608 lines
25 KiB
C
608 lines
25 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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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to
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* deal in the Software without restriction, including without limitation the
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* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
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* sell copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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* DEALINGS IN THE SOFTWARE.
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*
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* Copyright (c) 2003-2004, Keir Fraser
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* Copyright (c) 2012, Spectra Logic Corporation
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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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#ifndef blkif_vdev_t
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#define blkif_vdev_t uint16_t
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#endif
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#define blkif_sector_t uint64_t
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/*
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* Feature and Parameter Negotiation
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* =================================
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* The two halves of a Xen block driver utilize nodes within the XenStore to
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* communicate capabilities and to negotiate operating parameters. This
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* section enumerates these nodes which reside in the respective front and
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* backend portions of the XenStore, following the XenBus convention.
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*
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* All data in the XenStore is stored as strings. Nodes specifying numeric
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* values are encoded in decimal. Integer value ranges listed below are
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* expressed as fixed sized integer types capable of storing the conversion
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* of a properly formated node string, without loss of information.
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*
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* Any specified default value is in effect if the corresponding XenBus node
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* is not present in the XenStore.
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*
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* XenStore nodes in sections marked "PRIVATE" are solely for use by the
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* driver side whose XenBus tree contains them.
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*
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* XenStore nodes marked "DEPRECATED" in their notes section should only be
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* used to provide interoperability with legacy implementations.
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*
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* See the XenBus state transition diagram below for details on when XenBus
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* nodes must be published and when they can be queried.
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*
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*****************************************************************************
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* Backend XenBus Nodes
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*****************************************************************************
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*
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*------------------ Backend Device Identification (PRIVATE) ------------------
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*
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* mode
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* Values: "r" (read only), "w" (writable)
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*
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* The read or write access permissions to the backing store to be
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* granted to the frontend.
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*
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* params
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* Values: string
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*
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* A free formatted string providing sufficient information for the
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* backend driver to open the backing device. (e.g. the path to the
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* file or block device representing the backing store.)
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*
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* type
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* Values: "file", "phy", "tap"
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*
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* The type of the backing device/object.
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*
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*--------------------------------- Features ---------------------------------
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*
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* feature-barrier
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* Values: 0/1 (boolean)
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* Default Value: 0
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*
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* A value of "1" indicates that the backend can process requests
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* containing the BLKIF_OP_WRITE_BARRIER request opcode. Requests
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* of this type may still be returned at any time with the
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* BLKIF_RSP_EOPNOTSUPP result code.
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*
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* feature-flush-cache
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* Values: 0/1 (boolean)
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* Default Value: 0
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*
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* A value of "1" indicates that the backend can process requests
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* containing the BLKIF_OP_FLUSH_DISKCACHE request opcode. Requests
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* of this type may still be returned at any time with the
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* BLKIF_RSP_EOPNOTSUPP result code.
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*
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* feature-discard
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* Values: 0/1 (boolean)
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* Default Value: 0
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*
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* A value of "1" indicates that the backend can process requests
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* containing the BLKIF_OP_DISCARD request opcode. Requests
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* of this type may still be returned at any time with the
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* BLKIF_RSP_EOPNOTSUPP result code.
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*
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* feature-persistent
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* Values: 0/1 (boolean)
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* Default Value: 0
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* Notes: 7
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*
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* A value of "1" indicates that the backend can keep the grants used
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* by the frontend driver mapped, so the same set of grants should be
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* used in all transactions. The maximum number of grants the backend
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* can map persistently depends on the implementation, but ideally it
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* should be RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST. Using this
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* feature the backend doesn't need to unmap each grant, preventing
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* costly TLB flushes. The backend driver should only map grants
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* persistently if the frontend supports it. If a backend driver chooses
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* to use the persistent protocol when the frontend doesn't support it,
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* it will probably hit the maximum number of persistently mapped grants
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* (due to the fact that the frontend won't be reusing the same grants),
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* and fall back to non-persistent mode. Backend implementations may
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* shrink or expand the number of persistently mapped grants without
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* notifying the frontend depending on memory constraints (this might
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* cause a performance degradation).
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*
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* If a backend driver wants to limit the maximum number of persistently
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* mapped grants to a value less than RING_SIZE *
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* BLKIF_MAX_SEGMENTS_PER_REQUEST a LRU strategy should be used to
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* discard the grants that are less commonly used. Using a LRU in the
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* backend driver paired with a LIFO queue in the frontend will
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* allow us to have better performance in this scenario.
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*
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*----------------------- Request Transport Parameters ------------------------
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*
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* max-ring-page-order
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* Values: <uint32_t>
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* Default Value: 0
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* Notes: 1, 3
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*
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* The maximum supported size of the request ring buffer in units of
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* lb(machine pages). (e.g. 0 == 1 page, 1 = 2 pages, 2 == 4 pages,
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* etc.).
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*
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* max-ring-pages
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* Values: <uint32_t>
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* Default Value: 1
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* Notes: DEPRECATED, 2, 3
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*
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* The maximum supported size of the request ring buffer in units of
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* machine pages. The value must be a power of 2.
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*
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*------------------------- Backend Device Properties -------------------------
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*
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* discard-alignment
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* Values: <uint32_t>
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* Default Value: 0
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* Notes: 4, 5
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*
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* The offset, in bytes from the beginning of the virtual block device,
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* to the first, addressable, discard extent on the underlying device.
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*
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* discard-granularity
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* Values: <uint32_t>
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* Default Value: <"sector-size">
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* Notes: 4
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*
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* The size, in bytes, of the individually addressable discard extents
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* of the underlying device.
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*
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* discard-secure
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* Values: 0/1 (boolean)
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* Default Value: 0
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* Notes: 10
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*
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* A value of "1" indicates that the backend can process BLKIF_OP_DISCARD
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* requests with the BLKIF_DISCARD_SECURE flag set.
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*
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* info
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* Values: <uint32_t> (bitmap)
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*
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* A collection of bit flags describing attributes of the backing
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* device. The VDISK_* macros define the meaning of each bit
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* location.
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*
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* sector-size
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* Values: <uint32_t>
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*
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* The logical sector size, in bytes, of the backend device.
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*
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* physical-sector-size
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* Values: <uint32_t>
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*
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* The physical sector size, in bytes, of the backend device.
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*
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* sectors
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* Values: <uint64_t>
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*
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* The size of the backend device, expressed in units of its logical
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* sector size ("sector-size").
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*
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*****************************************************************************
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* Frontend XenBus Nodes
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*****************************************************************************
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*
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*----------------------- Request Transport Parameters -----------------------
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*
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* event-channel
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* Values: <uint32_t>
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*
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* The identifier of the Xen event channel used to signal activity
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* in the ring buffer.
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*
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* ring-ref
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* Values: <uint32_t>
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* Notes: 6
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*
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* The Xen grant reference granting permission for the backend to map
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* the sole page in a single page sized ring buffer.
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*
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* ring-ref%u
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* Values: <uint32_t>
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* Notes: 6
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*
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* For a frontend providing a multi-page ring, a "number of ring pages"
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* sized list of nodes, each containing a Xen grant reference granting
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* permission for the backend to map the page of the ring located
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* at page index "%u". Page indexes are zero based.
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*
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* protocol
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* Values: string (XEN_IO_PROTO_ABI_*)
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* Default Value: XEN_IO_PROTO_ABI_NATIVE
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*
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* The machine ABI rules governing the format of all ring request and
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* response structures.
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*
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* ring-page-order
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* Values: <uint32_t>
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* Default Value: 0
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* Maximum Value: MAX(ffs(max-ring-pages) - 1, max-ring-page-order)
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* Notes: 1, 3
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*
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* The size of the frontend allocated request ring buffer in units
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* of lb(machine pages). (e.g. 0 == 1 page, 1 = 2 pages, 2 == 4 pages,
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* etc.).
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*
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* num-ring-pages
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* Values: <uint32_t>
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* Default Value: 1
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* Maximum Value: MAX(max-ring-pages,(0x1 << max-ring-page-order))
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* Notes: DEPRECATED, 2, 3
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*
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* The size of the frontend allocated request ring buffer in units of
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* machine pages. The value must be a power of 2.
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*
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* feature-persistent
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* Values: 0/1 (boolean)
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* Default Value: 0
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* Notes: 7, 8, 9
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*
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* A value of "1" indicates that the frontend will reuse the same grants
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* for all transactions, allowing the backend to map them with write
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* access (even when it should be read-only). If the frontend hits the
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* maximum number of allowed persistently mapped grants, it can fallback
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* to non persistent mode. This will cause a performance degradation,
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* since the the backend driver will still try to map those grants
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* persistently. Since the persistent grants protocol is compatible with
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* the previous protocol, a frontend driver can choose to work in
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* persistent mode even when the backend doesn't support it.
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*
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* It is recommended that the frontend driver stores the persistently
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* mapped grants in a LIFO queue, so a subset of all persistently mapped
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* grants gets used commonly. This is done in case the backend driver
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* decides to limit the maximum number of persistently mapped grants
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* to a value less than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST.
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*
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*------------------------- Virtual Device Properties -------------------------
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*
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* device-type
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* Values: "disk", "cdrom", "floppy", etc.
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*
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* virtual-device
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* Values: <uint32_t>
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*
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* A value indicating the physical device to virtualize within the
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* frontend's domain. (e.g. "The first ATA disk", "The third SCSI
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* disk", etc.)
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*
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* See docs/misc/vbd-interface.txt for details on the format of this
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* value.
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*
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* Notes
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* -----
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* (1) Multi-page ring buffer scheme first developed in the Citrix XenServer
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* PV drivers.
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* (2) Multi-page ring buffer scheme first used in some RedHat distributions
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* including a distribution deployed on certain nodes of the Amazon
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* EC2 cluster.
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* (3) Support for multi-page ring buffers was implemented independently,
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* in slightly different forms, by both Citrix and RedHat/Amazon.
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* For full interoperability, block front and backends should publish
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* identical ring parameters, adjusted for unit differences, to the
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* XenStore nodes used in both schemes.
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* (4) Devices that support discard functionality may internally allocate space
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* (discardable extents) in units that are larger than the exported logical
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* block size. If the backing device has such discardable extents the
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* backend should provide both discard-granularity and discard-alignment.
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* Providing just one of the two may be considered an error by the frontend.
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* Backends supporting discard should include discard-granularity and
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* discard-alignment even if it supports discarding individual sectors.
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* Frontends should assume discard-alignment == 0 and discard-granularity
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* == sector size if these keys are missing.
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* (5) The discard-alignment parameter allows a physical device to be
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* partitioned into virtual devices that do not necessarily begin or
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* end on a discardable extent boundary.
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* (6) When there is only a single page allocated to the request ring,
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* 'ring-ref' is used to communicate the grant reference for this
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* page to the backend. When using a multi-page ring, the 'ring-ref'
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* node is not created. Instead 'ring-ref0' - 'ring-refN' are used.
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* (7) When using persistent grants data has to be copied from/to the page
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* where the grant is currently mapped. The overhead of doing this copy
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* however doesn't suppress the speed improvement of not having to unmap
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* the grants.
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* (8) The frontend driver has to allow the backend driver to map all grants
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* with write access, even when they should be mapped read-only, since
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* further requests may reuse these grants and require write permissions.
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* (9) Linux implementation doesn't have a limit on the maximum number of
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* grants that can be persistently mapped in the frontend driver, but
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* due to the frontent driver implementation it should never be bigger
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* than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST.
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*(10) The discard-secure property may be present and will be set to 1 if the
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* backing device supports secure discard.
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*/
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/*
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* STATE DIAGRAMS
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*
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*****************************************************************************
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* Startup *
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*****************************************************************************
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*
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* Tool stack creates front and back nodes with state XenbusStateInitialising.
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*
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* Front Back
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* ================================= =====================================
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* XenbusStateInitialising XenbusStateInitialising
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* o Query virtual device o Query backend device identification
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* properties. data.
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* o Setup OS device instance. o Open and validate backend device.
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* o Publish backend features and
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* transport parameters.
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* |
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* |
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* V
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* XenbusStateInitWait
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*
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* o Query backend features and
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* transport parameters.
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* o Allocate and initialize the
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* request ring.
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* o Publish transport parameters
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* that will be in effect during
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* this connection.
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* |
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* |
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* V
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* XenbusStateInitialised
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*
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* o Query frontend transport parameters.
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* o Connect to the request ring and
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* event channel.
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* o Publish backend device properties.
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* |
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* |
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* V
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* XenbusStateConnected
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*
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* o Query backend device properties.
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* o Finalize OS virtual device
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* instance.
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* |
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* |
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* V
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* XenbusStateConnected
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*
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* Note: Drivers that do not support any optional features, or the negotiation
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* of transport parameters, can skip certain states in the state machine:
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*
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* o A frontend may transition to XenbusStateInitialised without
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* waiting for the backend to enter XenbusStateInitWait. In this
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* case, default transport parameters are in effect and any
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* transport parameters published by the frontend must contain
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* their default values.
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*
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* o A backend may transition to XenbusStateInitialised, bypassing
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* XenbusStateInitWait, without waiting for the frontend to first
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* enter the XenbusStateInitialised state. In this case, default
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* transport parameters are in effect and any transport parameters
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* published by the backend must contain their default values.
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*
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* Drivers that support optional features and/or transport parameter
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* negotiation must tolerate these additional state transition paths.
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* In general this means performing the work of any skipped state
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* transition, if it has not already been performed, in addition to the
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* work associated with entry into the current state.
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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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* All writes issued prior to a request with the BLKIF_OP_WRITE_BARRIER
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* operation code ("barrier request") must be completed prior to the
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* execution of the barrier request. All writes issued after the barrier
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* request must not execute until after the completion of the barrier request.
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*
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* Optional. See "feature-barrier" XenBus node documentation above.
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*/
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#define BLKIF_OP_WRITE_BARRIER 2
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/*
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* Commit any uncommitted contents of the backing device's volatile cache
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* to stable storage.
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*
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* Optional. See "feature-flush-cache" XenBus node documentation above.
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*/
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#define BLKIF_OP_FLUSH_DISKCACHE 3
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/*
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* Used in SLES sources for device specific command packet
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* contained within the request. Reserved for that purpose.
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*/
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#define BLKIF_OP_RESERVED_1 4
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/*
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* Indicate to the backend device that a region of storage is no longer in
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* use, and may be discarded at any time without impact to the client. If
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* the BLKIF_DISCARD_SECURE flag is set on the request, all copies of the
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* discarded region on the device must be rendered unrecoverable before the
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* command returns.
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*
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* This operation is analogous to performing a trim (ATA) or unamp (SCSI),
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* command on a native device.
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*
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* More information about trim/unmap operations can be found 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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*
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* Optional. See "feature-discard", "discard-alignment",
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* "discard-granularity", and "discard-secure" in the XenBus node
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* documentation above.
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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
|
|
* in blkif_request_indirect should be filled by the frontend with the
|
|
* grant references of the pages that are holding the indirect segments.
|
|
* These pages are filled with an array of blkif_request_segment that hold the
|
|
* information about the segments. The number of indirect pages to use is
|
|
* determined by the number of segments an indirect request contains. Every
|
|
* indirect page can contain a maximum of
|
|
* (PAGE_SIZE / sizeof(struct blkif_request_segment)) segments, so to
|
|
* calculate the number of indirect pages to use we have to do
|
|
* ceil(indirect_segments / (PAGE_SIZE / sizeof(struct blkif_request_segment))).
|
|
*
|
|
* If a backend does not recognize BLKIF_OP_INDIRECT, it should *not*
|
|
* create the "feature-max-indirect-segments" node!
|
|
*/
|
|
#define BLKIF_OP_INDIRECT 6
|
|
|
|
/*
|
|
* 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
|
|
|
|
/*
|
|
* Maximum number of indirect pages to use per request.
|
|
*/
|
|
#define BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST 8
|
|
|
|
/*
|
|
* 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 "physical-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;
|
|
};
|
|
|
|
/*
|
|
* Starting ring element for any I/O request.
|
|
*/
|
|
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_DISCARD
|
|
* 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_request_indirect {
|
|
uint8_t operation; /* BLKIF_OP_INDIRECT */
|
|
uint8_t indirect_op; /* BLKIF_OP_{READ/WRITE} */
|
|
uint16_t nr_segments; /* number of segments */
|
|
uint64_t id; /* private guest value, echoed in resp */
|
|
blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */
|
|
blkif_vdev_t handle; /* same as for read/write requests */
|
|
grant_ref_t indirect_grefs[BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST];
|
|
#ifdef __i386__
|
|
uint64_t pad; /* Make it 64 byte aligned on i386 */
|
|
#endif
|
|
};
|
|
typedef struct blkif_request_indirect blkif_request_indirect_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-file-style: "BSD"
|
|
* c-basic-offset: 4
|
|
* tab-width: 4
|
|
* indent-tabs-mode: nil
|
|
* End:
|
|
*/
|