blkif.h revision 214077 
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 <xen/interface/io/ring.h>
31#include <xen/interface/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 associated with a request header block.
82 */
83#define BLKIF_MAX_SEGMENTS_PER_HEADER_BLOCK  11
84
85/*
86 * Maximum scatter/gather segments associated with a segment block.
87 */
88#define BLKIF_MAX_SEGMENTS_PER_SEGMENT_BLOCK 14
89
90/*
91 * Maximum scatter/gather segments per request (header + segment blocks).
92 */
93#define BLKIF_MAX_SEGMENTS_PER_REQUEST 255
94
95struct blkif_request_segment {
96    grant_ref_t gref;        /* reference to I/O buffer frame        */
97    /* @first_sect: first sector in frame to transfer (inclusive).   */
98    /* @last_sect: last sector in frame to transfer (inclusive).     */
99    uint8_t     first_sect, last_sect;
100};
101typedef struct blkif_request_segment blkif_request_segment_t;
102
103struct blkif_request {
104    uint8_t        operation;    /* BLKIF_OP_???                         */
105    uint8_t        nr_segments;  /* number of segments                   */
106    blkif_vdev_t   handle;       /* only for read/write requests         */
107    uint64_t       id;           /* private guest value, echoed in resp  */
108    blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
109    struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_HEADER_BLOCK];
110};
111typedef struct blkif_request blkif_request_t;
112
113struct blkif_response {
114    uint64_t        id;              /* copied from request */
115    uint8_t         operation;       /* copied from request */
116    int16_t         status;          /* BLKIF_RSP_???       */
117};
118typedef struct blkif_response blkif_response_t;
119
120/*
121 * STATUS RETURN CODES.
122 */
123 /* Operation not supported (only happens on barrier writes). */
124#define BLKIF_RSP_EOPNOTSUPP  -2
125 /* Operation failed for some unspecified reason (-EIO). */
126#define BLKIF_RSP_ERROR       -1
127 /* Operation completed successfully. */
128#define BLKIF_RSP_OKAY         0
129
130/*
131 * Generate blkif ring structures and types.
132 */
133
134DEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response);
135
136#define BLKRING_GET_SG_REQUEST(_r, _idx)				\
137    ((struct blkif_request_segment *)RING_GET_REQUEST(_r, _idx))
138
139#define VDISK_CDROM        0x1
140#define VDISK_REMOVABLE    0x2
141#define VDISK_READONLY     0x4
142
143/*
144 * The number of ring request blocks required to handle an I/O
145 * request containing _segs segments.
146 */
147#define BLKIF_SEGS_TO_BLOCKS(_segs)					\
148	((((_segs - BLKIF_MAX_SEGMENTS_PER_HEADER_BLOCK)		\
149	 + (BLKIF_MAX_SEGMENTS_PER_SEGMENT_BLOCK - 1))			\
150        / BLKIF_MAX_SEGMENTS_PER_SEGMENT_BLOCK) + /*header_block*/1)
151
152#endif /* __XEN_PUBLIC_IO_BLKIF_H__ */
153
154/*
155 * Local variables:
156 * mode: C
157 * c-set-style: "BSD"
158 * c-basic-offset: 4
159 * tab-width: 4
160 * indent-tabs-mode: nil
161 * End:
162 */
163