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 * Multiple hardware queues/rings: 32 * If supported, the backend will write the key "multi-queue-max-queues" to 33 * the directory for that vbd, and set its value to the maximum supported 34 * number of queues. 35 * Frontends that are aware of this feature and wish to use it can write the 36 * key "multi-queue-num-queues" with the number they wish to use, which must be 37 * greater than zero, and no more than the value reported by the backend in 38 * "multi-queue-max-queues". 39 * 40 * For frontends requesting just one queue, the usual event-channel and 41 * ring-ref keys are written as before, simplifying the backend processing 42 * to avoid distinguishing between a frontend that doesn't understand the 43 * multi-queue feature, and one that does, but requested only one queue. 44 * 45 * Frontends requesting two or more queues must not write the toplevel 46 * event-channel and ring-ref keys, instead writing those keys under sub-keys 47 * having the name "queue-N" where N is the integer ID of the queue/ring for 48 * which those keys belong. Queues are indexed from zero. 49 * For example, a frontend with two queues must write the following set of 50 * queue-related keys: 51 * 52 * /local/domain/1/device/vbd/0/multi-queue-num-queues = "2" 53 * /local/domain/1/device/vbd/0/queue-0 = "" 54 * /local/domain/1/device/vbd/0/queue-0/ring-ref = "<ring-ref#0>" 55 * /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn#0>" 56 * /local/domain/1/device/vbd/0/queue-1 = "" 57 * /local/domain/1/device/vbd/0/queue-1/ring-ref = "<ring-ref#1>" 58 * /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn#1>" 59 * 60 * It is also possible to use multiple queues/rings together with 61 * feature multi-page ring buffer. 62 * For example, a frontend requests two queues/rings and the size of each ring 63 * buffer is two pages must write the following set of related keys: 64 * 65 * /local/domain/1/device/vbd/0/multi-queue-num-queues = "2" 66 * /local/domain/1/device/vbd/0/ring-page-order = "1" 67 * /local/domain/1/device/vbd/0/queue-0 = "" 68 * /local/domain/1/device/vbd/0/queue-0/ring-ref0 = "<ring-ref#0>" 69 * /local/domain/1/device/vbd/0/queue-0/ring-ref1 = "<ring-ref#1>" 70 * /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn#0>" 71 * /local/domain/1/device/vbd/0/queue-1 = "" 72 * /local/domain/1/device/vbd/0/queue-1/ring-ref0 = "<ring-ref#2>" 73 * /local/domain/1/device/vbd/0/queue-1/ring-ref1 = "<ring-ref#3>" 74 * /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn#1>" 75 * 76 */ 77 78 /* 79 * REQUEST CODES. 80 */ 81 #define BLKIF_OP_READ 0 82 #define BLKIF_OP_WRITE 1 83 /* 84 * Recognised only if "feature-barrier" is present in backend xenbus info. 85 * The "feature_barrier" node contains a boolean indicating whether barrier 86 * requests are likely to succeed or fail. Either way, a barrier request 87 * may fail at any time with BLKIF_RSP_EOPNOTSUPP if it is unsupported by 88 * the underlying block-device hardware. The boolean simply indicates whether 89 * or not it is worthwhile for the frontend to attempt barrier requests. 90 * If a backend does not recognise BLKIF_OP_WRITE_BARRIER, it should *not* 91 * create the "feature-barrier" node! 92 */ 93 #define BLKIF_OP_WRITE_BARRIER 2 94 95 /* 96 * Recognised if "feature-flush-cache" is present in backend xenbus 97 * info. A flush will ask the underlying storage hardware to flush its 98 * non-volatile caches as appropriate. The "feature-flush-cache" node 99 * contains a boolean indicating whether flush requests are likely to 100 * succeed or fail. Either way, a flush request may fail at any time 101 * with BLKIF_RSP_EOPNOTSUPP if it is unsupported by the underlying 102 * block-device hardware. The boolean simply indicates whether or not it 103 * is worthwhile for the frontend to attempt flushes. If a backend does 104 * not recognise BLKIF_OP_WRITE_FLUSH_CACHE, it should *not* create the 105 * "feature-flush-cache" node! 106 */ 107 #define BLKIF_OP_FLUSH_DISKCACHE 3 108 109 /* 110 * Recognised only if "feature-discard" is present in backend xenbus info. 111 * The "feature-discard" node contains a boolean indicating whether trim 112 * (ATA) or unmap (SCSI) - conviently called discard requests are likely 113 * to succeed or fail. Either way, a discard request 114 * may fail at any time with BLKIF_RSP_EOPNOTSUPP if it is unsupported by 115 * the underlying block-device hardware. The boolean simply indicates whether 116 * or not it is worthwhile for the frontend to attempt discard requests. 117 * If a backend does not recognise BLKIF_OP_DISCARD, it should *not* 118 * create the "feature-discard" node! 119 * 120 * Discard operation is a request for the underlying block device to mark 121 * extents to be erased. However, discard does not guarantee that the blocks 122 * will be erased from the device - it is just a hint to the device 123 * controller that these blocks are no longer in use. What the device 124 * controller does with that information is left to the controller. 125 * Discard operations are passed with sector_number as the 126 * sector index to begin discard operations at and nr_sectors as the number of 127 * sectors to be discarded. The specified sectors should be discarded if the 128 * underlying block device supports trim (ATA) or unmap (SCSI) operations, 129 * or a BLKIF_RSP_EOPNOTSUPP should be returned. 130 * More information about trim/unmap operations at: 131 * http://t13.org/Documents/UploadedDocuments/docs2008/ 132 * e07154r6-Data_Set_Management_Proposal_for_ATA-ACS2.doc 133 * http://www.seagate.com/staticfiles/support/disc/manuals/ 134 * Interface%20manuals/100293068c.pdf 135 * The backend can optionally provide three extra XenBus attributes to 136 * further optimize the discard functionality: 137 * 'discard-alignment' - Devices that support discard functionality may 138 * internally allocate space in units that are bigger than the exported 139 * logical block size. The discard-alignment parameter indicates how many bytes 140 * the beginning of the partition is offset from the internal allocation unit's 141 * natural alignment. 142 * 'discard-granularity' - Devices that support discard functionality may 143 * internally allocate space using units that are bigger than the logical block 144 * size. The discard-granularity parameter indicates the size of the internal 145 * allocation unit in bytes if reported by the device. Otherwise the 146 * discard-granularity will be set to match the device's physical block size. 147 * 'discard-secure' - All copies of the discarded sectors (potentially created 148 * by garbage collection) must also be erased. To use this feature, the flag 149 * BLKIF_DISCARD_SECURE must be set in the blkif_request_trim. 150 */ 151 #define BLKIF_OP_DISCARD 5 152 153 /* 154 * Recognized if "feature-max-indirect-segments" in present in the backend 155 * xenbus info. The "feature-max-indirect-segments" node contains the maximum 156 * number of segments allowed by the backend per request. If the node is 157 * present, the frontend might use blkif_request_indirect structs in order to 158 * issue requests with more than BLKIF_MAX_SEGMENTS_PER_REQUEST (11). The 159 * maximum number of indirect segments is fixed by the backend, but the 160 * frontend can issue requests with any number of indirect segments as long as 161 * it's less than the number provided by the backend. The indirect_grefs field 162 * in blkif_request_indirect should be filled by the frontend with the 163 * grant references of the pages that are holding the indirect segments. 164 * These pages are filled with an array of blkif_request_segment that hold the 165 * information about the segments. The number of indirect pages to use is 166 * determined by the number of segments an indirect request contains. Every 167 * indirect page can contain a maximum of 168 * (PAGE_SIZE / sizeof(struct blkif_request_segment)) segments, so to 169 * calculate the number of indirect pages to use we have to do 170 * ceil(indirect_segments / (PAGE_SIZE / sizeof(struct blkif_request_segment))). 171 * 172 * If a backend does not recognize BLKIF_OP_INDIRECT, it should *not* 173 * create the "feature-max-indirect-segments" node! 174 */ 175 #define BLKIF_OP_INDIRECT 6 176 177 /* 178 * Maximum scatter/gather segments per request. 179 * This is carefully chosen so that sizeof(struct blkif_ring) <= PAGE_SIZE. 180 * NB. This could be 12 if the ring indexes weren't stored in the same page. 181 */ 182 #define BLKIF_MAX_SEGMENTS_PER_REQUEST 11 183 184 #define BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST 8 185 186 struct blkif_request_segment { 187 grant_ref_t gref; /* reference to I/O buffer frame */ 188 /* @first_sect: first sector in frame to transfer (inclusive). */ 189 /* @last_sect: last sector in frame to transfer (inclusive). */ 190 uint8_t first_sect, last_sect; 191 }; 192 193 struct blkif_request_rw { 194 uint8_t nr_segments; /* number of segments */ 195 blkif_vdev_t handle; /* only for read/write requests */ 196 #ifndef CONFIG_X86_32 197 uint32_t _pad1; /* offsetof(blkif_request,u.rw.id) == 8 */ 198 #endif 199 uint64_t id; /* private guest value, echoed in resp */ 200 blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */ 201 struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST]; 202 } __attribute__((__packed__)); 203 204 struct blkif_request_discard { 205 uint8_t flag; /* BLKIF_DISCARD_SECURE or zero. */ 206 #define BLKIF_DISCARD_SECURE (1<<0) /* ignored if discard-secure=0 */ 207 blkif_vdev_t _pad1; /* only for read/write requests */ 208 #ifndef CONFIG_X86_32 209 uint32_t _pad2; /* offsetof(blkif_req..,u.discard.id)==8*/ 210 #endif 211 uint64_t id; /* private guest value, echoed in resp */ 212 blkif_sector_t sector_number; 213 uint64_t nr_sectors; 214 uint8_t _pad3; 215 } __attribute__((__packed__)); 216 217 struct blkif_request_other { 218 uint8_t _pad1; 219 blkif_vdev_t _pad2; /* only for read/write requests */ 220 #ifndef CONFIG_X86_32 221 uint32_t _pad3; /* offsetof(blkif_req..,u.other.id)==8*/ 222 #endif 223 uint64_t id; /* private guest value, echoed in resp */ 224 } __attribute__((__packed__)); 225 226 struct blkif_request_indirect { 227 uint8_t indirect_op; 228 uint16_t nr_segments; 229 #ifndef CONFIG_X86_32 230 uint32_t _pad1; /* offsetof(blkif_...,u.indirect.id) == 8 */ 231 #endif 232 uint64_t id; 233 blkif_sector_t sector_number; 234 blkif_vdev_t handle; 235 uint16_t _pad2; 236 grant_ref_t indirect_grefs[BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST]; 237 #ifndef CONFIG_X86_32 238 uint32_t _pad3; /* make it 64 byte aligned */ 239 #else 240 uint64_t _pad3; /* make it 64 byte aligned */ 241 #endif 242 } __attribute__((__packed__)); 243 244 struct blkif_request { 245 uint8_t operation; /* BLKIF_OP_??? */ 246 union { 247 struct blkif_request_rw rw; 248 struct blkif_request_discard discard; 249 struct blkif_request_other other; 250 struct blkif_request_indirect indirect; 251 } u; 252 } __attribute__((__packed__)); 253 254 struct blkif_response { 255 uint64_t id; /* copied from request */ 256 uint8_t operation; /* copied from request */ 257 int16_t status; /* BLKIF_RSP_??? */ 258 }; 259 260 /* 261 * STATUS RETURN CODES. 262 */ 263 /* Operation not supported (only happens on barrier writes). */ 264 #define BLKIF_RSP_EOPNOTSUPP -2 265 /* Operation failed for some unspecified reason (-EIO). */ 266 #define BLKIF_RSP_ERROR -1 267 /* Operation completed successfully. */ 268 #define BLKIF_RSP_OKAY 0 269 270 /* 271 * Generate blkif ring structures and types. 272 */ 273 274 DEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response); 275 276 #define VDISK_CDROM 0x1 277 #define VDISK_REMOVABLE 0x2 278 #define VDISK_READONLY 0x4 279 280 /* Xen-defined major numbers for virtual disks, they look strangely 281 * familiar */ 282 #define XEN_IDE0_MAJOR 3 283 #define XEN_IDE1_MAJOR 22 284 #define XEN_SCSI_DISK0_MAJOR 8 285 #define XEN_SCSI_DISK1_MAJOR 65 286 #define XEN_SCSI_DISK2_MAJOR 66 287 #define XEN_SCSI_DISK3_MAJOR 67 288 #define XEN_SCSI_DISK4_MAJOR 68 289 #define XEN_SCSI_DISK5_MAJOR 69 290 #define XEN_SCSI_DISK6_MAJOR 70 291 #define XEN_SCSI_DISK7_MAJOR 71 292 #define XEN_SCSI_DISK8_MAJOR 128 293 #define XEN_SCSI_DISK9_MAJOR 129 294 #define XEN_SCSI_DISK10_MAJOR 130 295 #define XEN_SCSI_DISK11_MAJOR 131 296 #define XEN_SCSI_DISK12_MAJOR 132 297 #define XEN_SCSI_DISK13_MAJOR 133 298 #define XEN_SCSI_DISK14_MAJOR 134 299 #define XEN_SCSI_DISK15_MAJOR 135 300 301 #endif /* __XEN_PUBLIC_IO_BLKIF_H__ */ 302