/******************************************************************************
* 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
/*
* Used in SLES sources for device specific command packet
* contained within the request. Reserved for that purpose.
*/
#define BLKIF_OP_RESERVED_1 4
/*
* Recognised only if "feature-discard" is present in backend xenbus info.
* The "feature-discard" node contains a boolean indicating whether trim
* (ATA) or unmap (SCSI) - conviently called discard requests are likely
* to succeed or fail. Either way, a discard 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 discard requests.
* If a backend does not recognise BLKIF_OP_DISCARD, it should *not*
* create the "feature-discard" node!
*
* Discard operation is a request for the underlying block device to mark
* extents to be erased. However, discard does not guarantee that the blocks
* will be erased from the device - it is just a hint to the device
* controller that these blocks are no longer in use. What the device
* controller does with that information is left to the controller.
* Discard operations are passed with sector_number as the
* sector index to begin discard operations at and nr_sectors as the number of
* sectors to be discarded. The specified sectors should be discarded if the
* underlying block device supports trim (ATA) or unmap (SCSI) operations,
* or a BLKIF_RSP_EOPNOTSUPP should be returned.
* More information about trim/unmap operations at:
* http://t13.org/Documents/UploadedDocuments/docs2008/
* e07154r6-Data_Set_Management_Proposal_for_ATA-ACS2.doc
* http://www.seagate.com/staticfiles/support/disc/manuals/
* Interface%20manuals/100293068c.pdf
* The backend can optionally provide these extra XenBus attributes to
* further optimize the discard functionality:
* 'discard-aligment' - Devices that support discard functionality may
* internally allocate space in units that are bigger than the exported
* logical block size. The discard-alignment parameter indicates how many bytes
* the beginning of the partition is offset from the internal allocation unit's
* natural alignment. Do not confuse this with natural disk alignment offset.
* 'discard-granularity' - Devices that support discard functionality may
* internally allocate space using units that are bigger than the logical block
* size. The discard-granularity parameter indicates the size of the internal
* allocation unit in bytes if reported by the device. Otherwise the
* discard-granularity will be set to match the device's physical block size.
* It is the minimum size you can discard.
* 'discard-secure' - All copies of the discarded sectors (potentially created
* by garbage collection) must also be erased. To use this feature, the flag
* BLKIF_DISCARD_SECURE must be set in the blkif_request_discard.
*/
#define BLKIF_OP_DISCARD 5
/*
* 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;
/*
* Cast to this structure when blkif_request.operation == BLKIF_OP_TRIM
* sizeof(struct blkif_request_discard) <= sizeof(struct blkif_request)
*/
struct blkif_request_discard {
uint8_t operation; /* BLKIF_OP_DISCARD */
uint8_t flag; /* BLKIF_DISCARD_SECURE or zero */
#define BLKIF_DISCARD_SECURE (1<<0) /* ignored if discard-secure=0 */
blkif_vdev_t handle; /* same as for read/write requests */
uint64_t id; /* private guest value, echoed in resp */
blkif_sector_t sector_number;/* start sector idx on disk */
uint64_t nr_sectors; /* number of contiguous sectors to discard*/
};
typedef struct blkif_request_discard blkif_request_discard_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:
*/