OvmfPkg/Include/IndustryStandard/Xen/io/blkif.h

   1 /******************************************************************************
   2  * blkif.h
   3  *
   4  * Unified block-device I/O interface for Xen guest OSes.
   5  *
   6  * SPDX-License-Identifier: MIT
   7  *
   8  * Copyright (c) 2003-2004, Keir Fraser
   9  * Copyright (c) 2012, Spectra Logic Corporation
  10  */
  11
  12 #ifndef __XEN_PUBLIC_IO_BLKIF_H__
  13 #define __XEN_PUBLIC_IO_BLKIF_H__
  14
  15 #include "ring.h"
  16 #include "../grant_table.h"
  17
  18 /*
  19  * Front->back notifications: When enqueuing a new request, sending a
  20  * notification can be made conditional on req_event (i.e., the generic
  21  * hold-off mechanism provided by the ring macros). Backends must set
  22  * req_event appropriately (e.g., using RING_FINAL_CHECK_FOR_REQUESTS()).
  23  *
  24  * Back->front notifications: When enqueuing a new response, sending a
  25  * notification can be made conditional on rsp_event (i.e., the generic
  26  * hold-off mechanism provided by the ring macros). Frontends must set
  27  * rsp_event appropriately (e.g., using RING_FINAL_CHECK_FOR_RESPONSES()).
  28  */
  29
  30 #ifndef blkif_vdev_t
  31 #define blkif_vdev_t  UINT16
  32 #endif
  33 #define blkif_sector_t  UINT64
  34
  35 /*
  36  * Feature and Parameter Negotiation
  37  * =================================
  38  * The two halves of a Xen block driver utilize nodes within the XenStore to
  39  * communicate capabilities and to negotiate operating parameters.  This
  40  * section enumerates these nodes which reside in the respective front and
  41  * backend portions of the XenStore, following the XenBus convention.
  42  *
  43  * All data in the XenStore is stored as strings.  Nodes specifying numeric
  44  * values are encoded in decimal.  Integer value ranges listed below are
  45  * expressed as fixed sized integer types capable of storing the conversion
  46  * of a properly formatted node string, without loss of information.
  47  *
  48  * Any specified default value is in effect if the corresponding XenBus node
  49  * is not present in the XenStore.
  50  *
  51  * XenStore nodes in sections marked "PRIVATE" are solely for use by the
  52  * driver side whose XenBus tree contains them.
  53  *
  54  * XenStore nodes marked "DEPRECATED" in their notes section should only be
  55  * used to provide interoperability with legacy implementations.
  56  *
  57  * See the XenBus state transition diagram below for details on when XenBus
  58  * nodes must be published and when they can be queried.
  59  *
  60  *****************************************************************************
  61  *                            Backend XenBus Nodes
  62  *****************************************************************************
  63  *
  64  *------------------ Backend Device Identification (PRIVATE) ------------------
  65  *
  66  * mode
  67  *      Values:         "r" (read only), "w" (writable)
  68  *
  69  *      The read or write access permissions to the backing store to be
  70  *      granted to the frontend.
  71  *
  72  * params
  73  *      Values:         string
  74  *
  75  *      A free formatted string providing sufficient information for the
  76  *      backend driver to open the backing device.  (e.g. the path to the
  77  *      file or block device representing the backing store.)
  78  *
  79  * type
  80  *      Values:         "file", "phy", "tap"
  81  *
  82  *      The type of the backing device/object.
  83  *
  84  *--------------------------------- Features ---------------------------------
  85  *
  86  * feature-barrier
  87  *      Values:         0/1 (boolean)
  88  *      Default Value:  0
  89  *
  90  *      A value of "1" indicates that the backend can process requests
  91  *      containing the BLKIF_OP_WRITE_BARRIER request opcode.  Requests
  92  *      of this type may still be returned at any time with the
  93  *      BLKIF_RSP_EOPNOTSUPP result code.
  94  *
  95  * feature-flush-cache
  96  *      Values:         0/1 (boolean)
  97  *      Default Value:  0
  98  *
  99  *      A value of "1" indicates that the backend can process requests
 100  *      containing the BLKIF_OP_FLUSH_DISKCACHE request opcode.  Requests
 101  *      of this type may still be returned at any time with the
 102  *      BLKIF_RSP_EOPNOTSUPP result code.
 103  *
 104  * feature-discard
 105  *      Values:         0/1 (boolean)
 106  *      Default Value:  0
 107  *
 108  *      A value of "1" indicates that the backend can process requests
 109  *      containing the BLKIF_OP_DISCARD request opcode.  Requests
 110  *      of this type may still be returned at any time with the
 111  *      BLKIF_RSP_EOPNOTSUPP result code.
 112  *
 113  * feature-persistent
 114  *      Values:         0/1 (boolean)
 115  *      Default Value:  0
 116  *      Notes: 7
 117  *
 118  *      A value of "1" indicates that the backend can keep the grants used
 119  *      by the frontend driver mapped, so the same set of grants should be
 120  *      used in all transactions. The maximum number of grants the backend
 121  *      can map persistently depends on the implementation, but ideally it
 122  *      should be RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST. Using this
 123  *      feature the backend doesn't need to unmap each grant, preventing
 124  *      costly TLB flushes. The backend driver should only map grants
 125  *      persistently if the frontend supports it. If a backend driver chooses
 126  *      to use the persistent protocol when the frontend doesn't support it,
 127  *      it will probably hit the maximum number of persistently mapped grants
 128  *      (due to the fact that the frontend won't be reusing the same grants),
 129  *      and fall back to non-persistent mode. Backend implementations may
 130  *      shrink or expand the number of persistently mapped grants without
 131  *      notifying the frontend depending on memory constraints (this might
 132  *      cause a performance degradation).
 133  *
 134  *      If a backend driver wants to limit the maximum number of persistently
 135  *      mapped grants to a value less than RING_SIZE *
 136  *      BLKIF_MAX_SEGMENTS_PER_REQUEST a LRU strategy should be used to
 137  *      discard the grants that are less commonly used. Using a LRU in the
 138  *      backend driver paired with a LIFO queue in the frontend will
 139  *      allow us to have better performance in this scenario.
 140  *
 141  *----------------------- Request Transport Parameters ------------------------
 142  *
 143  * max-ring-page-order
 144  *      Values:         <UINT32>
 145  *      Default Value:  0
 146  *      Notes:          1, 3
 147  *
 148  *      The maximum supported size of the request ring buffer in units of
 149  *      lb(machine pages). (e.g. 0 == 1 page,  1 = 2 pages, 2 == 4 pages,
 150  *      etc.).
 151  *
 152  * max-ring-pages
 153  *      Values:         <UINT32>
 154  *      Default Value:  1
 155  *      Notes:          DEPRECATED, 2, 3
 156  *
 157  *      The maximum supported size of the request ring buffer in units of
 158  *      machine pages.  The value must be a power of 2.
 159  *
 160  *------------------------- Backend Device Properties -------------------------
 161  *
 162  * discard-alignment
 163  *      Values:         <UINT32>
 164  *      Default Value:  0
 165  *      Notes:          4, 5
 166  *
 167  *      The offset, in bytes from the beginning of the virtual block device,
 168  *      to the first, addressable, discard extent on the underlying device.
 169  *
 170  * discard-granularity
 171  *      Values:         <UINT32>
 172  *      Default Value:  <"sector-size">
 173  *      Notes:          4
 174  *
 175  *      The size, in bytes, of the individually addressable discard extents
 176  *      of the underlying device.
 177  *
 178  * discard-secure
 179  *      Values:         0/1 (boolean)
 180  *      Default Value:  0
 181  *      Notes:          10
 182  *
 183  *      A value of "1" indicates that the backend can process BLKIF_OP_DISCARD
 184  *      requests with the BLKIF_DISCARD_SECURE flag set.
 185  *
 186  * info
 187  *      Values:         <UINT32> (bitmap)
 188  *
 189  *      A collection of bit flags describing attributes of the backing
 190  *      device.  The VDISK_* macros define the meaning of each bit
 191  *      location.
 192  *
 193  * sector-size
 194  *      Values:         <UINT32>
 195  *
 196  *      The logical sector size, in bytes, of the backend device.
 197  *
 198  * physical-sector-size
 199  *      Values:         <UINT32>
 200  *
 201  *      The physical sector size, in bytes, of the backend device.
 202  *
 203  * sectors
 204  *      Values:         <UINT64>
 205  *
 206  *      The size of the backend device, expressed in units of its logical
 207  *      sector size ("sector-size").
 208  *
 209  *****************************************************************************
 210  *                            Frontend XenBus Nodes
 211  *****************************************************************************
 212  *
 213  *----------------------- Request Transport Parameters -----------------------
 214  *
 215  * event-channel
 216  *      Values:         <UINT32>
 217  *
 218  *      The identifier of the Xen event channel used to signal activity
 219  *      in the ring buffer.
 220  *
 221  * ring-ref
 222  *      Values:         <UINT32>
 223  *      Notes:          6
 224  *
 225  *      The Xen grant reference granting permission for the backend to map
 226  *      the sole page in a single page sized ring buffer.
 227  *
 228  * ring-ref%u
 229  *      Values:         <UINT32>
 230  *      Notes:          6
 231  *
 232  *      For a frontend providing a multi-page ring, a "number of ring pages"
 233  *      sized list of nodes, each containing a Xen grant reference granting
 234  *      permission for the backend to map the page of the ring located
 235  *      at page index "%u".  Page indexes are zero based.
 236  *
 237  * protocol
 238  *      Values:         string (XEN_IO_PROTO_ABI_*)
 239  *      Default Value:  XEN_IO_PROTO_ABI_NATIVE
 240  *
 241  *      The machine ABI rules governing the format of all ring request and
 242  *      response structures.
 243  *
 244  * ring-page-order
 245  *      Values:         <UINT32>
 246  *      Default Value:  0
 247  *      Maximum Value:  MAX(ffs(max-ring-pages) - 1, max-ring-page-order)
 248  *      Notes:          1, 3
 249  *
 250  *      The size of the frontend allocated request ring buffer in units
 251  *      of lb(machine pages). (e.g. 0 == 1 page, 1 = 2 pages, 2 == 4 pages,
 252  *      etc.).
 253  *
 254  * num-ring-pages
 255  *      Values:         <UINT32>
 256  *      Default Value:  1
 257  *      Maximum Value:  MAX(max-ring-pages,(0x1 << max-ring-page-order))
 258  *      Notes:          DEPRECATED, 2, 3
 259  *
 260  *      The size of the frontend allocated request ring buffer in units of
 261  *      machine pages.  The value must be a power of 2.
 262  *
 263  * feature-persistent
 264  *      Values:         0/1 (boolean)
 265  *      Default Value:  0
 266  *      Notes: 7, 8, 9
 267  *
 268  *      A value of "1" indicates that the frontend will reuse the same grants
 269  *      for all transactions, allowing the backend to map them with write
 270  *      access (even when it should be read-only). If the frontend hits the
 271  *      maximum number of allowed persistently mapped grants, it can fallback
 272  *      to non persistent mode. This will cause a performance degradation,
 273  *      since the backend driver will still try to map those grants
 274  *      persistently. Since the persistent grants protocol is compatible with
 275  *      the previous protocol, a frontend driver can choose to work in
 276  *      persistent mode even when the backend doesn't support it.
 277  *
 278  *      It is recommended that the frontend driver stores the persistently
 279  *      mapped grants in a LIFO queue, so a subset of all persistently mapped
 280  *      grants gets used commonly. This is done in case the backend driver
 281  *      decides to limit the maximum number of persistently mapped grants
 282  *      to a value less than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST.
 283  *
 284  *------------------------- Virtual Device Properties -------------------------
 285  *
 286  * device-type
 287  *      Values:         "disk", "cdrom", "floppy", etc.
 288  *
 289  * virtual-device
 290  *      Values:         <UINT32>
 291  *
 292  *      A value indicating the physical device to virtualize within the
 293  *      frontend's domain.  (e.g. "The first ATA disk", "The third SCSI
 294  *      disk", etc.)
 295  *
 296  *      See docs/misc/vbd-interface.txt for details on the format of this
 297  *      value.
 298  *
 299  * Notes
 300  * -----
 301  * (1) Multi-page ring buffer scheme first developed in the Citrix XenServer
 302  *     PV drivers.
 303  * (2) Multi-page ring buffer scheme first used in some RedHat distributions
 304  *     including a distribution deployed on certain nodes of the Amazon
 305  *     EC2 cluster.
 306  * (3) Support for multi-page ring buffers was implemented independently,
 307  *     in slightly different forms, by both Citrix and RedHat/Amazon.
 308  *     For full interoperability, block front and backends should publish
 309  *     identical ring parameters, adjusted for unit differences, to the
 310  *     XenStore nodes used in both schemes.
 311  * (4) Devices that support discard functionality may internally allocate space
 312  *     (discardable extents) in units that are larger than the exported logical
 313  *     block size. If the backing device has such discardable extents the
 314  *     backend should provide both discard-granularity and discard-alignment.
 315  *     Providing just one of the two may be considered an error by the frontend.
 316  *     Backends supporting discard should include discard-granularity and
 317  *     discard-alignment even if it supports discarding individual sectors.
 318  *     Frontends should assume discard-alignment == 0 and discard-granularity
 319  *     == sector size if these keys are missing.
 320  * (5) The discard-alignment parameter allows a physical device to be
 321  *     partitioned into virtual devices that do not necessarily begin or
 322  *     end on a discardable extent boundary.
 323  * (6) When there is only a single page allocated to the request ring,
 324  *     'ring-ref' is used to communicate the grant reference for this
 325  *     page to the backend.  When using a multi-page ring, the 'ring-ref'
 326  *     node is not created.  Instead 'ring-ref0' - 'ring-refN' are used.
 327  * (7) When using persistent grants data has to be copied from/to the page
 328  *     where the grant is currently mapped. The overhead of doing this copy
 329  *     however doesn't suppress the speed improvement of not having to unmap
 330  *     the grants.
 331  * (8) The frontend driver has to allow the backend driver to map all grants
 332  *     with write access, even when they should be mapped read-only, since
 333  *     further requests may reuse these grants and require write permissions.
 334  * (9) Linux implementation doesn't have a limit on the maximum number of
 335  *     grants that can be persistently mapped in the frontend driver, but
 336  *     due to the frontent driver implementation it should never be bigger
 337  *     than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST.
 338  *(10) The discard-secure property may be present and will be set to 1 if the
 339  *     backing device supports secure discard.
 340  */
 341
 342 /*
 343  * STATE DIAGRAMS
 344  *
 345  *****************************************************************************
 346  *                                   Startup                                 *
 347  *****************************************************************************
 348  *
 349  * Tool stack creates front and back nodes with state XenbusStateInitialising.
 350  *
 351  * Front                                Back
 352  * =================================    =====================================
 353  * XenbusStateInitialising              XenbusStateInitialising
 354  *  o Query virtual device               o Query backend device identification
 355  *    properties.                          data.
 356  *  o Setup OS device instance.          o Open and validate backend device.
 357  *                                       o Publish backend features and
 358  *                                         transport parameters.
 359  *                                                      |
 360  *                                                      |
 361  *                                                      V
 362  *                                      XenbusStateInitWait
 363  *
 364  * o Query backend features and
 365  *   transport parameters.
 366  * o Allocate and initialize the
 367  *   request ring.
 368  * o Publish transport parameters
 369  *   that will be in effect during
 370  *   this connection.
 371  *              |
 372  *              |
 373  *              V
 374  * XenbusStateInitialised
 375  *
 376  *                                       o Query frontend transport parameters.
 377  *                                       o Connect to the request ring and
 378  *                                         event channel.
 379  *                                       o Publish backend device properties.
 380  *                                                      |
 381  *                                                      |
 382  *                                                      V
 383  *                                      XenbusStateConnected
 384  *
 385  *  o Query backend device properties.
 386  *  o Finalize OS virtual device
 387  *    instance.
 388  *              |
 389  *              |
 390  *              V
 391  * XenbusStateConnected
 392  *
 393  * Note: Drivers that do not support any optional features, or the negotiation
 394  *       of transport parameters, can skip certain states in the state machine:
 395  *
 396  *       o A frontend may transition to XenbusStateInitialised without
 397  *         waiting for the backend to enter XenbusStateInitWait.  In this
 398  *         case, default transport parameters are in effect and any
 399  *         transport parameters published by the frontend must contain
 400  *         their default values.
 401  *
 402  *       o A backend may transition to XenbusStateInitialised, bypassing
 403  *         XenbusStateInitWait, without waiting for the frontend to first
 404  *         enter the XenbusStateInitialised state.  In this case, default
 405  *         transport parameters are in effect and any transport parameters
 406  *         published by the backend must contain their default values.
 407  *
 408  *       Drivers that support optional features and/or transport parameter
 409  *       negotiation must tolerate these additional state transition paths.
 410  *       In general this means performing the work of any skipped state
 411  *       transition, if it has not already been performed, in addition to the
 412  *       work associated with entry into the current state.
 413  */
 414
 415 /*
 416  * REQUEST CODES.
 417  */
 418 #define BLKIF_OP_READ   0
 419 #define BLKIF_OP_WRITE  1
 420
 421 /*
 422  * All writes issued prior to a request with the BLKIF_OP_WRITE_BARRIER
 423  * operation code ("barrier request") must be completed prior to the
 424  * execution of the barrier request.  All writes issued after the barrier
 425  * request must not execute until after the completion of the barrier request.
 426  *
 427  * Optional.  See "feature-barrier" XenBus node documentation above.
 428  */
 429 #define BLKIF_OP_WRITE_BARRIER  2
 430
 431 /*
 432  * Commit any uncommitted contents of the backing device's volatile cache
 433  * to stable storage.
 434  *
 435  * Optional.  See "feature-flush-cache" XenBus node documentation above.
 436  */
 437 #define BLKIF_OP_FLUSH_DISKCACHE  3
 438
 439 /*
 440  * Used in SLES sources for device specific command packet
 441  * contained within the request. Reserved for that purpose.
 442  */
 443 #define BLKIF_OP_RESERVED_1  4
 444
 445 /*
 446  * Indicate to the backend device that a region of storage is no longer in
 447  * use, and may be discarded at any time without impact to the client.  If
 448  * the BLKIF_DISCARD_SECURE flag is set on the request, all copies of the
 449  * discarded region on the device must be rendered unrecoverable before the
 450  * command returns.
 451  *
 452  * This operation is analogous to performing a trim (ATA) or unamp (SCSI),
 453  * command on a native device.
 454  *
 455  * More information about trim/unmap operations can be found at:
 456  * http://t13.org/Documents/UploadedDocuments/docs2008/
 457  *     e07154r6-Data_Set_Management_Proposal_for_ATA-ACS2.doc
 458  * http://www.seagate.com/staticfiles/support/disc/manuals/
 459  *     Interface%20manuals/100293068c.pdf
 460  *
 461  * Optional.  See "feature-discard", "discard-alignment",
 462  * "discard-granularity", and "discard-secure" in the XenBus node
 463  * documentation above.
 464  */
 465 #define BLKIF_OP_DISCARD  5
 466
 467 /*
 468  * Recognized if "feature-max-indirect-segments" in present in the backend
 469  * xenbus info. The "feature-max-indirect-segments" node contains the maximum
 470  * number of segments allowed by the backend per request. If the node is
 471  * present, the frontend might use blkif_request_indirect structs in order to
 472  * issue requests with more than BLKIF_MAX_SEGMENTS_PER_REQUEST (11). The
 473  * maximum number of indirect segments is fixed by the backend, but the
 474  * frontend can issue requests with any number of indirect segments as long as
 475  * it's less than the number provided by the backend. The indirect_grefs field
 476  * in blkif_request_indirect should be filled by the frontend with the
 477  * grant references of the pages that are holding the indirect segments.
 478  * These pages are filled with an array of blkif_request_segment that hold the
 479  * information about the segments. The number of indirect pages to use is
 480  * determined by the number of segments an indirect request contains. Every
 481  * indirect page can contain a maximum of
 482  * (PAGE_SIZE / sizeof(struct blkif_request_segment)) segments, so to
 483  * calculate the number of indirect pages to use we have to do
 484  * ceil(indirect_segments / (PAGE_SIZE / sizeof(struct blkif_request_segment))).
 485  *
 486  * If a backend does not recognize BLKIF_OP_INDIRECT, it should *not*
 487  * create the "feature-max-indirect-segments" node!
 488  */
 489 #define BLKIF_OP_INDIRECT  6
 490
 491 /*
 492  * Maximum scatter/gather segments per request.
 493  * This is carefully chosen so that sizeof(blkif_ring_t) <= PAGE_SIZE.
 494  * NB. This could be 12 if the ring indexes weren't stored in the same page.
 495  */
 496 #define BLKIF_MAX_SEGMENTS_PER_REQUEST  11
 497
 498 /*
 499  * Maximum number of indirect pages to use per request.
 500  */
 501 #define BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST  8
 502
 503 /*
 504  * NB. first_sect and last_sect in blkif_request_segment, as well as
 505  * sector_number in blkif_request, are always expressed in 512-byte units.
 506  * However they must be properly aligned to the real sector size of the
 507  * physical disk, which is reported in the "physical-sector-size" node in
 508  * the backend xenbus info. Also the xenbus "sectors" node is expressed in
 509  * 512-byte units.
 510  */
 511 struct blkif_request_segment {
 512   grant_ref_t    gref;       /* reference to I/O buffer frame        */
 513   /* @first_sect: first sector in frame to transfer (inclusive).   */
 514   /* @last_sect: last sector in frame to transfer (inclusive).     */
 515   UINT8          first_sect, last_sect;
 516 };
 517
 518 /*
 519  * Starting ring element for any I/O request.
 520  */
 521 #if defined (MDE_CPU_IA32)
 522 //
 523 // pack(4) is necessary when these structs are compiled for Ia32.
 524 // Without it, the struct will have a different alignment than the one
 525 // a backend expect for a 32bit guest.
 526 //
 527   #pragma pack(4)
 528 #endif
 529 struct blkif_request {
 530   UINT8                           operation;     /* BLKIF_OP_???                         */
 531   UINT8                           nr_segments;   /* number of segments                   */
 532   blkif_vdev_t                    handle;        /* only for read/write requests         */
 533   UINT64                          id;            /* private guest value, echoed in resp  */
 534   blkif_sector_t                  sector_number; /* start sector idx on disk (r/w only)  */
 535   struct blkif_request_segment    seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 536 };
 537
 538 typedef struct blkif_request blkif_request_t;
 539
 540 /*
 541  * Cast to this structure when blkif_request.operation == BLKIF_OP_DISCARD
 542  * sizeof(struct blkif_request_discard) <= sizeof(struct blkif_request)
 543  */
 544 struct blkif_request_discard {
 545   UINT8             operation;         /* BLKIF_OP_DISCARD                     */
 546   UINT8             flag;              /* BLKIF_DISCARD_SECURE or zero         */
 547   #define BLKIF_DISCARD_SECURE  (1<<0) /* ignored if discard-secure=0      */
 548   blkif_vdev_t      handle;            /* same as for read/write requests      */
 549   UINT64            id;                /* private guest value, echoed in resp  */
 550   blkif_sector_t    sector_number;     /* start sector idx on disk             */
 551   UINT64            nr_sectors;        /* number of contiguous sectors to discard*/
 552 };
 553
 554 typedef struct blkif_request_discard blkif_request_discard_t;
 555
 556 struct blkif_request_indirect {
 557   UINT8             operation;     /* BLKIF_OP_INDIRECT                    */
 558   UINT8             indirect_op;   /* BLKIF_OP_{READ/WRITE}                */
 559   UINT16            nr_segments;   /* number of segments                   */
 560   UINT64            id;            /* private guest value, echoed in resp  */
 561   blkif_sector_t    sector_number; /* start sector idx on disk (r/w only)  */
 562   blkif_vdev_t      handle;        /* same as for read/write requests      */
 563   grant_ref_t       indirect_grefs[BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST];
 564  #ifdef MDE_CPU_IA32
 565   UINT64            pad;       /* Make it 64 byte aligned on i386      */
 566  #endif
 567 };
 568
 569 typedef struct blkif_request_indirect blkif_request_indirect_t;
 570
 571 struct blkif_response {
 572   UINT64    id;                    /* copied from request */
 573   UINT8     operation;             /* copied from request */
 574   INT16     status;                /* BLKIF_RSP_???       */
 575 };
 576
 577 typedef struct blkif_response blkif_response_t;
 578 #if defined (MDE_CPU_IA32)
 579   #pragma pack()
 580 #endif
 581
 582 /*
 583  * STATUS RETURN CODES.
 584  */
 585 /* Operation not supported (only happens on barrier writes). */
 586 #define BLKIF_RSP_EOPNOTSUPP  -2
 587 /* Operation failed for some unspecified reason (-EIO). */
 588 #define BLKIF_RSP_ERROR  -1
 589 /* Operation completed successfully. */
 590 #define BLKIF_RSP_OKAY  0
 591
 592 /*
 593  * Generate blkif ring structures and types.
 594  */
 595 DEFINE_RING_TYPES (blkif, struct blkif_request, struct blkif_response);
 596
 597 #define VDISK_CDROM      0x1
 598 #define VDISK_REMOVABLE  0x2
 599 #define VDISK_READONLY   0x4
 600
 601 #endif /* __XEN_PUBLIC_IO_BLKIF_H__ */
 602
 603 /*
 604  * Local variables:
 605  * mode: C
 606  * c-file-style: "BSD"
 607  * c-basic-offset: 4
 608  * tab-width: 4
 609  * indent-tabs-mode: nil
 610  * End:
 611  */