include/xen/interface/io/blkif.h

   1 /******************************************************************************
   2  * blkif.h
   3  *
   4  * Unified block-device I/O interface for Xen guest OSes.
   5  *
   6  * Copyright (c) 2003-2004, Keir Fraser
   7  */
   8
   9 #ifndef __XEN_PUBLIC_IO_BLKIF_H__
  10 #define __XEN_PUBLIC_IO_BLKIF_H__
  11
  12 #include "ring.h"
  13 #include "../grant_table.h"
  14
  15 /*
  16  * Front->back notifications: When enqueuing a new request, sending a
  17  * notification can be made conditional on req_event (i.e., the generic
  18  * hold-off mechanism provided by the ring macros). Backends must set
  19  * req_event appropriately (e.g., using RING_FINAL_CHECK_FOR_REQUESTS()).
  20  *
  21  * Back->front notifications: When enqueuing a new response, sending a
  22  * notification can be made conditional on rsp_event (i.e., the generic
  23  * hold-off mechanism provided by the ring macros). Frontends must set
  24  * rsp_event appropriately (e.g., using RING_FINAL_CHECK_FOR_RESPONSES()).
  25  */
  26
  27 typedef uint16_t blkif_vdev_t;
  28 typedef uint64_t blkif_sector_t;
  29
  30 /*
  31  * REQUEST CODES.
  32  */
  33 #define BLKIF_OP_READ              0
  34 #define BLKIF_OP_WRITE             1
  35 /*
  36  * Recognised only if "feature-barrier" is present in backend xenbus info.
  37  * The "feature_barrier" node contains a boolean indicating whether barrier
  38  * requests are likely to succeed or fail. Either way, a barrier request
  39  * may fail at any time with BLKIF_RSP_EOPNOTSUPP if it is unsupported by
  40  * the underlying block-device hardware. The boolean simply indicates whether
  41  * or not it is worthwhile for the frontend to attempt barrier requests.
  42  * If a backend does not recognise BLKIF_OP_WRITE_BARRIER, it should *not*
  43  * create the "feature-barrier" node!
  44  */
  45 #define BLKIF_OP_WRITE_BARRIER     2
  46
  47 /*
  48  * Recognised if "feature-flush-cache" is present in backend xenbus
  49  * info.  A flush will ask the underlying storage hardware to flush its
  50  * non-volatile caches as appropriate.  The "feature-flush-cache" node
  51  * contains a boolean indicating whether flush requests are likely to
  52  * succeed or fail. Either way, a flush request may fail at any time
  53  * with BLKIF_RSP_EOPNOTSUPP if it is unsupported by the underlying
  54  * block-device hardware. The boolean simply indicates whether or not it
  55  * is worthwhile for the frontend to attempt flushes.  If a backend does
  56  * not recognise BLKIF_OP_WRITE_FLUSH_CACHE, it should *not* create the
  57  * "feature-flush-cache" node!
  58  */
  59 #define BLKIF_OP_FLUSH_DISKCACHE   3
  60 /*
  61  * Maximum scatter/gather segments per request.
  62  * This is carefully chosen so that sizeof(struct blkif_ring) <= PAGE_SIZE.
  63  * NB. This could be 12 if the ring indexes weren't stored in the same page.
  64  */
  65 #define BLKIF_MAX_SEGMENTS_PER_REQUEST 11
  66
  67 struct blkif_request_rw {
  68         blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
  69         struct blkif_request_segment {
  70                 grant_ref_t gref;        /* reference to I/O buffer frame        */
  71                 /* @first_sect: first sector in frame to transfer (inclusive).   */
  72                 /* @last_sect: last sector in frame to transfer (inclusive).     */
  73                 uint8_t     first_sect, last_sect;
  74         } seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
  75 };
  76
  77 struct blkif_request {
  78         uint8_t        operation;    /* BLKIF_OP_???                         */
  79         uint8_t        nr_segments;  /* number of segments                   */
  80         blkif_vdev_t   handle;       /* only for read/write requests         */
  81         uint64_t       id;           /* private guest value, echoed in resp  */
  82         union {
  83                 struct blkif_request_rw rw;
  84         } u;
  85 };
  86
  87 struct blkif_response {
  88         uint64_t        id;              /* copied from request */
  89         uint8_t         operation;       /* copied from request */
  90         int16_t         status;          /* BLKIF_RSP_???       */
  91 };
  92
  93 /*
  94  * STATUS RETURN CODES.
  95  */
  96  /* Operation not supported (only happens on barrier writes). */
  97 #define BLKIF_RSP_EOPNOTSUPP  -2
  98  /* Operation failed for some unspecified reason (-EIO). */
  99 #define BLKIF_RSP_ERROR       -1
 100  /* Operation completed successfully. */
 101 #define BLKIF_RSP_OKAY         0
 102
 103 /*
 104  * Generate blkif ring structures and types.
 105  */
 106
 107 DEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response);
 108
 109 #define VDISK_CDROM        0x1
 110 #define VDISK_REMOVABLE    0x2
 111 #define VDISK_READONLY     0x4
 112
 113 /* Xen-defined major numbers for virtual disks, they look strangely
 114  * familiar */
 115 #define XEN_IDE0_MAJOR  3
 116 #define XEN_IDE1_MAJOR  22
 117 #define XEN_SCSI_DISK0_MAJOR    8
 118 #define XEN_SCSI_DISK1_MAJOR    65
 119 #define XEN_SCSI_DISK2_MAJOR    66
 120 #define XEN_SCSI_DISK3_MAJOR    67
 121 #define XEN_SCSI_DISK4_MAJOR    68
 122 #define XEN_SCSI_DISK5_MAJOR    69
 123 #define XEN_SCSI_DISK6_MAJOR    70
 124 #define XEN_SCSI_DISK7_MAJOR    71
 125 #define XEN_SCSI_DISK8_MAJOR    128
 126 #define XEN_SCSI_DISK9_MAJOR    129
 127 #define XEN_SCSI_DISK10_MAJOR   130
 128 #define XEN_SCSI_DISK11_MAJOR   131
 129 #define XEN_SCSI_DISK12_MAJOR   132
 130 #define XEN_SCSI_DISK13_MAJOR   133
 131 #define XEN_SCSI_DISK14_MAJOR   134
 132 #define XEN_SCSI_DISK15_MAJOR   135
 133
 134 #endif /* __XEN_PUBLIC_IO_BLKIF_H__ */