[GitHub/MotorolaMobilityLLC/kernel-slsi.git] / drivers / lguest / io.c

/* Simple I/O model for guests, based on shared memory.
 * 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;
}
Commit	Line	Data
d7e28ffe RR	1	/* Simple I/O model for guests, based on shared memory.
	2	* Copyright (C) 2006 Rusty Russell IBM Corporation
	3	*
	4	* This program is free software; you can redistribute it and/or modify
	5	* it under the terms of the GNU General Public License as published by
	6	* the Free Software Foundation; either version 2 of the License, or
	7	* (at your option) any later version.
	8	*
	9	* This program is distributed in the hope that it will be useful,
	10	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	11	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	12	* GNU General Public License for more details.
	13	*
	14	* You should have received a copy of the GNU General Public License
	15	* along with this program; if not, write to the Free Software
	16	* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
	17	*/
	18	#include <linux/types.h>
	19	#include <linux/futex.h>
	20	#include <linux/jhash.h>
	21	#include <linux/mm.h>
	22	#include <linux/highmem.h>
	23	#include <linux/uaccess.h>
	24	#include "lg.h"
	25
	26	static struct list_head dma_hash[61];
	27
	28	void lguest_io_init(void)
	29	{
	30	unsigned int i;
	31
	32	for (i = 0; i < ARRAY_SIZE(dma_hash); i++)
	33	INIT_LIST_HEAD(&dma_hash[i]);
	34	}
	35
	36	/* FIXME: allow multi-page lengths. */
	37	static int check_dma_list(struct lguest lg, const struct lguest_dma dma)
	38	{
	39	unsigned int i;
	40
	41	for (i = 0; i < LGUEST_MAX_DMA_SECTIONS; i++) {
	42	if (!dma->len[i])
	43	return 1;
	44	if (!lguest_address_ok(lg, dma->addr[i], dma->len[i]))
	45	goto kill;
	46	if (dma->len[i] > PAGE_SIZE)
	47	goto kill;
	48	/* We could do over a page, but is it worth it? */
	49	if ((dma->addr[i] % PAGE_SIZE) + dma->len[i] > PAGE_SIZE)
	50	goto kill;
	51	}
	52	return 1;
	53
	54	kill:
	55	kill_guest(lg, "bad DMA entry: %u@%#lx", dma->len[i], dma->addr[i]);
	56	return 0;
	57	}
	58
	59	static unsigned int hash(const union futex_key *key)
	60	{
	61	return jhash2((u32*)&key->both.word,
	62	(sizeof(key->both.word)+sizeof(key->both.ptr))/4,
	63	key->both.offset)
	64	% ARRAY_SIZE(dma_hash);
65	}
66
67	static inline int key_eq(const union futex_key a, const union futex_key b)
68	{
69	return (a->both.word == b->both.word
70	&& a->both.ptr == b->both.ptr
71	&& a->both.offset == b->both.offset);
72	}
73
74	/* Must hold read lock on dmainfo owner's current->mm->mmap_sem */
75	static void unlink_dma(struct lguest_dma_info *dmainfo)
76	{
77	BUG_ON(!mutex_is_locked(&lguest_lock));
78	dmainfo->interrupt = 0;
79	list_del(&dmainfo->list);
80	drop_futex_key_refs(&dmainfo->key);
81	}
82
83	static int unbind_dma(struct lguest *lg,
84	const union futex_key *key,
85	unsigned long dmas)
86	{
87	int i, ret = 0;
88
89	for (i = 0; i < LGUEST_MAX_DMA; i++) {
90	if (key_eq(key, &lg->dma[i].key) && dmas == lg->dma[i].dmas) {
91	unlink_dma(&lg->dma[i]);
92	ret = 1;
93	break;
94	}
95	}
96	return ret;
97	}
98
99	int bind_dma(struct lguest *lg,
100	unsigned long ukey, unsigned long dmas, u16 numdmas, u8 interrupt)
101	{
102	unsigned int i;
103	int ret = 0;
104	union futex_key key;
105	struct rw_semaphore *fshared = &current->mm->mmap_sem;
106
107	if (interrupt >= LGUEST_IRQS)
108	return 0;
109
110	mutex_lock(&lguest_lock);
111	down_read(fshared);
112	if (get_futex_key((u32 __user *)ukey, fshared, &key) != 0) {
113	kill_guest(lg, "bad dma key %#lx", ukey);
114	goto unlock;
115	}
116	get_futex_key_refs(&key);
117
118	if (interrupt == 0)
119	ret = unbind_dma(lg, &key, dmas);
120	else {
121	for (i = 0; i < LGUEST_MAX_DMA; i++) {
122	if (lg->dma[i].interrupt)
123	continue;
124
125	lg->dma[i].dmas = dmas;
126	lg->dma[i].num_dmas = numdmas;
127	lg->dma[i].next_dma = 0;
128	lg->dma[i].key = key;
129	lg->dma[i].guestid = lg->guestid;
130	lg->dma[i].interrupt = interrupt;
131	list_add(&lg->dma[i].list, &dma_hash[hash(&key)]);
132	ret = 1;
133	goto unlock;
134	}
135	}
136	drop_futex_key_refs(&key);
137	unlock:
138	up_read(fshared);
139	mutex_unlock(&lguest_lock);
140	return ret;
141	}
142
143	/* lgread from another guest */
144	static int lgread_other(struct lguest *lg,
145	void *buf, u32 addr, unsigned bytes)
146	{
147	if (!lguest_address_ok(lg, addr, bytes)
148	\|\| access_process_vm(lg->tsk, addr, buf, bytes, 0) != bytes) {
149	memset(buf, 0, bytes);
150	kill_guest(lg, "bad address in registered DMA struct");
151	return 0;
152	}
153	return 1;
154	}
155
156	/* lgwrite to another guest */
157	static int lgwrite_other(struct lguest *lg, u32 addr,
158	const void *buf, unsigned bytes)
159	{
160	if (!lguest_address_ok(lg, addr, bytes)
161	\|\| (access_process_vm(lg->tsk, addr, (void *)buf, bytes, 1)
162	!= bytes)) {
163	kill_guest(lg, "bad address writing to registered DMA");
164	return 0;
165	}
166	return 1;
167	}
168
169	static u32 copy_data(struct lguest *srclg,
170	const struct lguest_dma *src,
171	const struct lguest_dma *dst,
172	struct page *pages[])
173	{
174	unsigned int totlen, si, di, srcoff, dstoff;
175	void *maddr = NULL;
176
177	totlen = 0;
178	si = di = 0;
179	srcoff = dstoff = 0;
180	while (si < LGUEST_MAX_DMA_SECTIONS && src->len[si]
181	&& di < LGUEST_MAX_DMA_SECTIONS && dst->len[di]) {
182	u32 len = min(src->len[si] - srcoff, dst->len[di] - dstoff);
183
184	if (!maddr)
185	maddr = kmap(pages[di]);
186
187	/* FIXME: This is not completely portable, since
188	archs do different things for copy_to_user_page. */
189	if (copy_from_user(maddr + (dst->addr[di] + dstoff)%PAGE_SIZE,
6d14bfe7	190	(void __user *)src->addr[si], len) != 0) {
d7e28ffe RR	191	kill_guest(srclg, "bad address in sending DMA");
	192	totlen = 0;
	193	break;
	194	}
	195
	196	totlen += len;
	197	srcoff += len;
	198	dstoff += len;
	199	if (srcoff == src->len[si]) {
	200	si++;
	201	srcoff = 0;
	202	}
	203	if (dstoff == dst->len[di]) {
	204	kunmap(pages[di]);
	205	maddr = NULL;
	206	di++;
	207	dstoff = 0;
	208	}
	209	}
	210
	211	if (maddr)
	212	kunmap(pages[di]);
	213
	214	return totlen;
	215	}
	216
	217	/* Src is us, ie. current. */
	218	static u32 do_dma(struct lguest srclg, const struct lguest_dma src,
	219	struct lguest dstlg, const struct lguest_dma dst)
	220	{
	221	int i;
	222	u32 ret;
	223	struct page *pages[LGUEST_MAX_DMA_SECTIONS];
	224
	225	if (!check_dma_list(dstlg, dst) \|\| !check_dma_list(srclg, src))
	226	return 0;
	227
	228	/* First get the destination pages */
	229	for (i = 0; i < LGUEST_MAX_DMA_SECTIONS; i++) {
	230	if (dst->len[i] == 0)
	231	break;
	232	if (get_user_pages(dstlg->tsk, dstlg->mm,
	233	dst->addr[i], 1, 1, 1, pages+i, NULL)
	234	!= 1) {
	235	kill_guest(dstlg, "Error mapping DMA pages");
	236	ret = 0;
	237	goto drop_pages;
	238	}
	239	}
	240
	241	/* Now copy until we run out of src or dst. */
	242	ret = copy_data(srclg, src, dst, pages);
	243
	244	drop_pages:
	245	while (--i >= 0)
	246	put_page(pages[i]);
	247	return ret;
	248	}
	249
	250	static int dma_transfer(struct lguest *srclg,
	251	unsigned long udma,
	252	struct lguest_dma_info *dst)
	253	{
	254	struct lguest_dma dst_dma, src_dma;
255	struct lguest *dstlg;
256	u32 i, dma = 0;
257
258	dstlg = &lguests[dst->guestid];
259	/* Get our dma list. */
260	lgread(srclg, &src_dma, udma, sizeof(src_dma));
261
262	/* We can't deadlock against them dmaing to us, because this
263	* is all under the lguest_lock. */
264	down_read(&dstlg->mm->mmap_sem);
265
266	for (i = 0; i < dst->num_dmas; i++) {
267	dma = (dst->next_dma + i) % dst->num_dmas;
268	if (!lgread_other(dstlg, &dst_dma,
269	dst->dmas + dma * sizeof(struct lguest_dma),
270	sizeof(dst_dma))) {
271	goto fail;
272	}
273	if (!dst_dma.used_len)
274	break;
275	}
276	if (i != dst->num_dmas) {
277	unsigned long used_lenp;
278	unsigned int ret;
279
280	ret = do_dma(srclg, &src_dma, dstlg, &dst_dma);
281	/* Put used length in src. */
282	lgwrite_u32(srclg,
283	udma+offsetof(struct lguest_dma, used_len), ret);
284	if (ret == 0 && src_dma.len[0] != 0)
285	goto fail;
286
287	/* Make sure destination sees contents before length. */
288	wmb();
289	used_lenp = dst->dmas
290	+ dma * sizeof(struct lguest_dma)
291	+ offsetof(struct lguest_dma, used_len);
292	lgwrite_other(dstlg, used_lenp, &ret, sizeof(ret));
293	dst->next_dma++;
294	}
295	up_read(&dstlg->mm->mmap_sem);
296
297	/* Do this last so dst doesn't simply sleep on lock. */
298	set_bit(dst->interrupt, dstlg->irqs_pending);
299	wake_up_process(dstlg->tsk);
300	return i == dst->num_dmas;
301
302	fail:
303	up_read(&dstlg->mm->mmap_sem);
304	return 0;
305	}
306
307	void send_dma(struct lguest *lg, unsigned long ukey, unsigned long udma)
308	{
309	union futex_key key;
310	int empty = 0;
311	struct rw_semaphore *fshared = &current->mm->mmap_sem;
312
313	again:
314	mutex_lock(&lguest_lock);
315	down_read(fshared);
316	if (get_futex_key((u32 __user *)ukey, fshared, &key) != 0) {
317	kill_guest(lg, "bad sending DMA key");
318	goto unlock;
319	}
320	/* Shared mapping? Look for other guests... */
321	if (key.shared.offset & 1) {
322	struct lguest_dma_info *i;
323	list_for_each_entry(i, &dma_hash[hash(&key)], list) {
324	if (i->guestid == lg->guestid)
325	continue;
326	if (!key_eq(&key, &i->key))
327	continue;
328
329	empty += dma_transfer(lg, udma, i);
330	break;
331	}
332	if (empty == 1) {
333	/* Give any recipients one chance to restock. */
334	up_read(&current->mm->mmap_sem);
335	mutex_unlock(&lguest_lock);
336	empty++;
337	goto again;
338	}
339	} else {
340	/* Private mapping: tell our userspace. */
341	lg->dma_is_pending = 1;
342	lg->pending_dma = udma;
343	lg->pending_key = ukey;
344	}
345	unlock:
346	up_read(fshared);
347	mutex_unlock(&lguest_lock);
348	}
349
350	void release_all_dma(struct lguest *lg)
351	{
352	unsigned int i;
353
354	BUG_ON(!mutex_is_locked(&lguest_lock));
355
356	down_read(&lg->mm->mmap_sem);
357	for (i = 0; i < LGUEST_MAX_DMA; i++) {
358	if (lg->dma[i].interrupt)
359	unlink_dma(&lg->dma[i]);
360	}
361	up_read(&lg->mm->mmap_sem);
362	}
363
364	/* Userspace wants a dma buffer from this guest. */
365	unsigned long get_dma_buffer(struct lguest *lg,
366	unsigned long ukey, unsigned long *interrupt)
367	{
368	unsigned long ret = 0;
369	union futex_key key;
370	struct lguest_dma_info *i;
371	struct rw_semaphore *fshared = &current->mm->mmap_sem;
372
373	mutex_lock(&lguest_lock);
374	down_read(fshared);
375	if (get_futex_key((u32 __user *)ukey, fshared, &key) != 0) {
376	kill_guest(lg, "bad registered DMA buffer");
377	goto unlock;
378	}
379	list_for_each_entry(i, &dma_hash[hash(&key)], list) {
380	if (key_eq(&key, &i->key) && i->guestid == lg->guestid) {
381	unsigned int j;
382	for (j = 0; j < i->num_dmas; j++) {
383	struct lguest_dma dma;
384
385	ret = i->dmas + j * sizeof(struct lguest_dma);
386	lgread(lg, &dma, ret, sizeof(dma));
387	if (dma.used_len == 0)
388	break;
389	}
390	*interrupt = i->interrupt;
391	break;
392	}
393	}
394	unlock:
395	up_read(fshared);
396	mutex_unlock(&lguest_lock);
397	return ret;
398	}
399