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 <xen/interface/io/ring.h>
  13 #include <xen/interface/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 /*
  62  * Recognised only if "feature-discard" is present in backend xenbus info.
  63  * The "feature-discard" node contains a boolean indicating whether trim
  64  * (ATA) or unmap (SCSI) - conviently called discard requests are likely
  65  * to succeed or fail. Either way, a discard request
  66  * may fail at any time with BLKIF_RSP_EOPNOTSUPP if it is unsupported by
  67  * the underlying block-device hardware. The boolean simply indicates whether
  68  * or not it is worthwhile for the frontend to attempt discard requests.
  69  * If a backend does not recognise BLKIF_OP_DISCARD, it should *not*
  70  * create the "feature-discard" node!
  71  *
  72  * Discard operation is a request for the underlying block device to mark
  73  * extents to be erased. However, discard does not guarantee that the blocks
  74  * will be erased from the device - it is just a hint to the device
  75  * controller that these blocks are no longer in use. What the device
  76  * controller does with that information is left to the controller.
  77  * Discard operations are passed with sector_number as the
  78  * sector index to begin discard operations at and nr_sectors as the number of
  79  * sectors to be discarded. The specified sectors should be discarded if the
  80  * underlying block device supports trim (ATA) or unmap (SCSI) operations,
  81  * or a BLKIF_RSP_EOPNOTSUPP  should be returned.
  82  * More information about trim/unmap operations at:
  83  * http://t13.org/Documents/UploadedDocuments/docs2008/
  84  *     e07154r6-Data_Set_Management_Proposal_for_ATA-ACS2.doc
  85  * http://www.seagate.com/staticfiles/support/disc/manuals/
  86  *     Interface%20manuals/100293068c.pdf
  87  * The backend can optionally provide three extra XenBus attributes to
  88  * further optimize the discard functionality:
  89  * 'discard-aligment' - Devices that support discard functionality may
  90  * internally allocate space in units that are bigger than the exported
  91  * logical block size. The discard-alignment parameter indicates how many bytes
  92  * the beginning of the partition is offset from the internal allocation unit's
  93  * natural alignment.
  94  * 'discard-granularity'  - Devices that support discard functionality may
  95  * internally allocate space using units that are bigger than the logical block
  96  * size. The discard-granularity parameter indicates the size of the internal
  97  * allocation unit in bytes if reported by the device. Otherwise the
  98  * discard-granularity will be set to match the device's physical block size.
  99  * 'discard-secure' - All copies of the discarded sectors (potentially created
 100  * by garbage collection) must also be erased.  To use this feature, the flag
 101  * BLKIF_DISCARD_SECURE must be set in the blkif_request_trim.
 102  */
 103 #define BLKIF_OP_DISCARD           5
 104
 105 /*
 106  * Recognized if "feature-max-indirect-segments" in present in the backend
 107  * xenbus info. The "feature-max-indirect-segments" node contains the maximum
 108  * number of segments allowed by the backend per request. If the node is
 109  * present, the frontend might use blkif_request_indirect structs in order to
 110  * issue requests with more than BLKIF_MAX_SEGMENTS_PER_REQUEST (11). The
 111  * maximum number of indirect segments is fixed by the backend, but the
 112  * frontend can issue requests with any number of indirect segments as long as
 113  * it's less than the number provided by the backend. The indirect_grefs field
 114  * in blkif_request_indirect should be filled by the frontend with the
 115  * grant references of the pages that are holding the indirect segments.
 116  * These pages are filled with an array of blkif_request_segment that hold the
 117  * information about the segments. The number of indirect pages to use is
 118  * determined by the number of segments an indirect request contains. Every
 119  * indirect page can contain a maximum of
 120  * (PAGE_SIZE / sizeof(struct blkif_request_segment)) segments, so to
 121  * calculate the number of indirect pages to use we have to do
 122  * ceil(indirect_segments / (PAGE_SIZE / sizeof(struct blkif_request_segment))).
 123  *
 124  * If a backend does not recognize BLKIF_OP_INDIRECT, it should *not*
 125  * create the "feature-max-indirect-segments" node!
 126  */
 127 #define BLKIF_OP_INDIRECT          6
 128
 129 /*
 130  * Maximum scatter/gather segments per request.
 131  * This is carefully chosen so that sizeof(struct blkif_ring) <= PAGE_SIZE.
 132  * NB. This could be 12 if the ring indexes weren't stored in the same page.
 133  */
 134 #define BLKIF_MAX_SEGMENTS_PER_REQUEST 11
 135
 136 #define BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST 8
 137
 138 struct blkif_request_segment {
 139                 grant_ref_t gref;        /* reference to I/O buffer frame        */
 140                 /* @first_sect: first sector in frame to transfer (inclusive).   */
 141                 /* @last_sect: last sector in frame to transfer (inclusive).     */
 142                 uint8_t     first_sect, last_sect;
 143 };
 144
 145 struct blkif_request_rw {
 146         uint8_t        nr_segments;  /* number of segments                   */
 147         blkif_vdev_t   handle;       /* only for read/write requests         */
 148 #ifndef CONFIG_X86_32
 149         uint32_t       _pad1;        /* offsetof(blkif_request,u.rw.id) == 8 */
 150 #endif
 151         uint64_t       id;           /* private guest value, echoed in resp  */
 152         blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
 153         struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 154 } __attribute__((__packed__));
 155
 156 struct blkif_request_discard {
 157         uint8_t        flag;         /* BLKIF_DISCARD_SECURE or zero.        */
 158 #define BLKIF_DISCARD_SECURE (1<<0)  /* ignored if discard-secure=0          */
 159         blkif_vdev_t   _pad1;        /* only for read/write requests         */
 160 #ifndef CONFIG_X86_32
 161         uint32_t       _pad2;        /* offsetof(blkif_req..,u.discard.id)==8*/
 162 #endif
 163         uint64_t       id;           /* private guest value, echoed in resp  */
 164         blkif_sector_t sector_number;
 165         uint64_t       nr_sectors;
 166         uint8_t        _pad3;
 167 } __attribute__((__packed__));
 168
 169 struct blkif_request_other {
 170         uint8_t      _pad1;
 171         blkif_vdev_t _pad2;        /* only for read/write requests         */
 172 #ifndef CONFIG_X86_32
 173         uint32_t     _pad3;        /* offsetof(blkif_req..,u.other.id)==8*/
 174 #endif
 175         uint64_t     id;           /* private guest value, echoed in resp  */
 176 } __attribute__((__packed__));
 177
 178 struct blkif_request_indirect {
 179         uint8_t        indirect_op;
 180         uint16_t       nr_segments;
 181 #ifndef CONFIG_X86_32
 182         uint32_t       _pad1;        /* offsetof(blkif_...,u.indirect.id) == 8 */
 183 #endif
 184         uint64_t       id;
 185         blkif_sector_t sector_number;
 186         blkif_vdev_t   handle;
 187         uint16_t       _pad2;
 188         grant_ref_t    indirect_grefs[BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST];
 189 #ifndef CONFIG_X86_32
 190         uint32_t      _pad3;         /* make it 64 byte aligned */
 191 #else
 192         uint64_t      _pad3;         /* make it 64 byte aligned */
 193 #endif
 194 } __attribute__((__packed__));
 195
 196 struct blkif_request {
 197         uint8_t        operation;    /* BLKIF_OP_???                         */
 198         union {
 199                 struct blkif_request_rw rw;
 200                 struct blkif_request_discard discard;
 201                 struct blkif_request_other other;
 202                 struct blkif_request_indirect indirect;
 203         } u;
 204 } __attribute__((__packed__));
 205
 206 struct blkif_response {
 207         uint64_t        id;              /* copied from request */
 208         uint8_t         operation;       /* copied from request */
 209         int16_t         status;          /* BLKIF_RSP_???       */
 210 };
 211
 212 /*
 213  * STATUS RETURN CODES.
 214  */
 215  /* Operation not supported (only happens on barrier writes). */
 216 #define BLKIF_RSP_EOPNOTSUPP  -2
 217  /* Operation failed for some unspecified reason (-EIO). */
 218 #define BLKIF_RSP_ERROR       -1
 219  /* Operation completed successfully. */
 220 #define BLKIF_RSP_OKAY         0
 221
 222 /*
 223  * Generate blkif ring structures and types.
 224  */
 225
 226 DEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response);
 227
 228 #define VDISK_CDROM        0x1
 229 #define VDISK_REMOVABLE    0x2
 230 #define VDISK_READONLY     0x4
 231
 232 /* Xen-defined major numbers for virtual disks, they look strangely
 233  * familiar */
 234 #define XEN_IDE0_MAJOR  3
 235 #define XEN_IDE1_MAJOR  22
 236 #define XEN_SCSI_DISK0_MAJOR    8
 237 #define XEN_SCSI_DISK1_MAJOR    65
 238 #define XEN_SCSI_DISK2_MAJOR    66
 239 #define XEN_SCSI_DISK3_MAJOR    67
 240 #define XEN_SCSI_DISK4_MAJOR    68
 241 #define XEN_SCSI_DISK5_MAJOR    69
 242 #define XEN_SCSI_DISK6_MAJOR    70
 243 #define XEN_SCSI_DISK7_MAJOR    71
 244 #define XEN_SCSI_DISK8_MAJOR    128
 245 #define XEN_SCSI_DISK9_MAJOR    129
 246 #define XEN_SCSI_DISK10_MAJOR   130
 247 #define XEN_SCSI_DISK11_MAJOR   131
 248 #define XEN_SCSI_DISK12_MAJOR   132
 249 #define XEN_SCSI_DISK13_MAJOR   133
 250 #define XEN_SCSI_DISK14_MAJOR   134
 251 #define XEN_SCSI_DISK15_MAJOR   135
 252
 253 #endif /* __XEN_PUBLIC_IO_BLKIF_H__ */