1/* SPDX-License-Identifier: MIT */ 2/****************************************************************************** 3 * blkif.h 4 * 5 * Unified block-device I/O interface for Xen guest OSes. 6 * 7 * Copyright (c) 2003-2004, Keir Fraser 8 */ 9 10#ifndef __XEN_PUBLIC_IO_BLKIF_H__ 11#define __XEN_PUBLIC_IO_BLKIF_H__ 12 13#include <xen/interface/io/ring.h> 14#include <xen/interface/grant_table.h> 15 16/* 17 * Front->back notifications: When enqueuing a new request, sending a 18 * notification can be made conditional on req_event (i.e., the generic 19 * hold-off mechanism provided by the ring macros). Backends must set 20 * req_event appropriately (e.g., using RING_FINAL_CHECK_FOR_REQUESTS()). 21 * 22 * Back->front notifications: When enqueuing a new response, sending a 23 * notification can be made conditional on rsp_event (i.e., the generic 24 * hold-off mechanism provided by the ring macros). Frontends must set 25 * rsp_event appropriately (e.g., using RING_FINAL_CHECK_FOR_RESPONSES()). 26 */ 27 28typedef uint16_t blkif_vdev_t; 29typedef uint64_t blkif_sector_t; 30 31/* 32 * Multiple hardware queues/rings: 33 * If supported, the backend will write the key "multi-queue-max-queues" to 34 * the directory for that vbd, and set its value to the maximum supported 35 * number of queues. 36 * Frontends that are aware of this feature and wish to use it can write the 37 * key "multi-queue-num-queues" with the number they wish to use, which must be 38 * greater than zero, and no more than the value reported by the backend in 39 * "multi-queue-max-queues". 40 * 41 * For frontends requesting just one queue, the usual event-channel and 42 * ring-ref keys are written as before, simplifying the backend processing 43 * to avoid distinguishing between a frontend that doesn't understand the 44 * multi-queue feature, and one that does, but requested only one queue. 45 * 46 * Frontends requesting two or more queues must not write the toplevel 47 * event-channel and ring-ref keys, instead writing those keys under sub-keys 48 * having the name "queue-N" where N is the integer ID of the queue/ring for 49 * which those keys belong. Queues are indexed from zero. 50 * For example, a frontend with two queues must write the following set of 51 * queue-related keys: 52 * 53 * /local/domain/1/device/vbd/0/multi-queue-num-queues = "2" 54 * /local/domain/1/device/vbd/0/queue-0 = "" 55 * /local/domain/1/device/vbd/0/queue-0/ring-ref = "<ring-ref#0>" 56 * /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn#0>" 57 * /local/domain/1/device/vbd/0/queue-1 = "" 58 * /local/domain/1/device/vbd/0/queue-1/ring-ref = "<ring-ref#1>" 59 * /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn#1>" 60 * 61 * It is also possible to use multiple queues/rings together with 62 * feature multi-page ring buffer. 63 * For example, a frontend requests two queues/rings and the size of each ring 64 * buffer is two pages must write the following set of related keys: 65 * 66 * /local/domain/1/device/vbd/0/multi-queue-num-queues = "2" 67 * /local/domain/1/device/vbd/0/ring-page-order = "1" 68 * /local/domain/1/device/vbd/0/queue-0 = "" 69 * /local/domain/1/device/vbd/0/queue-0/ring-ref0 = "<ring-ref#0>" 70 * /local/domain/1/device/vbd/0/queue-0/ring-ref1 = "<ring-ref#1>" 71 * /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn#0>" 72 * /local/domain/1/device/vbd/0/queue-1 = "" 73 * /local/domain/1/device/vbd/0/queue-1/ring-ref0 = "<ring-ref#2>" 74 * /local/domain/1/device/vbd/0/queue-1/ring-ref1 = "<ring-ref#3>" 75 * /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn#1>" 76 * 77 */ 78 79/* 80 * REQUEST CODES. 81 */ 82#define BLKIF_OP_READ 0 83#define BLKIF_OP_WRITE 1 84/* 85 * Recognised only if "feature-barrier" is present in backend xenbus info. 86 * The "feature_barrier" node contains a boolean indicating whether barrier 87 * requests are likely to succeed or fail. Either way, a barrier request 88 * may fail at any time with BLKIF_RSP_EOPNOTSUPP if it is unsupported by 89 * the underlying block-device hardware. The boolean simply indicates whether 90 * or not it is worthwhile for the frontend to attempt barrier requests. 91 * If a backend does not recognise BLKIF_OP_WRITE_BARRIER, it should *not* 92 * create the "feature-barrier" node! 93 */ 94#define BLKIF_OP_WRITE_BARRIER 2 95 96/* 97 * Recognised if "feature-flush-cache" is present in backend xenbus 98 * info. A flush will ask the underlying storage hardware to flush its 99 * non-volatile caches as appropriate. The "feature-flush-cache" node 100 * contains a boolean indicating whether flush requests are likely to 101 * succeed or fail. Either way, a flush request may fail at any time 102 * with BLKIF_RSP_EOPNOTSUPP if it is unsupported by the underlying 103 * block-device hardware. The boolean simply indicates whether or not it 104 * is worthwhile for the frontend to attempt flushes. If a backend does 105 * not recognise BLKIF_OP_WRITE_FLUSH_CACHE, it should *not* create the 106 * "feature-flush-cache" node! 107 */ 108#define BLKIF_OP_FLUSH_DISKCACHE 3 109 110/* 111 * Recognised only if "feature-discard" is present in backend xenbus info. 112 * The "feature-discard" node contains a boolean indicating whether trim 113 * (ATA) or unmap (SCSI) - conviently called discard requests are likely 114 * to succeed or fail. Either way, a discard request 115 * may fail at any time with BLKIF_RSP_EOPNOTSUPP if it is unsupported by 116 * the underlying block-device hardware. The boolean simply indicates whether 117 * or not it is worthwhile for the frontend to attempt discard requests. 118 * If a backend does not recognise BLKIF_OP_DISCARD, it should *not* 119 * create the "feature-discard" node! 120 * 121 * Discard operation is a request for the underlying block device to mark 122 * extents to be erased. However, discard does not guarantee that the blocks 123 * will be erased from the device - it is just a hint to the device 124 * controller that these blocks are no longer in use. What the device 125 * controller does with that information is left to the controller. 126 * Discard operations are passed with sector_number as the 127 * sector index to begin discard operations at and nr_sectors as the number of 128 * sectors to be discarded. The specified sectors should be discarded if the 129 * underlying block device supports trim (ATA) or unmap (SCSI) operations, 130 * or a BLKIF_RSP_EOPNOTSUPP should be returned. 131 * More information about trim/unmap operations at: 132 * http://t13.org/Documents/UploadedDocuments/docs2008/ 133 * e07154r6-Data_Set_Management_Proposal_for_ATA-ACS2.doc 134 * http://www.seagate.com/staticfiles/support/disc/manuals/ 135 * Interface%20manuals/100293068c.pdf 136 * The backend can optionally provide three extra XenBus attributes to 137 * further optimize the discard functionality: 138 * 'discard-alignment' - Devices that support discard functionality may 139 * internally allocate space in units that are bigger than the exported 140 * logical block size. The discard-alignment parameter indicates how many bytes 141 * the beginning of the partition is offset from the internal allocation unit's 142 * natural alignment. 143 * 'discard-granularity' - Devices that support discard functionality may 144 * internally allocate space using units that are bigger than the logical block 145 * size. The discard-granularity parameter indicates the size of the internal 146 * allocation unit in bytes if reported by the device. Otherwise the 147 * discard-granularity will be set to match the device's physical block size. 148 * 'discard-secure' - All copies of the discarded sectors (potentially created 149 * by garbage collection) must also be erased. To use this feature, the flag 150 * BLKIF_DISCARD_SECURE must be set in the blkif_request_trim. 151 */ 152#define BLKIF_OP_DISCARD 5 153 154/* 155 * Recognized if "feature-max-indirect-segments" in present in the backend 156 * xenbus info. The "feature-max-indirect-segments" node contains the maximum 157 * number of segments allowed by the backend per request. If the node is 158 * present, the frontend might use blkif_request_indirect structs in order to 159 * issue requests with more than BLKIF_MAX_SEGMENTS_PER_REQUEST (11). The 160 * maximum number of indirect segments is fixed by the backend, but the 161 * frontend can issue requests with any number of indirect segments as long as 162 * it's less than the number provided by the backend. The indirect_grefs field 163 * in blkif_request_indirect should be filled by the frontend with the 164 * grant references of the pages that are holding the indirect segments. 165 * These pages are filled with an array of blkif_request_segment that hold the 166 * information about the segments. The number of indirect pages to use is 167 * determined by the number of segments an indirect request contains. Every 168 * indirect page can contain a maximum of 169 * (PAGE_SIZE / sizeof(struct blkif_request_segment)) segments, so to 170 * calculate the number of indirect pages to use we have to do 171 * ceil(indirect_segments / (PAGE_SIZE / sizeof(struct blkif_request_segment))). 172 * 173 * If a backend does not recognize BLKIF_OP_INDIRECT, it should *not* 174 * create the "feature-max-indirect-segments" node! 175 */ 176#define BLKIF_OP_INDIRECT 6 177 178/* 179 * Maximum scatter/gather segments per request. 180 * This is carefully chosen so that sizeof(struct blkif_ring) <= PAGE_SIZE. 181 * NB. This could be 12 if the ring indexes weren't stored in the same page. 182 */ 183#define BLKIF_MAX_SEGMENTS_PER_REQUEST 11 184 185#define BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST 8 186 187struct blkif_request_segment { 188 grant_ref_t gref; /* reference to I/O buffer frame */ 189 /* @first_sect: first sector in frame to transfer (inclusive). */ 190 /* @last_sect: last sector in frame to transfer (inclusive). */ 191 uint8_t first_sect, last_sect; 192}; 193 194struct blkif_request_rw { 195 uint8_t nr_segments; /* number of segments */ 196 blkif_vdev_t handle; /* only for read/write requests */ 197#ifndef CONFIG_X86_32 198 uint32_t _pad1; /* offsetof(blkif_request,u.rw.id) == 8 */ 199#endif 200 uint64_t id; /* private guest value, echoed in resp */ 201 blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */ 202 struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST]; 203} __attribute__((__packed__)); 204 205struct blkif_request_discard { 206 uint8_t flag; /* BLKIF_DISCARD_SECURE or zero. */ 207#define BLKIF_DISCARD_SECURE (1<<0) /* ignored if discard-secure=0 */ 208 blkif_vdev_t _pad1; /* only for read/write requests */ 209#ifndef CONFIG_X86_32 210 uint32_t _pad2; /* offsetof(blkif_req..,u.discard.id)==8*/ 211#endif 212 uint64_t id; /* private guest value, echoed in resp */ 213 blkif_sector_t sector_number; 214 uint64_t nr_sectors; 215 uint8_t _pad3; 216} __attribute__((__packed__)); 217 218struct blkif_request_other { 219 uint8_t _pad1; 220 blkif_vdev_t _pad2; /* only for read/write requests */ 221#ifndef CONFIG_X86_32 222 uint32_t _pad3; /* offsetof(blkif_req..,u.other.id)==8*/ 223#endif 224 uint64_t id; /* private guest value, echoed in resp */ 225} __attribute__((__packed__)); 226 227struct blkif_request_indirect { 228 uint8_t indirect_op; 229 uint16_t nr_segments; 230#ifndef CONFIG_X86_32 231 uint32_t _pad1; /* offsetof(blkif_...,u.indirect.id) == 8 */ 232#endif 233 uint64_t id; 234 blkif_sector_t sector_number; 235 blkif_vdev_t handle; 236 uint16_t _pad2; 237 grant_ref_t indirect_grefs[BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST]; 238#ifndef CONFIG_X86_32 239 uint32_t _pad3; /* make it 64 byte aligned */ 240#else 241 uint64_t _pad3; /* make it 64 byte aligned */ 242#endif 243} __attribute__((__packed__)); 244 245struct blkif_request { 246 uint8_t operation; /* BLKIF_OP_??? */ 247 union { 248 struct blkif_request_rw rw; 249 struct blkif_request_discard discard; 250 struct blkif_request_other other; 251 struct blkif_request_indirect indirect; 252 } u; 253} __attribute__((__packed__)); 254 255struct blkif_response { 256 uint64_t id; /* copied from request */ 257 uint8_t operation; /* copied from request */ 258 int16_t status; /* BLKIF_RSP_??? */ 259}; 260 261/* 262 * STATUS RETURN CODES. 263 */ 264 /* Operation not supported (only happens on barrier writes). */ 265#define BLKIF_RSP_EOPNOTSUPP -2 266 /* Operation failed for some unspecified reason (-EIO). */ 267#define BLKIF_RSP_ERROR -1 268 /* Operation completed successfully. */ 269#define BLKIF_RSP_OKAY 0 270 271/* 272 * Generate blkif ring structures and types. 273 */ 274 275DEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response); 276 277#define VDISK_CDROM 0x1 278#define VDISK_REMOVABLE 0x2 279#define VDISK_READONLY 0x4 280 281/* Xen-defined major numbers for virtual disks, they look strangely 282 * familiar */ 283#define XEN_IDE0_MAJOR 3 284#define XEN_IDE1_MAJOR 22 285#define XEN_SCSI_DISK0_MAJOR 8 286#define XEN_SCSI_DISK1_MAJOR 65 287#define XEN_SCSI_DISK2_MAJOR 66 288#define XEN_SCSI_DISK3_MAJOR 67 289#define XEN_SCSI_DISK4_MAJOR 68 290#define XEN_SCSI_DISK5_MAJOR 69 291#define XEN_SCSI_DISK6_MAJOR 70 292#define XEN_SCSI_DISK7_MAJOR 71 293#define XEN_SCSI_DISK8_MAJOR 128 294#define XEN_SCSI_DISK9_MAJOR 129 295#define XEN_SCSI_DISK10_MAJOR 130 296#define XEN_SCSI_DISK11_MAJOR 131 297#define XEN_SCSI_DISK12_MAJOR 132 298#define XEN_SCSI_DISK13_MAJOR 133 299#define XEN_SCSI_DISK14_MAJOR 134 300#define XEN_SCSI_DISK15_MAJOR 135 301 302#endif /* __XEN_PUBLIC_IO_BLKIF_H__ */ 303