95 lines
3.3 KiB
C
95 lines
3.3 KiB
C
/******************************************************************************
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* blkif.h
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*
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* Unified block-device I/O interface for Xen guest OSes.
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*
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* Copyright (c) 2003-2004, Keir Fraser
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*/
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#ifndef __XEN_PUBLIC_IO_BLKIF_H__
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#define __XEN_PUBLIC_IO_BLKIF_H__
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#include "ring.h"
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#include "../grant_table.h"
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/*
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* Front->back notifications: When enqueuing a new request, sending a
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* notification can be made conditional on req_event (i.e., the generic
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* hold-off mechanism provided by the ring macros). Backends must set
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* req_event appropriately (e.g., using RING_FINAL_CHECK_FOR_REQUESTS()).
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*
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* Back->front notifications: When enqueuing a new response, sending a
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* notification can be made conditional on rsp_event (i.e., the generic
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* hold-off mechanism provided by the ring macros). Frontends must set
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* rsp_event appropriately (e.g., using RING_FINAL_CHECK_FOR_RESPONSES()).
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*/
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typedef uint16_t blkif_vdev_t;
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typedef uint64_t blkif_sector_t;
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/*
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* REQUEST CODES.
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*/
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#define BLKIF_OP_READ 0
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#define BLKIF_OP_WRITE 1
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/*
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* Recognised only if "feature-barrier" is present in backend xenbus info.
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* The "feature_barrier" node contains a boolean indicating whether barrier
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* requests are likely to succeed or fail. Either way, a barrier request
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* may fail at any time with BLKIF_RSP_EOPNOTSUPP if it is unsupported by
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* the underlying block-device hardware. The boolean simply indicates whether
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* or not it is worthwhile for the frontend to attempt barrier requests.
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* If a backend does not recognise BLKIF_OP_WRITE_BARRIER, it should *not*
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* create the "feature-barrier" node!
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*/
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#define BLKIF_OP_WRITE_BARRIER 2
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/*
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* Maximum scatter/gather segments per request.
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* This is carefully chosen so that sizeof(struct blkif_ring) <= PAGE_SIZE.
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* NB. This could be 12 if the ring indexes weren't stored in the same page.
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*/
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#define BLKIF_MAX_SEGMENTS_PER_REQUEST 11
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struct blkif_request {
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uint8_t operation; /* BLKIF_OP_??? */
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uint8_t nr_segments; /* number of segments */
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blkif_vdev_t handle; /* only for read/write requests */
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uint64_t id; /* private guest value, echoed in resp */
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blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */
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struct blkif_request_segment {
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grant_ref_t gref; /* reference to I/O buffer frame */
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/* @first_sect: first sector in frame to transfer (inclusive). */
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/* @last_sect: last sector in frame to transfer (inclusive). */
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uint8_t first_sect, last_sect;
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} seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
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};
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struct blkif_response {
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uint64_t id; /* copied from request */
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uint8_t operation; /* copied from request */
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int16_t status; /* BLKIF_RSP_??? */
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};
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/*
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* STATUS RETURN CODES.
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*/
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/* Operation not supported (only happens on barrier writes). */
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#define BLKIF_RSP_EOPNOTSUPP -2
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/* Operation failed for some unspecified reason (-EIO). */
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#define BLKIF_RSP_ERROR -1
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/* Operation completed successfully. */
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#define BLKIF_RSP_OKAY 0
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/*
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* Generate blkif ring structures and types.
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*/
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DEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response);
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#define VDISK_CDROM 0x1
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#define VDISK_REMOVABLE 0x2
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#define VDISK_READONLY 0x4
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#endif /* __XEN_PUBLIC_IO_BLKIF_H__ */
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