1 /* SPDX-License-Identifier: MIT */ 2 /****************************************************************************** 3 * blkif.h 4 * 5 * Unified block-device I/O interface for Xen guest OSes. 6 * 7 * Copyright (c) 2003-2004, Keir Fraser 8 * Copyright (c) 2012, Spectra Logic Corporation 9 */ 10 11 #ifndef __XEN_PUBLIC_IO_BLKIF_H__ 12 #define __XEN_PUBLIC_IO_BLKIF_H__ 13 14 #include "ring.h" 15 #include "../grant_table.h" 16 17 /* 18 * Front->back notifications: When enqueuing a new request, sending a 19 * notification can be made conditional on req_event (i.e., the generic 20 * hold-off mechanism provided by the ring macros). Backends must set 21 * req_event appropriately (e.g., using RING_FINAL_CHECK_FOR_REQUESTS()). 22 * 23 * Back->front notifications: When enqueuing a new response, sending a 24 * notification can be made conditional on rsp_event (i.e., the generic 25 * hold-off mechanism provided by the ring macros). Frontends must set 26 * rsp_event appropriately (e.g., using RING_FINAL_CHECK_FOR_RESPONSES()). 27 */ 28 29 #ifndef blkif_vdev_t 30 #define blkif_vdev_t uint16_t 31 #endif 32 #define blkif_sector_t uint64_t 33 34 /* 35 * Feature and Parameter Negotiation 36 * ================================= 37 * The two halves of a Xen block driver utilize nodes within the XenStore to 38 * communicate capabilities and to negotiate operating parameters. This 39 * section enumerates these nodes which reside in the respective front and 40 * backend portions of the XenStore, following the XenBus convention. 41 * 42 * All data in the XenStore is stored as strings. Nodes specifying numeric 43 * values are encoded in decimal. Integer value ranges listed below are 44 * expressed as fixed sized integer types capable of storing the conversion 45 * of a properly formated node string, without loss of information. 46 * 47 * Any specified default value is in effect if the corresponding XenBus node 48 * is not present in the XenStore. 49 * 50 * XenStore nodes in sections marked "PRIVATE" are solely for use by the 51 * driver side whose XenBus tree contains them. 52 * 53 * XenStore nodes marked "DEPRECATED" in their notes section should only be 54 * used to provide interoperability with legacy implementations. 55 * 56 * See the XenBus state transition diagram below for details on when XenBus 57 * nodes must be published and when they can be queried. 58 * 59 ***************************************************************************** 60 * Backend XenBus Nodes 61 ***************************************************************************** 62 * 63 *------------------ Backend Device Identification (PRIVATE) ------------------ 64 * 65 * mode 66 * Values: "r" (read only), "w" (writable) 67 * 68 * The read or write access permissions to the backing store to be 69 * granted to the frontend. 70 * 71 * params 72 * Values: string 73 * 74 * A free formatted string providing sufficient information for the 75 * hotplug script to attach the device and provide a suitable 76 * handler (ie: a block device) for blkback to use. 77 * 78 * physical-device 79 * Values: "MAJOR:MINOR" 80 * Notes: 11 81 * 82 * MAJOR and MINOR are the major number and minor number of the 83 * backing device respectively. 84 * 85 * physical-device-path 86 * Values: path string 87 * 88 * A string that contains the absolute path to the disk image. On 89 * NetBSD and Linux this is always a block device, while on FreeBSD 90 * it can be either a block device or a regular file. 91 * 92 * type 93 * Values: "file", "phy", "tap" 94 * 95 * The type of the backing device/object. 96 * 97 * 98 * direct-io-safe 99 * Values: 0/1 (boolean) 100 * Default Value: 0 101 * 102 * The underlying storage is not affected by the direct IO memory 103 * lifetime bug. See: 104 * https://lists.xen.org/archives/html/xen-devel/2012-12/msg01154.html 105 * 106 * Therefore this option gives the backend permission to use 107 * O_DIRECT, notwithstanding that bug. 108 * 109 * That is, if this option is enabled, use of O_DIRECT is safe, 110 * in circumstances where we would normally have avoided it as a 111 * workaround for that bug. This option is not relevant for all 112 * backends, and even not necessarily supported for those for 113 * which it is relevant. A backend which knows that it is not 114 * affected by the bug can ignore this option. 115 * 116 * This option doesn't require a backend to use O_DIRECT, so it 117 * should not be used to try to control the caching behaviour. 118 * 119 *--------------------------------- Features --------------------------------- 120 * 121 * feature-barrier 122 * Values: 0/1 (boolean) 123 * Default Value: 0 124 * 125 * A value of "1" indicates that the backend can process requests 126 * containing the BLKIF_OP_WRITE_BARRIER request opcode. Requests 127 * of this type may still be returned at any time with the 128 * BLKIF_RSP_EOPNOTSUPP result code. 129 * 130 * feature-flush-cache 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_FLUSH_DISKCACHE 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-discard 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_DISCARD 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-persistent 149 * Values: 0/1 (boolean) 150 * Default Value: 0 151 * Notes: 7 152 * 153 * A value of "1" indicates that the backend can keep the grants used 154 * by the frontend driver mapped, so the same set of grants should be 155 * used in all transactions. The maximum number of grants the backend 156 * can map persistently depends on the implementation, but ideally it 157 * should be RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST. Using this 158 * feature the backend doesn't need to unmap each grant, preventing 159 * costly TLB flushes. The backend driver should only map grants 160 * persistently if the frontend supports it. If a backend driver chooses 161 * to use the persistent protocol when the frontend doesn't support it, 162 * it will probably hit the maximum number of persistently mapped grants 163 * (due to the fact that the frontend won't be reusing the same grants), 164 * and fall back to non-persistent mode. Backend implementations may 165 * shrink or expand the number of persistently mapped grants without 166 * notifying the frontend depending on memory constraints (this might 167 * cause a performance degradation). 168 * 169 * If a backend driver wants to limit the maximum number of persistently 170 * mapped grants to a value less than RING_SIZE * 171 * BLKIF_MAX_SEGMENTS_PER_REQUEST a LRU strategy should be used to 172 * discard the grants that are less commonly used. Using a LRU in the 173 * backend driver paired with a LIFO queue in the frontend will 174 * allow us to have better performance in this scenario. 175 * 176 *----------------------- Request Transport Parameters ------------------------ 177 * 178 * max-ring-page-order 179 * Values: <uint32_t> 180 * Default Value: 0 181 * Notes: 1, 3 182 * 183 * The maximum supported size of the request ring buffer in units of 184 * lb(machine pages). (e.g. 0 == 1 page, 1 = 2 pages, 2 == 4 pages, 185 * etc.). 186 * 187 * max-ring-pages 188 * Values: <uint32_t> 189 * Default Value: 1 190 * Notes: DEPRECATED, 2, 3 191 * 192 * The maximum supported size of the request ring buffer in units of 193 * machine pages. The value must be a power of 2. 194 * 195 *------------------------- Backend Device Properties ------------------------- 196 * 197 * discard-enable 198 * Values: 0/1 (boolean) 199 * Default Value: 1 200 * 201 * This optional property, set by the toolstack, instructs the backend 202 * to offer (or not to offer) discard to the frontend. If the property 203 * is missing the backend should offer discard if the backing storage 204 * actually supports it. 205 * 206 * discard-alignment 207 * Values: <uint32_t> 208 * Default Value: 0 209 * Notes: 4, 5 210 * 211 * The offset, in bytes from the beginning of the virtual block device, 212 * to the first, addressable, discard extent on the underlying device. 213 * 214 * discard-granularity 215 * Values: <uint32_t> 216 * Default Value: <"sector-size"> 217 * Notes: 4 218 * 219 * The size, in bytes, of the individually addressable discard extents 220 * of the underlying device. 221 * 222 * discard-secure 223 * Values: 0/1 (boolean) 224 * Default Value: 0 225 * Notes: 10 226 * 227 * A value of "1" indicates that the backend can process BLKIF_OP_DISCARD 228 * requests with the BLKIF_DISCARD_SECURE flag set. 229 * 230 * info 231 * Values: <uint32_t> (bitmap) 232 * 233 * A collection of bit flags describing attributes of the backing 234 * device. The VDISK_* macros define the meaning of each bit 235 * location. 236 * 237 * sector-size 238 * Values: <uint32_t> 239 * 240 * The logical block size, in bytes, of the underlying storage. This 241 * must be a power of two with a minimum value of 512. 242 * 243 * NOTE: Because of implementation bugs in some frontends this must be 244 * set to 512, unless the frontend advertizes a non-zero value 245 * in its "feature-large-sector-size" xenbus node. (See below). 246 * 247 * physical-sector-size 248 * Values: <uint32_t> 249 * Default Value: <"sector-size"> 250 * 251 * The physical block size, in bytes, of the backend storage. This 252 * must be an integer multiple of "sector-size". 253 * 254 * sectors 255 * Values: <uint64_t> 256 * 257 * The size of the backend device, expressed in units of "sector-size". 258 * The product of "sector-size" and "sectors" must also be an integer 259 * multiple of "physical-sector-size", if that node is present. 260 * 261 ***************************************************************************** 262 * Frontend XenBus Nodes 263 ***************************************************************************** 264 * 265 *----------------------- Request Transport Parameters ----------------------- 266 * 267 * event-channel 268 * Values: <uint32_t> 269 * 270 * The identifier of the Xen event channel used to signal activity 271 * in the ring buffer. 272 * 273 * ring-ref 274 * Values: <uint32_t> 275 * Notes: 6 276 * 277 * The Xen grant reference granting permission for the backend to map 278 * the sole page in a single page sized ring buffer. 279 * 280 * ring-ref%u 281 * Values: <uint32_t> 282 * Notes: 6 283 * 284 * For a frontend providing a multi-page ring, a "number of ring pages" 285 * sized list of nodes, each containing a Xen grant reference granting 286 * permission for the backend to map the page of the ring located 287 * at page index "%u". Page indexes are zero based. 288 * 289 * protocol 290 * Values: string (XEN_IO_PROTO_ABI_*) 291 * Default Value: XEN_IO_PROTO_ABI_NATIVE 292 * 293 * The machine ABI rules governing the format of all ring request and 294 * response structures. 295 * 296 * ring-page-order 297 * Values: <uint32_t> 298 * Default Value: 0 299 * Maximum Value: MAX(ffs(max-ring-pages) - 1, max-ring-page-order) 300 * Notes: 1, 3 301 * 302 * The size of the frontend allocated request ring buffer in units 303 * of lb(machine pages). (e.g. 0 == 1 page, 1 = 2 pages, 2 == 4 pages, 304 * etc.). 305 * 306 * num-ring-pages 307 * Values: <uint32_t> 308 * Default Value: 1 309 * Maximum Value: MAX(max-ring-pages,(0x1 << max-ring-page-order)) 310 * Notes: DEPRECATED, 2, 3 311 * 312 * The size of the frontend allocated request ring buffer in units of 313 * machine pages. The value must be a power of 2. 314 * 315 *--------------------------------- Features --------------------------------- 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 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 * feature-large-sector-size 339 * Values: 0/1 (boolean) 340 * Default Value: 0 341 * 342 * A value of "1" indicates that the frontend will correctly supply and 343 * interpret all sector-based quantities in terms of the "sector-size" 344 * value supplied in the backend info, whatever that may be set to. 345 * If this node is not present or its value is "0" then it is assumed 346 * that the frontend requires that the logical block size is 512 as it 347 * is hardcoded (which is the case in some frontend implementations). 348 * 349 * trusted 350 * Values: 0/1 (boolean) 351 * Default value: 1 352 * 353 * A value of "0" indicates that the frontend should not trust the 354 * backend, and should deploy whatever measures available to protect from 355 * a malicious backend on the other end. 356 * 357 *------------------------- Virtual Device Properties ------------------------- 358 * 359 * device-type 360 * Values: "disk", "cdrom", "floppy", etc. 361 * 362 * virtual-device 363 * Values: <uint32_t> 364 * 365 * A value indicating the physical device to virtualize within the 366 * frontend's domain. (e.g. "The first ATA disk", "The third SCSI 367 * disk", etc.) 368 * 369 * See docs/misc/vbd-interface.txt for details on the format of this 370 * value. 371 * 372 * Notes 373 * ----- 374 * (1) Multi-page ring buffer scheme first developed in the Citrix XenServer 375 * PV drivers. 376 * (2) Multi-page ring buffer scheme first used in some RedHat distributions 377 * including a distribution deployed on certain nodes of the Amazon 378 * EC2 cluster. 379 * (3) Support for multi-page ring buffers was implemented independently, 380 * in slightly different forms, by both Citrix and RedHat/Amazon. 381 * For full interoperability, block front and backends should publish 382 * identical ring parameters, adjusted for unit differences, to the 383 * XenStore nodes used in both schemes. 384 * (4) Devices that support discard functionality may internally allocate space 385 * (discardable extents) in units that are larger than the exported logical 386 * block size. If the backing device has such discardable extents the 387 * backend should provide both discard-granularity and discard-alignment. 388 * Providing just one of the two may be considered an error by the frontend. 389 * Backends supporting discard should include discard-granularity and 390 * discard-alignment even if it supports discarding individual sectors. 391 * Frontends should assume discard-alignment == 0 and discard-granularity 392 * == sector size if these keys are missing. 393 * (5) The discard-alignment parameter allows a physical device to be 394 * partitioned into virtual devices that do not necessarily begin or 395 * end on a discardable extent boundary. 396 * (6) When there is only a single page allocated to the request ring, 397 * 'ring-ref' is used to communicate the grant reference for this 398 * page to the backend. When using a multi-page ring, the 'ring-ref' 399 * node is not created. Instead 'ring-ref0' - 'ring-refN' are used. 400 * (7) When using persistent grants data has to be copied from/to the page 401 * where the grant is currently mapped. The overhead of doing this copy 402 * however doesn't suppress the speed improvement of not having to unmap 403 * the grants. 404 * (8) The frontend driver has to allow the backend driver to map all grants 405 * with write access, even when they should be mapped read-only, since 406 * further requests may reuse these grants and require write permissions. 407 * (9) Linux implementation doesn't have a limit on the maximum number of 408 * grants that can be persistently mapped in the frontend driver, but 409 * due to the frontent driver implementation it should never be bigger 410 * than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST. 411 *(10) The discard-secure property may be present and will be set to 1 if the 412 * backing device supports secure discard. 413 *(11) Only used by Linux and NetBSD. 414 */ 415 416 /* 417 * Multiple hardware queues/rings: 418 * If supported, the backend will write the key "multi-queue-max-queues" to 419 * the directory for that vbd, and set its value to the maximum supported 420 * number of queues. 421 * Frontends that are aware of this feature and wish to use it can write the 422 * key "multi-queue-num-queues" with the number they wish to use, which must be 423 * greater than zero, and no more than the value reported by the backend in 424 * "multi-queue-max-queues". 425 * 426 * For frontends requesting just one queue, the usual event-channel and 427 * ring-ref keys are written as before, simplifying the backend processing 428 * to avoid distinguishing between a frontend that doesn't understand the 429 * multi-queue feature, and one that does, but requested only one queue. 430 * 431 * Frontends requesting two or more queues must not write the toplevel 432 * event-channel and ring-ref keys, instead writing those keys under sub-keys 433 * having the name "queue-N" where N is the integer ID of the queue/ring for 434 * which those keys belong. Queues are indexed from zero. 435 * For example, a frontend with two queues must write the following set of 436 * queue-related keys: 437 * 438 * /local/domain/1/device/vbd/0/multi-queue-num-queues = "2" 439 * /local/domain/1/device/vbd/0/queue-0 = "" 440 * /local/domain/1/device/vbd/0/queue-0/ring-ref = "<ring-ref#0>" 441 * /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn#0>" 442 * /local/domain/1/device/vbd/0/queue-1 = "" 443 * /local/domain/1/device/vbd/0/queue-1/ring-ref = "<ring-ref#1>" 444 * /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn#1>" 445 * 446 * It is also possible to use multiple queues/rings together with 447 * feature multi-page ring buffer. 448 * For example, a frontend requests two queues/rings and the size of each ring 449 * buffer is two pages must write the following set of related keys: 450 * 451 * /local/domain/1/device/vbd/0/multi-queue-num-queues = "2" 452 * /local/domain/1/device/vbd/0/ring-page-order = "1" 453 * /local/domain/1/device/vbd/0/queue-0 = "" 454 * /local/domain/1/device/vbd/0/queue-0/ring-ref0 = "<ring-ref#0>" 455 * /local/domain/1/device/vbd/0/queue-0/ring-ref1 = "<ring-ref#1>" 456 * /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn#0>" 457 * /local/domain/1/device/vbd/0/queue-1 = "" 458 * /local/domain/1/device/vbd/0/queue-1/ring-ref0 = "<ring-ref#2>" 459 * /local/domain/1/device/vbd/0/queue-1/ring-ref1 = "<ring-ref#3>" 460 * /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn#1>" 461 * 462 */ 463 464 /* 465 * STATE DIAGRAMS 466 * 467 ***************************************************************************** 468 * Startup * 469 ***************************************************************************** 470 * 471 * Tool stack creates front and back nodes with state XenbusStateInitialising. 472 * 473 * Front Back 474 * ================================= ===================================== 475 * XenbusStateInitialising XenbusStateInitialising 476 * o Query virtual device o Query backend device identification 477 * properties. data. 478 * o Setup OS device instance. o Open and validate backend device. 479 * o Publish backend features and 480 * transport parameters. 481 * | 482 * | 483 * V 484 * XenbusStateInitWait 485 * 486 * o Query backend features and 487 * transport parameters. 488 * o Allocate and initialize the 489 * request ring. 490 * o Publish transport parameters 491 * that will be in effect during 492 * this connection. 493 * | 494 * | 495 * V 496 * XenbusStateInitialised 497 * 498 * o Query frontend transport parameters. 499 * o Connect to the request ring and 500 * event channel. 501 * o Publish backend device properties. 502 * | 503 * | 504 * V 505 * XenbusStateConnected 506 * 507 * o Query backend device properties. 508 * o Finalize OS virtual device 509 * instance. 510 * | 511 * | 512 * V 513 * XenbusStateConnected 514 * 515 * Note: Drivers that do not support any optional features, or the negotiation 516 * of transport parameters, can skip certain states in the state machine: 517 * 518 * o A frontend may transition to XenbusStateInitialised without 519 * waiting for the backend to enter XenbusStateInitWait. In this 520 * case, default transport parameters are in effect and any 521 * transport parameters published by the frontend must contain 522 * their default values. 523 * 524 * o A backend may transition to XenbusStateInitialised, bypassing 525 * XenbusStateInitWait, without waiting for the frontend to first 526 * enter the XenbusStateInitialised state. In this case, default 527 * transport parameters are in effect and any transport parameters 528 * published by the backend must contain their default values. 529 * 530 * Drivers that support optional features and/or transport parameter 531 * negotiation must tolerate these additional state transition paths. 532 * In general this means performing the work of any skipped state 533 * transition, if it has not already been performed, in addition to the 534 * work associated with entry into the current state. 535 */ 536 537 /* 538 * REQUEST CODES. 539 */ 540 #define BLKIF_OP_READ 0 541 #define BLKIF_OP_WRITE 1 542 /* 543 * All writes issued prior to a request with the BLKIF_OP_WRITE_BARRIER 544 * operation code ("barrier request") must be completed prior to the 545 * execution of the barrier request. All writes issued after the barrier 546 * request must not execute until after the completion of the barrier request. 547 * 548 * Optional. See "feature-barrier" XenBus node documentation above. 549 */ 550 #define BLKIF_OP_WRITE_BARRIER 2 551 /* 552 * Commit any uncommitted contents of the backing device's volatile cache 553 * to stable storage. 554 * 555 * Optional. See "feature-flush-cache" XenBus node documentation above. 556 */ 557 #define BLKIF_OP_FLUSH_DISKCACHE 3 558 /* 559 * Used in SLES sources for device specific command packet 560 * contained within the request. Reserved for that purpose. 561 */ 562 #define BLKIF_OP_RESERVED_1 4 563 /* 564 * Indicate to the backend device that a region of storage is no longer in 565 * use, and may be discarded at any time without impact to the client. If 566 * the BLKIF_DISCARD_SECURE flag is set on the request, all copies of the 567 * discarded region on the device must be rendered unrecoverable before the 568 * command returns. 569 * 570 * This operation is analogous to performing a trim (ATA) or unamp (SCSI), 571 * command on a native device. 572 * 573 * More information about trim/unmap operations can be found at: 574 * http://t13.org/Documents/UploadedDocuments/docs2008/ 575 * e07154r6-Data_Set_Management_Proposal_for_ATA-ACS2.doc 576 * http://www.seagate.com/staticfiles/support/disc/manuals/ 577 * Interface%20manuals/100293068c.pdf 578 * 579 * Optional. See "feature-discard", "discard-alignment", 580 * "discard-granularity", and "discard-secure" in the XenBus node 581 * documentation above. 582 */ 583 #define BLKIF_OP_DISCARD 5 584 585 /* 586 * Recognized if "feature-max-indirect-segments" in present in the backend 587 * xenbus info. The "feature-max-indirect-segments" node contains the maximum 588 * number of segments allowed by the backend per request. If the node is 589 * present, the frontend might use blkif_request_indirect structs in order to 590 * issue requests with more than BLKIF_MAX_SEGMENTS_PER_REQUEST (11). The 591 * maximum number of indirect segments is fixed by the backend, but the 592 * frontend can issue requests with any number of indirect segments as long as 593 * it's less than the number provided by the backend. The indirect_grefs field 594 * in blkif_request_indirect should be filled by the frontend with the 595 * grant references of the pages that are holding the indirect segments. 596 * These pages are filled with an array of blkif_request_segment that hold the 597 * information about the segments. The number of indirect pages to use is 598 * determined by the number of segments an indirect request contains. Every 599 * indirect page can contain a maximum of 600 * (PAGE_SIZE / sizeof(struct blkif_request_segment)) segments, so to 601 * calculate the number of indirect pages to use we have to do 602 * ceil(indirect_segments / (PAGE_SIZE / sizeof(struct blkif_request_segment))). 603 * 604 * If a backend does not recognize BLKIF_OP_INDIRECT, it should *not* 605 * create the "feature-max-indirect-segments" node! 606 */ 607 #define BLKIF_OP_INDIRECT 6 608 609 /* 610 * Maximum scatter/gather segments per request. 611 * This is carefully chosen so that sizeof(blkif_ring_t) <= PAGE_SIZE. 612 * NB. This could be 12 if the ring indexes weren't stored in the same page. 613 */ 614 #define BLKIF_MAX_SEGMENTS_PER_REQUEST 11 615 616 /* 617 * Maximum number of indirect pages to use per request. 618 */ 619 #define BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST 8 620 621 /* 622 * NB. 'first_sect' and 'last_sect' in blkif_request_segment, as well as 623 * 'sector_number' in blkif_request, blkif_request_discard and 624 * blkif_request_indirect are sector-based quantities. See the description 625 * of the "feature-large-sector-size" frontend xenbus node above for 626 * more information. 627 */ 628 struct blkif_request_segment { 629 grant_ref_t gref; /* reference to I/O buffer frame */ 630 /* @first_sect: first sector in frame to transfer (inclusive). */ 631 /* @last_sect: last sector in frame to transfer (inclusive). */ 632 uint8_t first_sect, last_sect; 633 }; 634 635 /* 636 * Starting ring element for any I/O request. 637 */ 638 struct blkif_request { 639 uint8_t operation; /* BLKIF_OP_??? */ 640 uint8_t nr_segments; /* number of segments */ 641 blkif_vdev_t handle; /* only for read/write requests */ 642 uint64_t id; /* private guest value, echoed in resp */ 643 blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */ 644 struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST]; 645 }; 646 typedef struct blkif_request blkif_request_t; 647 648 /* 649 * Cast to this structure when blkif_request.operation == BLKIF_OP_DISCARD 650 * sizeof(struct blkif_request_discard) <= sizeof(struct blkif_request) 651 */ 652 struct blkif_request_discard { 653 uint8_t operation; /* BLKIF_OP_DISCARD */ 654 uint8_t flag; /* BLKIF_DISCARD_SECURE or zero */ 655 #define BLKIF_DISCARD_SECURE (1<<0) /* ignored if discard-secure=0 */ 656 blkif_vdev_t handle; /* same as for read/write requests */ 657 uint64_t id; /* private guest value, echoed in resp */ 658 blkif_sector_t sector_number;/* start sector idx on disk */ 659 uint64_t nr_sectors; /* number of contiguous sectors to discard*/ 660 }; 661 typedef struct blkif_request_discard blkif_request_discard_t; 662 663 struct blkif_request_indirect { 664 uint8_t operation; /* BLKIF_OP_INDIRECT */ 665 uint8_t indirect_op; /* BLKIF_OP_{READ/WRITE} */ 666 uint16_t nr_segments; /* number of segments */ 667 uint64_t id; /* private guest value, echoed in resp */ 668 blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */ 669 blkif_vdev_t handle; /* same as for read/write requests */ 670 grant_ref_t indirect_grefs[BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST]; 671 #ifdef __i386__ 672 uint64_t pad; /* Make it 64 byte aligned on i386 */ 673 #endif 674 }; 675 typedef struct blkif_request_indirect blkif_request_indirect_t; 676 677 struct blkif_response { 678 uint64_t id; /* copied from request */ 679 uint8_t operation; /* copied from request */ 680 int16_t status; /* BLKIF_RSP_??? */ 681 }; 682 typedef struct blkif_response blkif_response_t; 683 684 /* 685 * STATUS RETURN CODES. 686 */ 687 /* Operation not supported (only happens on barrier writes). */ 688 #define BLKIF_RSP_EOPNOTSUPP -2 689 /* Operation failed for some unspecified reason (-EIO). */ 690 #define BLKIF_RSP_ERROR -1 691 /* Operation completed successfully. */ 692 #define BLKIF_RSP_OKAY 0 693 694 /* 695 * Generate blkif ring structures and types. 696 */ 697 DEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response); 698 699 #define VDISK_CDROM 0x1 700 #define VDISK_REMOVABLE 0x2 701 #define VDISK_READONLY 0x4 702 703 #endif /* __XEN_PUBLIC_IO_BLKIF_H__ */ 704 705 /* 706 * Local variables: 707 * mode: C 708 * c-file-style: "BSD" 709 * c-basic-offset: 4 710 * tab-width: 4 711 * indent-tabs-mode: nil 712 * End: 713 */ 714