1181624Skmacy/****************************************************************************** 2181624Skmacy * blkif.h 3231743Sgibbs * 4181624Skmacy * Unified block-device I/O interface for Xen guest OSes. 5231743Sgibbs * 6181624Skmacy * Permission is hereby granted, free of charge, to any person obtaining a copy 7181624Skmacy * of this software and associated documentation files (the "Software"), to 8181624Skmacy * deal in the Software without restriction, including without limitation the 9181624Skmacy * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or 10181624Skmacy * sell copies of the Software, and to permit persons to whom the Software is 11181624Skmacy * furnished to do so, subject to the following conditions: 12181624Skmacy * 13181624Skmacy * The above copyright notice and this permission notice shall be included in 14181624Skmacy * all copies or substantial portions of the Software. 15181624Skmacy * 16181624Skmacy * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 17181624Skmacy * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 18181624Skmacy * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 19181624Skmacy * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 20181624Skmacy * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 21181624Skmacy * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 22181624Skmacy * DEALINGS IN THE SOFTWARE. 23181624Skmacy * 24181624Skmacy * Copyright (c) 2003-2004, Keir Fraser 25231743Sgibbs * Copyright (c) 2012, Spectra Logic Corporation 26181624Skmacy */ 27181624Skmacy 28181624Skmacy#ifndef __XEN_PUBLIC_IO_BLKIF_H__ 29181624Skmacy#define __XEN_PUBLIC_IO_BLKIF_H__ 30181624Skmacy 31251767Sgibbs#include "ring.h" 32251767Sgibbs#include "../grant_table.h" 33181624Skmacy 34181624Skmacy/* 35181624Skmacy * Front->back notifications: When enqueuing a new request, sending a 36181624Skmacy * notification can be made conditional on req_event (i.e., the generic 37181624Skmacy * hold-off mechanism provided by the ring macros). Backends must set 38181624Skmacy * req_event appropriately (e.g., using RING_FINAL_CHECK_FOR_REQUESTS()). 39231743Sgibbs * 40181624Skmacy * Back->front notifications: When enqueuing a new response, sending a 41181624Skmacy * notification can be made conditional on rsp_event (i.e., the generic 42181624Skmacy * hold-off mechanism provided by the ring macros). Frontends must set 43181624Skmacy * rsp_event appropriately (e.g., using RING_FINAL_CHECK_FOR_RESPONSES()). 44181624Skmacy */ 45181624Skmacy 46181624Skmacy#ifndef blkif_vdev_t 47181624Skmacy#define blkif_vdev_t uint16_t 48181624Skmacy#endif 49181624Skmacy#define blkif_sector_t uint64_t 50181624Skmacy 51181624Skmacy/* 52231743Sgibbs * Feature and Parameter Negotiation 53231743Sgibbs * ================================= 54231743Sgibbs * The two halves of a Xen block driver utilize nodes within the XenStore to 55231743Sgibbs * communicate capabilities and to negotiate operating parameters. This 56231743Sgibbs * section enumerates these nodes which reside in the respective front and 57231743Sgibbs * backend portions of the XenStore, following the XenBus convention. 58231743Sgibbs * 59231743Sgibbs * All data in the XenStore is stored as strings. Nodes specifying numeric 60231743Sgibbs * values are encoded in decimal. Integer value ranges listed below are 61231743Sgibbs * expressed as fixed sized integer types capable of storing the conversion 62288917Sroyger * of a properly formated node string, without loss of information. 63231743Sgibbs * 64231743Sgibbs * Any specified default value is in effect if the corresponding XenBus node 65231743Sgibbs * is not present in the XenStore. 66231743Sgibbs * 67231743Sgibbs * XenStore nodes in sections marked "PRIVATE" are solely for use by the 68231743Sgibbs * driver side whose XenBus tree contains them. 69231743Sgibbs * 70232308Sgibbs * XenStore nodes marked "DEPRECATED" in their notes section should only be 71232308Sgibbs * used to provide interoperability with legacy implementations. 72232308Sgibbs * 73231743Sgibbs * See the XenBus state transition diagram below for details on when XenBus 74231743Sgibbs * nodes must be published and when they can be queried. 75231743Sgibbs * 76231743Sgibbs ***************************************************************************** 77231743Sgibbs * Backend XenBus Nodes 78231743Sgibbs ***************************************************************************** 79231743Sgibbs * 80231743Sgibbs *------------------ Backend Device Identification (PRIVATE) ------------------ 81231743Sgibbs * 82231743Sgibbs * mode 83231743Sgibbs * Values: "r" (read only), "w" (writable) 84231743Sgibbs * 85231743Sgibbs * The read or write access permissions to the backing store to be 86231743Sgibbs * granted to the frontend. 87231743Sgibbs * 88231743Sgibbs * params 89231743Sgibbs * Values: string 90231743Sgibbs * 91288917Sroyger * A free formatted string providing sufficient information for the 92288917Sroyger * backend driver to open the backing device. (e.g. the path to the 93288917Sroyger * file or block device representing the backing store.) 94231743Sgibbs * 95288917Sroyger * physical-device 96288917Sroyger * Values: "MAJOR:MINOR" 97288917Sroyger * 98288917Sroyger * MAJOR and MINOR are the major number and minor number of the 99288917Sroyger * backing device respectively. 100288917Sroyger * 101231743Sgibbs * type 102231743Sgibbs * Values: "file", "phy", "tap" 103231743Sgibbs * 104231743Sgibbs * The type of the backing device/object. 105231743Sgibbs * 106286062Scperciva * 107286062Scperciva * direct-io-safe 108286062Scperciva * Values: 0/1 (boolean) 109286062Scperciva * Default Value: 0 110286062Scperciva * 111286062Scperciva * The underlying storage is not affected by the direct IO memory 112286062Scperciva * lifetime bug. See: 113286062Scperciva * http://lists.xen.org/archives/html/xen-devel/2012-12/msg01154.html 114286062Scperciva * 115286062Scperciva * Therefore this option gives the backend permission to use 116286062Scperciva * O_DIRECT, notwithstanding that bug. 117286062Scperciva * 118286062Scperciva * That is, if this option is enabled, use of O_DIRECT is safe, 119286062Scperciva * in circumstances where we would normally have avoided it as a 120286062Scperciva * workaround for that bug. This option is not relevant for all 121286062Scperciva * backends, and even not necessarily supported for those for 122286062Scperciva * which it is relevant. A backend which knows that it is not 123286062Scperciva * affected by the bug can ignore this option. 124286062Scperciva * 125286062Scperciva * This option doesn't require a backend to use O_DIRECT, so it 126286062Scperciva * should not be used to try to control the caching behaviour. 127286062Scperciva * 128231743Sgibbs *--------------------------------- Features --------------------------------- 129231743Sgibbs * 130231743Sgibbs * feature-barrier 131231743Sgibbs * Values: 0/1 (boolean) 132231743Sgibbs * Default Value: 0 133231743Sgibbs * 134231743Sgibbs * A value of "1" indicates that the backend can process requests 135231743Sgibbs * containing the BLKIF_OP_WRITE_BARRIER request opcode. Requests 136231743Sgibbs * of this type may still be returned at any time with the 137231743Sgibbs * BLKIF_RSP_EOPNOTSUPP result code. 138231743Sgibbs * 139231743Sgibbs * feature-flush-cache 140231743Sgibbs * Values: 0/1 (boolean) 141231743Sgibbs * Default Value: 0 142231743Sgibbs * 143231743Sgibbs * A value of "1" indicates that the backend can process requests 144231743Sgibbs * containing the BLKIF_OP_FLUSH_DISKCACHE request opcode. Requests 145231743Sgibbs * of this type may still be returned at any time with the 146231743Sgibbs * BLKIF_RSP_EOPNOTSUPP result code. 147231743Sgibbs * 148231743Sgibbs * feature-discard 149231743Sgibbs * Values: 0/1 (boolean) 150231743Sgibbs * Default Value: 0 151231743Sgibbs * 152231743Sgibbs * A value of "1" indicates that the backend can process requests 153231743Sgibbs * containing the BLKIF_OP_DISCARD request opcode. Requests 154231743Sgibbs * of this type may still be returned at any time with the 155231743Sgibbs * BLKIF_RSP_EOPNOTSUPP result code. 156231743Sgibbs * 157286062Scperciva * feature-persistent 158286062Scperciva * Values: 0/1 (boolean) 159286062Scperciva * Default Value: 0 160286062Scperciva * Notes: 7 161286062Scperciva * 162286062Scperciva * A value of "1" indicates that the backend can keep the grants used 163286062Scperciva * by the frontend driver mapped, so the same set of grants should be 164286062Scperciva * used in all transactions. The maximum number of grants the backend 165286062Scperciva * can map persistently depends on the implementation, but ideally it 166286062Scperciva * should be RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST. Using this 167286062Scperciva * feature the backend doesn't need to unmap each grant, preventing 168286062Scperciva * costly TLB flushes. The backend driver should only map grants 169286062Scperciva * persistently if the frontend supports it. If a backend driver chooses 170286062Scperciva * to use the persistent protocol when the frontend doesn't support it, 171286062Scperciva * it will probably hit the maximum number of persistently mapped grants 172286062Scperciva * (due to the fact that the frontend won't be reusing the same grants), 173286062Scperciva * and fall back to non-persistent mode. Backend implementations may 174286062Scperciva * shrink or expand the number of persistently mapped grants without 175286062Scperciva * notifying the frontend depending on memory constraints (this might 176286062Scperciva * cause a performance degradation). 177286062Scperciva * 178286062Scperciva * If a backend driver wants to limit the maximum number of persistently 179286062Scperciva * mapped grants to a value less than RING_SIZE * 180286062Scperciva * BLKIF_MAX_SEGMENTS_PER_REQUEST a LRU strategy should be used to 181286062Scperciva * discard the grants that are less commonly used. Using a LRU in the 182286062Scperciva * backend driver paired with a LIFO queue in the frontend will 183286062Scperciva * allow us to have better performance in this scenario. 184286062Scperciva * 185231743Sgibbs *----------------------- Request Transport Parameters ------------------------ 186231743Sgibbs * 187231743Sgibbs * max-ring-page-order 188231743Sgibbs * Values: <uint32_t> 189231743Sgibbs * Default Value: 0 190231743Sgibbs * Notes: 1, 3 191231743Sgibbs * 192231743Sgibbs * The maximum supported size of the request ring buffer in units of 193231743Sgibbs * lb(machine pages). (e.g. 0 == 1 page, 1 = 2 pages, 2 == 4 pages, 194231743Sgibbs * etc.). 195231743Sgibbs * 196231743Sgibbs * max-ring-pages 197231743Sgibbs * Values: <uint32_t> 198231743Sgibbs * Default Value: 1 199232308Sgibbs * Notes: DEPRECATED, 2, 3 200231743Sgibbs * 201231743Sgibbs * The maximum supported size of the request ring buffer in units of 202231743Sgibbs * machine pages. The value must be a power of 2. 203231743Sgibbs * 204231743Sgibbs *------------------------- Backend Device Properties ------------------------- 205231743Sgibbs * 206286062Scperciva * discard-enable 207286062Scperciva * Values: 0/1 (boolean) 208286062Scperciva * Default Value: 1 209286062Scperciva * 210286062Scperciva * This optional property, set by the toolstack, instructs the backend 211286062Scperciva * to offer discard to the frontend. If the property is missing the 212286062Scperciva * backend should offer discard if the backing storage actually supports 213286062Scperciva * it. This optional property, set by the toolstack, requests that the 214286062Scperciva * backend offer, or not offer, discard to the frontend. 215286062Scperciva * 216232308Sgibbs * discard-alignment 217231743Sgibbs * Values: <uint32_t> 218231743Sgibbs * Default Value: 0 219231743Sgibbs * Notes: 4, 5 220231743Sgibbs * 221231743Sgibbs * The offset, in bytes from the beginning of the virtual block device, 222231743Sgibbs * to the first, addressable, discard extent on the underlying device. 223231743Sgibbs * 224231743Sgibbs * discard-granularity 225231743Sgibbs * Values: <uint32_t> 226231743Sgibbs * Default Value: <"sector-size"> 227231743Sgibbs * Notes: 4 228231743Sgibbs * 229231743Sgibbs * The size, in bytes, of the individually addressable discard extents 230231743Sgibbs * of the underlying device. 231231743Sgibbs * 232231743Sgibbs * discard-secure 233231743Sgibbs * Values: 0/1 (boolean) 234231743Sgibbs * Default Value: 0 235286062Scperciva * Notes: 10 236231743Sgibbs * 237231743Sgibbs * A value of "1" indicates that the backend can process BLKIF_OP_DISCARD 238231743Sgibbs * requests with the BLKIF_DISCARD_SECURE flag set. 239231743Sgibbs * 240231743Sgibbs * info 241231743Sgibbs * Values: <uint32_t> (bitmap) 242231743Sgibbs * 243231743Sgibbs * A collection of bit flags describing attributes of the backing 244231743Sgibbs * device. The VDISK_* macros define the meaning of each bit 245231743Sgibbs * location. 246231743Sgibbs * 247231743Sgibbs * sector-size 248231743Sgibbs * Values: <uint32_t> 249231743Sgibbs * 250286062Scperciva * The logical sector size, in bytes, of the backend device. 251231743Sgibbs * 252286062Scperciva * physical-sector-size 253286062Scperciva * Values: <uint32_t> 254286062Scperciva * 255286062Scperciva * The physical sector size, in bytes, of the backend device. 256286062Scperciva * 257231743Sgibbs * sectors 258231743Sgibbs * Values: <uint64_t> 259231743Sgibbs * 260286062Scperciva * The size of the backend device, expressed in units of its logical 261231743Sgibbs * sector size ("sector-size"). 262231743Sgibbs * 263231743Sgibbs ***************************************************************************** 264231743Sgibbs * Frontend XenBus Nodes 265231743Sgibbs ***************************************************************************** 266231743Sgibbs * 267231743Sgibbs *----------------------- Request Transport Parameters ----------------------- 268231743Sgibbs * 269231743Sgibbs * event-channel 270231743Sgibbs * Values: <uint32_t> 271231743Sgibbs * 272231743Sgibbs * The identifier of the Xen event channel used to signal activity 273231743Sgibbs * in the ring buffer. 274231743Sgibbs * 275231743Sgibbs * ring-ref 276231743Sgibbs * Values: <uint32_t> 277231743Sgibbs * Notes: 6 278231743Sgibbs * 279231743Sgibbs * The Xen grant reference granting permission for the backend to map 280231743Sgibbs * the sole page in a single page sized ring buffer. 281231743Sgibbs * 282231743Sgibbs * ring-ref%u 283231743Sgibbs * Values: <uint32_t> 284231743Sgibbs * Notes: 6 285231743Sgibbs * 286232308Sgibbs * For a frontend providing a multi-page ring, a "number of ring pages" 287232308Sgibbs * sized list of nodes, each containing a Xen grant reference granting 288231743Sgibbs * permission for the backend to map the page of the ring located 289231743Sgibbs * at page index "%u". Page indexes are zero based. 290231743Sgibbs * 291231743Sgibbs * protocol 292231743Sgibbs * Values: string (XEN_IO_PROTO_ABI_*) 293231743Sgibbs * Default Value: XEN_IO_PROTO_ABI_NATIVE 294231743Sgibbs * 295231743Sgibbs * The machine ABI rules governing the format of all ring request and 296231743Sgibbs * response structures. 297231743Sgibbs * 298231743Sgibbs * ring-page-order 299231743Sgibbs * Values: <uint32_t> 300231743Sgibbs * Default Value: 0 301231743Sgibbs * Maximum Value: MAX(ffs(max-ring-pages) - 1, max-ring-page-order) 302231743Sgibbs * Notes: 1, 3 303231743Sgibbs * 304231743Sgibbs * The size of the frontend allocated request ring buffer in units 305231743Sgibbs * of lb(machine pages). (e.g. 0 == 1 page, 1 = 2 pages, 2 == 4 pages, 306231743Sgibbs * etc.). 307231743Sgibbs * 308231743Sgibbs * num-ring-pages 309231743Sgibbs * Values: <uint32_t> 310231743Sgibbs * Default Value: 1 311231743Sgibbs * Maximum Value: MAX(max-ring-pages,(0x1 << max-ring-page-order)) 312232308Sgibbs * Notes: DEPRECATED, 2, 3 313231743Sgibbs * 314231743Sgibbs * The size of the frontend allocated request ring buffer in units of 315231743Sgibbs * machine pages. The value must be a power of 2. 316231743Sgibbs * 317286062Scperciva * feature-persistent 318286062Scperciva * Values: 0/1 (boolean) 319286062Scperciva * Default Value: 0 320286062Scperciva * Notes: 7, 8, 9 321286062Scperciva * 322286062Scperciva * A value of "1" indicates that the frontend will reuse the same grants 323286062Scperciva * for all transactions, allowing the backend to map them with write 324286062Scperciva * access (even when it should be read-only). If the frontend hits the 325286062Scperciva * maximum number of allowed persistently mapped grants, it can fallback 326286062Scperciva * to non persistent mode. This will cause a performance degradation, 327300050Seadler * since the backend driver will still try to map those grants 328286062Scperciva * persistently. Since the persistent grants protocol is compatible with 329286062Scperciva * the previous protocol, a frontend driver can choose to work in 330286062Scperciva * persistent mode even when the backend doesn't support it. 331286062Scperciva * 332286062Scperciva * It is recommended that the frontend driver stores the persistently 333286062Scperciva * mapped grants in a LIFO queue, so a subset of all persistently mapped 334286062Scperciva * grants gets used commonly. This is done in case the backend driver 335286062Scperciva * decides to limit the maximum number of persistently mapped grants 336286062Scperciva * to a value less than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST. 337286062Scperciva * 338231743Sgibbs *------------------------- Virtual Device Properties ------------------------- 339231743Sgibbs * 340231743Sgibbs * device-type 341231743Sgibbs * Values: "disk", "cdrom", "floppy", etc. 342231743Sgibbs * 343231743Sgibbs * virtual-device 344231743Sgibbs * Values: <uint32_t> 345231743Sgibbs * 346231743Sgibbs * A value indicating the physical device to virtualize within the 347231743Sgibbs * frontend's domain. (e.g. "The first ATA disk", "The third SCSI 348231743Sgibbs * disk", etc.) 349231743Sgibbs * 350231743Sgibbs * See docs/misc/vbd-interface.txt for details on the format of this 351231743Sgibbs * value. 352231743Sgibbs * 353231743Sgibbs * Notes 354231743Sgibbs * ----- 355231743Sgibbs * (1) Multi-page ring buffer scheme first developed in the Citrix XenServer 356231743Sgibbs * PV drivers. 357286062Scperciva * (2) Multi-page ring buffer scheme first used in some RedHat distributions 358231743Sgibbs * including a distribution deployed on certain nodes of the Amazon 359231743Sgibbs * EC2 cluster. 360231743Sgibbs * (3) Support for multi-page ring buffers was implemented independently, 361286062Scperciva * in slightly different forms, by both Citrix and RedHat/Amazon. 362231743Sgibbs * For full interoperability, block front and backends should publish 363231743Sgibbs * identical ring parameters, adjusted for unit differences, to the 364231743Sgibbs * XenStore nodes used in both schemes. 365286062Scperciva * (4) Devices that support discard functionality may internally allocate space 366286062Scperciva * (discardable extents) in units that are larger than the exported logical 367286062Scperciva * block size. If the backing device has such discardable extents the 368286062Scperciva * backend should provide both discard-granularity and discard-alignment. 369286062Scperciva * Providing just one of the two may be considered an error by the frontend. 370286062Scperciva * Backends supporting discard should include discard-granularity and 371286062Scperciva * discard-alignment even if it supports discarding individual sectors. 372286062Scperciva * Frontends should assume discard-alignment == 0 and discard-granularity 373286062Scperciva * == sector size if these keys are missing. 374231743Sgibbs * (5) The discard-alignment parameter allows a physical device to be 375231743Sgibbs * partitioned into virtual devices that do not necessarily begin or 376231743Sgibbs * end on a discardable extent boundary. 377231743Sgibbs * (6) When there is only a single page allocated to the request ring, 378231743Sgibbs * 'ring-ref' is used to communicate the grant reference for this 379231743Sgibbs * page to the backend. When using a multi-page ring, the 'ring-ref' 380231743Sgibbs * node is not created. Instead 'ring-ref0' - 'ring-refN' are used. 381286062Scperciva * (7) When using persistent grants data has to be copied from/to the page 382286062Scperciva * where the grant is currently mapped. The overhead of doing this copy 383286062Scperciva * however doesn't suppress the speed improvement of not having to unmap 384286062Scperciva * the grants. 385286062Scperciva * (8) The frontend driver has to allow the backend driver to map all grants 386286062Scperciva * with write access, even when they should be mapped read-only, since 387286062Scperciva * further requests may reuse these grants and require write permissions. 388286062Scperciva * (9) Linux implementation doesn't have a limit on the maximum number of 389286062Scperciva * grants that can be persistently mapped in the frontend driver, but 390286062Scperciva * due to the frontent driver implementation it should never be bigger 391286062Scperciva * than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST. 392286062Scperciva *(10) The discard-secure property may be present and will be set to 1 if the 393286062Scperciva * backing device supports secure discard. 394231743Sgibbs */ 395231743Sgibbs 396231743Sgibbs/* 397231743Sgibbs * STATE DIAGRAMS 398231743Sgibbs * 399231743Sgibbs ***************************************************************************** 400231743Sgibbs * Startup * 401231743Sgibbs ***************************************************************************** 402231743Sgibbs * 403231743Sgibbs * Tool stack creates front and back nodes with state XenbusStateInitialising. 404231743Sgibbs * 405231743Sgibbs * Front Back 406231743Sgibbs * ================================= ===================================== 407231743Sgibbs * XenbusStateInitialising XenbusStateInitialising 408231743Sgibbs * o Query virtual device o Query backend device identification 409231743Sgibbs * properties. data. 410231743Sgibbs * o Setup OS device instance. o Open and validate backend device. 411231743Sgibbs * o Publish backend features and 412231743Sgibbs * transport parameters. 413231743Sgibbs * | 414231743Sgibbs * | 415231743Sgibbs * V 416231743Sgibbs * XenbusStateInitWait 417231743Sgibbs * 418231743Sgibbs * o Query backend features and 419231743Sgibbs * transport parameters. 420231743Sgibbs * o Allocate and initialize the 421231743Sgibbs * request ring. 422231743Sgibbs * o Publish transport parameters 423231743Sgibbs * that will be in effect during 424231743Sgibbs * this connection. 425231743Sgibbs * | 426231743Sgibbs * | 427231743Sgibbs * V 428231743Sgibbs * XenbusStateInitialised 429231743Sgibbs * 430231743Sgibbs * o Query frontend transport parameters. 431231743Sgibbs * o Connect to the request ring and 432231743Sgibbs * event channel. 433231743Sgibbs * o Publish backend device properties. 434231743Sgibbs * | 435231743Sgibbs * | 436231743Sgibbs * V 437231743Sgibbs * XenbusStateConnected 438231743Sgibbs * 439231743Sgibbs * o Query backend device properties. 440231743Sgibbs * o Finalize OS virtual device 441231743Sgibbs * instance. 442231743Sgibbs * | 443231743Sgibbs * | 444231743Sgibbs * V 445231743Sgibbs * XenbusStateConnected 446231743Sgibbs * 447231743Sgibbs * Note: Drivers that do not support any optional features, or the negotiation 448231743Sgibbs * of transport parameters, can skip certain states in the state machine: 449231743Sgibbs * 450231743Sgibbs * o A frontend may transition to XenbusStateInitialised without 451231743Sgibbs * waiting for the backend to enter XenbusStateInitWait. In this 452231743Sgibbs * case, default transport parameters are in effect and any 453231743Sgibbs * transport parameters published by the frontend must contain 454231743Sgibbs * their default values. 455231743Sgibbs * 456231743Sgibbs * o A backend may transition to XenbusStateInitialised, bypassing 457231743Sgibbs * XenbusStateInitWait, without waiting for the frontend to first 458231743Sgibbs * enter the XenbusStateInitialised state. In this case, default 459231743Sgibbs * transport parameters are in effect and any transport parameters 460231743Sgibbs * published by the backend must contain their default values. 461231743Sgibbs * 462231743Sgibbs * Drivers that support optional features and/or transport parameter 463231743Sgibbs * negotiation must tolerate these additional state transition paths. 464231743Sgibbs * In general this means performing the work of any skipped state 465231743Sgibbs * transition, if it has not already been performed, in addition to the 466231743Sgibbs * work associated with entry into the current state. 467231743Sgibbs */ 468231743Sgibbs 469231743Sgibbs/* 470181624Skmacy * REQUEST CODES. 471181624Skmacy */ 472181624Skmacy#define BLKIF_OP_READ 0 473181624Skmacy#define BLKIF_OP_WRITE 1 474181624Skmacy/* 475231743Sgibbs * All writes issued prior to a request with the BLKIF_OP_WRITE_BARRIER 476231743Sgibbs * operation code ("barrier request") must be completed prior to the 477231743Sgibbs * execution of the barrier request. All writes issued after the barrier 478231743Sgibbs * request must not execute until after the completion of the barrier request. 479231743Sgibbs * 480231743Sgibbs * Optional. See "feature-barrier" XenBus node documentation above. 481181624Skmacy */ 482181624Skmacy#define BLKIF_OP_WRITE_BARRIER 2 483183375Skmacy/* 484231743Sgibbs * Commit any uncommitted contents of the backing device's volatile cache 485231743Sgibbs * to stable storage. 486231743Sgibbs * 487231743Sgibbs * Optional. See "feature-flush-cache" XenBus node documentation above. 488183375Skmacy */ 489183375Skmacy#define BLKIF_OP_FLUSH_DISKCACHE 3 490231743Sgibbs/* 491231743Sgibbs * Used in SLES sources for device specific command packet 492231743Sgibbs * contained within the request. Reserved for that purpose. 493231743Sgibbs */ 494231743Sgibbs#define BLKIF_OP_RESERVED_1 4 495231743Sgibbs/* 496231743Sgibbs * Indicate to the backend device that a region of storage is no longer in 497231743Sgibbs * use, and may be discarded at any time without impact to the client. If 498231743Sgibbs * the BLKIF_DISCARD_SECURE flag is set on the request, all copies of the 499231743Sgibbs * discarded region on the device must be rendered unrecoverable before the 500231743Sgibbs * command returns. 501231743Sgibbs * 502288917Sroyger * This operation is analogous to performing a trim (ATA) or unamp (SCSI), 503231743Sgibbs * command on a native device. 504231743Sgibbs * 505231743Sgibbs * More information about trim/unmap operations can be found at: 506231743Sgibbs * http://t13.org/Documents/UploadedDocuments/docs2008/ 507231743Sgibbs * e07154r6-Data_Set_Management_Proposal_for_ATA-ACS2.doc 508231743Sgibbs * http://www.seagate.com/staticfiles/support/disc/manuals/ 509231743Sgibbs * Interface%20manuals/100293068c.pdf 510231743Sgibbs * 511231743Sgibbs * Optional. See "feature-discard", "discard-alignment", 512231743Sgibbs * "discard-granularity", and "discard-secure" in the XenBus node 513231743Sgibbs * documentation above. 514231743Sgibbs */ 515231743Sgibbs#define BLKIF_OP_DISCARD 5 516181624Skmacy 517181624Skmacy/* 518286062Scperciva * Recognized if "feature-max-indirect-segments" in present in the backend 519286062Scperciva * xenbus info. The "feature-max-indirect-segments" node contains the maximum 520286062Scperciva * number of segments allowed by the backend per request. If the node is 521286062Scperciva * present, the frontend might use blkif_request_indirect structs in order to 522286062Scperciva * issue requests with more than BLKIF_MAX_SEGMENTS_PER_REQUEST (11). The 523286062Scperciva * maximum number of indirect segments is fixed by the backend, but the 524286062Scperciva * frontend can issue requests with any number of indirect segments as long as 525286062Scperciva * it's less than the number provided by the backend. The indirect_grefs field 526286062Scperciva * in blkif_request_indirect should be filled by the frontend with the 527286062Scperciva * grant references of the pages that are holding the indirect segments. 528286062Scperciva * These pages are filled with an array of blkif_request_segment that hold the 529286062Scperciva * information about the segments. The number of indirect pages to use is 530286062Scperciva * determined by the number of segments an indirect request contains. Every 531286062Scperciva * indirect page can contain a maximum of 532286062Scperciva * (PAGE_SIZE / sizeof(struct blkif_request_segment)) segments, so to 533286062Scperciva * calculate the number of indirect pages to use we have to do 534286062Scperciva * ceil(indirect_segments / (PAGE_SIZE / sizeof(struct blkif_request_segment))). 535286062Scperciva * 536286062Scperciva * If a backend does not recognize BLKIF_OP_INDIRECT, it should *not* 537286062Scperciva * create the "feature-max-indirect-segments" node! 538286062Scperciva */ 539286062Scperciva#define BLKIF_OP_INDIRECT 6 540286062Scperciva 541286062Scperciva/* 542284664Scperciva * Maximum scatter/gather segments per request. 543284664Scperciva * This is carefully chosen so that sizeof(blkif_ring_t) <= PAGE_SIZE. 544284664Scperciva * NB. This could be 12 if the ring indexes weren't stored in the same page. 545214077Sgibbs */ 546284296Sroyger#define BLKIF_MAX_SEGMENTS_PER_REQUEST 11 547214077Sgibbs 548231743Sgibbs/* 549286062Scperciva * Maximum number of indirect pages to use per request. 550286062Scperciva */ 551286062Scperciva#define BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST 8 552286062Scperciva 553286062Scperciva/* 554231743Sgibbs * NB. first_sect and last_sect in blkif_request_segment, as well as 555231743Sgibbs * sector_number in blkif_request, are always expressed in 512-byte units. 556231743Sgibbs * However they must be properly aligned to the real sector size of the 557286062Scperciva * physical disk, which is reported in the "physical-sector-size" node in 558286062Scperciva * the backend xenbus info. Also the xenbus "sectors" node is expressed in 559286062Scperciva * 512-byte units. 560231743Sgibbs */ 561181624Skmacystruct blkif_request_segment { 562181624Skmacy grant_ref_t gref; /* reference to I/O buffer frame */ 563181624Skmacy /* @first_sect: first sector in frame to transfer (inclusive). */ 564181624Skmacy /* @last_sect: last sector in frame to transfer (inclusive). */ 565181624Skmacy uint8_t first_sect, last_sect; 566181624Skmacy}; 567181624Skmacy 568231743Sgibbs/* 569231743Sgibbs * Starting ring element for any I/O request. 570231743Sgibbs */ 571181624Skmacystruct blkif_request { 572181624Skmacy uint8_t operation; /* BLKIF_OP_??? */ 573181624Skmacy uint8_t nr_segments; /* number of segments */ 574181624Skmacy blkif_vdev_t handle; /* only for read/write requests */ 575181624Skmacy uint64_t id; /* private guest value, echoed in resp */ 576181624Skmacy blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */ 577288917Sroyger struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST]; 578181624Skmacy}; 579181624Skmacytypedef struct blkif_request blkif_request_t; 580181624Skmacy 581231743Sgibbs/* 582231743Sgibbs * Cast to this structure when blkif_request.operation == BLKIF_OP_DISCARD 583231743Sgibbs * sizeof(struct blkif_request_discard) <= sizeof(struct blkif_request) 584231743Sgibbs */ 585231743Sgibbsstruct blkif_request_discard { 586231743Sgibbs uint8_t operation; /* BLKIF_OP_DISCARD */ 587231743Sgibbs uint8_t flag; /* BLKIF_DISCARD_SECURE or zero */ 588231743Sgibbs#define BLKIF_DISCARD_SECURE (1<<0) /* ignored if discard-secure=0 */ 589231743Sgibbs blkif_vdev_t handle; /* same as for read/write requests */ 590231743Sgibbs uint64_t id; /* private guest value, echoed in resp */ 591231743Sgibbs blkif_sector_t sector_number;/* start sector idx on disk */ 592231743Sgibbs uint64_t nr_sectors; /* number of contiguous sectors to discard*/ 593231743Sgibbs}; 594231743Sgibbstypedef struct blkif_request_discard blkif_request_discard_t; 595231743Sgibbs 596286062Scpercivastruct blkif_request_indirect { 597286062Scperciva uint8_t operation; /* BLKIF_OP_INDIRECT */ 598286062Scperciva uint8_t indirect_op; /* BLKIF_OP_{READ/WRITE} */ 599286062Scperciva uint16_t nr_segments; /* number of segments */ 600286062Scperciva uint64_t id; /* private guest value, echoed in resp */ 601286062Scperciva blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */ 602286062Scperciva blkif_vdev_t handle; /* same as for read/write requests */ 603286062Scperciva grant_ref_t indirect_grefs[BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST]; 604286062Scperciva#ifdef __i386__ 605286062Scperciva uint64_t pad; /* Make it 64 byte aligned on i386 */ 606286062Scperciva#endif 607286062Scperciva}; 608286062Scpercivatypedef struct blkif_request_indirect blkif_request_indirect_t; 609286062Scperciva 610181624Skmacystruct blkif_response { 611181624Skmacy uint64_t id; /* copied from request */ 612181624Skmacy uint8_t operation; /* copied from request */ 613181624Skmacy int16_t status; /* BLKIF_RSP_??? */ 614181624Skmacy}; 615181624Skmacytypedef struct blkif_response blkif_response_t; 616181624Skmacy 617181624Skmacy/* 618181624Skmacy * STATUS RETURN CODES. 619181624Skmacy */ 620181624Skmacy /* Operation not supported (only happens on barrier writes). */ 621181624Skmacy#define BLKIF_RSP_EOPNOTSUPP -2 622181624Skmacy /* Operation failed for some unspecified reason (-EIO). */ 623181624Skmacy#define BLKIF_RSP_ERROR -1 624181624Skmacy /* Operation completed successfully. */ 625181624Skmacy#define BLKIF_RSP_OKAY 0 626181624Skmacy 627181624Skmacy/* 628181624Skmacy * Generate blkif ring structures and types. 629181624Skmacy */ 630181624SkmacyDEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response); 631181624Skmacy 632231743Sgibbs#define VDISK_CDROM 0x1 633231743Sgibbs#define VDISK_REMOVABLE 0x2 634231743Sgibbs#define VDISK_READONLY 0x4 635231743Sgibbs 636181624Skmacy#endif /* __XEN_PUBLIC_IO_BLKIF_H__ */ 637181624Skmacy 638181624Skmacy/* 639181624Skmacy * Local variables: 640181624Skmacy * mode: C 641286062Scperciva * c-file-style: "BSD" 642181624Skmacy * c-basic-offset: 4 643181624Skmacy * tab-width: 4 644181624Skmacy * indent-tabs-mode: nil 645181624Skmacy * End: 646181624Skmacy */ 647