xref: /illumos-gate/usr/src/uts/common/xen/public/io/blkif.h (revision 55fea89d)

/******************************************************************************
 * blkif.h
 *
 * Unified block-device I/O interface for Xen guest OSes.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 *
 * Copyright (c) 2003-2004, Keir Fraser
 */

#ifndef __XEN_PUBLIC_IO_BLKIF_H__
#define __XEN_PUBLIC_IO_BLKIF_H__

#include "ring.h"
#include "../grant_table.h"

/*
 * Front->back notifications: When enqueuing a new request, sending a
 * notification can be made conditional on req_event (i.e., the generic
 * hold-off mechanism provided by the ring macros). Backends must set
 * req_event appropriately (e.g., using RING_FINAL_CHECK_FOR_REQUESTS()).
 *
 * Back->front notifications: When enqueuing a new response, sending a
 * notification can be made conditional on rsp_event (i.e., the generic
 * hold-off mechanism provided by the ring macros). Frontends must set
 * rsp_event appropriately (e.g., using RING_FINAL_CHECK_FOR_RESPONSES()).
 */

#ifndef blkif_vdev_t
#define blkif_vdev_t   uint16_t
#endif
#define blkif_sector_t uint64_t

/*
 * REQUEST CODES.
 */
#define BLKIF_OP_READ              0
#define BLKIF_OP_WRITE             1
/*
 * Recognised only if "feature-barrier" is present in backend xenbus info.
 * The "feature-barrier" node contains a boolean indicating whether barrier
 * requests are likely to succeed or fail. Either way, a barrier request
 * may fail at any time with BLKIF_RSP_EOPNOTSUPP if it is unsupported by
 * the underlying block-device hardware. The boolean simply indicates whether
 * or not it is worthwhile for the frontend to attempt barrier requests.
 * If a backend does not recognise BLKIF_OP_WRITE_BARRIER, it should *not*
 * create the "feature-barrier" node!
 */
#define BLKIF_OP_WRITE_BARRIER     2
/*
 * Recognised if "feature-flush-cache" is present in backend xenbus
 * info.  A flush will ask the underlying storage hardware to flush its
 * non-volatile caches as appropriate.  The "feature-flush-cache" node
 * contains a boolean indicating whether flush requests are likely to
 * succeed or fail. Either way, a flush request may fail at any time
 * with BLKIF_RSP_EOPNOTSUPP if it is unsupported by the underlying
 * block-device hardware. The boolean simply indicates whether or not it
 * is worthwhile for the frontend to attempt flushes.  If a backend does
 * not recognise BLKIF_OP_WRITE_FLUSH_CACHE, it should *not* create the
 * "feature-flush-cache" node!
 */
#define BLKIF_OP_FLUSH_DISKCACHE   3

/*
 * Maximum scatter/gather segments per request.
 * This is carefully chosen so that sizeof(blkif_ring_t) <= PAGE_SIZE.
 * NB. This could be 12 if the ring indexes weren't stored in the same page.
 */
#define BLKIF_MAX_SEGMENTS_PER_REQUEST 11

/*
 * NB. first_sect and last_sect in blkif_request_segment, as well as
 * sector_number in blkif_request, are always expressed in 512-byte units.
 * However they must be properly aligned to the real sector size of the
 * physical disk, which is reported in the "sector-size" node in the backend
 * xenbus info. Also the xenbus "sectors" node is expressed in 512-byte units.
 */
struct blkif_request_segment {
    grant_ref_t gref;        /* reference to I/O buffer frame        */
    /* @first_sect: first sector in frame to transfer (inclusive).   */
    /* @last_sect: last sector in frame to transfer (inclusive).     */
    uint8_t     first_sect, last_sect;
};

struct blkif_request {
    uint8_t        operation;    /* BLKIF_OP_???                         */
    uint8_t        nr_segments;  /* number of segments                   */
    blkif_vdev_t   handle;       /* only for read/write requests         */
    uint64_t       id;           /* private guest value, echoed in resp  */
    blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
    struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
};
typedef struct blkif_request blkif_request_t;

struct blkif_response {
    uint64_t        id;              /* copied from request */
    uint8_t         operation;       /* copied from request */
    int16_t         status;          /* BLKIF_RSP_???       */
};
typedef struct blkif_response blkif_response_t;

/*
 * STATUS RETURN CODES.
 */
 /* Operation not supported (only happens on barrier writes). */
#define BLKIF_RSP_EOPNOTSUPP  -2
 /* Operation failed for some unspecified reason (-EIO). */
#define BLKIF_RSP_ERROR       -1
 /* Operation completed successfully. */
#define BLKIF_RSP_OKAY         0

/*
 * Generate blkif ring structures and types.
 */

DEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response);

#define VDISK_CDROM        0x1
#define VDISK_REMOVABLE    0x2
#define VDISK_READONLY     0x4

#endif /* __XEN_PUBLIC_IO_BLKIF_H__ */

/*
 * Local variables:
 * mode: C
 * c-set-style: "BSD"
 * c-basic-offset: 4
 * tab-width: 4
 * indent-tabs-mode: nil
 * End:
 */