include/xen/interface/io/vscsiif.h

   1 /******************************************************************************
   2  * vscsiif.h
   3  *
   4  * Based on the blkif.h code.
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a copy
   7  * of this software and associated documentation files (the "Software"), to
   8  * deal in the Software without restriction, including without limitation the
   9  * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
  10  * sell copies of the Software, and to permit persons to whom the Software is
  11  * furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  19  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  21  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  22  * DEALINGS IN THE SOFTWARE.
  23  *
  24  * Copyright(c) FUJITSU Limited 2008.
  25  */
  26
  27 #ifndef __XEN__PUBLIC_IO_SCSI_H__
  28 #define __XEN__PUBLIC_IO_SCSI_H__
  29
  30 #include "ring.h"
  31 #include "../grant_table.h"
  32
  33 /*
  34  * Feature and Parameter Negotiation
  35  * =================================
  36  * The two halves of a Xen pvSCSI driver utilize nodes within the XenStore to
  37  * communicate capabilities and to negotiate operating parameters.  This
  38  * section enumerates these nodes which reside in the respective front and
  39  * backend portions of the XenStore, following the XenBus convention.
  40  *
  41  * Any specified default value is in effect if the corresponding XenBus node
  42  * is not present in the XenStore.
  43  *
  44  * XenStore nodes in sections marked "PRIVATE" are solely for use by the
  45  * driver side whose XenBus tree contains them.
  46  *
  47  *****************************************************************************
  48  *                            Backend XenBus Nodes
  49  *****************************************************************************
  50  *
  51  *------------------ Backend Device Identification (PRIVATE) ------------------
  52  *
  53  * p-devname
  54  *      Values:         string
  55  *
  56  *      A free string used to identify the physical device (e.g. a disk name).
  57  *
  58  * p-dev
  59  *      Values:         string
  60  *
  61  *      A string specifying the backend device: either a 4-tuple "h:c:t:l"
  62  *      (host, controller, target, lun, all integers), or a WWN (e.g.
  63  *      "naa.60014054ac780582").
  64  *
  65  * v-dev
  66  *      Values:         string
  67  *
  68  *      A string specifying the frontend device in form of a 4-tuple "h:c:t:l"
  69  *      (host, controller, target, lun, all integers).
  70  *
  71  *--------------------------------- Features ---------------------------------
  72  *
  73  * feature-sg-grant
  74  *      Values:         unsigned [VSCSIIF_SG_TABLESIZE...65535]
  75  *      Default Value:  0
  76  *
  77  *      Specifies the maximum number of scatter/gather elements in grant pages
  78  *      supported. If not set, the backend supports up to VSCSIIF_SG_TABLESIZE
  79  *      SG elements specified directly in the request.
  80  *
  81  *****************************************************************************
  82  *                            Frontend XenBus Nodes
  83  *****************************************************************************
  84  *
  85  *----------------------- Request Transport Parameters -----------------------
  86  *
  87  * event-channel
  88  *      Values:         unsigned
  89  *
  90  *      The identifier of the Xen event channel used to signal activity
  91  *      in the ring buffer.
  92  *
  93  * ring-ref
  94  *      Values:         unsigned
  95  *
  96  *      The Xen grant reference granting permission for the backend to map
  97  *      the sole page in a single page sized ring buffer.
  98  *
  99  * protocol
 100  *      Values:         string (XEN_IO_PROTO_ABI_*)
 101  *      Default Value:  XEN_IO_PROTO_ABI_NATIVE
 102  *
 103  *      The machine ABI rules governing the format of all ring request and
 104  *      response structures.
 105  */
 106
 107 /* Requests from the frontend to the backend */
 108
 109 /*
 110  * Request a SCSI operation specified via a CDB in vscsiif_request.cmnd.
 111  * The target is specified via channel, id and lun.
 112  *
 113  * The operation to be performed is specified via a CDB in cmnd[], the length
 114  * of the CDB is in cmd_len. sc_data_direction specifies the direction of data
 115  * (to the device, from the device, or none at all).
 116  *
 117  * If data is to be transferred to or from the device the buffer(s) in the
 118  * guest memory is/are specified via one or multiple scsiif_request_segment
 119  * descriptors each specifying a memory page via a grant_ref_t, a offset into
 120  * the page and the length of the area in that page. All scsiif_request_segment
 121  * areas concatenated form the resulting data buffer used by the operation.
 122  * If the number of scsiif_request_segment areas is not too large (less than
 123  * or equal VSCSIIF_SG_TABLESIZE) the areas can be specified directly in the
 124  * seg[] array and the number of valid scsiif_request_segment elements is to be
 125  * set in nr_segments.
 126  *
 127  * If "feature-sg-grant" in the Xenstore is set it is possible to specify more
 128  * than VSCSIIF_SG_TABLESIZE scsiif_request_segment elements via indirection.
 129  * The maximum number of allowed scsiif_request_segment elements is the value
 130  * of the "feature-sg-grant" entry from Xenstore. When using indirection the
 131  * seg[] array doesn't contain specifications of the data buffers, but
 132  * references to scsiif_request_segment arrays, which in turn reference the
 133  * data buffers. While nr_segments holds the number of populated seg[] entries
 134  * (plus the set VSCSIIF_SG_GRANT bit), the number of scsiif_request_segment
 135  * elements referencing the target data buffers is calculated from the lengths
 136  * of the seg[] elements (the sum of all valid seg[].length divided by the
 137  * size of one scsiif_request_segment structure).
 138  */
 139 #define VSCSIIF_ACT_SCSI_CDB            1
 140
 141 /*
 142  * Request abort of a running operation for the specified target given by
 143  * channel, id, lun and the operation's rqid in ref_rqid.
 144  */
 145 #define VSCSIIF_ACT_SCSI_ABORT          2
 146
 147 /*
 148  * Request a device reset of the specified target (channel and id).
 149  */
 150 #define VSCSIIF_ACT_SCSI_RESET          3
 151
 152 /*
 153  * Preset scatter/gather elements for a following request. Deprecated.
 154  * Keeping the define only to avoid usage of the value "4" for other actions.
 155  */
 156 #define VSCSIIF_ACT_SCSI_SG_PRESET      4
 157
 158 /*
 159  * Maximum scatter/gather segments per request.
 160  *
 161  * Considering balance between allocating at least 16 "vscsiif_request"
 162  * structures on one page (4096 bytes) and the number of scatter/gather
 163  * elements needed, we decided to use 26 as a magic number.
 164  *
 165  * If "feature-sg-grant" is set, more scatter/gather elements can be specified
 166  * by placing them in one or more (up to VSCSIIF_SG_TABLESIZE) granted pages.
 167  * In this case the vscsiif_request seg elements don't contain references to
 168  * the user data, but to the SG elements referencing the user data.
 169  */
 170 #define VSCSIIF_SG_TABLESIZE            26
 171
 172 /*
 173  * based on Linux kernel 2.6.18, still valid
 174  * Changing these values requires support of multiple protocols via the rings
 175  * as "old clients" will blindly use these values and the resulting structure
 176  * sizes.
 177  */
 178 #define VSCSIIF_MAX_COMMAND_SIZE        16
 179 #define VSCSIIF_SENSE_BUFFERSIZE        96
 180
 181 struct scsiif_request_segment {
 182         grant_ref_t gref;
 183         uint16_t offset;
 184         uint16_t length;
 185 };
 186
 187 #define VSCSIIF_SG_PER_PAGE (PAGE_SIZE / sizeof(struct scsiif_request_segment))
 188
 189 /* Size of one request is 252 bytes */
 190 struct vscsiif_request {
 191         uint16_t rqid;          /* private guest value, echoed in resp  */
 192         uint8_t act;            /* command between backend and frontend */
 193         uint8_t cmd_len;        /* valid CDB bytes */
 194
 195         uint8_t cmnd[VSCSIIF_MAX_COMMAND_SIZE]; /* the CDB */
 196         uint16_t timeout_per_command;   /* deprecated */
 197         uint16_t channel, id, lun;      /* (virtual) device specification */
 198         uint16_t ref_rqid;              /* command abort reference */
 199         uint8_t sc_data_direction;      /* for DMA_TO_DEVICE(1)
 200                                            DMA_FROM_DEVICE(2)
 201                                            DMA_NONE(3) requests */
 202         uint8_t nr_segments;            /* Number of pieces of scatter-gather */
 203 /*
 204  * flag in nr_segments: SG elements via grant page
 205  *
 206  * If VSCSIIF_SG_GRANT is set, the low 7 bits of nr_segments specify the number
 207  * of grant pages containing SG elements. Usable if "feature-sg-grant" set.
 208  */
 209 #define VSCSIIF_SG_GRANT        0x80
 210
 211         struct scsiif_request_segment seg[VSCSIIF_SG_TABLESIZE];
 212         uint32_t reserved[3];
 213 };
 214
 215 /* Size of one response is 252 bytes */
 216 struct vscsiif_response {
 217         uint16_t rqid;          /* identifies request */
 218         uint8_t padding;
 219         uint8_t sense_len;
 220         uint8_t sense_buffer[VSCSIIF_SENSE_BUFFERSIZE];
 221         int32_t rslt;
 222         uint32_t residual_len;  /* request bufflen -
 223                                    return the value from physical device */
 224         uint32_t reserved[36];
 225 };
 226
 227 DEFINE_RING_TYPES(vscsiif, struct vscsiif_request, struct vscsiif_response);
 228
 229 #endif /*__XEN__PUBLIC_IO_SCSI_H__*/