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TOMOYO Linux Cross Reference
Linux/include/xen/interface/io/blkif.h

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  1 /* SPDX-License-Identifier: GPL-2.0 */
  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 
 28 typedef uint16_t blkif_vdev_t;
 29 typedef 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 
187 struct 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 
194 struct 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 
205 struct 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 
218 struct 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 
227 struct 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 
245 struct 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 
255 struct 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 
275 DEFINE_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 

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