blkif.h revision 287802
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 formatted 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 * Data used by the backend driver to locate and configure the backing 92 * device. The format and semantics of this data vary according to the 93 * backing device in use and are outside the scope of this specification. 94 * 95 * type 96 * Values: "file", "phy", "tap" 97 * 98 * The type of the backing device/object. 99 * 100 * 101 * direct-io-safe 102 * Values: 0/1 (boolean) 103 * Default Value: 0 104 * 105 * The underlying storage is not affected by the direct IO memory 106 * lifetime bug. See: 107 * http://lists.xen.org/archives/html/xen-devel/2012-12/msg01154.html 108 * 109 * Therefore this option gives the backend permission to use 110 * O_DIRECT, notwithstanding that bug. 111 * 112 * That is, if this option is enabled, use of O_DIRECT is safe, 113 * in circumstances where we would normally have avoided it as a 114 * workaround for that bug. This option is not relevant for all 115 * backends, and even not necessarily supported for those for 116 * which it is relevant. A backend which knows that it is not 117 * affected by the bug can ignore this option. 118 * 119 * This option doesn't require a backend to use O_DIRECT, so it 120 * should not be used to try to control the caching behaviour. 121 * 122 *--------------------------------- Features --------------------------------- 123 * 124 * feature-barrier 125 * Values: 0/1 (boolean) 126 * Default Value: 0 127 * 128 * A value of "1" indicates that the backend can process requests 129 * containing the BLKIF_OP_WRITE_BARRIER request opcode. Requests 130 * of this type may still be returned at any time with the 131 * BLKIF_RSP_EOPNOTSUPP result code. 132 * 133 * feature-flush-cache 134 * Values: 0/1 (boolean) 135 * Default Value: 0 136 * 137 * A value of "1" indicates that the backend can process requests 138 * containing the BLKIF_OP_FLUSH_DISKCACHE request opcode. Requests 139 * of this type may still be returned at any time with the 140 * BLKIF_RSP_EOPNOTSUPP result code. 141 * 142 * feature-discard 143 * Values: 0/1 (boolean) 144 * Default Value: 0 145 * 146 * A value of "1" indicates that the backend can process requests 147 * containing the BLKIF_OP_DISCARD request opcode. Requests 148 * of this type may still be returned at any time with the 149 * BLKIF_RSP_EOPNOTSUPP result code. 150 * 151 * feature-persistent 152 * Values: 0/1 (boolean) 153 * Default Value: 0 154 * Notes: 7 155 * 156 * A value of "1" indicates that the backend can keep the grants used 157 * by the frontend driver mapped, so the same set of grants should be 158 * used in all transactions. The maximum number of grants the backend 159 * can map persistently depends on the implementation, but ideally it 160 * should be RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST. Using this 161 * feature the backend doesn't need to unmap each grant, preventing 162 * costly TLB flushes. The backend driver should only map grants 163 * persistently if the frontend supports it. If a backend driver chooses 164 * to use the persistent protocol when the frontend doesn't support it, 165 * it will probably hit the maximum number of persistently mapped grants 166 * (due to the fact that the frontend won't be reusing the same grants), 167 * and fall back to non-persistent mode. Backend implementations may 168 * shrink or expand the number of persistently mapped grants without 169 * notifying the frontend depending on memory constraints (this might 170 * cause a performance degradation). 171 * 172 * If a backend driver wants to limit the maximum number of persistently 173 * mapped grants to a value less than RING_SIZE * 174 * BLKIF_MAX_SEGMENTS_PER_REQUEST a LRU strategy should be used to 175 * discard the grants that are less commonly used. Using a LRU in the 176 * backend driver paired with a LIFO queue in the frontend will 177 * allow us to have better performance in this scenario. 178 * 179 *----------------------- Request Transport Parameters ------------------------ 180 * 181 * max-ring-page-order 182 * Values: <uint32_t> 183 * Default Value: 0 184 * Notes: 1, 3 185 * 186 * The maximum supported size of the request ring buffer in units of 187 * lb(machine pages). (e.g. 0 == 1 page, 1 = 2 pages, 2 == 4 pages, 188 * etc.). 189 * 190 * max-ring-pages 191 * Values: <uint32_t> 192 * Default Value: 1 193 * Notes: DEPRECATED, 2, 3 194 * 195 * The maximum supported size of the request ring buffer in units of 196 * machine pages. The value must be a power of 2. 197 * 198 *------------------------- Backend Device Properties ------------------------- 199 * 200 * discard-enable 201 * Values: 0/1 (boolean) 202 * Default Value: 1 203 * 204 * This optional property, set by the toolstack, instructs the backend 205 * to offer discard to the frontend. If the property is missing the 206 * backend should offer discard if the backing storage actually supports 207 * it. This optional property, set by the toolstack, requests that the 208 * backend offer, or not offer, discard to the frontend. 209 * 210 * discard-alignment 211 * Values: <uint32_t> 212 * Default Value: 0 213 * Notes: 4, 5 214 * 215 * The offset, in bytes from the beginning of the virtual block device, 216 * to the first, addressable, discard extent on the underlying device. 217 * 218 * discard-granularity 219 * Values: <uint32_t> 220 * Default Value: <"sector-size"> 221 * Notes: 4 222 * 223 * The size, in bytes, of the individually addressable discard extents 224 * of the underlying device. 225 * 226 * discard-secure 227 * Values: 0/1 (boolean) 228 * Default Value: 0 229 * Notes: 10 230 * 231 * A value of "1" indicates that the backend can process BLKIF_OP_DISCARD 232 * requests with the BLKIF_DISCARD_SECURE flag set. 233 * 234 * info 235 * Values: <uint32_t> (bitmap) 236 * 237 * A collection of bit flags describing attributes of the backing 238 * device. The VDISK_* macros define the meaning of each bit 239 * location. 240 * 241 * sector-size 242 * Values: <uint32_t> 243 * 244 * The logical sector size, in bytes, of the backend device. 245 * 246 * physical-sector-size 247 * Values: <uint32_t> 248 * 249 * The physical sector size, in bytes, of the backend device. 250 * 251 * sectors 252 * Values: <uint64_t> 253 * 254 * The size of the backend device, expressed in units of its logical 255 * sector size ("sector-size"). 256 * 257 ***************************************************************************** 258 * Frontend XenBus Nodes 259 ***************************************************************************** 260 * 261 *----------------------- Request Transport Parameters ----------------------- 262 * 263 * event-channel 264 * Values: <uint32_t> 265 * 266 * The identifier of the Xen event channel used to signal activity 267 * in the ring buffer. 268 * 269 * ring-ref 270 * Values: <uint32_t> 271 * Notes: 6 272 * 273 * The Xen grant reference granting permission for the backend to map 274 * the sole page in a single page sized ring buffer. 275 * 276 * ring-ref%u 277 * Values: <uint32_t> 278 * Notes: 6 279 * 280 * For a frontend providing a multi-page ring, a "number of ring pages" 281 * sized list of nodes, each containing a Xen grant reference granting 282 * permission for the backend to map the page of the ring located 283 * at page index "%u". Page indexes are zero based. 284 * 285 * protocol 286 * Values: string (XEN_IO_PROTO_ABI_*) 287 * Default Value: XEN_IO_PROTO_ABI_NATIVE 288 * 289 * The machine ABI rules governing the format of all ring request and 290 * response structures. 291 * 292 * ring-page-order 293 * Values: <uint32_t> 294 * Default Value: 0 295 * Maximum Value: MAX(ffs(max-ring-pages) - 1, max-ring-page-order) 296 * Notes: 1, 3 297 * 298 * The size of the frontend allocated request ring buffer in units 299 * of lb(machine pages). (e.g. 0 == 1 page, 1 = 2 pages, 2 == 4 pages, 300 * etc.). 301 * 302 * num-ring-pages 303 * Values: <uint32_t> 304 * Default Value: 1 305 * Maximum Value: MAX(max-ring-pages,(0x1 << max-ring-page-order)) 306 * Notes: DEPRECATED, 2, 3 307 * 308 * The size of the frontend allocated request ring buffer in units of 309 * machine pages. The value must be a power of 2. 310 * 311 * feature-persistent 312 * Values: 0/1 (boolean) 313 * Default Value: 0 314 * Notes: 7, 8, 9 315 * 316 * A value of "1" indicates that the frontend will reuse the same grants 317 * for all transactions, allowing the backend to map them with write 318 * access (even when it should be read-only). If the frontend hits the 319 * maximum number of allowed persistently mapped grants, it can fallback 320 * to non persistent mode. This will cause a performance degradation, 321 * since the the backend driver will still try to map those grants 322 * persistently. Since the persistent grants protocol is compatible with 323 * the previous protocol, a frontend driver can choose to work in 324 * persistent mode even when the backend doesn't support it. 325 * 326 * It is recommended that the frontend driver stores the persistently 327 * mapped grants in a LIFO queue, so a subset of all persistently mapped 328 * grants gets used commonly. This is done in case the backend driver 329 * decides to limit the maximum number of persistently mapped grants 330 * to a value less than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST. 331 * 332 *------------------------- Virtual Device Properties ------------------------- 333 * 334 * device-type 335 * Values: "disk", "cdrom", "floppy", etc. 336 * 337 * virtual-device 338 * Values: <uint32_t> 339 * 340 * A value indicating the physical device to virtualize within the 341 * frontend's domain. (e.g. "The first ATA disk", "The third SCSI 342 * disk", etc.) 343 * 344 * See docs/misc/vbd-interface.txt for details on the format of this 345 * value. 346 * 347 * Notes 348 * ----- 349 * (1) Multi-page ring buffer scheme first developed in the Citrix XenServer 350 * PV drivers. 351 * (2) Multi-page ring buffer scheme first used in some RedHat distributions 352 * including a distribution deployed on certain nodes of the Amazon 353 * EC2 cluster. 354 * (3) Support for multi-page ring buffers was implemented independently, 355 * in slightly different forms, by both Citrix and RedHat/Amazon. 356 * For full interoperability, block front and backends should publish 357 * identical ring parameters, adjusted for unit differences, to the 358 * XenStore nodes used in both schemes. 359 * (4) Devices that support discard functionality may internally allocate space 360 * (discardable extents) in units that are larger than the exported logical 361 * block size. If the backing device has such discardable extents the 362 * backend should provide both discard-granularity and discard-alignment. 363 * Providing just one of the two may be considered an error by the frontend. 364 * Backends supporting discard should include discard-granularity and 365 * discard-alignment even if it supports discarding individual sectors. 366 * Frontends should assume discard-alignment == 0 and discard-granularity 367 * == sector size if these keys are missing. 368 * (5) The discard-alignment parameter allows a physical device to be 369 * partitioned into virtual devices that do not necessarily begin or 370 * end on a discardable extent boundary. 371 * (6) When there is only a single page allocated to the request ring, 372 * 'ring-ref' is used to communicate the grant reference for this 373 * page to the backend. When using a multi-page ring, the 'ring-ref' 374 * node is not created. Instead 'ring-ref0' - 'ring-refN' are used. 375 * (7) When using persistent grants data has to be copied from/to the page 376 * where the grant is currently mapped. The overhead of doing this copy 377 * however doesn't suppress the speed improvement of not having to unmap 378 * the grants. 379 * (8) The frontend driver has to allow the backend driver to map all grants 380 * with write access, even when they should be mapped read-only, since 381 * further requests may reuse these grants and require write permissions. 382 * (9) Linux implementation doesn't have a limit on the maximum number of 383 * grants that can be persistently mapped in the frontend driver, but 384 * due to the frontent driver implementation it should never be bigger 385 * than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST. 386 *(10) The discard-secure property may be present and will be set to 1 if the 387 * backing device supports secure discard. 388 */ 389 390/* 391 * STATE DIAGRAMS 392 * 393 ***************************************************************************** 394 * Startup * 395 ***************************************************************************** 396 * 397 * Tool stack creates front and back nodes with state XenbusStateInitialising. 398 * 399 * Front Back 400 * ================================= ===================================== 401 * XenbusStateInitialising XenbusStateInitialising 402 * o Query virtual device o Query backend device identification 403 * properties. data. 404 * o Setup OS device instance. o Open and validate backend device. 405 * o Publish backend features and 406 * transport parameters. 407 * | 408 * | 409 * V 410 * XenbusStateInitWait 411 * 412 * o Query backend features and 413 * transport parameters. 414 * o Allocate and initialize the 415 * request ring. 416 * o Publish transport parameters 417 * that will be in effect during 418 * this connection. 419 * | 420 * | 421 * V 422 * XenbusStateInitialised 423 * 424 * o Query frontend transport parameters. 425 * o Connect to the request ring and 426 * event channel. 427 * o Publish backend device properties. 428 * | 429 * | 430 * V 431 * XenbusStateConnected 432 * 433 * o Query backend device properties. 434 * o Finalize OS virtual device 435 * instance. 436 * | 437 * | 438 * V 439 * XenbusStateConnected 440 * 441 * Note: Drivers that do not support any optional features, or the negotiation 442 * of transport parameters, can skip certain states in the state machine: 443 * 444 * o A frontend may transition to XenbusStateInitialised without 445 * waiting for the backend to enter XenbusStateInitWait. In this 446 * case, default transport parameters are in effect and any 447 * transport parameters published by the frontend must contain 448 * their default values. 449 * 450 * o A backend may transition to XenbusStateInitialised, bypassing 451 * XenbusStateInitWait, without waiting for the frontend to first 452 * enter the XenbusStateInitialised state. In this case, default 453 * transport parameters are in effect and any transport parameters 454 * published by the backend must contain their default values. 455 * 456 * Drivers that support optional features and/or transport parameter 457 * negotiation must tolerate these additional state transition paths. 458 * In general this means performing the work of any skipped state 459 * transition, if it has not already been performed, in addition to the 460 * work associated with entry into the current state. 461 */ 462 463/* 464 * REQUEST CODES. 465 */ 466#define BLKIF_OP_READ 0 467#define BLKIF_OP_WRITE 1 468/* 469 * All writes issued prior to a request with the BLKIF_OP_WRITE_BARRIER 470 * operation code ("barrier request") must be completed prior to the 471 * execution of the barrier request. All writes issued after the barrier 472 * request must not execute until after the completion of the barrier request. 473 * 474 * Optional. See "feature-barrier" XenBus node documentation above. 475 */ 476#define BLKIF_OP_WRITE_BARRIER 2 477/* 478 * Commit any uncommitted contents of the backing device's volatile cache 479 * to stable storage. 480 * 481 * Optional. See "feature-flush-cache" XenBus node documentation above. 482 */ 483#define BLKIF_OP_FLUSH_DISKCACHE 3 484/* 485 * Used in SLES sources for device specific command packet 486 * contained within the request. Reserved for that purpose. 487 */ 488#define BLKIF_OP_RESERVED_1 4 489/* 490 * Indicate to the backend device that a region of storage is no longer in 491 * use, and may be discarded at any time without impact to the client. If 492 * the BLKIF_DISCARD_SECURE flag is set on the request, all copies of the 493 * discarded region on the device must be rendered unrecoverable before the 494 * command returns. 495 * 496 * This operation is analogous to performing a trim (ATA) or unmap (SCSI), 497 * command on a native device. 498 * 499 * More information about trim/unmap operations can be found at: 500 * http://t13.org/Documents/UploadedDocuments/docs2008/ 501 * e07154r6-Data_Set_Management_Proposal_for_ATA-ACS2.doc 502 * http://www.seagate.com/staticfiles/support/disc/manuals/ 503 * Interface%20manuals/100293068c.pdf 504 * 505 * Optional. See "feature-discard", "discard-alignment", 506 * "discard-granularity", and "discard-secure" in the XenBus node 507 * documentation above. 508 */ 509#define BLKIF_OP_DISCARD 5 510 511/* 512 * Recognized if "feature-max-indirect-segments" in present in the backend 513 * xenbus info. The "feature-max-indirect-segments" node contains the maximum 514 * number of segments allowed by the backend per request. If the node is 515 * present, the frontend might use blkif_request_indirect structs in order to 516 * issue requests with more than BLKIF_MAX_SEGMENTS_PER_REQUEST (11). The 517 * maximum number of indirect segments is fixed by the backend, but the 518 * frontend can issue requests with any number of indirect segments as long as 519 * it's less than the number provided by the backend. The indirect_grefs field 520 * in blkif_request_indirect should be filled by the frontend with the 521 * grant references of the pages that are holding the indirect segments. 522 * These pages are filled with an array of blkif_request_segment that hold the 523 * information about the segments. The number of indirect pages to use is 524 * determined by the number of segments an indirect request contains. Every 525 * indirect page can contain a maximum of 526 * (PAGE_SIZE / sizeof(struct blkif_request_segment)) segments, so to 527 * calculate the number of indirect pages to use we have to do 528 * ceil(indirect_segments / (PAGE_SIZE / sizeof(struct blkif_request_segment))). 529 * 530 * If a backend does not recognize BLKIF_OP_INDIRECT, it should *not* 531 * create the "feature-max-indirect-segments" node! 532 */ 533#define BLKIF_OP_INDIRECT 6 534 535/* 536 * Maximum scatter/gather segments per request. 537 * This is carefully chosen so that sizeof(blkif_ring_t) <= PAGE_SIZE. 538 * NB. This could be 12 if the ring indexes weren't stored in the same page. 539 */ 540#define BLKIF_MAX_SEGMENTS_PER_REQUEST 11 541 542/* 543 * Maximum number of indirect pages to use per request. 544 */ 545#define BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST 8 546 547/* 548 * NB. first_sect and last_sect in blkif_request_segment, as well as 549 * sector_number in blkif_request, are always expressed in 512-byte units. 550 * However they must be properly aligned to the real sector size of the 551 * physical disk, which is reported in the "physical-sector-size" node in 552 * the backend xenbus info. Also the xenbus "sectors" node is expressed in 553 * 512-byte units. 554 */ 555struct blkif_request_segment { 556 grant_ref_t gref; /* reference to I/O buffer frame */ 557 /* @first_sect: first sector in frame to transfer (inclusive). */ 558 /* @last_sect: last sector in frame to transfer (inclusive). */ 559 uint8_t first_sect, last_sect; 560}; 561typedef struct blkif_request_segment blkif_request_segment_t; 562 563/* 564 * Starting ring element for any I/O request. 565 */ 566struct blkif_request { 567 uint8_t operation; /* BLKIF_OP_??? */ 568 uint8_t nr_segments; /* number of segments */ 569 blkif_vdev_t handle; /* only for read/write requests */ 570 uint64_t id; /* private guest value, echoed in resp */ 571 blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */ 572 blkif_request_segment_t seg[BLKIF_MAX_SEGMENTS_PER_REQUEST]; 573}; 574typedef struct blkif_request blkif_request_t; 575 576/* 577 * Cast to this structure when blkif_request.operation == BLKIF_OP_DISCARD 578 * sizeof(struct blkif_request_discard) <= sizeof(struct blkif_request) 579 */ 580struct blkif_request_discard { 581 uint8_t operation; /* BLKIF_OP_DISCARD */ 582 uint8_t flag; /* BLKIF_DISCARD_SECURE or zero */ 583#define BLKIF_DISCARD_SECURE (1<<0) /* ignored if discard-secure=0 */ 584 blkif_vdev_t handle; /* same as for read/write requests */ 585 uint64_t id; /* private guest value, echoed in resp */ 586 blkif_sector_t sector_number;/* start sector idx on disk */ 587 uint64_t nr_sectors; /* number of contiguous sectors to discard*/ 588}; 589typedef struct blkif_request_discard blkif_request_discard_t; 590 591struct blkif_request_indirect { 592 uint8_t operation; /* BLKIF_OP_INDIRECT */ 593 uint8_t indirect_op; /* BLKIF_OP_{READ/WRITE} */ 594 uint16_t nr_segments; /* number of segments */ 595 uint64_t id; /* private guest value, echoed in resp */ 596 blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */ 597 blkif_vdev_t handle; /* same as for read/write requests */ 598 grant_ref_t indirect_grefs[BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST]; 599#ifdef __i386__ 600 uint64_t pad; /* Make it 64 byte aligned on i386 */ 601#endif 602}; 603typedef struct blkif_request_indirect blkif_request_indirect_t; 604 605struct blkif_response { 606 uint64_t id; /* copied from request */ 607 uint8_t operation; /* copied from request */ 608 int16_t status; /* BLKIF_RSP_??? */ 609}; 610typedef struct blkif_response blkif_response_t; 611 612/* 613 * STATUS RETURN CODES. 614 */ 615 /* Operation not supported (only happens on barrier writes). */ 616#define BLKIF_RSP_EOPNOTSUPP -2 617 /* Operation failed for some unspecified reason (-EIO). */ 618#define BLKIF_RSP_ERROR -1 619 /* Operation completed successfully. */ 620#define BLKIF_RSP_OKAY 0 621 622/* 623 * Generate blkif ring structures and types. 624 */ 625DEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response); 626 627#define VDISK_CDROM 0x1 628#define VDISK_REMOVABLE 0x2 629#define VDISK_READONLY 0x4 630 631#endif /* __XEN_PUBLIC_IO_BLKIF_H__ */ 632 633/* 634 * Local variables: 635 * mode: C 636 * c-file-style: "BSD" 637 * c-basic-offset: 4 638 * tab-width: 4 639 * indent-tabs-mode: nil 640 * End: 641 */ 642