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  * Maximum scatter/gather segments per request.
  49  * This is carefully chosen so that sizeof(struct blkif_ring) <= PAGE_SIZE.
  50  * NB. This could be 12 if the ring indexes weren't stored in the same page.
  51  */
  52 #define BLKIF_MAX_SEGMENTS_PER_REQUEST 11
  53
  54 struct blkif_request_rw {
  55         blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
  56         struct blkif_request_segment {
  57                 grant_ref_t gref;        /* reference to I/O buffer frame        */
  58                 /* @first_sect: first sector in frame to transfer (inclusive).   */
  59                 /* @last_sect: last sector in frame to transfer (inclusive).     */
  60                 uint8_t     first_sect, last_sect;
  61         } seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
  62 };
  63
  64 struct blkif_request {
  65         uint8_t        operation;    /* BLKIF_OP_???                         */
  66         uint8_t        nr_segments;  /* number of segments                   */
  67         blkif_vdev_t   handle;       /* only for read/write requests         */
  68         uint64_t       id;           /* private guest value, echoed in resp  */
  69         union {
  70                 struct blkif_request_rw rw;
  71         } u;
  72 };
  73
  74 struct blkif_response {
  75         uint64_t        id;              /* copied from request */
  76         uint8_t         operation;       /* copied from request */
  77         int16_t         status;          /* BLKIF_RSP_???       */
  78 };
  79
  80 /*
  81  * STATUS RETURN CODES.
  82  */
  83  /* Operation not supported (only happens on barrier writes). */
  84 #define BLKIF_RSP_EOPNOTSUPP  -2
  85  /* Operation failed for some unspecified reason (-EIO). */
  86 #define BLKIF_RSP_ERROR       -1
  87  /* Operation completed successfully. */
  88 #define BLKIF_RSP_OKAY         0
  89
  90 /*
  91  * Generate blkif ring structures and types.
  92  */
  93
  94 DEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response);
  95
  96 #define VDISK_CDROM        0x1
  97 #define VDISK_REMOVABLE    0x2
  98 #define VDISK_READONLY     0x4
  99
 100 /* Xen-defined major numbers for virtual disks, they look strangely
 101  * familiar */
 102 #define XEN_IDE0_MAJOR  3
 103 #define XEN_IDE1_MAJOR  22
 104 #define XEN_SCSI_DISK0_MAJOR    8
 105 #define XEN_SCSI_DISK1_MAJOR    65
 106 #define XEN_SCSI_DISK2_MAJOR    66
 107 #define XEN_SCSI_DISK3_MAJOR    67
 108 #define XEN_SCSI_DISK4_MAJOR    68
 109 #define XEN_SCSI_DISK5_MAJOR    69
 110 #define XEN_SCSI_DISK6_MAJOR    70
 111 #define XEN_SCSI_DISK7_MAJOR    71
 112 #define XEN_SCSI_DISK8_MAJOR    128
 113 #define XEN_SCSI_DISK9_MAJOR    129
 114 #define XEN_SCSI_DISK10_MAJOR   130
 115 #define XEN_SCSI_DISK11_MAJOR   131
 116 #define XEN_SCSI_DISK12_MAJOR   132
 117 #define XEN_SCSI_DISK13_MAJOR   133
 118 #define XEN_SCSI_DISK14_MAJOR   134
 119 #define XEN_SCSI_DISK15_MAJOR   135
 120
 121 #endif /* __XEN_PUBLIC_IO_BLKIF_H__ */