1/****************************************************************************** 2 * blkif.h 3 * 4 * Unified block-device I/O interface for Xen guest OSes. 5 * 6 * Permission is hereby granted, free of charge, to any person obtaining a copy 7 * of this software and associated documentation files (the "Software"), to 8 * deal in the Software without restriction, including without limitation the 9 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or 10 * sell copies of the Software, and to permit persons to whom the Software is 11 * furnished to do so, subject to the following conditions: 12 * 13 * The above copyright notice and this permission notice shall be included in 14 * all copies or substantial portions of the Software. 15 * 16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 19 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 21 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 22 * DEALINGS IN THE SOFTWARE. 23 * 24 * Copyright (c) 2003-2004, Keir Fraser 25 * Copyright (c) 2012, Spectra Logic Corporation 26 */ 27 28#ifndef __XEN_PUBLIC_IO_BLKIF_H__ 29#define __XEN_PUBLIC_IO_BLKIF_H__ 30 31#include "ring.h" 32#include "../grant_table.h" 33 34/* 35 * Front->back notifications: When enqueuing a new request, sending a 36 * notification can be made conditional on req_event (i.e., the generic 37 * hold-off mechanism provided by the ring macros). Backends must set 38 * req_event appropriately (e.g., using RING_FINAL_CHECK_FOR_REQUESTS()). 39 * 40 * Back->front notifications: When enqueuing a new response, sending a 41 * notification can be made conditional on rsp_event (i.e., the generic 42 * hold-off mechanism provided by the ring macros). Frontends must set 43 * rsp_event appropriately (e.g., using RING_FINAL_CHECK_FOR_RESPONSES()). 44 */ 45 46#ifndef blkif_vdev_t 47#define blkif_vdev_t uint16_t 48#endif 49#define blkif_sector_t uint64_t 50 51/* 52 * Feature and Parameter Negotiation 53 * ================================= 54 * The two halves of a Xen block driver utilize nodes within the XenStore to 55 * communicate capabilities and to negotiate operating parameters. This 56 * section enumerates these nodes which reside in the respective front and 57 * backend portions of the XenStore, following the XenBus convention. 58 * 59 * All data in the XenStore is stored as strings. Nodes specifying numeric 60 * values are encoded in decimal. Integer value ranges listed below are 61 * expressed as fixed sized integer types capable of storing the conversion 62 * of a properly formated node string, without loss of information. 63 * 64 * Any specified default value is in effect if the corresponding XenBus node 65 * is not present in the XenStore. 66 * 67 * XenStore nodes in sections marked "PRIVATE" are solely for use by the 68 * driver side whose XenBus tree contains them. 69 * 70 * XenStore nodes marked "DEPRECATED" in their notes section should only be 71 * used to provide interoperability with legacy implementations. 72 * 73 * See the XenBus state transition diagram below for details on when XenBus 74 * nodes must be published and when they can be queried. 75 * 76 ***************************************************************************** 77 * Backend XenBus Nodes 78 ***************************************************************************** 79 * 80 *------------------ Backend Device Identification (PRIVATE) ------------------ 81 * 82 * mode 83 * Values: "r" (read only), "w" (writable) 84 * 85 * The read or write access permissions to the backing store to be 86 * granted to the frontend. 87 * 88 * params 89 * Values: string 90 * 91 * A free formatted string providing sufficient information for the 92 * backend driver to open the backing device. (e.g. the path to the 93 * file or block device representing the backing store.) 94 * 95 * physical-device 96 * Values: "MAJOR:MINOR" 97 * 98 * MAJOR and MINOR are the major number and minor number of the 99 * backing device respectively. 100 * 101 * type 102 * Values: "file", "phy", "tap" 103 * 104 * The type of the backing device/object. 105 * 106 * 107 * direct-io-safe 108 * Values: 0/1 (boolean) 109 * Default Value: 0 110 * 111 * The underlying storage is not affected by the direct IO memory 112 * lifetime bug. See: 113 * http://lists.xen.org/archives/html/xen-devel/2012-12/msg01154.html 114 * 115 * Therefore this option gives the backend permission to use 116 * O_DIRECT, notwithstanding that bug. 117 * 118 * That is, if this option is enabled, use of O_DIRECT is safe, 119 * in circumstances where we would normally have avoided it as a 120 * workaround for that bug. This option is not relevant for all 121 * backends, and even not necessarily supported for those for 122 * which it is relevant. A backend which knows that it is not 123 * affected by the bug can ignore this option. 124 * 125 * This option doesn't require a backend to use O_DIRECT, so it 126 * should not be used to try to control the caching behaviour. 127 * 128 *--------------------------------- Features --------------------------------- 129 * 130 * feature-barrier 131 * Values: 0/1 (boolean) 132 * Default Value: 0 133 * 134 * A value of "1" indicates that the backend can process requests 135 * containing the BLKIF_OP_WRITE_BARRIER request opcode. Requests 136 * of this type may still be returned at any time with the 137 * BLKIF_RSP_EOPNOTSUPP result code. 138 * 139 * feature-flush-cache 140 * Values: 0/1 (boolean) 141 * Default Value: 0 142 * 143 * A value of "1" indicates that the backend can process requests 144 * containing the BLKIF_OP_FLUSH_DISKCACHE request opcode. Requests 145 * of this type may still be returned at any time with the 146 * BLKIF_RSP_EOPNOTSUPP result code. 147 * 148 * feature-discard 149 * Values: 0/1 (boolean) 150 * Default Value: 0 151 * 152 * A value of "1" indicates that the backend can process requests 153 * containing the BLKIF_OP_DISCARD request opcode. Requests 154 * of this type may still be returned at any time with the 155 * BLKIF_RSP_EOPNOTSUPP result code. 156 * 157 * feature-persistent 158 * Values: 0/1 (boolean) 159 * Default Value: 0 160 * Notes: 7 161 * 162 * A value of "1" indicates that the backend can keep the grants used 163 * by the frontend driver mapped, so the same set of grants should be 164 * used in all transactions. The maximum number of grants the backend 165 * can map persistently depends on the implementation, but ideally it 166 * should be RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST. Using this 167 * feature the backend doesn't need to unmap each grant, preventing 168 * costly TLB flushes. The backend driver should only map grants 169 * persistently if the frontend supports it. If a backend driver chooses 170 * to use the persistent protocol when the frontend doesn't support it, 171 * it will probably hit the maximum number of persistently mapped grants 172 * (due to the fact that the frontend won't be reusing the same grants), 173 * and fall back to non-persistent mode. Backend implementations may 174 * shrink or expand the number of persistently mapped grants without 175 * notifying the frontend depending on memory constraints (this might 176 * cause a performance degradation). 177 * 178 * If a backend driver wants to limit the maximum number of persistently 179 * mapped grants to a value less than RING_SIZE * 180 * BLKIF_MAX_SEGMENTS_PER_REQUEST a LRU strategy should be used to 181 * discard the grants that are less commonly used. Using a LRU in the 182 * backend driver paired with a LIFO queue in the frontend will 183 * allow us to have better performance in this scenario. 184 * 185 *----------------------- Request Transport Parameters ------------------------ 186 * 187 * max-ring-page-order 188 * Values: <uint32_t> 189 * Default Value: 0 190 * Notes: 1, 3 191 * 192 * The maximum supported size of the request ring buffer in units of 193 * lb(machine pages). (e.g. 0 == 1 page, 1 = 2 pages, 2 == 4 pages, 194 * etc.). 195 * 196 * max-ring-pages 197 * Values: <uint32_t> 198 * Default Value: 1 199 * Notes: DEPRECATED, 2, 3 200 * 201 * The maximum supported size of the request ring buffer in units of 202 * machine pages. The value must be a power of 2. 203 * 204 *------------------------- Backend Device Properties ------------------------- 205 * 206 * discard-enable 207 * Values: 0/1 (boolean) 208 * Default Value: 1 209 * 210 * This optional property, set by the toolstack, instructs the backend 211 * to offer discard to the frontend. If the property is missing the 212 * backend should offer discard if the backing storage actually supports 213 * it. This optional property, set by the toolstack, requests that the 214 * backend offer, or not offer, discard to the frontend. 215 * 216 * discard-alignment 217 * Values: <uint32_t> 218 * Default Value: 0 219 * Notes: 4, 5 220 * 221 * The offset, in bytes from the beginning of the virtual block device, 222 * to the first, addressable, discard extent on the underlying device. 223 * 224 * discard-granularity 225 * Values: <uint32_t> 226 * Default Value: <"sector-size"> 227 * Notes: 4 228 * 229 * The size, in bytes, of the individually addressable discard extents 230 * of the underlying device. 231 * 232 * discard-secure 233 * Values: 0/1 (boolean) 234 * Default Value: 0 235 * Notes: 10 236 * 237 * A value of "1" indicates that the backend can process BLKIF_OP_DISCARD 238 * requests with the BLKIF_DISCARD_SECURE flag set. 239 * 240 * info 241 * Values: <uint32_t> (bitmap) 242 * 243 * A collection of bit flags describing attributes of the backing 244 * device. The VDISK_* macros define the meaning of each bit 245 * location. 246 * 247 * sector-size 248 * Values: <uint32_t> 249 * 250 * The logical sector size, in bytes, of the backend device. 251 * 252 * physical-sector-size 253 * Values: <uint32_t> 254 * 255 * The physical sector size, in bytes, of the backend device. 256 * 257 * sectors 258 * Values: <uint64_t> 259 * 260 * The size of the backend device, expressed in units of its logical 261 * sector size ("sector-size"). 262 * 263 ***************************************************************************** 264 * Frontend XenBus Nodes 265 ***************************************************************************** 266 * 267 *----------------------- Request Transport Parameters ----------------------- 268 * 269 * event-channel 270 * Values: <uint32_t> 271 * 272 * The identifier of the Xen event channel used to signal activity 273 * in the ring buffer. 274 * 275 * ring-ref 276 * Values: <uint32_t> 277 * Notes: 6 278 * 279 * The Xen grant reference granting permission for the backend to map 280 * the sole page in a single page sized ring buffer. 281 * 282 * ring-ref%u 283 * Values: <uint32_t> 284 * Notes: 6 285 * 286 * For a frontend providing a multi-page ring, a "number of ring pages" 287 * sized list of nodes, each containing a Xen grant reference granting 288 * permission for the backend to map the page of the ring located 289 * at page index "%u". Page indexes are zero based. 290 * 291 * protocol 292 * Values: string (XEN_IO_PROTO_ABI_*) 293 * Default Value: XEN_IO_PROTO_ABI_NATIVE 294 * 295 * The machine ABI rules governing the format of all ring request and 296 * response structures. 297 * 298 * ring-page-order 299 * Values: <uint32_t> 300 * Default Value: 0 301 * Maximum Value: MAX(ffs(max-ring-pages) - 1, max-ring-page-order) 302 * Notes: 1, 3 303 * 304 * The size of the frontend allocated request ring buffer in units 305 * of lb(machine pages). (e.g. 0 == 1 page, 1 = 2 pages, 2 == 4 pages, 306 * etc.). 307 * 308 * num-ring-pages 309 * Values: <uint32_t> 310 * Default Value: 1 311 * Maximum Value: MAX(max-ring-pages,(0x1 << max-ring-page-order)) 312 * Notes: DEPRECATED, 2, 3 313 * 314 * The size of the frontend allocated request ring buffer in units of 315 * machine pages. The value must be a power of 2. 316 * 317 * feature-persistent 318 * Values: 0/1 (boolean) 319 * Default Value: 0 320 * Notes: 7, 8, 9 321 * 322 * A value of "1" indicates that the frontend will reuse the same grants 323 * for all transactions, allowing the backend to map them with write 324 * access (even when it should be read-only). If the frontend hits the 325 * maximum number of allowed persistently mapped grants, it can fallback 326 * to non persistent mode. This will cause a performance degradation, 327 * since the backend driver will still try to map those grants 328 * persistently. Since the persistent grants protocol is compatible with 329 * the previous protocol, a frontend driver can choose to work in 330 * persistent mode even when the backend doesn't support it. 331 * 332 * It is recommended that the frontend driver stores the persistently 333 * mapped grants in a LIFO queue, so a subset of all persistently mapped 334 * grants gets used commonly. This is done in case the backend driver 335 * decides to limit the maximum number of persistently mapped grants 336 * to a value less than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST. 337 * 338 *------------------------- Virtual Device Properties ------------------------- 339 * 340 * device-type 341 * Values: "disk", "cdrom", "floppy", etc. 342 * 343 * virtual-device 344 * Values: <uint32_t> 345 * 346 * A value indicating the physical device to virtualize within the 347 * frontend's domain. (e.g. "The first ATA disk", "The third SCSI 348 * disk", etc.) 349 * 350 * See docs/misc/vbd-interface.txt for details on the format of this 351 * value. 352 * 353 * Notes 354 * ----- 355 * (1) Multi-page ring buffer scheme first developed in the Citrix XenServer 356 * PV drivers. 357 * (2) Multi-page ring buffer scheme first used in some RedHat distributions 358 * including a distribution deployed on certain nodes of the Amazon 359 * EC2 cluster. 360 * (3) Support for multi-page ring buffers was implemented independently, 361 * in slightly different forms, by both Citrix and RedHat/Amazon. 362 * For full interoperability, block front and backends should publish 363 * identical ring parameters, adjusted for unit differences, to the 364 * XenStore nodes used in both schemes. 365 * (4) Devices that support discard functionality may internally allocate space 366 * (discardable extents) in units that are larger than the exported logical 367 * block size. If the backing device has such discardable extents the 368 * backend should provide both discard-granularity and discard-alignment. 369 * Providing just one of the two may be considered an error by the frontend. 370 * Backends supporting discard should include discard-granularity and 371 * discard-alignment even if it supports discarding individual sectors. 372 * Frontends should assume discard-alignment == 0 and discard-granularity 373 * == sector size if these keys are missing. 374 * (5) The discard-alignment parameter allows a physical device to be 375 * partitioned into virtual devices that do not necessarily begin or 376 * end on a discardable extent boundary. 377 * (6) When there is only a single page allocated to the request ring, 378 * 'ring-ref' is used to communicate the grant reference for this 379 * page to the backend. When using a multi-page ring, the 'ring-ref' 380 * node is not created. Instead 'ring-ref0' - 'ring-refN' are used. 381 * (7) When using persistent grants data has to be copied from/to the page 382 * where the grant is currently mapped. The overhead of doing this copy 383 * however doesn't suppress the speed improvement of not having to unmap 384 * the grants. 385 * (8) The frontend driver has to allow the backend driver to map all grants 386 * with write access, even when they should be mapped read-only, since 387 * further requests may reuse these grants and require write permissions. 388 * (9) Linux implementation doesn't have a limit on the maximum number of 389 * grants that can be persistently mapped in the frontend driver, but 390 * due to the frontent driver implementation it should never be bigger 391 * than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST. 392 *(10) The discard-secure property may be present and will be set to 1 if the 393 * backing device supports secure discard. 394 */ 395 396/* 397 * STATE DIAGRAMS 398 * 399 ***************************************************************************** 400 * Startup * 401 ***************************************************************************** 402 * 403 * Tool stack creates front and back nodes with state XenbusStateInitialising. 404 * 405 * Front Back 406 * ================================= ===================================== 407 * XenbusStateInitialising XenbusStateInitialising 408 * o Query virtual device o Query backend device identification 409 * properties. data. 410 * o Setup OS device instance. o Open and validate backend device. 411 * o Publish backend features and 412 * transport parameters. 413 * | 414 * | 415 * V 416 * XenbusStateInitWait 417 * 418 * o Query backend features and 419 * transport parameters. 420 * o Allocate and initialize the 421 * request ring. 422 * o Publish transport parameters 423 * that will be in effect during 424 * this connection. 425 * | 426 * | 427 * V 428 * XenbusStateInitialised 429 * 430 * o Query frontend transport parameters. 431 * o Connect to the request ring and 432 * event channel. 433 * o Publish backend device properties. 434 * | 435 * | 436 * V 437 * XenbusStateConnected 438 * 439 * o Query backend device properties. 440 * o Finalize OS virtual device 441 * instance. 442 * | 443 * | 444 * V 445 * XenbusStateConnected 446 * 447 * Note: Drivers that do not support any optional features, or the negotiation 448 * of transport parameters, can skip certain states in the state machine: 449 * 450 * o A frontend may transition to XenbusStateInitialised without 451 * waiting for the backend to enter XenbusStateInitWait. In this 452 * case, default transport parameters are in effect and any 453 * transport parameters published by the frontend must contain 454 * their default values. 455 * 456 * o A backend may transition to XenbusStateInitialised, bypassing 457 * XenbusStateInitWait, without waiting for the frontend to first 458 * enter the XenbusStateInitialised state. In this case, default 459 * transport parameters are in effect and any transport parameters 460 * published by the backend must contain their default values. 461 * 462 * Drivers that support optional features and/or transport parameter 463 * negotiation must tolerate these additional state transition paths. 464 * In general this means performing the work of any skipped state 465 * transition, if it has not already been performed, in addition to the 466 * work associated with entry into the current state. 467 */ 468 469/* 470 * REQUEST CODES. 471 */ 472#define BLKIF_OP_READ 0 473#define BLKIF_OP_WRITE 1 474/* 475 * All writes issued prior to a request with the BLKIF_OP_WRITE_BARRIER 476 * operation code ("barrier request") must be completed prior to the 477 * execution of the barrier request. All writes issued after the barrier 478 * request must not execute until after the completion of the barrier request. 479 * 480 * Optional. See "feature-barrier" XenBus node documentation above. 481 */ 482#define BLKIF_OP_WRITE_BARRIER 2 483/* 484 * Commit any uncommitted contents of the backing device's volatile cache 485 * to stable storage. 486 * 487 * Optional. See "feature-flush-cache" XenBus node documentation above. 488 */ 489#define BLKIF_OP_FLUSH_DISKCACHE 3 490/* 491 * Used in SLES sources for device specific command packet 492 * contained within the request. Reserved for that purpose. 493 */ 494#define BLKIF_OP_RESERVED_1 4 495/* 496 * Indicate to the backend device that a region of storage is no longer in 497 * use, and may be discarded at any time without impact to the client. If 498 * the BLKIF_DISCARD_SECURE flag is set on the request, all copies of the 499 * discarded region on the device must be rendered unrecoverable before the 500 * command returns. 501 * 502 * This operation is analogous to performing a trim (ATA) or unamp (SCSI), 503 * command on a native device. 504 * 505 * More information about trim/unmap operations can be found at: 506 * http://t13.org/Documents/UploadedDocuments/docs2008/ 507 * e07154r6-Data_Set_Management_Proposal_for_ATA-ACS2.doc 508 * http://www.seagate.com/staticfiles/support/disc/manuals/ 509 * Interface%20manuals/100293068c.pdf 510 * 511 * Optional. See "feature-discard", "discard-alignment", 512 * "discard-granularity", and "discard-secure" in the XenBus node 513 * documentation above. 514 */ 515#define BLKIF_OP_DISCARD 5 516 517/* 518 * Recognized if "feature-max-indirect-segments" in present in the backend 519 * xenbus info. The "feature-max-indirect-segments" node contains the maximum 520 * number of segments allowed by the backend per request. If the node is 521 * present, the frontend might use blkif_request_indirect structs in order to 522 * issue requests with more than BLKIF_MAX_SEGMENTS_PER_REQUEST (11). The 523 * maximum number of indirect segments is fixed by the backend, but the 524 * frontend can issue requests with any number of indirect segments as long as 525 * it's less than the number provided by the backend. The indirect_grefs field 526 * in blkif_request_indirect should be filled by the frontend with the 527 * grant references of the pages that are holding the indirect segments. 528 * These pages are filled with an array of blkif_request_segment that hold the 529 * information about the segments. The number of indirect pages to use is 530 * determined by the number of segments an indirect request contains. Every 531 * indirect page can contain a maximum of 532 * (PAGE_SIZE / sizeof(struct blkif_request_segment)) segments, so to 533 * calculate the number of indirect pages to use we have to do 534 * ceil(indirect_segments / (PAGE_SIZE / sizeof(struct blkif_request_segment))). 535 * 536 * If a backend does not recognize BLKIF_OP_INDIRECT, it should *not* 537 * create the "feature-max-indirect-segments" node! 538 */ 539#define BLKIF_OP_INDIRECT 6 540 541/* 542 * Maximum scatter/gather segments per request. 543 * This is carefully chosen so that sizeof(blkif_ring_t) <= PAGE_SIZE. 544 * NB. This could be 12 if the ring indexes weren't stored in the same page. 545 */ 546#define BLKIF_MAX_SEGMENTS_PER_REQUEST 11 547 548/* 549 * Maximum number of indirect pages to use per request. 550 */ 551#define BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST 8 552 553/* 554 * NB. first_sect and last_sect in blkif_request_segment, as well as 555 * sector_number in blkif_request, are always expressed in 512-byte units. 556 * However they must be properly aligned to the real sector size of the 557 * physical disk, which is reported in the "physical-sector-size" node in 558 * the backend xenbus info. Also the xenbus "sectors" node is expressed in 559 * 512-byte units. 560 */ 561struct blkif_request_segment { 562 grant_ref_t gref; /* reference to I/O buffer frame */ 563 /* @first_sect: first sector in frame to transfer (inclusive). */ 564 /* @last_sect: last sector in frame to transfer (inclusive). */ 565 uint8_t first_sect, last_sect; 566}; 567 568/* 569 * Starting ring element for any I/O request. 570 */ 571struct blkif_request { 572 uint8_t operation; /* BLKIF_OP_??? */ 573 uint8_t nr_segments; /* number of segments */ 574 blkif_vdev_t handle; /* only for read/write requests */ 575 uint64_t id; /* private guest value, echoed in resp */ 576 blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */ 577 struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST]; 578}; 579typedef struct blkif_request blkif_request_t; 580 581/* 582 * Cast to this structure when blkif_request.operation == BLKIF_OP_DISCARD 583 * sizeof(struct blkif_request_discard) <= sizeof(struct blkif_request) 584 */ 585struct blkif_request_discard { 586 uint8_t operation; /* BLKIF_OP_DISCARD */ 587 uint8_t flag; /* BLKIF_DISCARD_SECURE or zero */ 588#define BLKIF_DISCARD_SECURE (1<<0) /* ignored if discard-secure=0 */ 589 blkif_vdev_t handle; /* same as for read/write requests */ 590 uint64_t id; /* private guest value, echoed in resp */ 591 blkif_sector_t sector_number;/* start sector idx on disk */ 592 uint64_t nr_sectors; /* number of contiguous sectors to discard*/ 593}; 594typedef struct blkif_request_discard blkif_request_discard_t; 595 596struct blkif_request_indirect { 597 uint8_t operation; /* BLKIF_OP_INDIRECT */ 598 uint8_t indirect_op; /* BLKIF_OP_{READ/WRITE} */ 599 uint16_t nr_segments; /* number of segments */ 600 uint64_t id; /* private guest value, echoed in resp */ 601 blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */ 602 blkif_vdev_t handle; /* same as for read/write requests */ 603 grant_ref_t indirect_grefs[BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST]; 604#ifdef __i386__ 605 uint64_t pad; /* Make it 64 byte aligned on i386 */ 606#endif 607}; 608typedef struct blkif_request_indirect blkif_request_indirect_t; 609 610struct blkif_response { 611 uint64_t id; /* copied from request */ 612 uint8_t operation; /* copied from request */ 613 int16_t status; /* BLKIF_RSP_??? */ 614}; 615typedef struct blkif_response blkif_response_t; 616 617/* 618 * STATUS RETURN CODES. 619 */ 620 /* Operation not supported (only happens on barrier writes). */ 621#define BLKIF_RSP_EOPNOTSUPP -2 622 /* Operation failed for some unspecified reason (-EIO). */ 623#define BLKIF_RSP_ERROR -1 624 /* Operation completed successfully. */ 625#define BLKIF_RSP_OKAY 0 626 627/* 628 * Generate blkif ring structures and types. 629 */ 630DEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response); 631 632#define VDISK_CDROM 0x1 633#define VDISK_REMOVABLE 0x2 634#define VDISK_READONLY 0x4 635 636#endif /* __XEN_PUBLIC_IO_BLKIF_H__ */ 637 638/* 639 * Local variables: 640 * mode: C 641 * c-file-style: "BSD" 642 * c-basic-offset: 4 643 * tab-width: 4 644 * indent-tabs-mode: nil 645 * End: 646 */ 647