blkif.h revision 183375 
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 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
87struct blkif_request_segment {
88    grant_ref_t gref;        /* reference to I/O buffer frame        */
89    /* @first_sect: first sector in frame to transfer (inclusive).   */
90    /* @last_sect: last sector in frame to transfer (inclusive).     */
91    uint8_t     first_sect, last_sect;
92};
93
94struct blkif_request {
95    uint8_t        operation;    /* BLKIF_OP_???                         */
96    uint8_t        nr_segments;  /* number of segments                   */
97    blkif_vdev_t   handle;       /* only for read/write requests         */
98    uint64_t       id;           /* private guest value, echoed in resp  */
99    blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
100    struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
101};
102typedef struct blkif_request blkif_request_t;
103
104struct blkif_response {
105    uint64_t        id;              /* copied from request */
106    uint8_t         operation;       /* copied from request */
107    int16_t         status;          /* BLKIF_RSP_???       */
108};
109typedef struct blkif_response blkif_response_t;
110
111/*
112 * STATUS RETURN CODES.
113 */
114 /* Operation not supported (only happens on barrier writes). */
115#define BLKIF_RSP_EOPNOTSUPP  -2
116 /* Operation failed for some unspecified reason (-EIO). */
117#define BLKIF_RSP_ERROR       -1
118 /* Operation completed successfully. */
119#define BLKIF_RSP_OKAY         0
120
121/*
122 * Generate blkif ring structures and types.
123 */
124
125DEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response);
126
127#define VDISK_CDROM        0x1
128#define VDISK_REMOVABLE    0x2
129#define VDISK_READONLY     0x4
130
131#endif /* __XEN_PUBLIC_IO_BLKIF_H__ */
132
133/*
134 * Local variables:
135 * mode: C
136 * c-set-style: "BSD"
137 * c-basic-offset: 4
138 * tab-width: 4
139 * indent-tabs-mode: nil
140 * End:
141 */
142