1 /*
2  * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
3  */
4 
5 /*
6  * This file contains code imported from the OFED rds source file rdma.c
7  * Oracle elects to have and use the contents of rdma.c under and governed
8  * by the OpenIB.org BSD license (see below for full license text). However,
9  * the following notice accompanied the original version of this file:
10  */
11 
12 /*
13  * Copyright (c) 2007 Oracle.  All rights reserved.
14  *
15  * This software is available to you under a choice of one of two
16  * licenses.  You may choose to be licensed under the terms of the GNU
17  * General Public License (GPL) Version 2, available from the file
18  * COPYING in the main directory of this source tree, or the
19  * OpenIB.org BSD license below:
20  *
21  *     Redistribution and use in source and binary forms, with or
22  *     without modification, are permitted provided that the following
23  *     conditions are met:
24  *
25  *      - Redistributions of source code must retain the above
26  *        copyright notice, this list of conditions and the following
27  *        disclaimer.
28  *
29  *      - Redistributions in binary form must reproduce the above
30  *        copyright notice, this list of conditions and the following
31  *        disclaimer in the documentation and/or other materials
32  *        provided with the distribution.
33  *
34  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
35  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
36  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
37  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
38  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
39  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
40  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
41  * SOFTWARE.
42  *
43  */
44 #include <sys/ib/clients/of/rdma/ib_verbs.h>
45 #include <sys/ib/clients/of/rdma/ib_addr.h>
46 #include <sys/ib/clients/of/rdma/rdma_cm.h>
47 
48 #include <sys/ib/clients/rdsv3/ib.h>
49 #include <sys/ib/clients/rdsv3/rdma.h>
50 #include <sys/ib/clients/rdsv3/rdsv3_debug.h>
51 
52 #define	DMA_TO_DEVICE 0
53 #define	DMA_FROM_DEVICE 1
54 #define	RB_CLEAR_NODE(nodep) AVL_SETPARENT(nodep, nodep);
55 
56 /*
57  * XXX
58  *  - build with sparse
59  *  - should we limit the size of a mr region?  let transport return failure?
60  *  - should we detect duplicate keys on a socket?  hmm.
61  *  - an rdma is an mlock, apply rlimit?
62  */
63 
64 /*
65  * get the number of pages by looking at the page indices that the start and
66  * end addresses fall in.
67  *
68  * Returns 0 if the vec is invalid.  It is invalid if the number of bytes
69  * causes the address to wrap or overflows an unsigned int.  This comes
70  * from being stored in the 'length' member of 'struct rdsv3_scatterlist'.
71  */
72 static unsigned int
73 rdsv3_pages_in_vec(struct rds_iovec *vec)
74 {
75 	if ((vec->addr + vec->bytes <= vec->addr) ||
76 	    (vec->bytes > (uint64_t)UINT_MAX)) {
77 		return (0);
78 	}
79 
80 	return (((vec->addr + vec->bytes + PAGESIZE - 1) >>
81 	    PAGESHIFT) - (vec->addr >> PAGESHIFT));
82 }
83 
84 static struct rdsv3_mr *
85 rdsv3_mr_tree_walk(struct avl_tree *root, uint32_t key,
86 	struct rdsv3_mr *insert)
87 {
88 	struct rdsv3_mr *mr;
89 	avl_index_t where;
90 
91 	mr = avl_find(root, &key, &where);
92 	if ((mr == NULL) && (insert != NULL)) {
93 		avl_insert(root, (void *)insert, where);
94 		atomic_inc_32(&insert->r_refcount);
95 		return (NULL);
96 	}
97 
98 	return (mr);
99 }
100 
101 /*
102  * Destroy the transport-specific part of a MR.
103  */
104 static void
105 rdsv3_destroy_mr(struct rdsv3_mr *mr)
106 {
107 	struct rdsv3_sock *rs = mr->r_sock;
108 	void *trans_private = NULL;
109 	avl_node_t *np;
110 
111 	RDSV3_DPRINTF5("rdsv3_destroy_mr",
112 	    "RDS: destroy mr key is %x refcnt %u",
113 	    mr->r_key, atomic_get(&mr->r_refcount));
114 
115 	if (test_and_set_bit(RDSV3_MR_DEAD, &mr->r_state))
116 		return;
117 
118 	mutex_enter(&rs->rs_rdma_lock);
119 	np = &mr->r_rb_node;
120 	if (AVL_XPARENT(np) != np)
121 		avl_remove(&rs->rs_rdma_keys, mr);
122 	trans_private = mr->r_trans_private;
123 	mr->r_trans_private = NULL;
124 	mutex_exit(&rs->rs_rdma_lock);
125 
126 	if (trans_private)
127 		mr->r_trans->free_mr(trans_private, mr->r_invalidate);
128 }
129 
130 void
131 __rdsv3_put_mr_final(struct rdsv3_mr *mr)
132 {
133 	rdsv3_destroy_mr(mr);
134 	kmem_free(mr, sizeof (*mr));
135 }
136 
137 /*
138  * By the time this is called we can't have any more ioctls called on
139  * the socket so we don't need to worry about racing with others.
140  */
141 void
142 rdsv3_rdma_drop_keys(struct rdsv3_sock *rs)
143 {
144 	struct rdsv3_mr *mr;
145 	struct avl_node *node;
146 
147 	/* Release any MRs associated with this socket */
148 	mutex_enter(&rs->rs_rdma_lock);
149 	while ((node = avl_first(&rs->rs_rdma_keys))) {
150 		mr = container_of(node, struct rdsv3_mr, r_rb_node);
151 		if (mr->r_trans == rs->rs_transport)
152 			mr->r_invalidate = 0;
153 		avl_remove(&rs->rs_rdma_keys, &mr->r_rb_node);
154 		RB_CLEAR_NODE(&mr->r_rb_node)
155 		mutex_exit(&rs->rs_rdma_lock);
156 		rdsv3_destroy_mr(mr);
157 		rdsv3_mr_put(mr);
158 		mutex_enter(&rs->rs_rdma_lock);
159 	}
160 	mutex_exit(&rs->rs_rdma_lock);
161 
162 	if (rs->rs_transport && rs->rs_transport->flush_mrs)
163 		rs->rs_transport->flush_mrs();
164 }
165 
166 static int
167 __rdsv3_rdma_map(struct rdsv3_sock *rs, struct rds_get_mr_args *args,
168 	uint64_t *cookie_ret, struct rdsv3_mr **mr_ret)
169 {
170 	struct rdsv3_mr *mr = NULL, *found;
171 	void *trans_private;
172 	rds_rdma_cookie_t cookie;
173 	unsigned int nents = 0;
174 	int ret;
175 
176 	if (rs->rs_bound_addr == 0) {
177 		ret = -ENOTCONN; /* XXX not a great errno */
178 		goto out;
179 	}
180 
181 	if (!rs->rs_transport->get_mr) {
182 		ret = -EOPNOTSUPP;
183 		goto out;
184 	}
185 
186 	mr = kmem_zalloc(sizeof (struct rdsv3_mr), KM_NOSLEEP);
187 	if (!mr) {
188 		ret = -ENOMEM;
189 		goto out;
190 	}
191 
192 	mr->r_refcount = 1;
193 	RB_CLEAR_NODE(&mr->r_rb_node);
194 	mr->r_trans = rs->rs_transport;
195 	mr->r_sock = rs;
196 
197 	if (args->flags & RDS_RDMA_USE_ONCE)
198 		mr->r_use_once = 1;
199 	if (args->flags & RDS_RDMA_INVALIDATE)
200 		mr->r_invalidate = 1;
201 	if (args->flags & RDS_RDMA_READWRITE)
202 		mr->r_write = 1;
203 
204 	/*
205 	 * Obtain a transport specific MR. If this succeeds, the
206 	 * s/g list is now owned by the MR.
207 	 * Note that dma_map() implies that pending writes are
208 	 * flushed to RAM, so no dma_sync is needed here.
209 	 */
210 	trans_private = rs->rs_transport->get_mr(&args->vec, nents, rs,
211 	    &mr->r_key);
212 
213 	if (IS_ERR(trans_private)) {
214 		ret = PTR_ERR(trans_private);
215 		goto out;
216 	}
217 
218 	mr->r_trans_private = trans_private;
219 
220 	/*
221 	 * The user may pass us an unaligned address, but we can only
222 	 * map page aligned regions. So we keep the offset, and build
223 	 * a 64bit cookie containing <R_Key, offset> and pass that
224 	 * around.
225 	 */
226 	cookie = rdsv3_rdma_make_cookie(mr->r_key, args->vec.addr & ~PAGEMASK);
227 	if (cookie_ret)
228 		*cookie_ret = cookie;
229 
230 	/*
231 	 * copy value of cookie to user address at args->cookie_addr
232 	 */
233 	if (args->cookie_addr) {
234 		ret = ddi_copyout((void *)&cookie,
235 		    (void *)((intptr_t)args->cookie_addr),
236 		    sizeof (rds_rdma_cookie_t), 0);
237 		if (ret != 0) {
238 			ret = -EFAULT;
239 			goto out;
240 		}
241 	}
242 
243 	RDSV3_DPRINTF5("__rdsv3_rdma_map",
244 	    "RDS: get_mr mr 0x%p addr 0x%llx key 0x%x",
245 	    mr, args->vec.addr, mr->r_key);
246 	/*
247 	 * Inserting the new MR into the rbtree bumps its
248 	 * reference count.
249 	 */
250 	mutex_enter(&rs->rs_rdma_lock);
251 	found = rdsv3_mr_tree_walk(&rs->rs_rdma_keys, mr->r_key, mr);
252 	mutex_exit(&rs->rs_rdma_lock);
253 
254 	ASSERT(!(found && found != mr));
255 
256 	if (mr_ret) {
257 		atomic_inc_32(&mr->r_refcount);
258 		*mr_ret = mr;
259 	}
260 
261 	ret = 0;
262 out:
263 	if (mr)
264 		rdsv3_mr_put(mr);
265 	return (ret);
266 }
267 
268 int
269 rdsv3_get_mr(struct rdsv3_sock *rs, const void *optval, int optlen)
270 {
271 	struct rds_get_mr_args args;
272 
273 	if (optlen != sizeof (struct rds_get_mr_args))
274 		return (-EINVAL);
275 
276 #if 1
277 	bcopy((struct rds_get_mr_args *)optval, &args,
278 	    sizeof (struct rds_get_mr_args));
279 #else
280 	if (ddi_copyin(optval, &args, optlen, 0))
281 		return (-EFAULT);
282 #endif
283 
284 	return (__rdsv3_rdma_map(rs, &args, NULL, NULL));
285 }
286 
287 int
288 rdsv3_get_mr_for_dest(struct rdsv3_sock *rs, const void *optval,
289     int optlen)
290 {
291 	struct rds_get_mr_for_dest_args args;
292 	struct rds_get_mr_args new_args;
293 
294 	if (optlen != sizeof (struct rds_get_mr_for_dest_args))
295 		return (-EINVAL);
296 
297 #if 1
298 	bcopy((struct rds_get_mr_for_dest_args *)optval, &args,
299 	    sizeof (struct rds_get_mr_for_dest_args));
300 #else
301 	if (ddi_copyin(optval, &args, optlen, 0))
302 		return (-EFAULT);
303 #endif
304 
305 	/*
306 	 * Initially, just behave like get_mr().
307 	 * TODO: Implement get_mr as wrapper around this
308 	 *	 and deprecate it.
309 	 */
310 	new_args.vec = args.vec;
311 	new_args.cookie_addr = args.cookie_addr;
312 	new_args.flags = args.flags;
313 
314 	return (__rdsv3_rdma_map(rs, &new_args, NULL, NULL));
315 }
316 
317 /*
318  * Free the MR indicated by the given R_Key
319  */
320 int
321 rdsv3_free_mr(struct rdsv3_sock *rs, const void *optval, int optlen)
322 {
323 	struct rds_free_mr_args args;
324 	struct rdsv3_mr *mr;
325 
326 	if (optlen != sizeof (struct rds_free_mr_args))
327 		return (-EINVAL);
328 
329 #if 1
330 	bcopy((struct rds_free_mr_args *)optval, &args,
331 	    sizeof (struct rds_free_mr_args));
332 #else
333 	if (ddi_copyin((struct rds_free_mr_args *)optval, &args,
334 	    sizeof (struct rds_free_mr_args), 0))
335 		return (-EFAULT);
336 #endif
337 
338 	/* Special case - a null cookie means flush all unused MRs */
339 	if (args.cookie == 0) {
340 		if (!rs->rs_transport || !rs->rs_transport->flush_mrs)
341 			return (-EINVAL);
342 		rs->rs_transport->flush_mrs();
343 		return (0);
344 	}
345 
346 	/*
347 	 * Look up the MR given its R_key and remove it from the rbtree
348 	 * so nobody else finds it.
349 	 * This should also prevent races with rdsv3_rdma_unuse.
350 	 */
351 	mutex_enter(&rs->rs_rdma_lock);
352 	mr = rdsv3_mr_tree_walk(&rs->rs_rdma_keys,
353 	    rdsv3_rdma_cookie_key(args.cookie), NULL);
354 	if (mr) {
355 		avl_remove(&rs->rs_rdma_keys, &mr->r_rb_node);
356 		RB_CLEAR_NODE(&mr->r_rb_node);
357 		if (args.flags & RDS_RDMA_INVALIDATE)
358 			mr->r_invalidate = 1;
359 	}
360 	mutex_exit(&rs->rs_rdma_lock);
361 
362 	if (!mr)
363 		return (-EINVAL);
364 
365 	/*
366 	 * call rdsv3_destroy_mr() ourselves so that we're sure it's done
367 	 * by time we return.  If we let rdsv3_mr_put() do it it might not
368 	 * happen until someone else drops their ref.
369 	 */
370 	rdsv3_destroy_mr(mr);
371 	rdsv3_mr_put(mr);
372 	return (0);
373 }
374 
375 /*
376  * This is called when we receive an extension header that
377  * tells us this MR was used. It allows us to implement
378  * use_once semantics
379  */
380 void
381 rdsv3_rdma_unuse(struct rdsv3_sock *rs, uint32_t r_key, int force)
382 {
383 	struct rdsv3_mr *mr;
384 	int zot_me = 0;
385 
386 	RDSV3_DPRINTF4("rdsv3_rdma_unuse", "Enter rkey: 0x%x", r_key);
387 
388 	mutex_enter(&rs->rs_rdma_lock);
389 	mr = rdsv3_mr_tree_walk(&rs->rs_rdma_keys, r_key, NULL);
390 	if (!mr) {
391 		RDSV3_DPRINTF4("rdsv3_rdma_unuse",
392 		    "rdsv3: trying to unuse MR with unknown r_key %u!", r_key);
393 		mutex_exit(&rs->rs_rdma_lock);
394 		return;
395 	}
396 
397 	if (mr->r_use_once || force) {
398 		avl_remove(&rs->rs_rdma_keys, &mr->r_rb_node);
399 		RB_CLEAR_NODE(&mr->r_rb_node);
400 		zot_me = 1;
401 	} else {
402 		atomic_inc_32(&mr->r_refcount);
403 	}
404 	mutex_exit(&rs->rs_rdma_lock);
405 
406 	/*
407 	 * May have to issue a dma_sync on this memory region.
408 	 * Note we could avoid this if the operation was a RDMA READ,
409 	 * but at this point we can't tell.
410 	 */
411 	if (mr->r_trans->sync_mr)
412 		mr->r_trans->sync_mr(mr->r_trans_private, DMA_FROM_DEVICE);
413 
414 	/*
415 	 * If the MR was marked as invalidate, this will
416 	 * trigger an async flush.
417 	 */
418 	if (zot_me)
419 		rdsv3_destroy_mr(mr);
420 	rdsv3_mr_put(mr);
421 	RDSV3_DPRINTF4("rdsv3_rdma_unuse", "Return");
422 }
423 
424 void
425 rdsv3_rdma_free_op(struct rdsv3_rdma_op *ro)
426 {
427 	unsigned int i;
428 
429 	/* deallocate RDMA resources on rdsv3_message */
430 	for (i = 0; i < ro->r_nents; i++) {
431 		ddi_umem_unlock(ro->r_rdma_sg[i].umem_cookie);
432 	}
433 
434 	if (ro->r_notifier)
435 		kmem_free(ro->r_notifier, sizeof (*ro->r_notifier));
436 	kmem_free(ro, sizeof (*ro));
437 }
438 
439 /*
440  * args is a pointer to an in-kernel copy in the sendmsg cmsg.
441  */
442 static struct rdsv3_rdma_op *
443 rdsv3_rdma_prepare(struct rdsv3_sock *rs, struct rds_rdma_args *args)
444 {
445 	struct rds_iovec vec;
446 	struct rdsv3_rdma_op *op = NULL;
447 	unsigned int nr_bytes;
448 	struct rds_iovec *local_vec;
449 	unsigned int nr;
450 	unsigned int i;
451 	ddi_umem_cookie_t umem_cookie;
452 	size_t umem_len;
453 	caddr_t umem_addr;
454 	int ret;
455 
456 	if (rs->rs_bound_addr == 0) {
457 		ret = -ENOTCONN; /* XXX not a great errno */
458 		goto out;
459 	}
460 
461 	if (args->nr_local > (uint64_t)UINT_MAX) {
462 		ret = -EMSGSIZE;
463 		goto out;
464 	}
465 
466 	op = kmem_zalloc(offsetof(struct rdsv3_rdma_op,
467 	    r_rdma_sg[args->nr_local]), KM_NOSLEEP);
468 	if (op == NULL) {
469 		ret = -ENOMEM;
470 		goto out;
471 	}
472 
473 	op->r_write = !!(args->flags & RDS_RDMA_READWRITE);
474 	op->r_fence = !!(args->flags & RDS_RDMA_FENCE);
475 	op->r_notify = !!(args->flags & RDS_RDMA_NOTIFY_ME);
476 	op->r_recverr = rs->rs_recverr;
477 
478 	if (op->r_notify || op->r_recverr) {
479 		/*
480 		 * We allocate an uninitialized notifier here, because
481 		 * we don't want to do that in the completion handler. We
482 		 * would have to use GFP_ATOMIC there, and don't want to deal
483 		 * with failed allocations.
484 		 */
485 		op->r_notifier = kmem_alloc(sizeof (struct rdsv3_notifier),
486 		    KM_NOSLEEP);
487 		if (!op->r_notifier) {
488 			ret = -ENOMEM;
489 			goto out;
490 		}
491 		op->r_notifier->n_user_token = args->user_token;
492 		op->r_notifier->n_status = RDS_RDMA_SUCCESS;
493 	}
494 
495 	/*
496 	 * The cookie contains the R_Key of the remote memory region, and
497 	 * optionally an offset into it. This is how we implement RDMA into
498 	 * unaligned memory.
499 	 * When setting up the RDMA, we need to add that offset to the
500 	 * destination address (which is really an offset into the MR)
501 	 * FIXME: We may want to move this into ib_rdma.c
502 	 */
503 	op->r_key = rdsv3_rdma_cookie_key(args->cookie);
504 	op->r_remote_addr = args->remote_vec.addr +
505 	    rdsv3_rdma_cookie_offset(args->cookie);
506 
507 	nr_bytes = 0;
508 
509 	RDSV3_DPRINTF5("rdsv3_rdma_prepare",
510 	    "RDS: rdma prepare nr_local %llu rva %llx rkey %x",
511 	    (unsigned long long)args->nr_local,
512 	    (unsigned long long)args->remote_vec.addr,
513 	    op->r_key);
514 
515 	local_vec = (struct rds_iovec *)(unsigned long) args->local_vec_addr;
516 
517 	/* pin the scatter list of user buffers */
518 	for (i = 0; i < args->nr_local; i++) {
519 		if (ddi_copyin(&local_vec[i], &vec,
520 		    sizeof (struct rds_iovec), 0)) {
521 			ret = -EFAULT;
522 			goto out;
523 		}
524 
525 		nr = rdsv3_pages_in_vec(&vec);
526 		if (nr == 0) {
527 			RDSV3_DPRINTF2("rdsv3_rdma_prepare",
528 			    "rdsv3_pages_in_vec returned 0");
529 			ret = -EINVAL;
530 			goto out;
531 		}
532 
533 		rs->rs_user_addr = vec.addr;
534 		rs->rs_user_bytes = vec.bytes;
535 
536 		/* pin user memory pages */
537 		umem_len = ptob(btopr(vec.bytes +
538 		    ((uintptr_t)vec.addr & PAGEOFFSET)));
539 		umem_addr = (caddr_t)((uintptr_t)vec.addr & ~PAGEOFFSET);
540 		ret = umem_lockmemory(umem_addr, umem_len,
541 		    DDI_UMEMLOCK_WRITE | DDI_UMEMLOCK_READ,
542 		    &umem_cookie, NULL, NULL);
543 		if (ret != 0) {
544 			RDSV3_DPRINTF2("rdsv3_rdma_prepare",
545 			    "umem_lockmemory() returned %d", ret);
546 			ret = -EFAULT;
547 			goto out;
548 		}
549 		op->r_rdma_sg[i].umem_cookie = umem_cookie;
550 		op->r_rdma_sg[i].iovec = vec;
551 		nr_bytes += vec.bytes;
552 
553 		RDSV3_DPRINTF5("rdsv3_rdma_prepare",
554 		    "RDS: nr_bytes %u nr %u vec.bytes %llu vec.addr %llx",
555 		    nr_bytes, nr, vec.bytes, vec.addr);
556 	}
557 	op->r_nents = i;
558 
559 	if (nr_bytes > args->remote_vec.bytes) {
560 		RDSV3_DPRINTF2("rdsv3_rdma_prepare",
561 		    "RDS nr_bytes %u remote_bytes %u do not match",
562 		    nr_bytes, (unsigned int) args->remote_vec.bytes);
563 		ret = -EINVAL;
564 		goto out;
565 	}
566 	op->r_bytes = nr_bytes;
567 
568 	ret = 0;
569 out:
570 	if (ret) {
571 		if (op)
572 			rdsv3_rdma_free_op(op);
573 		op = ERR_PTR(ret);
574 	}
575 	return (op);
576 }
577 
578 #define	CEIL(x, y)	(((x) + (y) - 1) / (y))
579 
580 /*
581  * The application asks for a RDMA transfer.
582  * Extract all arguments and set up the rdma_op
583  */
584 int
585 rdsv3_cmsg_rdma_args(struct rdsv3_sock *rs, struct rdsv3_message *rm,
586 	struct cmsghdr *cmsg)
587 {
588 	struct rdsv3_rdma_op *op;
589 	/* uint64_t alignment on the buffer */
590 	uint64_t buf[CEIL(CMSG_LEN(sizeof (struct rds_rdma_args)),
591 	    sizeof (uint64_t))];
592 
593 	if (cmsg->cmsg_len != CMSG_LEN(sizeof (struct rds_rdma_args)) ||
594 	    rm->m_rdma_op != NULL)
595 		return (-EINVAL);
596 
597 	ASSERT(sizeof (buf) >= cmsg->cmsg_len && ((uintptr_t)buf & 0x7) == 0);
598 
599 	bcopy(CMSG_DATA(cmsg), (char *)buf, cmsg->cmsg_len);
600 	op = rdsv3_rdma_prepare(rs, (struct rds_rdma_args *)buf);
601 
602 	if (IS_ERR(op))
603 		return (PTR_ERR(op));
604 	rdsv3_stats_inc(s_send_rdma);
605 	rm->m_rdma_op = op;
606 	return (0);
607 }
608 
609 /*
610  * The application wants us to pass an RDMA destination (aka MR)
611  * to the remote
612  */
613 int
614 rdsv3_cmsg_rdma_dest(struct rdsv3_sock *rs, struct rdsv3_message *rm,
615 	struct cmsghdr *cmsg)
616 {
617 	struct rdsv3_mr *mr;
618 	uint32_t r_key;
619 	int err = 0;
620 
621 	if (cmsg->cmsg_len != CMSG_LEN(sizeof (rds_rdma_cookie_t)) ||
622 	    rm->m_rdma_cookie != 0)
623 		return (-EINVAL);
624 
625 	(void) memcpy(&rm->m_rdma_cookie, CMSG_DATA(cmsg),
626 	    sizeof (rm->m_rdma_cookie));
627 
628 	/*
629 	 * We are reusing a previously mapped MR here. Most likely, the
630 	 * application has written to the buffer, so we need to explicitly
631 	 * flush those writes to RAM. Otherwise the HCA may not see them
632 	 * when doing a DMA from that buffer.
633 	 */
634 	r_key = rdsv3_rdma_cookie_key(rm->m_rdma_cookie);
635 
636 	mutex_enter(&rs->rs_rdma_lock);
637 	mr = rdsv3_mr_tree_walk(&rs->rs_rdma_keys, r_key, NULL);
638 	if (!mr)
639 		err = -EINVAL;	/* invalid r_key */
640 	else
641 		atomic_inc_32(&mr->r_refcount);
642 	mutex_exit(&rs->rs_rdma_lock);
643 
644 	if (mr) {
645 		mr->r_trans->sync_mr(mr->r_trans_private, DMA_TO_DEVICE);
646 		rm->m_rdma_mr = mr;
647 	}
648 	return (err);
649 }
650 
651 /*
652  * The application passes us an address range it wants to enable RDMA
653  * to/from. We map the area, and save the <R_Key,offset> pair
654  * in rm->m_rdma_cookie. This causes it to be sent along to the peer
655  * in an extension header.
656  */
657 int
658 rdsv3_cmsg_rdma_map(struct rdsv3_sock *rs, struct rdsv3_message *rm,
659 	struct cmsghdr *cmsg)
660 {
661 	/* uint64_t alignment on the buffer */
662 	uint64_t buf[CEIL(CMSG_LEN(sizeof (struct rds_get_mr_args)),
663 	    sizeof (uint64_t))];
664 	int status;
665 
666 	if (cmsg->cmsg_len != CMSG_LEN(sizeof (struct rds_get_mr_args)) ||
667 	    rm->m_rdma_cookie != 0)
668 		return (-EINVAL);
669 
670 	ASSERT(sizeof (buf) >= cmsg->cmsg_len && ((uintptr_t)buf & 0x7) == 0);
671 
672 	bcopy(CMSG_DATA(cmsg), (char *)buf, cmsg->cmsg_len);
673 	status = __rdsv3_rdma_map(rs, (struct rds_get_mr_args *)buf,
674 	    &rm->m_rdma_cookie, &rm->m_rdma_mr);
675 
676 	return (status);
677 }
678