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 * hotplug script to attach the device and provide a suitable 93 * handler (ie: a block device) for blkback to use. 94 * 95 * physical-device 96 * Values: "MAJOR:MINOR" 97 * Notes: 11 98 * 99 * MAJOR and MINOR are the major number and minor number of the 100 * backing device respectively. 101 * 102 * physical-device-path 103 * Values: path string 104 * 105 * A string that contains the absolute path to the disk image. On 106 * NetBSD and Linux this is always a block device, while on FreeBSD 107 * it can be either a block device or a regular file. 108 * 109 * type 110 * Values: "file", "phy", "tap" 111 * 112 * The type of the backing device/object. 113 * 114 * 115 * direct-io-safe 116 * Values: 0/1 (boolean) 117 * Default Value: 0 118 * 119 * The underlying storage is not affected by the direct IO memory 120 * lifetime bug. See: 121 * http://lists.xen.org/archives/html/xen-devel/2012-12/msg01154.html 122 * 123 * Therefore this option gives the backend permission to use 124 * O_DIRECT, notwithstanding that bug. 125 * 126 * That is, if this option is enabled, use of O_DIRECT is safe, 127 * in circumstances where we would normally have avoided it as a 128 * workaround for that bug. This option is not relevant for all 129 * backends, and even not necessarily supported for those for 130 * which it is relevant. A backend which knows that it is not 131 * affected by the bug can ignore this option. 132 * 133 * This option doesn't require a backend to use O_DIRECT, so it 134 * should not be used to try to control the caching behaviour. 135 * 136 *--------------------------------- Features --------------------------------- 137 * 138 * feature-barrier 139 * Values: 0/1 (boolean) 140 * Default Value: 0 141 * 142 * A value of "1" indicates that the backend can process requests 143 * containing the BLKIF_OP_WRITE_BARRIER request opcode. Requests 144 * of this type may still be returned at any time with the 145 * BLKIF_RSP_EOPNOTSUPP result code. 146 * 147 * feature-flush-cache 148 * Values: 0/1 (boolean) 149 * Default Value: 0 150 * 151 * A value of "1" indicates that the backend can process requests 152 * containing the BLKIF_OP_FLUSH_DISKCACHE request opcode. Requests 153 * of this type may still be returned at any time with the 154 * BLKIF_RSP_EOPNOTSUPP result code. 155 * 156 * feature-discard 157 * Values: 0/1 (boolean) 158 * Default Value: 0 159 * 160 * A value of "1" indicates that the backend can process requests 161 * containing the BLKIF_OP_DISCARD request opcode. Requests 162 * of this type may still be returned at any time with the 163 * BLKIF_RSP_EOPNOTSUPP result code. 164 * 165 * feature-persistent 166 * Values: 0/1 (boolean) 167 * Default Value: 0 168 * Notes: 7 169 * 170 * A value of "1" indicates that the backend can keep the grants used 171 * by the frontend driver mapped, so the same set of grants should be 172 * used in all transactions. The maximum number of grants the backend 173 * can map persistently depends on the implementation, but ideally it 174 * should be RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST. Using this 175 * feature the backend doesn't need to unmap each grant, preventing 176 * costly TLB flushes. The backend driver should only map grants 177 * persistently if the frontend supports it. If a backend driver chooses 178 * to use the persistent protocol when the frontend doesn't support it, 179 * it will probably hit the maximum number of persistently mapped grants 180 * (due to the fact that the frontend won't be reusing the same grants), 181 * and fall back to non-persistent mode. Backend implementations may 182 * shrink or expand the number of persistently mapped grants without 183 * notifying the frontend depending on memory constraints (this might 184 * cause a performance degradation). 185 * 186 * If a backend driver wants to limit the maximum number of persistently 187 * mapped grants to a value less than RING_SIZE * 188 * BLKIF_MAX_SEGMENTS_PER_REQUEST a LRU strategy should be used to 189 * discard the grants that are less commonly used. Using a LRU in the 190 * backend driver paired with a LIFO queue in the frontend will 191 * allow us to have better performance in this scenario. 192 * 193 *----------------------- Request Transport Parameters ------------------------ 194 * 195 * max-ring-page-order 196 * Values: <uint32_t> 197 * Default Value: 0 198 * Notes: 1, 3 199 * 200 * The maximum supported size of the request ring buffer in units of 201 * lb(machine pages). (e.g. 0 == 1 page, 1 = 2 pages, 2 == 4 pages, 202 * etc.). 203 * 204 * max-ring-pages 205 * Values: <uint32_t> 206 * Default Value: 1 207 * Notes: DEPRECATED, 2, 3 208 * 209 * The maximum supported size of the request ring buffer in units of 210 * machine pages. The value must be a power of 2. 211 * 212 *------------------------- Backend Device Properties ------------------------- 213 * 214 * discard-enable 215 * Values: 0/1 (boolean) 216 * Default Value: 1 217 * 218 * This optional property, set by the toolstack, instructs the backend 219 * to offer (or not to offer) discard to the frontend. If the property 220 * is missing the backend should offer discard if the backing storage 221 * actually supports it. 222 * 223 * discard-alignment 224 * Values: <uint32_t> 225 * Default Value: 0 226 * Notes: 4, 5 227 * 228 * The offset, in bytes from the beginning of the virtual block device, 229 * to the first, addressable, discard extent on the underlying device. 230 * 231 * discard-granularity 232 * Values: <uint32_t> 233 * Default Value: <"sector-size"> 234 * Notes: 4 235 * 236 * The size, in bytes, of the individually addressable discard extents 237 * of the underlying device. 238 * 239 * discard-secure 240 * Values: 0/1 (boolean) 241 * Default Value: 0 242 * Notes: 10 243 * 244 * A value of "1" indicates that the backend can process BLKIF_OP_DISCARD 245 * requests with the BLKIF_DISCARD_SECURE flag set. 246 * 247 * info 248 * Values: <uint32_t> (bitmap) 249 * 250 * A collection of bit flags describing attributes of the backing 251 * device. The VDISK_* macros define the meaning of each bit 252 * location. 253 * 254 * sector-size 255 * Values: <uint32_t> 256 * 257 * The logical sector size, in bytes, of the backend device. 258 * 259 * physical-sector-size 260 * Values: <uint32_t> 261 * 262 * The physical sector size, in bytes, of the backend device. 263 * 264 * sectors 265 * Values: <uint64_t> 266 * 267 * The size of the backend device, expressed in units of its logical 268 * sector size ("sector-size"). 269 * 270 ***************************************************************************** 271 * Frontend XenBus Nodes 272 ***************************************************************************** 273 * 274 *----------------------- Request Transport Parameters ----------------------- 275 * 276 * event-channel 277 * Values: <uint32_t> 278 * 279 * The identifier of the Xen event channel used to signal activity 280 * in the ring buffer. 281 * 282 * ring-ref 283 * Values: <uint32_t> 284 * Notes: 6 285 * 286 * The Xen grant reference granting permission for the backend to map 287 * the sole page in a single page sized ring buffer. 288 * 289 * ring-ref%u 290 * Values: <uint32_t> 291 * Notes: 6 292 * 293 * For a frontend providing a multi-page ring, a "number of ring pages" 294 * sized list of nodes, each containing a Xen grant reference granting 295 * permission for the backend to map the page of the ring located 296 * at page index "%u". Page indexes are zero based. 297 * 298 * protocol 299 * Values: string (XEN_IO_PROTO_ABI_*) 300 * Default Value: XEN_IO_PROTO_ABI_NATIVE 301 * 302 * The machine ABI rules governing the format of all ring request and 303 * response structures. 304 * 305 * ring-page-order 306 * Values: <uint32_t> 307 * Default Value: 0 308 * Maximum Value: MAX(ffs(max-ring-pages) - 1, max-ring-page-order) 309 * Notes: 1, 3 310 * 311 * The size of the frontend allocated request ring buffer in units 312 * of lb(machine pages). (e.g. 0 == 1 page, 1 = 2 pages, 2 == 4 pages, 313 * etc.). 314 * 315 * num-ring-pages 316 * Values: <uint32_t> 317 * Default Value: 1 318 * Maximum Value: MAX(max-ring-pages,(0x1 << max-ring-page-order)) 319 * Notes: DEPRECATED, 2, 3 320 * 321 * The size of the frontend allocated request ring buffer in units of 322 * machine pages. The value must be a power of 2. 323 * 324 * feature-persistent 325 * Values: 0/1 (boolean) 326 * Default Value: 0 327 * Notes: 7, 8, 9 328 * 329 * A value of "1" indicates that the frontend will reuse the same grants 330 * for all transactions, allowing the backend to map them with write 331 * access (even when it should be read-only). If the frontend hits the 332 * maximum number of allowed persistently mapped grants, it can fallback 333 * to non persistent mode. This will cause a performance degradation, 334 * since the the backend driver will still try to map those grants 335 * persistently. Since the persistent grants protocol is compatible with 336 * the previous protocol, a frontend driver can choose to work in 337 * persistent mode even when the backend doesn't support it. 338 * 339 * It is recommended that the frontend driver stores the persistently 340 * mapped grants in a LIFO queue, so a subset of all persistently mapped 341 * grants gets used commonly. This is done in case the backend driver 342 * decides to limit the maximum number of persistently mapped grants 343 * to a value less than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST. 344 * 345 *------------------------- Virtual Device Properties ------------------------- 346 * 347 * device-type 348 * Values: "disk", "cdrom", "floppy", etc. 349 * 350 * virtual-device 351 * Values: <uint32_t> 352 * 353 * A value indicating the physical device to virtualize within the 354 * frontend's domain. (e.g. "The first ATA disk", "The third SCSI 355 * disk", etc.) 356 * 357 * See docs/misc/vbd-interface.txt for details on the format of this 358 * value. 359 * 360 * Notes 361 * ----- 362 * (1) Multi-page ring buffer scheme first developed in the Citrix XenServer 363 * PV drivers. 364 * (2) Multi-page ring buffer scheme first used in some RedHat distributions 365 * including a distribution deployed on certain nodes of the Amazon 366 * EC2 cluster. 367 * (3) Support for multi-page ring buffers was implemented independently, 368 * in slightly different forms, by both Citrix and RedHat/Amazon. 369 * For full interoperability, block front and backends should publish 370 * identical ring parameters, adjusted for unit differences, to the 371 * XenStore nodes used in both schemes. 372 * (4) Devices that support discard functionality may internally allocate space 373 * (discardable extents) in units that are larger than the exported logical 374 * block size. If the backing device has such discardable extents the 375 * backend should provide both discard-granularity and discard-alignment. 376 * Providing just one of the two may be considered an error by the frontend. 377 * Backends supporting discard should include discard-granularity and 378 * discard-alignment even if it supports discarding individual sectors. 379 * Frontends should assume discard-alignment == 0 and discard-granularity 380 * == sector size if these keys are missing. 381 * (5) The discard-alignment parameter allows a physical device to be 382 * partitioned into virtual devices that do not necessarily begin or 383 * end on a discardable extent boundary. 384 * (6) When there is only a single page allocated to the request ring, 385 * 'ring-ref' is used to communicate the grant reference for this 386 * page to the backend. When using a multi-page ring, the 'ring-ref' 387 * node is not created. Instead 'ring-ref0' - 'ring-refN' are used. 388 * (7) When using persistent grants data has to be copied from/to the page 389 * where the grant is currently mapped. The overhead of doing this copy 390 * however doesn't suppress the speed improvement of not having to unmap 391 * the grants. 392 * (8) The frontend driver has to allow the backend driver to map all grants 393 * with write access, even when they should be mapped read-only, since 394 * further requests may reuse these grants and require write permissions. 395 * (9) Linux implementation doesn't have a limit on the maximum number of 396 * grants that can be persistently mapped in the frontend driver, but 397 * due to the frontent driver implementation it should never be bigger 398 * than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST. 399 *(10) The discard-secure property may be present and will be set to 1 if the 400 * backing device supports secure discard. 401 *(11) Only used by Linux and NetBSD. 402 */ 403 404/* 405 * Multiple hardware queues/rings: 406 * If supported, the backend will write the key "multi-queue-max-queues" to 407 * the directory for that vbd, and set its value to the maximum supported 408 * number of queues. 409 * Frontends that are aware of this feature and wish to use it can write the 410 * key "multi-queue-num-queues" with the number they wish to use, which must be 411 * greater than zero, and no more than the value reported by the backend in 412 * "multi-queue-max-queues". 413 * 414 * For frontends requesting just one queue, the usual event-channel and 415 * ring-ref keys are written as before, simplifying the backend processing 416 * to avoid distinguishing between a frontend that doesn't understand the 417 * multi-queue feature, and one that does, but requested only one queue. 418 * 419 * Frontends requesting two or more queues must not write the toplevel 420 * event-channel and ring-ref keys, instead writing those keys under sub-keys 421 * having the name "queue-N" where N is the integer ID of the queue/ring for 422 * which those keys belong. Queues are indexed from zero. 423 * For example, a frontend with two queues must write the following set of 424 * queue-related keys: 425 * 426 * /local/domain/1/device/vbd/0/multi-queue-num-queues = "2" 427 * /local/domain/1/device/vbd/0/queue-0 = "" 428 * /local/domain/1/device/vbd/0/queue-0/ring-ref = "<ring-ref#0>" 429 * /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn#0>" 430 * /local/domain/1/device/vbd/0/queue-1 = "" 431 * /local/domain/1/device/vbd/0/queue-1/ring-ref = "<ring-ref#1>" 432 * /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn#1>" 433 * 434 * It is also possible to use multiple queues/rings together with 435 * feature multi-page ring buffer. 436 * For example, a frontend requests two queues/rings and the size of each ring 437 * buffer is two pages must write the following set of related keys: 438 * 439 * /local/domain/1/device/vbd/0/multi-queue-num-queues = "2" 440 * /local/domain/1/device/vbd/0/ring-page-order = "1" 441 * /local/domain/1/device/vbd/0/queue-0 = "" 442 * /local/domain/1/device/vbd/0/queue-0/ring-ref0 = "<ring-ref#0>" 443 * /local/domain/1/device/vbd/0/queue-0/ring-ref1 = "<ring-ref#1>" 444 * /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn#0>" 445 * /local/domain/1/device/vbd/0/queue-1 = "" 446 * /local/domain/1/device/vbd/0/queue-1/ring-ref0 = "<ring-ref#2>" 447 * /local/domain/1/device/vbd/0/queue-1/ring-ref1 = "<ring-ref#3>" 448 * /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn#1>" 449 * 450 */ 451 452/* 453 * STATE DIAGRAMS 454 * 455 ***************************************************************************** 456 * Startup * 457 ***************************************************************************** 458 * 459 * Tool stack creates front and back nodes with state XenbusStateInitialising. 460 * 461 * Front Back 462 * ================================= ===================================== 463 * XenbusStateInitialising XenbusStateInitialising 464 * o Query virtual device o Query backend device identification 465 * properties. data. 466 * o Setup OS device instance. o Open and validate backend device. 467 * o Publish backend features and 468 * transport parameters. 469 * | 470 * | 471 * V 472 * XenbusStateInitWait 473 * 474 * o Query backend features and 475 * transport parameters. 476 * o Allocate and initialize the 477 * request ring. 478 * o Publish transport parameters 479 * that will be in effect during 480 * this connection. 481 * | 482 * | 483 * V 484 * XenbusStateInitialised 485 * 486 * o Query frontend transport parameters. 487 * o Connect to the request ring and 488 * event channel. 489 * o Publish backend device properties. 490 * | 491 * | 492 * V 493 * XenbusStateConnected 494 * 495 * o Query backend device properties. 496 * o Finalize OS virtual device 497 * instance. 498 * | 499 * | 500 * V 501 * XenbusStateConnected 502 * 503 * Note: Drivers that do not support any optional features, or the negotiation 504 * of transport parameters, can skip certain states in the state machine: 505 * 506 * o A frontend may transition to XenbusStateInitialised without 507 * waiting for the backend to enter XenbusStateInitWait. In this 508 * case, default transport parameters are in effect and any 509 * transport parameters published by the frontend must contain 510 * their default values. 511 * 512 * o A backend may transition to XenbusStateInitialised, bypassing 513 * XenbusStateInitWait, without waiting for the frontend to first 514 * enter the XenbusStateInitialised state. In this case, default 515 * transport parameters are in effect and any transport parameters 516 * published by the backend must contain their default values. 517 * 518 * Drivers that support optional features and/or transport parameter 519 * negotiation must tolerate these additional state transition paths. 520 * In general this means performing the work of any skipped state 521 * transition, if it has not already been performed, in addition to the 522 * work associated with entry into the current state. 523 */ 524 525/* 526 * REQUEST CODES. 527 */ 528#define BLKIF_OP_READ 0 529#define BLKIF_OP_WRITE 1 530/* 531 * All writes issued prior to a request with the BLKIF_OP_WRITE_BARRIER 532 * operation code ("barrier request") must be completed prior to the 533 * execution of the barrier request. All writes issued after the barrier 534 * request must not execute until after the completion of the barrier request. 535 * 536 * Optional. See "feature-barrier" XenBus node documentation above. 537 */ 538#define BLKIF_OP_WRITE_BARRIER 2 539/* 540 * Commit any uncommitted contents of the backing device's volatile cache 541 * to stable storage. 542 * 543 * Optional. See "feature-flush-cache" XenBus node documentation above. 544 */ 545#define BLKIF_OP_FLUSH_DISKCACHE 3 546/* 547 * Used in SLES sources for device specific command packet 548 * contained within the request. Reserved for that purpose. 549 */ 550#define BLKIF_OP_RESERVED_1 4 551/* 552 * Indicate to the backend device that a region of storage is no longer in 553 * use, and may be discarded at any time without impact to the client. If 554 * the BLKIF_DISCARD_SECURE flag is set on the request, all copies of the 555 * discarded region on the device must be rendered unrecoverable before the 556 * command returns. 557 * 558 * This operation is analogous to performing a trim (ATA) or unamp (SCSI), 559 * command on a native device. 560 * 561 * More information about trim/unmap operations can be found at: 562 * http://t13.org/Documents/UploadedDocuments/docs2008/ 563 * e07154r6-Data_Set_Management_Proposal_for_ATA-ACS2.doc 564 * http://www.seagate.com/staticfiles/support/disc/manuals/ 565 * Interface%20manuals/100293068c.pdf 566 * 567 * Optional. See "feature-discard", "discard-alignment", 568 * "discard-granularity", and "discard-secure" in the XenBus node 569 * documentation above. 570 */ 571#define BLKIF_OP_DISCARD 5 572 573/* 574 * Recognized if "feature-max-indirect-segments" in present in the backend 575 * xenbus info. The "feature-max-indirect-segments" node contains the maximum 576 * number of segments allowed by the backend per request. If the node is 577 * present, the frontend might use blkif_request_indirect structs in order to 578 * issue requests with more than BLKIF_MAX_SEGMENTS_PER_REQUEST (11). The 579 * maximum number of indirect segments is fixed by the backend, but the 580 * frontend can issue requests with any number of indirect segments as long as 581 * it's less than the number provided by the backend. The indirect_grefs field 582 * in blkif_request_indirect should be filled by the frontend with the 583 * grant references of the pages that are holding the indirect segments. 584 * These pages are filled with an array of blkif_request_segment that hold the 585 * information about the segments. The number of indirect pages to use is 586 * determined by the number of segments an indirect request contains. Every 587 * indirect page can contain a maximum of 588 * (PAGE_SIZE / sizeof(struct blkif_request_segment)) segments, so to 589 * calculate the number of indirect pages to use we have to do 590 * ceil(indirect_segments / (PAGE_SIZE / sizeof(struct blkif_request_segment))). 591 * 592 * If a backend does not recognize BLKIF_OP_INDIRECT, it should *not* 593 * create the "feature-max-indirect-segments" node! 594 */ 595#define BLKIF_OP_INDIRECT 6 596 597/* 598 * Maximum scatter/gather segments per request. 599 * This is carefully chosen so that sizeof(blkif_ring_t) <= PAGE_SIZE. 600 * NB. This could be 12 if the ring indexes weren't stored in the same page. 601 */ 602#define BLKIF_MAX_SEGMENTS_PER_REQUEST 11 603 604/* 605 * Maximum number of indirect pages to use per request. 606 */ 607#define BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST 8 608 609/* 610 * NB. first_sect and last_sect in blkif_request_segment, as well as 611 * sector_number in blkif_request, are always expressed in 512-byte units. 612 * However they must be properly aligned to the real sector size of the 613 * physical disk, which is reported in the "physical-sector-size" node in 614 * the backend xenbus info. Also the xenbus "sectors" node is expressed in 615 * 512-byte units. 616 */ 617struct blkif_request_segment { 618 grant_ref_t gref; /* reference to I/O buffer frame */ 619 /* @first_sect: first sector in frame to transfer (inclusive). */ 620 /* @last_sect: last sector in frame to transfer (inclusive). */ 621 uint8_t first_sect, last_sect; 622}; 623 624/* 625 * Starting ring element for any I/O request. 626 */ 627struct blkif_request { 628 uint8_t operation; /* BLKIF_OP_??? */ 629 uint8_t nr_segments; /* number of segments */ 630 blkif_vdev_t handle; /* only for read/write requests */ 631 uint64_t id; /* private guest value, echoed in resp */ 632 blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */ 633 struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST]; 634}; 635typedef struct blkif_request blkif_request_t; 636 637/* 638 * Cast to this structure when blkif_request.operation == BLKIF_OP_DISCARD 639 * sizeof(struct blkif_request_discard) <= sizeof(struct blkif_request) 640 */ 641struct blkif_request_discard { 642 uint8_t operation; /* BLKIF_OP_DISCARD */ 643 uint8_t flag; /* BLKIF_DISCARD_SECURE or zero */ 644#define BLKIF_DISCARD_SECURE (1<<0) /* ignored if discard-secure=0 */ 645 blkif_vdev_t handle; /* same as for read/write requests */ 646 uint64_t id; /* private guest value, echoed in resp */ 647 blkif_sector_t sector_number;/* start sector idx on disk */ 648 uint64_t nr_sectors; /* number of contiguous sectors to discard*/ 649}; 650typedef struct blkif_request_discard blkif_request_discard_t; 651 652struct blkif_request_indirect { 653 uint8_t operation; /* BLKIF_OP_INDIRECT */ 654 uint8_t indirect_op; /* BLKIF_OP_{READ/WRITE} */ 655 uint16_t nr_segments; /* number of segments */ 656 uint64_t id; /* private guest value, echoed in resp */ 657 blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */ 658 blkif_vdev_t handle; /* same as for read/write requests */ 659 grant_ref_t indirect_grefs[BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST]; 660#ifdef __i386__ 661 uint64_t pad; /* Make it 64 byte aligned on i386 */ 662#endif 663}; 664typedef struct blkif_request_indirect blkif_request_indirect_t; 665 666struct blkif_response { 667 uint64_t id; /* copied from request */ 668 uint8_t operation; /* copied from request */ 669 int16_t status; /* BLKIF_RSP_??? */ 670}; 671typedef struct blkif_response blkif_response_t; 672 673/* 674 * STATUS RETURN CODES. 675 */ 676 /* Operation not supported (only happens on barrier writes). */ 677#define BLKIF_RSP_EOPNOTSUPP -2 678 /* Operation failed for some unspecified reason (-EIO). */ 679#define BLKIF_RSP_ERROR -1 680 /* Operation completed successfully. */ 681#define BLKIF_RSP_OKAY 0 682 683/* 684 * Generate blkif ring structures and types. 685 */ 686DEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response); 687 688#define VDISK_CDROM 0x1 689#define VDISK_REMOVABLE 0x2 690#define VDISK_READONLY 0x4 691 692#endif /* __XEN_PUBLIC_IO_BLKIF_H__ */ 693 694/* 695 * Local variables: 696 * mode: C 697 * c-file-style: "BSD" 698 * c-basic-offset: 4 699 * tab-width: 4 700 * indent-tabs-mode: nil 701 * End: 702 */ 703