303 lines
13 KiB
C
303 lines
13 KiB
C
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/* SPDX-License-Identifier: GPL-2.0 */
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/******************************************************************************
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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 <xen/interface/io/ring.h>
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#include <xen/interface/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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* Multiple hardware queues/rings:
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* If supported, the backend will write the key "multi-queue-max-queues" to
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* the directory for that vbd, and set its value to the maximum supported
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* number of queues.
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* Frontends that are aware of this feature and wish to use it can write the
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* key "multi-queue-num-queues" with the number they wish to use, which must be
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* greater than zero, and no more than the value reported by the backend in
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* "multi-queue-max-queues".
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*
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* For frontends requesting just one queue, the usual event-channel and
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* ring-ref keys are written as before, simplifying the backend processing
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* to avoid distinguishing between a frontend that doesn't understand the
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* multi-queue feature, and one that does, but requested only one queue.
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*
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* Frontends requesting two or more queues must not write the toplevel
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* event-channel and ring-ref keys, instead writing those keys under sub-keys
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* having the name "queue-N" where N is the integer ID of the queue/ring for
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* which those keys belong. Queues are indexed from zero.
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* For example, a frontend with two queues must write the following set of
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* queue-related keys:
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*
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* /local/domain/1/device/vbd/0/multi-queue-num-queues = "2"
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* /local/domain/1/device/vbd/0/queue-0 = ""
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* /local/domain/1/device/vbd/0/queue-0/ring-ref = "<ring-ref#0>"
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* /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn#0>"
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* /local/domain/1/device/vbd/0/queue-1 = ""
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* /local/domain/1/device/vbd/0/queue-1/ring-ref = "<ring-ref#1>"
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* /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn#1>"
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*
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* It is also possible to use multiple queues/rings together with
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* feature multi-page ring buffer.
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* For example, a frontend requests two queues/rings and the size of each ring
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* buffer is two pages must write the following set of related keys:
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*
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* /local/domain/1/device/vbd/0/multi-queue-num-queues = "2"
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* /local/domain/1/device/vbd/0/ring-page-order = "1"
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* /local/domain/1/device/vbd/0/queue-0 = ""
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* /local/domain/1/device/vbd/0/queue-0/ring-ref0 = "<ring-ref#0>"
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* /local/domain/1/device/vbd/0/queue-0/ring-ref1 = "<ring-ref#1>"
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* /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn#0>"
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* /local/domain/1/device/vbd/0/queue-1 = ""
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* /local/domain/1/device/vbd/0/queue-1/ring-ref0 = "<ring-ref#2>"
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* /local/domain/1/device/vbd/0/queue-1/ring-ref1 = "<ring-ref#3>"
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* /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn#1>"
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*
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*/
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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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* Recognised if "feature-flush-cache" is present in backend xenbus
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* info. A flush will ask the underlying storage hardware to flush its
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* non-volatile caches as appropriate. The "feature-flush-cache" node
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* contains a boolean indicating whether flush requests are likely to
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* succeed or fail. Either way, a flush request may fail at any time
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* with BLKIF_RSP_EOPNOTSUPP if it is unsupported by the underlying
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* block-device hardware. The boolean simply indicates whether or not it
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* is worthwhile for the frontend to attempt flushes. If a backend does
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* not recognise BLKIF_OP_WRITE_FLUSH_CACHE, it should *not* create the
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* "feature-flush-cache" node!
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*/
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#define BLKIF_OP_FLUSH_DISKCACHE 3
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/*
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* Recognised only if "feature-discard" is present in backend xenbus info.
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* The "feature-discard" node contains a boolean indicating whether trim
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* (ATA) or unmap (SCSI) - conviently called discard requests are likely
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* to succeed or fail. Either way, a discard 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 discard requests.
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* If a backend does not recognise BLKIF_OP_DISCARD, it should *not*
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* create the "feature-discard" node!
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*
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* Discard operation is a request for the underlying block device to mark
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* extents to be erased. However, discard does not guarantee that the blocks
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* will be erased from the device - it is just a hint to the device
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* controller that these blocks are no longer in use. What the device
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* controller does with that information is left to the controller.
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* Discard operations are passed with sector_number as the
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* sector index to begin discard operations at and nr_sectors as the number of
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* sectors to be discarded. The specified sectors should be discarded if the
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* underlying block device supports trim (ATA) or unmap (SCSI) operations,
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* or a BLKIF_RSP_EOPNOTSUPP should be returned.
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* More information about trim/unmap operations at:
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* http://t13.org/Documents/UploadedDocuments/docs2008/
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* e07154r6-Data_Set_Management_Proposal_for_ATA-ACS2.doc
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* http://www.seagate.com/staticfiles/support/disc/manuals/
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* Interface%20manuals/100293068c.pdf
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* The backend can optionally provide three extra XenBus attributes to
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* further optimize the discard functionality:
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* 'discard-alignment' - Devices that support discard functionality may
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* internally allocate space in units that are bigger than the exported
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* logical block size. The discard-alignment parameter indicates how many bytes
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* the beginning of the partition is offset from the internal allocation unit's
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* natural alignment.
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* 'discard-granularity' - Devices that support discard functionality may
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* internally allocate space using units that are bigger than the logical block
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* size. The discard-granularity parameter indicates the size of the internal
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* allocation unit in bytes if reported by the device. Otherwise the
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* discard-granularity will be set to match the device's physical block size.
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* 'discard-secure' - All copies of the discarded sectors (potentially created
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* by garbage collection) must also be erased. To use this feature, the flag
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* BLKIF_DISCARD_SECURE must be set in the blkif_request_trim.
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*/
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#define BLKIF_OP_DISCARD 5
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/*
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* Recognized if "feature-max-indirect-segments" in present in the backend
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* xenbus info. The "feature-max-indirect-segments" node contains the maximum
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* number of segments allowed by the backend per request. If the node is
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* present, the frontend might use blkif_request_indirect structs in order to
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* issue requests with more than BLKIF_MAX_SEGMENTS_PER_REQUEST (11). The
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* maximum number of indirect segments is fixed by the backend, but the
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* frontend can issue requests with any number of indirect segments as long as
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* it's less than the number provided by the backend. The indirect_grefs field
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* in blkif_request_indirect should be filled by the frontend with the
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* grant references of the pages that are holding the indirect segments.
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* These pages are filled with an array of blkif_request_segment that hold the
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* information about the segments. The number of indirect pages to use is
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* determined by the number of segments an indirect request contains. Every
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* indirect page can contain a maximum of
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* (PAGE_SIZE / sizeof(struct blkif_request_segment)) segments, so to
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* calculate the number of indirect pages to use we have to do
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* ceil(indirect_segments / (PAGE_SIZE / sizeof(struct blkif_request_segment))).
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*
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* If a backend does not recognize BLKIF_OP_INDIRECT, it should *not*
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* create the "feature-max-indirect-segments" node!
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*/
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#define BLKIF_OP_INDIRECT 6
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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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#define BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST 8
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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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};
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struct blkif_request_rw {
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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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#ifndef CONFIG_X86_32
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uint32_t _pad1; /* offsetof(blkif_request,u.rw.id) == 8 */
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#endif
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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 seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
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} __attribute__((__packed__));
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struct blkif_request_discard {
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uint8_t flag; /* BLKIF_DISCARD_SECURE or zero. */
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#define BLKIF_DISCARD_SECURE (1<<0) /* ignored if discard-secure=0 */
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blkif_vdev_t _pad1; /* only for read/write requests */
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#ifndef CONFIG_X86_32
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uint32_t _pad2; /* offsetof(blkif_req..,u.discard.id)==8*/
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#endif
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uint64_t id; /* private guest value, echoed in resp */
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blkif_sector_t sector_number;
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uint64_t nr_sectors;
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uint8_t _pad3;
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} __attribute__((__packed__));
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struct blkif_request_other {
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uint8_t _pad1;
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blkif_vdev_t _pad2; /* only for read/write requests */
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#ifndef CONFIG_X86_32
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uint32_t _pad3; /* offsetof(blkif_req..,u.other.id)==8*/
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#endif
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uint64_t id; /* private guest value, echoed in resp */
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} __attribute__((__packed__));
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struct blkif_request_indirect {
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uint8_t indirect_op;
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uint16_t nr_segments;
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#ifndef CONFIG_X86_32
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uint32_t _pad1; /* offsetof(blkif_...,u.indirect.id) == 8 */
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#endif
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uint64_t id;
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blkif_sector_t sector_number;
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blkif_vdev_t handle;
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uint16_t _pad2;
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grant_ref_t indirect_grefs[BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST];
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#ifndef CONFIG_X86_32
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uint32_t _pad3; /* make it 64 byte aligned */
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#else
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uint64_t _pad3; /* make it 64 byte aligned */
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#endif
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} __attribute__((__packed__));
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struct blkif_request {
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uint8_t operation; /* BLKIF_OP_??? */
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union {
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struct blkif_request_rw rw;
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struct blkif_request_discard discard;
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struct blkif_request_other other;
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struct blkif_request_indirect indirect;
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} u;
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} __attribute__((__packed__));
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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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/* Xen-defined major numbers for virtual disks, they look strangely
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* familiar */
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#define XEN_IDE0_MAJOR 3
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#define XEN_IDE1_MAJOR 22
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#define XEN_SCSI_DISK0_MAJOR 8
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#define XEN_SCSI_DISK1_MAJOR 65
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#define XEN_SCSI_DISK2_MAJOR 66
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#define XEN_SCSI_DISK3_MAJOR 67
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#define XEN_SCSI_DISK4_MAJOR 68
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#define XEN_SCSI_DISK5_MAJOR 69
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#define XEN_SCSI_DISK6_MAJOR 70
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#define XEN_SCSI_DISK7_MAJOR 71
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#define XEN_SCSI_DISK8_MAJOR 128
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#define XEN_SCSI_DISK9_MAJOR 129
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#define XEN_SCSI_DISK10_MAJOR 130
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#define XEN_SCSI_DISK11_MAJOR 131
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#define XEN_SCSI_DISK12_MAJOR 132
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#define XEN_SCSI_DISK13_MAJOR 133
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#define XEN_SCSI_DISK14_MAJOR 134
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#define XEN_SCSI_DISK15_MAJOR 135
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#endif /* __XEN_PUBLIC_IO_BLKIF_H__ */
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