lg->dma[i].key = key;
			lg->dma[i].guestid = lg->guestid;
			lg->dma[i].interrupt = interrupt;
			list_add(&lg->dma[i].list, &dma_hash[hash(&key)]);
			ret = 1;
			goto unlock;
		}
	}
	drop_futex_key_refs(&key);
unlock:
 	up_read(fshared);
	mutex_unlock(&lguest_lock);
	return ret;
}

/* lgread from another guest */
static int lgread_other(struct lguest *lg,
			void *buf, u32 addr, unsigned bytes)
{
	if (!lguest_address_ok(lg, addr, bytes)
	    || access_process_vm(lg->tsk, addr, buf, bytes, 0) != bytes) {
		memset(buf, 0, bytes);
		kill_guest(lg, "bad address in registered DMA struct");
		return 0;
	}
	return 1;
}

/* lgwrite to another guest */
static int lgwrite_other(struct lguest *lg, u32 addr,
			 const void *buf, unsigned bytes)
{
	if (!lguest_address_ok(lg, addr, bytes)
	    || (access_process_vm(lg->tsk, addr, (void *)buf, bytes, 1)
		!= bytes)) {
		kill_guest(lg, "bad address writing to registered DMA");
		return 0;
	}
	return 1;
}

static u32 copy_data(struct lguest *srclg,
		     const struct lguest_dma *src,
		     const struct lguest_dma *dst,
		     struct page *pages[])
{
	unsigned int totlen, si, di, srcoff, dstoff;
	void *maddr = NULL;

	totlen = 0;
	si = di = 0;
	srcoff = dstoff = 0;
	while (si < LGUEST_MAX_DMA_SECTIONS && src->len[si]
	       && di < LGUEST_MAX_DMA_SECTIONS && dst->len[di]) {
		u32 len = min(src->len[si] - srcoff, dst->len[di] - dstoff);

		if (!maddr)
			maddr = kmap(pages[di]);

		/* FIXME: This is not completely portable, since
		   archs do different things for copy_to_user_page. */
		if (copy_from_user(maddr + (dst->addr[di] + dstoff)%PAGE_SIZE,
				   (void __user *)src->addr[si], len) != 0) {
			kill_guest(srclg, "bad address in sending DMA");
			totlen = 0;
			break;
		}

		totlen += len;
		srcoff += len;
		dstoff += len;
		if (srcoff == src->len[si]) {
			si++;
			srcoff = 0;
		}
		if (dstoff == dst->len[di]) {
			kunmap(pages[di]);
			maddr = NULL;
			di++;
			dstoff = 0;
		}
	}

	if (maddr)
		kunmap(pages[di]);

	return totlen;
}

/* Src is us, ie. current. */
static u32 do_dma(struct lguest *srclg, const struct lguest_dma *src,
		  struct lguest *dstlg, const struct lguest_dma *dst)
{
	int i;
	u32 ret;
	struct page *pages[LGUEST_MAX_DMA_SECTIONS];

	if (!check_dma_list(dstlg, dst) || !check_dma_list(srclg, src))
		return 0;

	/* First get the destination pages */
	for (i = 0; i < LGUEST_MAX_DMA_SECTIONS; i++) {
		if (dst->len[i] == 0)
			break;
		if (get_user_pages(dstlg->tsk, dstlg->mm,
				   dst->addr[i], 1, 1, 1, pages+i, NULL)
		    != 1) {
			kill_guest(dstlg, "Error mapping DMA pages");
			ret = 0;
			goto drop_pages;
		}
	}

	/* Now copy until we run out of src or dst. */
	ret = copy_data(srclg, src, dst, pages);

drop_pages:
	while (--i >= 0)
		put_page(pages[i]);
	return ret;
}

static int dma_transfer(struct lguest *srclg,
			unsigned long udma,
			struct lguest_dma_info *dst)
{
	struct lguest_dma dst_dma, src_dma;
	struct lguest *dstlg;
	u32 i, dma = 0;

	dstlg = &lguests[dst->guestid];
	/* Get our dma list. */
	lgread(srclg, &src_dma, udma, sizeof(src_dma));

	/* We can't deadlock against them dmaing to us, because this
	 * is all under the lguest_lock. */
	down_read(&dstlg->mm->mmap_sem);

	for (i = 0; i < dst->num_dmas; i++) {
		dma = (dst->next_dma + i) % dst->num_dmas;
		if (!lgread_other(dstlg, &dst_dma,
				  dst->dmas + dma * sizeof(struct lguest_dma),
				  sizeof(dst_dma))) {
			goto fail;
		}
		if (!dst_dma.used_len)
			break;
	}
	if (i != dst->num_dmas) {
		unsigned long used_lenp;
		unsigned int ret;

		ret = do_dma(srclg, &src_dma, dstlg, &dst_dma);
		/* Put used length in src. */
		lgwrite_u32(srclg,
			    udma+offsetof(struct lguest_dma, used_len), ret);
		if (ret == 0 && src_dma.len[0] != 0)
			goto fail;

		/* Make sure destination sees contents before length. */
		wmb();
		used_lenp = dst->dmas
			+ dma * sizeof(struct lguest_dma)
			+ offsetof(struct lguest_dma, used_len);
		lgwrite_other(dstlg, used_lenp, &ret, sizeof(ret));
		dst->next_dma++;
	}
 	up_read(&dstlg->mm->mmap_sem);

	/* Do this last so dst doesn't simply sleep on lock. */
	set_bit(dst->interrupt, dstlg->irqs_pending);
	wake_up_process(dstlg->tsk);
	return i == dst->num_dmas;

fail:
	up_read(&dstlg->mm->mmap_sem);
	return 0;
}

void send_dma(struct lguest *lg, unsigned long ukey, unsigned long udma)
{
	union futex_key key;
	int empty = 0;
	struct rw_semaphore *fshared = &current->mm->mmap_sem;

again:
	mutex_lock(&lguest_lock);
	down_read(fshared);
	if (get_futex_key((u32 __user *)ukey, fshared, &key) != 0) {
		kill_guest(lg, "bad sending DMA key");
		goto unlock;
	}
	/* Shared mapping?  Look for other guests... */
	if (key.shared.offset & 1) {
		struct lguest_dma_info *i;
		list_for_each_entry(i, &dma_hash[hash(&key)], list) {
			if (i->guestid == lg->guestid)
				continue;
			if (!key_eq(&key, &i->key))
				continue;

			empty += dma_transfer(lg, udma, i);
			break;
		}
		if (empty == 1) {
			/* Give any recipients one chance to restock. */
			up_read(&current->mm->mmap_sem);
			mutex_unlock(&lguest_lock);
			empty++;
			goto again;
		}
	} else {
		/* Private mapping: tell our userspace. */
		lg->dma_is_pending = 1;
		lg->pending_dma = udma;
		lg->pending_key = ukey;
	}
unlock:
	up_read(fshared);
	mutex_unlock(&lguest_lock);
}

void release_all_dma(struct lguest *lg)
{
	unsigned int i;

	BUG_ON(!mutex_is_locked(&lguest_lock));

	down_read(&lg->mm->mmap_sem);
	for (i = 0; i < LGUEST_MAX_DMA; i++) {
		if (lg->dma[i].interrupt)
			unlink_dma(&lg->dma[i]);
	}
	up_read(&lg->mm->mmap_sem);
}

/* Userspace wants a dma buffer from this guest. */
unsigned long get_dma_buffer(struct lguest *lg,
			     unsigned long ukey, unsigned long *interrupt)
{
	unsigned long ret = 0;
	union futex_key key;
	struct lguest_dma_info *i;
	struct rw_semaphore *fshared = &current->mm->mmap_sem;

	mutex_lock(&lguest_lock);
	down_read(fshared);
	if (get_futex_key((u32 __user *)ukey, fshared, &key) != 0) {
		kill_guest(lg, "bad registered DMA buffer");
		goto unlock;
	}
	list_for_each_entry(i, &dma_hash[hash(&key)], list) {
		if (key_eq(&key, &i->key) && i->guestid == lg->guestid) {
			unsigned int j;
			for (j = 0; j < i->num_dmas; j++) {
				struct lguest_dma dma;

				ret = i->dmas + j * sizeof(struct lguest_dma);
				lgread(lg, &dma, ret, sizeof(dma));
				if (dma.used_len == 0)
					break;
			}
			*interrupt = i->interrupt;
			break;
		}
	}
unlock:
	up_read(fshared);
	mutex_unlock(&lguest_lock);
	return ret;
}