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 formatted 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 must 241 * be a power of two with a minimum value of 512. The sector size should 242 * only be used for request segment length and alignment. 243 * 244 * When exposing a device that uses a logical sector size of 4096, the 245 * only difference xenstore wise will be that 'sector-size' (and possibly 246 * 'physical-sector-size' if supported by the backend) will be 4096, but 247 * the 'sectors' node will still be calculated using 512 byte units. The 248 * sector base units in the ring requests fields will all be 512 byte 249 * based despite the logical sector size exposed in 'sector-size'. 250 * 251 * physical-sector-size 252 * Values: <uint32_t> 253 * Default Value: <"sector-size"> 254 * 255 * The physical block size, in bytes, of the backend storage. This 256 * must be an integer multiple of "sector-size". 257 * 258 * sectors 259 * Values: <uint64_t> 260 * 261 * The size of the backend device, expressed in units of 512b. The 262 * product of "sectors" * 512 must also be an integer multiple of 263 * "physical-sector-size", if that node is present. 264 * 265 ***************************************************************************** 266 * Frontend XenBus Nodes 267 ***************************************************************************** 268 * 269 *----------------------- Request Transport Parameters ----------------------- 270 * 271 * event-channel 272 * Values: <uint32_t> 273 * 274 * The identifier of the Xen event channel used to signal activity 275 * in the ring buffer. 276 * 277 * ring-ref 278 * Values: <uint32_t> 279 * Notes: 6 280 * 281 * The Xen grant reference granting permission for the backend to map 282 * the sole page in a single page sized ring buffer. 283 * 284 * ring-ref%u 285 * Values: <uint32_t> 286 * Notes: 6 287 * 288 * For a frontend providing a multi-page ring, a "number of ring pages" 289 * sized list of nodes, each containing a Xen grant reference granting 290 * permission for the backend to map the page of the ring located 291 * at page index "%u". Page indexes are zero based. 292 * 293 * protocol 294 * Values: string (XEN_IO_PROTO_ABI_*) 295 * Default Value: XEN_IO_PROTO_ABI_NATIVE 296 * 297 * The machine ABI rules governing the format of all ring request and 298 * response structures. 299 * 300 * ring-page-order 301 * Values: <uint32_t> 302 * Default Value: 0 303 * Maximum Value: MAX(ffs(max-ring-pages) - 1, max-ring-page-order) 304 * Notes: 1, 3 305 * 306 * The size of the frontend allocated request ring buffer in units 307 * of lb(machine pages). (e.g. 0 == 1 page, 1 = 2 pages, 2 == 4 pages, 308 * etc.). 309 * 310 * num-ring-pages 311 * Values: <uint32_t> 312 * Default Value: 1 313 * Maximum Value: MAX(max-ring-pages,(0x1 << max-ring-page-order)) 314 * Notes: DEPRECATED, 2, 3 315 * 316 * The size of the frontend allocated request ring buffer in units of 317 * machine pages. The value must be a power of 2. 318 * 319 *--------------------------------- Features --------------------------------- 320 * 321 * feature-persistent 322 * Values: 0/1 (boolean) 323 * Default Value: 0 324 * Notes: 7, 8, 9 325 * 326 * A value of "1" indicates that the frontend will reuse the same grants 327 * for all transactions, allowing the backend to map them with write 328 * access (even when it should be read-only). If the frontend hits the 329 * maximum number of allowed persistently mapped grants, it can fallback 330 * to non persistent mode. This will cause a performance degradation, 331 * since the backend driver will still try to map those grants 332 * persistently. Since the persistent grants protocol is compatible with 333 * the previous protocol, a frontend driver can choose to work in 334 * persistent mode even when the backend doesn't support it. 335 * 336 * It is recommended that the frontend driver stores the persistently 337 * mapped grants in a LIFO queue, so a subset of all persistently mapped 338 * grants gets used commonly. This is done in case the backend driver 339 * decides to limit the maximum number of persistently mapped grants 340 * to a value less than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST. 341 * 342 * feature-large-sector-size 343 * Values: 0/1 (boolean) 344 * Default Value: 0 345 * Notes: DEPRECATED, 12 346 * 347 * A value of "1" indicates that the frontend will correctly supply and 348 * interpret all sector-based quantities in terms of the "sector-size" 349 * value supplied in the backend info, whatever that may be set to. 350 * If this node is not present or its value is "0" then it is assumed 351 * that the frontend requires that the logical block size is 512 as it 352 * is hardcoded (which is the case in some frontend implementations). 353 * 354 * trusted 355 * Values: 0/1 (boolean) 356 * Default value: 1 357 * 358 * A value of "0" indicates that the frontend should not trust the 359 * backend, and should deploy whatever measures available to protect from 360 * a malicious backend on the other end. 361 * 362 *------------------------- Virtual Device Properties ------------------------- 363 * 364 * device-type 365 * Values: "disk", "cdrom", "floppy", etc. 366 * 367 * virtual-device 368 * Values: <uint32_t> 369 * 370 * A value indicating the physical device to virtualize within the 371 * frontend's domain. (e.g. "The first ATA disk", "The third SCSI 372 * disk", etc.) 373 * 374 * See docs/misc/vbd-interface.txt for details on the format of this 375 * value. 376 * 377 * Notes 378 * ----- 379 * (1) Multi-page ring buffer scheme first developed in the Citrix XenServer 380 * PV drivers. 381 * (2) Multi-page ring buffer scheme first used in some RedHat distributions 382 * including a distribution deployed on certain nodes of the Amazon 383 * EC2 cluster. 384 * (3) Support for multi-page ring buffers was implemented independently, 385 * in slightly different forms, by both Citrix and RedHat/Amazon. 386 * For full interoperability, block front and backends should publish 387 * identical ring parameters, adjusted for unit differences, to the 388 * XenStore nodes used in both schemes. 389 * (4) Devices that support discard functionality may internally allocate space 390 * (discardable extents) in units that are larger than the exported logical 391 * block size. If the backing device has such discardable extents the 392 * backend should provide both discard-granularity and discard-alignment. 393 * Providing just one of the two may be considered an error by the frontend. 394 * Backends supporting discard should include discard-granularity and 395 * discard-alignment even if it supports discarding individual sectors. 396 * Frontends should assume discard-alignment == 0 and discard-granularity 397 * == sector size if these keys are missing. 398 * (5) The discard-alignment parameter allows a physical device to be 399 * partitioned into virtual devices that do not necessarily begin or 400 * end on a discardable extent boundary. 401 * (6) When there is only a single page allocated to the request ring, 402 * 'ring-ref' is used to communicate the grant reference for this 403 * page to the backend. When using a multi-page ring, the 'ring-ref' 404 * node is not created. Instead 'ring-ref0' - 'ring-refN' are used. 405 * (7) When using persistent grants data has to be copied from/to the page 406 * where the grant is currently mapped. The overhead of doing this copy 407 * however doesn't suppress the speed improvement of not having to unmap 408 * the grants. 409 * (8) The frontend driver has to allow the backend driver to map all grants 410 * with write access, even when they should be mapped read-only, since 411 * further requests may reuse these grants and require write permissions. 412 * (9) Linux implementation doesn't have a limit on the maximum number of 413 * grants that can be persistently mapped in the frontend driver, but 414 * due to the frontent driver implementation it should never be bigger 415 * than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST. 416 *(10) The discard-secure property may be present and will be set to 1 if the 417 * backing device supports secure discard. 418 *(11) Only used by Linux and NetBSD. 419 *(12) Possibly only ever implemented by the QEMU Qdisk backend and the Windows 420 * PV block frontend. Other backends and frontends supported 'sector-size' 421 * values greater than 512 before such feature was added. Frontends should 422 * not expose this node, neither should backends make any decisions based 423 * on it being exposed by the frontend. 424 */ 425 426 /* 427 * Multiple hardware queues/rings: 428 * If supported, the backend will write the key "multi-queue-max-queues" to 429 * the directory for that vbd, and set its value to the maximum supported 430 * number of queues. 431 * Frontends that are aware of this feature and wish to use it can write the 432 * key "multi-queue-num-queues" with the number they wish to use, which must be 433 * greater than zero, and no more than the value reported by the backend in 434 * "multi-queue-max-queues". 435 * 436 * For frontends requesting just one queue, the usual event-channel and 437 * ring-ref keys are written as before, simplifying the backend processing 438 * to avoid distinguishing between a frontend that doesn't understand the 439 * multi-queue feature, and one that does, but requested only one queue. 440 * 441 * Frontends requesting two or more queues must not write the toplevel 442 * event-channel and ring-ref keys, instead writing those keys under sub-keys 443 * having the name "queue-N" where N is the integer ID of the queue/ring for 444 * which those keys belong. Queues are indexed from zero. 445 * For example, a frontend with two queues must write the following set of 446 * queue-related keys: 447 * 448 * /local/domain/1/device/vbd/0/multi-queue-num-queues = "2" 449 * /local/domain/1/device/vbd/0/queue-0 = "" 450 * /local/domain/1/device/vbd/0/queue-0/ring-ref = "<ring-ref#0>" 451 * /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn#0>" 452 * /local/domain/1/device/vbd/0/queue-1 = "" 453 * /local/domain/1/device/vbd/0/queue-1/ring-ref = "<ring-ref#1>" 454 * /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn#1>" 455 * 456 * It is also possible to use multiple queues/rings together with 457 * feature multi-page ring buffer. 458 * For example, a frontend requests two queues/rings and the size of each ring 459 * buffer is two pages must write the following set of related keys: 460 * 461 * /local/domain/1/device/vbd/0/multi-queue-num-queues = "2" 462 * /local/domain/1/device/vbd/0/ring-page-order = "1" 463 * /local/domain/1/device/vbd/0/queue-0 = "" 464 * /local/domain/1/device/vbd/0/queue-0/ring-ref0 = "<ring-ref#0>" 465 * /local/domain/1/device/vbd/0/queue-0/ring-ref1 = "<ring-ref#1>" 466 * /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn#0>" 467 * /local/domain/1/device/vbd/0/queue-1 = "" 468 * /local/domain/1/device/vbd/0/queue-1/ring-ref0 = "<ring-ref#2>" 469 * /local/domain/1/device/vbd/0/queue-1/ring-ref1 = "<ring-ref#3>" 470 * /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn#1>" 471 * 472 */ 473 474 /* 475 * STATE DIAGRAMS 476 * 477 ***************************************************************************** 478 * Startup * 479 ***************************************************************************** 480 * 481 * Tool stack creates front and back nodes with state XenbusStateInitialising. 482 * 483 * Front Back 484 * ================================= ===================================== 485 * XenbusStateInitialising XenbusStateInitialising 486 * o Query virtual device o Query backend device identification 487 * properties. data. 488 * o Setup OS device instance. o Open and validate backend device. 489 * o Publish backend features and 490 * transport parameters. 491 * | 492 * | 493 * V 494 * XenbusStateInitWait 495 * 496 * o Query backend features and 497 * transport parameters. 498 * o Allocate and initialize the 499 * request ring. 500 * o Publish transport parameters 501 * that will be in effect during 502 * this connection. 503 * | 504 * | 505 * V 506 * XenbusStateInitialised 507 * 508 * o Query frontend transport parameters. 509 * o Connect to the request ring and 510 * event channel. 511 * o Publish backend device properties. 512 * | 513 * | 514 * V 515 * XenbusStateConnected 516 * 517 * o Query backend device properties. 518 * o Finalize OS virtual device 519 * instance. 520 * | 521 * | 522 * V 523 * XenbusStateConnected 524 * 525 * Note: Drivers that do not support any optional features, or the negotiation 526 * of transport parameters, can skip certain states in the state machine: 527 * 528 * o A frontend may transition to XenbusStateInitialised without 529 * waiting for the backend to enter XenbusStateInitWait. In this 530 * case, default transport parameters are in effect and any 531 * transport parameters published by the frontend must contain 532 * their default values. 533 * 534 * o A backend may transition to XenbusStateInitialised, bypassing 535 * XenbusStateInitWait, without waiting for the frontend to first 536 * enter the XenbusStateInitialised state. In this case, default 537 * transport parameters are in effect and any transport parameters 538 * published by the backend must contain their default values. 539 * 540 * Drivers that support optional features and/or transport parameter 541 * negotiation must tolerate these additional state transition paths. 542 * In general this means performing the work of any skipped state 543 * transition, if it has not already been performed, in addition to the 544 * work associated with entry into the current state. 545 */ 546 547 /* 548 * REQUEST CODES. 549 */ 550 #define BLKIF_OP_READ 0 551 #define BLKIF_OP_WRITE 1 552 /* 553 * All writes issued prior to a request with the BLKIF_OP_WRITE_BARRIER 554 * operation code ("barrier request") must be completed prior to the 555 * execution of the barrier request. All writes issued after the barrier 556 * request must not execute until after the completion of the barrier request. 557 * 558 * Optional. See "feature-barrier" XenBus node documentation above. 559 */ 560 #define BLKIF_OP_WRITE_BARRIER 2 561 /* 562 * Commit any uncommitted contents of the backing device's volatile cache 563 * to stable storage. 564 * 565 * Optional. See "feature-flush-cache" XenBus node documentation above. 566 */ 567 #define BLKIF_OP_FLUSH_DISKCACHE 3 568 /* 569 * Used in SLES sources for device specific command packet 570 * contained within the request. Reserved for that purpose. 571 */ 572 #define BLKIF_OP_RESERVED_1 4 573 /* 574 * Indicate to the backend device that a region of storage is no longer in 575 * use, and may be discarded at any time without impact to the client. If 576 * the BLKIF_DISCARD_SECURE flag is set on the request, all copies of the 577 * discarded region on the device must be rendered unrecoverable before the 578 * command returns. 579 * 580 * This operation is analogous to performing a trim (ATA) or unamp (SCSI), 581 * command on a native device. 582 * 583 * More information about trim/unmap operations can be found at: 584 * http://t13.org/Documents/UploadedDocuments/docs2008/ 585 * e07154r6-Data_Set_Management_Proposal_for_ATA-ACS2.doc 586 * http://www.seagate.com/staticfiles/support/disc/manuals/ 587 * Interface%20manuals/100293068c.pdf 588 * 589 * Optional. See "feature-discard", "discard-alignment", 590 * "discard-granularity", and "discard-secure" in the XenBus node 591 * documentation above. 592 */ 593 #define BLKIF_OP_DISCARD 5 594 595 /* 596 * Recognized if "feature-max-indirect-segments" in present in the backend 597 * xenbus info. The "feature-max-indirect-segments" node contains the maximum 598 * number of segments allowed by the backend per request. If the node is 599 * present, the frontend might use blkif_request_indirect structs in order to 600 * issue requests with more than BLKIF_MAX_SEGMENTS_PER_REQUEST (11). The 601 * maximum number of indirect segments is fixed by the backend, but the 602 * frontend can issue requests with any number of indirect segments as long as 603 * it's less than the number provided by the backend. The indirect_grefs field 604 * in blkif_request_indirect should be filled by the frontend with the 605 * grant references of the pages that are holding the indirect segments. 606 * These pages are filled with an array of blkif_request_segment that hold the 607 * information about the segments. The number of indirect pages to use is 608 * determined by the number of segments an indirect request contains. Every 609 * indirect page can contain a maximum of 610 * (PAGE_SIZE / sizeof(struct blkif_request_segment)) segments, so to 611 * calculate the number of indirect pages to use we have to do 612 * ceil(indirect_segments / (PAGE_SIZE / sizeof(struct blkif_request_segment))). 613 * 614 * If a backend does not recognize BLKIF_OP_INDIRECT, it should *not* 615 * create the "feature-max-indirect-segments" node! 616 */ 617 #define BLKIF_OP_INDIRECT 6 618 619 /* 620 * Maximum scatter/gather segments per request. 621 * This is carefully chosen so that sizeof(blkif_ring_t) <= PAGE_SIZE. 622 * NB. This could be 12 if the ring indexes weren't stored in the same page. 623 */ 624 #define BLKIF_MAX_SEGMENTS_PER_REQUEST 11 625 626 /* 627 * Maximum number of indirect pages to use per request. 628 */ 629 #define BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST 8 630 631 /* 632 * NB. 'first_sect' and 'last_sect' in blkif_request_segment are all in units 633 * of 512 bytes, despite the 'sector-size' xenstore node possibly having a 634 * value greater than 512. 635 * 636 * The value in 'first_sect' and 'last_sect' fields must be setup so that the 637 * resulting segment offset and size is aligned to the logical sector size 638 * reported by the 'sector-size' xenstore node, see 'Backend Device Properties' 639 * section. 640 */ 641 struct blkif_request_segment { 642 grant_ref_t gref; /* reference to I/O buffer frame */ 643 /* @first_sect: first sector in frame to transfer (inclusive). */ 644 /* @last_sect: last sector in frame to transfer (inclusive). */ 645 uint8_t first_sect, last_sect; 646 }; 647 648 /* 649 * Starting ring element for any I/O request. 650 * 651 * The 'sector_number' field is in units of 512b, despite the value of the 652 * 'sector-size' xenstore node. Note however that the offset in 653 * 'sector_number' must be aligned to 'sector-size'. 654 */ 655 struct blkif_request { 656 uint8_t operation; /* BLKIF_OP_??? */ 657 uint8_t nr_segments; /* number of segments */ 658 blkif_vdev_t handle; /* only for read/write requests */ 659 uint64_t id; /* private guest value, echoed in resp */ 660 blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */ 661 struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST]; 662 }; 663 typedef struct blkif_request blkif_request_t; 664 665 /* 666 * Cast to this structure when blkif_request.operation == BLKIF_OP_DISCARD 667 * sizeof(struct blkif_request_discard) <= sizeof(struct blkif_request) 668 * 669 * The 'sector_number' field is in units of 512b, despite the value of the 670 * 'sector-size' xenstore node. Note however that the offset in 671 * 'sector_number' must be aligned to 'discard-granularity'. 672 */ 673 struct blkif_request_discard { 674 uint8_t operation; /* BLKIF_OP_DISCARD */ 675 uint8_t flag; /* BLKIF_DISCARD_SECURE or zero */ 676 #define BLKIF_DISCARD_SECURE (1<<0) /* ignored if discard-secure=0 */ 677 blkif_vdev_t handle; /* same as for read/write requests */ 678 uint64_t id; /* private guest value, echoed in resp */ 679 blkif_sector_t sector_number;/* start sector idx on disk */ 680 uint64_t nr_sectors; /* number of contiguous sectors to discard*/ 681 }; 682 typedef struct blkif_request_discard blkif_request_discard_t; 683 684 /* 685 * The 'sector_number' field is in units of 512b, despite the value of the 686 * 'sector-size' xenstore node. Note however that the offset in 687 * 'sector_number' must be aligned to 'sector-size'. 688 */ 689 struct blkif_request_indirect { 690 uint8_t operation; /* BLKIF_OP_INDIRECT */ 691 uint8_t indirect_op; /* BLKIF_OP_{READ/WRITE} */ 692 uint16_t nr_segments; /* number of segments */ 693 uint64_t id; /* private guest value, echoed in resp */ 694 blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */ 695 blkif_vdev_t handle; /* same as for read/write requests */ 696 grant_ref_t indirect_grefs[BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST]; 697 #ifdef __i386__ 698 uint64_t pad; /* Make it 64 byte aligned on i386 */ 699 #endif 700 }; 701 typedef struct blkif_request_indirect blkif_request_indirect_t; 702 703 struct blkif_response { 704 uint64_t id; /* copied from request */ 705 uint8_t operation; /* copied from request */ 706 int16_t status; /* BLKIF_RSP_??? */ 707 }; 708 typedef struct blkif_response blkif_response_t; 709 710 /* 711 * STATUS RETURN CODES. 712 */ 713 /* Operation not supported (only happens on barrier writes). */ 714 #define BLKIF_RSP_EOPNOTSUPP -2 715 /* Operation failed for some unspecified reason (-EIO). */ 716 #define BLKIF_RSP_ERROR -1 717 /* Operation completed successfully. */ 718 #define BLKIF_RSP_OKAY 0 719 720 /* 721 * Generate blkif ring structures and types. 722 */ 723 DEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response); 724 725 #define VDISK_CDROM 0x1 726 #define VDISK_REMOVABLE 0x2 727 #define VDISK_READONLY 0x4 728 729 #endif /* __XEN_PUBLIC_IO_BLKIF_H__ */ 730 731 /* 732 * Local variables: 733 * mode: C 734 * c-file-style: "BSD" 735 * c-basic-offset: 4 736 * tab-width: 4 737 * indent-tabs-mode: nil 738 * End: 739 */ 740