xref: /illumos-gate/usr/src/uts/common/xen/public/io/blkif.h (revision 55fea89d)
1 /******************************************************************************
2  * blkif.h
3  *
4  * Unified block-device I/O interface for Xen guest OSes.
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) 2003-2004, Keir Fraser
25  */
26 
27 #ifndef __XEN_PUBLIC_IO_BLKIF_H__
28 #define __XEN_PUBLIC_IO_BLKIF_H__
29 
30 #include "ring.h"
31 #include "../grant_table.h"
32 
33 /*
34  * Front->back notifications: When enqueuing a new request, sending a
35  * notification can be made conditional on req_event (i.e., the generic
36  * hold-off mechanism provided by the ring macros). Backends must set
37  * req_event appropriately (e.g., using RING_FINAL_CHECK_FOR_REQUESTS()).
38  *
39  * Back->front notifications: When enqueuing a new response, sending a
40  * notification can be made conditional on rsp_event (i.e., the generic
41  * hold-off mechanism provided by the ring macros). Frontends must set
42  * rsp_event appropriately (e.g., using RING_FINAL_CHECK_FOR_RESPONSES()).
43  */
44 
45 #ifndef blkif_vdev_t
46 #define blkif_vdev_t   uint16_t
47 #endif
48 #define blkif_sector_t uint64_t
49 
50 /*
51  * REQUEST CODES.
52  */
53 #define BLKIF_OP_READ              0
54 #define BLKIF_OP_WRITE             1
55 /*
56  * Recognised only if "feature-barrier" is present in backend xenbus info.
57  * The "feature-barrier" node contains a boolean indicating whether barrier
58  * requests are likely to succeed or fail. Either way, a barrier request
59  * may fail at any time with BLKIF_RSP_EOPNOTSUPP if it is unsupported by
60  * the underlying block-device hardware. The boolean simply indicates whether
61  * or not it is worthwhile for the frontend to attempt barrier requests.
62  * If a backend does not recognise BLKIF_OP_WRITE_BARRIER, it should *not*
63  * create the "feature-barrier" node!
64  */
65 #define BLKIF_OP_WRITE_BARRIER     2
66 /*
67  * Recognised if "feature-flush-cache" is present in backend xenbus
68  * info.  A flush will ask the underlying storage hardware to flush its
69  * non-volatile caches as appropriate.  The "feature-flush-cache" node
70  * contains a boolean indicating whether flush requests are likely to
71  * succeed or fail. Either way, a flush request may fail at any time
72  * with BLKIF_RSP_EOPNOTSUPP if it is unsupported by the underlying
73  * block-device hardware. The boolean simply indicates whether or not it
74  * is worthwhile for the frontend to attempt flushes.  If a backend does
75  * not recognise BLKIF_OP_WRITE_FLUSH_CACHE, it should *not* create the
76  * "feature-flush-cache" node!
77  */
78 #define BLKIF_OP_FLUSH_DISKCACHE   3
79 
80 /*
81  * Maximum scatter/gather segments per request.
82  * This is carefully chosen so that sizeof(blkif_ring_t) <= PAGE_SIZE.
83  * NB. This could be 12 if the ring indexes weren't stored in the same page.
84  */
85 #define BLKIF_MAX_SEGMENTS_PER_REQUEST 11
86 
87 /*
88  * NB. first_sect and last_sect in blkif_request_segment, as well as
89  * sector_number in blkif_request, are always expressed in 512-byte units.
90  * However they must be properly aligned to the real sector size of the
91  * physical disk, which is reported in the "sector-size" node in the backend
92  * xenbus info. Also the xenbus "sectors" node is expressed in 512-byte units.
93  */
94 struct blkif_request_segment {
95     grant_ref_t gref;        /* reference to I/O buffer frame        */
96     /* @first_sect: first sector in frame to transfer (inclusive).   */
97     /* @last_sect: last sector in frame to transfer (inclusive).     */
98     uint8_t     first_sect, last_sect;
99 };
100 
101 struct blkif_request {
102     uint8_t        operation;    /* BLKIF_OP_???                         */
103     uint8_t        nr_segments;  /* number of segments                   */
104     blkif_vdev_t   handle;       /* only for read/write requests         */
105     uint64_t       id;           /* private guest value, echoed in resp  */
106     blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
107     struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
108 };
109 typedef struct blkif_request blkif_request_t;
110 
111 struct blkif_response {
112     uint64_t        id;              /* copied from request */
113     uint8_t         operation;       /* copied from request */
114     int16_t         status;          /* BLKIF_RSP_???       */
115 };
116 typedef struct blkif_response blkif_response_t;
117 
118 /*
119  * STATUS RETURN CODES.
120  */
121  /* Operation not supported (only happens on barrier writes). */
122 #define BLKIF_RSP_EOPNOTSUPP  -2
123  /* Operation failed for some unspecified reason (-EIO). */
124 #define BLKIF_RSP_ERROR       -1
125  /* Operation completed successfully. */
126 #define BLKIF_RSP_OKAY         0
127 
128 /*
129  * Generate blkif ring structures and types.
130  */
131 
132 DEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response);
133 
134 #define VDISK_CDROM        0x1
135 #define VDISK_REMOVABLE    0x2
136 #define VDISK_READONLY     0x4
137 
138 #endif /* __XEN_PUBLIC_IO_BLKIF_H__ */
139 
140 /*
141  * Local variables:
142  * mode: C
143  * c-set-style: "BSD"
144  * c-basic-offset: 4
145  * tab-width: 4
146  * indent-tabs-mode: nil
147  * End:
148  */
149