1 /******************************************************************************* 2 * Filename: target_core_rd.c 3 * 4 * This file contains the Storage Engine <-> Ramdisk transport 5 * specific functions. 6 * 7 * (c) Copyright 2003-2013 Datera, Inc. 8 * 9 * Nicholas A. Bellinger <nab@kernel.org> 10 * 11 * This program is free software; you can redistribute it and/or modify 12 * it under the terms of the GNU General Public License as published by 13 * the Free Software Foundation; either version 2 of the License, or 14 * (at your option) any later version. 15 * 16 * This program is distributed in the hope that it will be useful, 17 * but WITHOUT ANY WARRANTY; without even the implied warranty of 18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 19 * GNU General Public License for more details. 20 * 21 * You should have received a copy of the GNU General Public License 22 * along with this program; if not, write to the Free Software 23 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. 24 * 25 ******************************************************************************/ 26 27 #include <linux/string.h> 28 #include <linux/parser.h> 29 #include <linux/highmem.h> 30 #include <linux/timer.h> 31 #include <linux/scatterlist.h> 32 #include <linux/slab.h> 33 #include <linux/spinlock.h> 34 #include <scsi/scsi_proto.h> 35 36 #include <target/target_core_base.h> 37 #include <target/target_core_backend.h> 38 39 #include "target_core_rd.h" 40 41 static inline struct rd_dev *RD_DEV(struct se_device *dev) 42 { 43 return container_of(dev, struct rd_dev, dev); 44 } 45 46 static int rd_attach_hba(struct se_hba *hba, u32 host_id) 47 { 48 struct rd_host *rd_host; 49 50 rd_host = kzalloc(sizeof(struct rd_host), GFP_KERNEL); 51 if (!rd_host) { 52 pr_err("Unable to allocate memory for struct rd_host\n"); 53 return -ENOMEM; 54 } 55 56 rd_host->rd_host_id = host_id; 57 58 hba->hba_ptr = rd_host; 59 60 pr_debug("CORE_HBA[%d] - TCM Ramdisk HBA Driver %s on" 61 " Generic Target Core Stack %s\n", hba->hba_id, 62 RD_HBA_VERSION, TARGET_CORE_VERSION); 63 64 return 0; 65 } 66 67 static void rd_detach_hba(struct se_hba *hba) 68 { 69 struct rd_host *rd_host = hba->hba_ptr; 70 71 pr_debug("CORE_HBA[%d] - Detached Ramdisk HBA: %u from" 72 " Generic Target Core\n", hba->hba_id, rd_host->rd_host_id); 73 74 kfree(rd_host); 75 hba->hba_ptr = NULL; 76 } 77 78 static u32 rd_release_sgl_table(struct rd_dev *rd_dev, struct rd_dev_sg_table *sg_table, 79 u32 sg_table_count) 80 { 81 struct page *pg; 82 struct scatterlist *sg; 83 u32 i, j, page_count = 0, sg_per_table; 84 85 for (i = 0; i < sg_table_count; i++) { 86 sg = sg_table[i].sg_table; 87 sg_per_table = sg_table[i].rd_sg_count; 88 89 for (j = 0; j < sg_per_table; j++) { 90 pg = sg_page(&sg[j]); 91 if (pg) { 92 __free_page(pg); 93 page_count++; 94 } 95 } 96 kfree(sg); 97 } 98 99 kfree(sg_table); 100 return page_count; 101 } 102 103 static void rd_release_device_space(struct rd_dev *rd_dev) 104 { 105 u32 page_count; 106 107 if (!rd_dev->sg_table_array || !rd_dev->sg_table_count) 108 return; 109 110 page_count = rd_release_sgl_table(rd_dev, rd_dev->sg_table_array, 111 rd_dev->sg_table_count); 112 113 pr_debug("CORE_RD[%u] - Released device space for Ramdisk" 114 " Device ID: %u, pages %u in %u tables total bytes %lu\n", 115 rd_dev->rd_host->rd_host_id, rd_dev->rd_dev_id, page_count, 116 rd_dev->sg_table_count, (unsigned long)page_count * PAGE_SIZE); 117 118 rd_dev->sg_table_array = NULL; 119 rd_dev->sg_table_count = 0; 120 } 121 122 123 /* rd_build_device_space(): 124 * 125 * 126 */ 127 static int rd_allocate_sgl_table(struct rd_dev *rd_dev, struct rd_dev_sg_table *sg_table, 128 u32 total_sg_needed, unsigned char init_payload) 129 { 130 u32 i = 0, j, page_offset = 0, sg_per_table; 131 u32 max_sg_per_table = (RD_MAX_ALLOCATION_SIZE / 132 sizeof(struct scatterlist)); 133 struct page *pg; 134 struct scatterlist *sg; 135 unsigned char *p; 136 137 while (total_sg_needed) { 138 unsigned int chain_entry = 0; 139 140 sg_per_table = (total_sg_needed > max_sg_per_table) ? 141 max_sg_per_table : total_sg_needed; 142 143 /* 144 * Reserve extra element for chain entry 145 */ 146 if (sg_per_table < total_sg_needed) 147 chain_entry = 1; 148 149 sg = kcalloc(sg_per_table + chain_entry, sizeof(*sg), 150 GFP_KERNEL); 151 if (!sg) { 152 pr_err("Unable to allocate scatterlist array" 153 " for struct rd_dev\n"); 154 return -ENOMEM; 155 } 156 157 sg_init_table(sg, sg_per_table + chain_entry); 158 159 if (i > 0) { 160 sg_chain(sg_table[i - 1].sg_table, 161 max_sg_per_table + 1, sg); 162 } 163 164 sg_table[i].sg_table = sg; 165 sg_table[i].rd_sg_count = sg_per_table; 166 sg_table[i].page_start_offset = page_offset; 167 sg_table[i++].page_end_offset = (page_offset + sg_per_table) 168 - 1; 169 170 for (j = 0; j < sg_per_table; j++) { 171 pg = alloc_pages(GFP_KERNEL, 0); 172 if (!pg) { 173 pr_err("Unable to allocate scatterlist" 174 " pages for struct rd_dev_sg_table\n"); 175 return -ENOMEM; 176 } 177 sg_assign_page(&sg[j], pg); 178 sg[j].length = PAGE_SIZE; 179 180 p = kmap(pg); 181 memset(p, init_payload, PAGE_SIZE); 182 kunmap(pg); 183 } 184 185 page_offset += sg_per_table; 186 total_sg_needed -= sg_per_table; 187 } 188 189 return 0; 190 } 191 192 static int rd_build_device_space(struct rd_dev *rd_dev) 193 { 194 struct rd_dev_sg_table *sg_table; 195 u32 sg_tables, total_sg_needed; 196 u32 max_sg_per_table = (RD_MAX_ALLOCATION_SIZE / 197 sizeof(struct scatterlist)); 198 int rc; 199 200 if (rd_dev->rd_page_count <= 0) { 201 pr_err("Illegal page count: %u for Ramdisk device\n", 202 rd_dev->rd_page_count); 203 return -EINVAL; 204 } 205 206 /* Don't need backing pages for NULLIO */ 207 if (rd_dev->rd_flags & RDF_NULLIO) 208 return 0; 209 210 total_sg_needed = rd_dev->rd_page_count; 211 212 sg_tables = (total_sg_needed / max_sg_per_table) + 1; 213 214 sg_table = kzalloc(sg_tables * sizeof(struct rd_dev_sg_table), GFP_KERNEL); 215 if (!sg_table) { 216 pr_err("Unable to allocate memory for Ramdisk" 217 " scatterlist tables\n"); 218 return -ENOMEM; 219 } 220 221 rd_dev->sg_table_array = sg_table; 222 rd_dev->sg_table_count = sg_tables; 223 224 rc = rd_allocate_sgl_table(rd_dev, sg_table, total_sg_needed, 0x00); 225 if (rc) 226 return rc; 227 228 pr_debug("CORE_RD[%u] - Built Ramdisk Device ID: %u space of" 229 " %u pages in %u tables\n", rd_dev->rd_host->rd_host_id, 230 rd_dev->rd_dev_id, rd_dev->rd_page_count, 231 rd_dev->sg_table_count); 232 233 return 0; 234 } 235 236 static void rd_release_prot_space(struct rd_dev *rd_dev) 237 { 238 u32 page_count; 239 240 if (!rd_dev->sg_prot_array || !rd_dev->sg_prot_count) 241 return; 242 243 page_count = rd_release_sgl_table(rd_dev, rd_dev->sg_prot_array, 244 rd_dev->sg_prot_count); 245 246 pr_debug("CORE_RD[%u] - Released protection space for Ramdisk" 247 " Device ID: %u, pages %u in %u tables total bytes %lu\n", 248 rd_dev->rd_host->rd_host_id, rd_dev->rd_dev_id, page_count, 249 rd_dev->sg_table_count, (unsigned long)page_count * PAGE_SIZE); 250 251 rd_dev->sg_prot_array = NULL; 252 rd_dev->sg_prot_count = 0; 253 } 254 255 static int rd_build_prot_space(struct rd_dev *rd_dev, int prot_length, int block_size) 256 { 257 struct rd_dev_sg_table *sg_table; 258 u32 total_sg_needed, sg_tables; 259 u32 max_sg_per_table = (RD_MAX_ALLOCATION_SIZE / 260 sizeof(struct scatterlist)); 261 int rc; 262 263 if (rd_dev->rd_flags & RDF_NULLIO) 264 return 0; 265 /* 266 * prot_length=8byte dif data 267 * tot sg needed = rd_page_count * (PGSZ/block_size) * 268 * (prot_length/block_size) + pad 269 * PGSZ canceled each other. 270 */ 271 total_sg_needed = (rd_dev->rd_page_count * prot_length / block_size) + 1; 272 273 sg_tables = (total_sg_needed / max_sg_per_table) + 1; 274 275 sg_table = kzalloc(sg_tables * sizeof(struct rd_dev_sg_table), GFP_KERNEL); 276 if (!sg_table) { 277 pr_err("Unable to allocate memory for Ramdisk protection" 278 " scatterlist tables\n"); 279 return -ENOMEM; 280 } 281 282 rd_dev->sg_prot_array = sg_table; 283 rd_dev->sg_prot_count = sg_tables; 284 285 rc = rd_allocate_sgl_table(rd_dev, sg_table, total_sg_needed, 0xff); 286 if (rc) 287 return rc; 288 289 pr_debug("CORE_RD[%u] - Built Ramdisk Device ID: %u prot space of" 290 " %u pages in %u tables\n", rd_dev->rd_host->rd_host_id, 291 rd_dev->rd_dev_id, total_sg_needed, rd_dev->sg_prot_count); 292 293 return 0; 294 } 295 296 static struct se_device *rd_alloc_device(struct se_hba *hba, const char *name) 297 { 298 struct rd_dev *rd_dev; 299 struct rd_host *rd_host = hba->hba_ptr; 300 301 rd_dev = kzalloc(sizeof(struct rd_dev), GFP_KERNEL); 302 if (!rd_dev) { 303 pr_err("Unable to allocate memory for struct rd_dev\n"); 304 return NULL; 305 } 306 307 rd_dev->rd_host = rd_host; 308 309 return &rd_dev->dev; 310 } 311 312 static int rd_configure_device(struct se_device *dev) 313 { 314 struct rd_dev *rd_dev = RD_DEV(dev); 315 struct rd_host *rd_host = dev->se_hba->hba_ptr; 316 int ret; 317 318 if (!(rd_dev->rd_flags & RDF_HAS_PAGE_COUNT)) { 319 pr_debug("Missing rd_pages= parameter\n"); 320 return -EINVAL; 321 } 322 323 ret = rd_build_device_space(rd_dev); 324 if (ret < 0) 325 goto fail; 326 327 dev->dev_attrib.hw_block_size = RD_BLOCKSIZE; 328 dev->dev_attrib.hw_max_sectors = UINT_MAX; 329 dev->dev_attrib.hw_queue_depth = RD_MAX_DEVICE_QUEUE_DEPTH; 330 dev->dev_attrib.is_nonrot = 1; 331 332 rd_dev->rd_dev_id = rd_host->rd_host_dev_id_count++; 333 334 pr_debug("CORE_RD[%u] - Added TCM MEMCPY Ramdisk Device ID: %u of" 335 " %u pages in %u tables, %lu total bytes\n", 336 rd_host->rd_host_id, rd_dev->rd_dev_id, rd_dev->rd_page_count, 337 rd_dev->sg_table_count, 338 (unsigned long)(rd_dev->rd_page_count * PAGE_SIZE)); 339 340 return 0; 341 342 fail: 343 rd_release_device_space(rd_dev); 344 return ret; 345 } 346 347 static void rd_dev_call_rcu(struct rcu_head *p) 348 { 349 struct se_device *dev = container_of(p, struct se_device, rcu_head); 350 struct rd_dev *rd_dev = RD_DEV(dev); 351 352 kfree(rd_dev); 353 } 354 355 static void rd_free_device(struct se_device *dev) 356 { 357 struct rd_dev *rd_dev = RD_DEV(dev); 358 359 rd_release_device_space(rd_dev); 360 call_rcu(&dev->rcu_head, rd_dev_call_rcu); 361 } 362 363 static struct rd_dev_sg_table *rd_get_sg_table(struct rd_dev *rd_dev, u32 page) 364 { 365 struct rd_dev_sg_table *sg_table; 366 u32 i, sg_per_table = (RD_MAX_ALLOCATION_SIZE / 367 sizeof(struct scatterlist)); 368 369 i = page / sg_per_table; 370 if (i < rd_dev->sg_table_count) { 371 sg_table = &rd_dev->sg_table_array[i]; 372 if ((sg_table->page_start_offset <= page) && 373 (sg_table->page_end_offset >= page)) 374 return sg_table; 375 } 376 377 pr_err("Unable to locate struct rd_dev_sg_table for page: %u\n", 378 page); 379 380 return NULL; 381 } 382 383 static struct rd_dev_sg_table *rd_get_prot_table(struct rd_dev *rd_dev, u32 page) 384 { 385 struct rd_dev_sg_table *sg_table; 386 u32 i, sg_per_table = (RD_MAX_ALLOCATION_SIZE / 387 sizeof(struct scatterlist)); 388 389 i = page / sg_per_table; 390 if (i < rd_dev->sg_prot_count) { 391 sg_table = &rd_dev->sg_prot_array[i]; 392 if ((sg_table->page_start_offset <= page) && 393 (sg_table->page_end_offset >= page)) 394 return sg_table; 395 } 396 397 pr_err("Unable to locate struct prot rd_dev_sg_table for page: %u\n", 398 page); 399 400 return NULL; 401 } 402 403 static sense_reason_t rd_do_prot_rw(struct se_cmd *cmd, bool is_read) 404 { 405 struct se_device *se_dev = cmd->se_dev; 406 struct rd_dev *dev = RD_DEV(se_dev); 407 struct rd_dev_sg_table *prot_table; 408 struct scatterlist *prot_sg; 409 u32 sectors = cmd->data_length / se_dev->dev_attrib.block_size; 410 u32 prot_offset, prot_page; 411 u32 prot_npages __maybe_unused; 412 u64 tmp; 413 sense_reason_t rc = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE; 414 415 tmp = cmd->t_task_lba * se_dev->prot_length; 416 prot_offset = do_div(tmp, PAGE_SIZE); 417 prot_page = tmp; 418 419 prot_table = rd_get_prot_table(dev, prot_page); 420 if (!prot_table) 421 return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE; 422 423 prot_sg = &prot_table->sg_table[prot_page - 424 prot_table->page_start_offset]; 425 426 if (is_read) 427 rc = sbc_dif_verify(cmd, cmd->t_task_lba, sectors, 0, 428 prot_sg, prot_offset); 429 else 430 rc = sbc_dif_verify(cmd, cmd->t_task_lba, sectors, 0, 431 cmd->t_prot_sg, 0); 432 433 if (!rc) 434 sbc_dif_copy_prot(cmd, sectors, is_read, prot_sg, prot_offset); 435 436 return rc; 437 } 438 439 static sense_reason_t 440 rd_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents, 441 enum dma_data_direction data_direction) 442 { 443 struct se_device *se_dev = cmd->se_dev; 444 struct rd_dev *dev = RD_DEV(se_dev); 445 struct rd_dev_sg_table *table; 446 struct scatterlist *rd_sg; 447 struct sg_mapping_iter m; 448 u32 rd_offset; 449 u32 rd_size; 450 u32 rd_page; 451 u32 src_len; 452 u64 tmp; 453 sense_reason_t rc; 454 455 if (dev->rd_flags & RDF_NULLIO) { 456 target_complete_cmd(cmd, SAM_STAT_GOOD); 457 return 0; 458 } 459 460 tmp = cmd->t_task_lba * se_dev->dev_attrib.block_size; 461 rd_offset = do_div(tmp, PAGE_SIZE); 462 rd_page = tmp; 463 rd_size = cmd->data_length; 464 465 table = rd_get_sg_table(dev, rd_page); 466 if (!table) 467 return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE; 468 469 rd_sg = &table->sg_table[rd_page - table->page_start_offset]; 470 471 pr_debug("RD[%u]: %s LBA: %llu, Size: %u Page: %u, Offset: %u\n", 472 dev->rd_dev_id, 473 data_direction == DMA_FROM_DEVICE ? "Read" : "Write", 474 cmd->t_task_lba, rd_size, rd_page, rd_offset); 475 476 if (cmd->prot_type && se_dev->dev_attrib.pi_prot_type && 477 data_direction == DMA_TO_DEVICE) { 478 rc = rd_do_prot_rw(cmd, false); 479 if (rc) 480 return rc; 481 } 482 483 src_len = PAGE_SIZE - rd_offset; 484 sg_miter_start(&m, sgl, sgl_nents, 485 data_direction == DMA_FROM_DEVICE ? 486 SG_MITER_TO_SG : SG_MITER_FROM_SG); 487 while (rd_size) { 488 u32 len; 489 void *rd_addr; 490 491 sg_miter_next(&m); 492 if (!(u32)m.length) { 493 pr_debug("RD[%u]: invalid sgl %p len %zu\n", 494 dev->rd_dev_id, m.addr, m.length); 495 sg_miter_stop(&m); 496 return TCM_INCORRECT_AMOUNT_OF_DATA; 497 } 498 len = min((u32)m.length, src_len); 499 if (len > rd_size) { 500 pr_debug("RD[%u]: size underrun page %d offset %d " 501 "size %d\n", dev->rd_dev_id, 502 rd_page, rd_offset, rd_size); 503 len = rd_size; 504 } 505 m.consumed = len; 506 507 rd_addr = sg_virt(rd_sg) + rd_offset; 508 509 if (data_direction == DMA_FROM_DEVICE) 510 memcpy(m.addr, rd_addr, len); 511 else 512 memcpy(rd_addr, m.addr, len); 513 514 rd_size -= len; 515 if (!rd_size) 516 continue; 517 518 src_len -= len; 519 if (src_len) { 520 rd_offset += len; 521 continue; 522 } 523 524 /* rd page completed, next one please */ 525 rd_page++; 526 rd_offset = 0; 527 src_len = PAGE_SIZE; 528 if (rd_page <= table->page_end_offset) { 529 rd_sg++; 530 continue; 531 } 532 533 table = rd_get_sg_table(dev, rd_page); 534 if (!table) { 535 sg_miter_stop(&m); 536 return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE; 537 } 538 539 /* since we increment, the first sg entry is correct */ 540 rd_sg = table->sg_table; 541 } 542 sg_miter_stop(&m); 543 544 if (cmd->prot_type && se_dev->dev_attrib.pi_prot_type && 545 data_direction == DMA_FROM_DEVICE) { 546 rc = rd_do_prot_rw(cmd, true); 547 if (rc) 548 return rc; 549 } 550 551 target_complete_cmd(cmd, SAM_STAT_GOOD); 552 return 0; 553 } 554 555 enum { 556 Opt_rd_pages, Opt_rd_nullio, Opt_err 557 }; 558 559 static match_table_t tokens = { 560 {Opt_rd_pages, "rd_pages=%d"}, 561 {Opt_rd_nullio, "rd_nullio=%d"}, 562 {Opt_err, NULL} 563 }; 564 565 static ssize_t rd_set_configfs_dev_params(struct se_device *dev, 566 const char *page, ssize_t count) 567 { 568 struct rd_dev *rd_dev = RD_DEV(dev); 569 char *orig, *ptr, *opts; 570 substring_t args[MAX_OPT_ARGS]; 571 int ret = 0, arg, token; 572 573 opts = kstrdup(page, GFP_KERNEL); 574 if (!opts) 575 return -ENOMEM; 576 577 orig = opts; 578 579 while ((ptr = strsep(&opts, ",\n")) != NULL) { 580 if (!*ptr) 581 continue; 582 583 token = match_token(ptr, tokens, args); 584 switch (token) { 585 case Opt_rd_pages: 586 match_int(args, &arg); 587 rd_dev->rd_page_count = arg; 588 pr_debug("RAMDISK: Referencing Page" 589 " Count: %u\n", rd_dev->rd_page_count); 590 rd_dev->rd_flags |= RDF_HAS_PAGE_COUNT; 591 break; 592 case Opt_rd_nullio: 593 match_int(args, &arg); 594 if (arg != 1) 595 break; 596 597 pr_debug("RAMDISK: Setting NULLIO flag: %d\n", arg); 598 rd_dev->rd_flags |= RDF_NULLIO; 599 break; 600 default: 601 break; 602 } 603 } 604 605 kfree(orig); 606 return (!ret) ? count : ret; 607 } 608 609 static ssize_t rd_show_configfs_dev_params(struct se_device *dev, char *b) 610 { 611 struct rd_dev *rd_dev = RD_DEV(dev); 612 613 ssize_t bl = sprintf(b, "TCM RamDisk ID: %u RamDisk Makeup: rd_mcp\n", 614 rd_dev->rd_dev_id); 615 bl += sprintf(b + bl, " PAGES/PAGE_SIZE: %u*%lu" 616 " SG_table_count: %u nullio: %d\n", rd_dev->rd_page_count, 617 PAGE_SIZE, rd_dev->sg_table_count, 618 !!(rd_dev->rd_flags & RDF_NULLIO)); 619 return bl; 620 } 621 622 static sector_t rd_get_blocks(struct se_device *dev) 623 { 624 struct rd_dev *rd_dev = RD_DEV(dev); 625 626 unsigned long long blocks_long = ((rd_dev->rd_page_count * PAGE_SIZE) / 627 dev->dev_attrib.block_size) - 1; 628 629 return blocks_long; 630 } 631 632 static int rd_init_prot(struct se_device *dev) 633 { 634 struct rd_dev *rd_dev = RD_DEV(dev); 635 636 if (!dev->dev_attrib.pi_prot_type) 637 return 0; 638 639 return rd_build_prot_space(rd_dev, dev->prot_length, 640 dev->dev_attrib.block_size); 641 } 642 643 static void rd_free_prot(struct se_device *dev) 644 { 645 struct rd_dev *rd_dev = RD_DEV(dev); 646 647 rd_release_prot_space(rd_dev); 648 } 649 650 static struct sbc_ops rd_sbc_ops = { 651 .execute_rw = rd_execute_rw, 652 }; 653 654 static sense_reason_t 655 rd_parse_cdb(struct se_cmd *cmd) 656 { 657 return sbc_parse_cdb(cmd, &rd_sbc_ops); 658 } 659 660 static const struct target_backend_ops rd_mcp_ops = { 661 .name = "rd_mcp", 662 .inquiry_prod = "RAMDISK-MCP", 663 .inquiry_rev = RD_MCP_VERSION, 664 .attach_hba = rd_attach_hba, 665 .detach_hba = rd_detach_hba, 666 .alloc_device = rd_alloc_device, 667 .configure_device = rd_configure_device, 668 .free_device = rd_free_device, 669 .parse_cdb = rd_parse_cdb, 670 .set_configfs_dev_params = rd_set_configfs_dev_params, 671 .show_configfs_dev_params = rd_show_configfs_dev_params, 672 .get_device_type = sbc_get_device_type, 673 .get_blocks = rd_get_blocks, 674 .init_prot = rd_init_prot, 675 .free_prot = rd_free_prot, 676 .tb_dev_attrib_attrs = sbc_attrib_attrs, 677 }; 678 679 int __init rd_module_init(void) 680 { 681 return transport_backend_register(&rd_mcp_ops); 682 } 683 684 void rd_module_exit(void) 685 { 686 target_backend_unregister(&rd_mcp_ops); 687 } 688