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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [win-pv-devel] [RFC PATCH 1/6] Update blkif.h
Pull the latest blkif.h from xen.git at
0d16ece0c5adb960ee4e45f12183bcac8fe6d50a
Signed-off-by: owensm <owen.smith@xxxxxxxxxx>
---
include/xen/io/blkif.h | 1100 ++++++++++++++++++++++++++----------------------
1 file changed, 597 insertions(+), 503 deletions(-)
diff --git a/include/xen/io/blkif.h b/include/xen/io/blkif.h
index c3e169c..f659881 100644
--- a/include/xen/io/blkif.h
+++ b/include/xen/io/blkif.h
@@ -1,29 +1,29 @@
/******************************************************************************
- * 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
- * Copyright (c) 2012, Spectra Logic Corporation
- */
+* 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
+* Copyright (c) 2012, Spectra Logic Corporation
+*/
#ifndef __XEN_PUBLIC_IO_BLKIF_H__
#define __XEN_PUBLIC_IO_BLKIF_H__
@@ -32,16 +32,16 @@
#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()).
- */
+* 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
@@ -49,487 +49,581 @@
#define blkif_sector_t uint64_t
/*
- * Feature and Parameter Negotiation
- * =================================
- * The two halves of a Xen block driver utilize nodes within the XenStore to
- * communicate capabilities and to negotiate operating parameters. This
- * section enumerates these nodes which reside in the respective front and
- * backend portions of the XenStore, following the XenBus convention.
- *
- * All data in the XenStore is stored as strings. Nodes specifying numeric
- * values are encoded in decimal. Integer value ranges listed below are
- * expressed as fixed sized integer types capable of storing the conversion
- * of a properly formated node string, without loss of information.
- *
- * Any specified default value is in effect if the corresponding XenBus node
- * is not present in the XenStore.
- *
- * XenStore nodes in sections marked "PRIVATE" are solely for use by the
- * driver side whose XenBus tree contains them.
- *
- * XenStore nodes marked "DEPRECATED" in their notes section should only be
- * used to provide interoperability with legacy implementations.
- *
- * See the XenBus state transition diagram below for details on when XenBus
- * nodes must be published and when they can be queried.
- *
- *****************************************************************************
- * Backend XenBus Nodes
- *****************************************************************************
- *
- *------------------ Backend Device Identification (PRIVATE) ------------------
- *
- * mode
- * Values: "r" (read only), "w" (writable)
- *
- * The read or write access permissions to the backing store to be
- * granted to the frontend.
- *
- * params
- * Values: string
- *
- * A free formatted string providing sufficient information for the
- * backend driver to open the backing device. (e.g. the path to the
- * file or block device representing the backing store.)
- *
- * type
- * Values: "file", "phy", "tap"
- *
- * The type of the backing device/object.
- *
- *--------------------------------- Features ---------------------------------
- *
- * feature-barrier
- * Values: 0/1 (boolean)
- * Default Value: 0
- *
- * A value of "1" indicates that the backend can process requests
- * containing the BLKIF_OP_WRITE_BARRIER request opcode. Requests
- * of this type may still be returned at any time with the
- * BLKIF_RSP_EOPNOTSUPP result code.
- *
- * feature-flush-cache
- * Values: 0/1 (boolean)
- * Default Value: 0
- *
- * A value of "1" indicates that the backend can process requests
- * containing the BLKIF_OP_FLUSH_DISKCACHE request opcode. Requests
- * of this type may still be returned at any time with the
- * BLKIF_RSP_EOPNOTSUPP result code.
- *
- * feature-discard
- * Values: 0/1 (boolean)
- * Default Value: 0
- *
- * A value of "1" indicates that the backend can process requests
- * containing the BLKIF_OP_DISCARD request opcode. Requests
- * of this type may still be returned at any time with the
- * BLKIF_RSP_EOPNOTSUPP result code.
- *
- * feature-persistent
- * Values: 0/1 (boolean)
- * Default Value: 0
- * Notes: 7
- *
- * A value of "1" indicates that the backend can keep the grants used
- * by the frontend driver mapped, so the same set of grants should be
- * used in all transactions. The maximum number of grants the backend
- * can map persistently depends on the implementation, but ideally it
- * should be RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST. Using this
- * feature the backend doesn't need to unmap each grant, preventing
- * costly TLB flushes. The backend driver should only map grants
- * persistently if the frontend supports it. If a backend driver chooses
- * to use the persistent protocol when the frontend doesn't support it,
- * it will probably hit the maximum number of persistently mapped grants
- * (due to the fact that the frontend won't be reusing the same grants),
- * and fall back to non-persistent mode. Backend implementations may
- * shrink or expand the number of persistently mapped grants without
- * notifying the frontend depending on memory constraints (this might
- * cause a performance degradation).
- *
- * If a backend driver wants to limit the maximum number of persistently
- * mapped grants to a value less than RING_SIZE *
- * BLKIF_MAX_SEGMENTS_PER_REQUEST a LRU strategy should be used to
- * discard the grants that are less commonly used. Using a LRU in the
- * backend driver paired with a LIFO queue in the frontend will
- * allow us to have better performance in this scenario.
- *
- *----------------------- Request Transport Parameters ------------------------
- *
- * max-ring-page-order
- * Values: <uint32_t>
- * Default Value: 0
- * Notes: 1, 3
- *
- * The maximum supported size of the request ring buffer in units of
- * lb(machine pages). (e.g. 0 == 1 page, 1 = 2 pages, 2 == 4 pages,
- * etc.).
- *
- * max-ring-pages
- * Values: <uint32_t>
- * Default Value: 1
- * Notes: DEPRECATED, 2, 3
- *
- * The maximum supported size of the request ring buffer in units of
- * machine pages. The value must be a power of 2.
- *
- *------------------------- Backend Device Properties -------------------------
- *
- * discard-alignment
- * Values: <uint32_t>
- * Default Value: 0
- * Notes: 4, 5
- *
- * The offset, in bytes from the beginning of the virtual block device,
- * to the first, addressable, discard extent on the underlying device.
- *
- * discard-granularity
- * Values: <uint32_t>
- * Default Value: <"sector-size">
- * Notes: 4
- *
- * The size, in bytes, of the individually addressable discard extents
- * of the underlying device.
- *
- * discard-secure
- * Values: 0/1 (boolean)
- * Default Value: 0
- * Notes: 10
- *
- * A value of "1" indicates that the backend can process BLKIF_OP_DISCARD
- * requests with the BLKIF_DISCARD_SECURE flag set.
- *
- * info
- * Values: <uint32_t> (bitmap)
- *
- * A collection of bit flags describing attributes of the backing
- * device. The VDISK_* macros define the meaning of each bit
- * location.
- *
- * sector-size
- * Values: <uint32_t>
- *
- * The logical sector size, in bytes, of the backend device.
- *
- * physical-sector-size
- * Values: <uint32_t>
- *
- * The physical sector size, in bytes, of the backend device.
- *
- * sectors
- * Values: <uint64_t>
- *
- * The size of the backend device, expressed in units of its logical
- * sector size ("sector-size").
- *
- *****************************************************************************
- * Frontend XenBus Nodes
- *****************************************************************************
- *
- *----------------------- Request Transport Parameters -----------------------
- *
- * event-channel
- * Values: <uint32_t>
- *
- * The identifier of the Xen event channel used to signal activity
- * in the ring buffer.
- *
- * ring-ref
- * Values: <uint32_t>
- * Notes: 6
- *
- * The Xen grant reference granting permission for the backend to map
- * the sole page in a single page sized ring buffer.
- *
- * ring-ref%u
- * Values: <uint32_t>
- * Notes: 6
- *
- * For a frontend providing a multi-page ring, a "number of ring pages"
- * sized list of nodes, each containing a Xen grant reference granting
- * permission for the backend to map the page of the ring located
- * at page index "%u". Page indexes are zero based.
- *
- * protocol
- * Values: string (XEN_IO_PROTO_ABI_*)
- * Default Value: XEN_IO_PROTO_ABI_NATIVE
- *
- * The machine ABI rules governing the format of all ring request and
- * response structures.
- *
- * ring-page-order
- * Values: <uint32_t>
- * Default Value: 0
- * Maximum Value: MAX(ffs(max-ring-pages) - 1, max-ring-page-order)
- * Notes: 1, 3
- *
- * The size of the frontend allocated request ring buffer in units
- * of lb(machine pages). (e.g. 0 == 1 page, 1 = 2 pages, 2 == 4 pages,
- * etc.).
- *
- * num-ring-pages
- * Values: <uint32_t>
- * Default Value: 1
- * Maximum Value: MAX(max-ring-pages,(0x1 << max-ring-page-order))
- * Notes: DEPRECATED, 2, 3
- *
- * The size of the frontend allocated request ring buffer in units of
- * machine pages. The value must be a power of 2.
- *
- * feature-persistent
- * Values: 0/1 (boolean)
- * Default Value: 0
- * Notes: 7, 8, 9
- *
- * A value of "1" indicates that the frontend will reuse the same grants
- * for all transactions, allowing the backend to map them with write
- * access (even when it should be read-only). If the frontend hits the
- * maximum number of allowed persistently mapped grants, it can fallback
- * to non persistent mode. This will cause a performance degradation,
- * since the the backend driver will still try to map those grants
- * persistently. Since the persistent grants protocol is compatible with
- * the previous protocol, a frontend driver can choose to work in
- * persistent mode even when the backend doesn't support it.
- *
- * It is recommended that the frontend driver stores the persistently
- * mapped grants in a LIFO queue, so a subset of all persistently mapped
- * grants gets used commonly. This is done in case the backend driver
- * decides to limit the maximum number of persistently mapped grants
- * to a value less than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST.
- *
- *------------------------- Virtual Device Properties -------------------------
- *
- * device-type
- * Values: "disk", "cdrom", "floppy", etc.
- *
- * virtual-device
- * Values: <uint32_t>
- *
- * A value indicating the physical device to virtualize within the
- * frontend's domain. (e.g. "The first ATA disk", "The third SCSI
- * disk", etc.)
- *
- * See docs/misc/vbd-interface.txt for details on the format of this
- * value.
- *
- * Notes
- * -----
- * (1) Multi-page ring buffer scheme first developed in the Citrix XenServer
- * PV drivers.
- * (2) Multi-page ring buffer scheme first used in some RedHat distributions
- * including a distribution deployed on certain nodes of the Amazon
- * EC2 cluster.
- * (3) Support for multi-page ring buffers was implemented independently,
- * in slightly different forms, by both Citrix and RedHat/Amazon.
- * For full interoperability, block front and backends should publish
- * identical ring parameters, adjusted for unit differences, to the
- * XenStore nodes used in both schemes.
- * (4) Devices that support discard functionality may internally allocate space
- * (discardable extents) in units that are larger than the exported logical
- * block size. If the backing device has such discardable extents the
- * backend should provide both discard-granularity and discard-alignment.
- * Providing just one of the two may be considered an error by the
frontend.
- * Backends supporting discard should include discard-granularity and
- * discard-alignment even if it supports discarding individual sectors.
- * Frontends should assume discard-alignment == 0 and discard-granularity
- * == sector size if these keys are missing.
- * (5) The discard-alignment parameter allows a physical device to be
- * partitioned into virtual devices that do not necessarily begin or
- * end on a discardable extent boundary.
- * (6) When there is only a single page allocated to the request ring,
- * 'ring-ref' is used to communicate the grant reference for this
- * page to the backend. When using a multi-page ring, the 'ring-ref'
- * node is not created. Instead 'ring-ref0' - 'ring-refN' are used.
- * (7) When using persistent grants data has to be copied from/to the page
- * where the grant is currently mapped. The overhead of doing this copy
- * however doesn't suppress the speed improvement of not having to unmap
- * the grants.
- * (8) The frontend driver has to allow the backend driver to map all grants
- * with write access, even when they should be mapped read-only, since
- * further requests may reuse these grants and require write permissions.
- * (9) Linux implementation doesn't have a limit on the maximum number of
- * grants that can be persistently mapped in the frontend driver, but
- * due to the frontent driver implementation it should never be bigger
- * than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST.
- *(10) The discard-secure property may be present and will be set to 1 if the
- * backing device supports secure discard.
- */
+* Feature and Parameter Negotiation
+* =================================
+* The two halves of a Xen block driver utilize nodes within the XenStore to
+* communicate capabilities and to negotiate operating parameters. This
+* section enumerates these nodes which reside in the respective front and
+* backend portions of the XenStore, following the XenBus convention.
+*
+* All data in the XenStore is stored as strings. Nodes specifying numeric
+* values are encoded in decimal. Integer value ranges listed below are
+* expressed as fixed sized integer types capable of storing the conversion
+* of a properly formated node string, without loss of information.
+*
+* Any specified default value is in effect if the corresponding XenBus node
+* is not present in the XenStore.
+*
+* XenStore nodes in sections marked "PRIVATE" are solely for use by the
+* driver side whose XenBus tree contains them.
+*
+* XenStore nodes marked "DEPRECATED" in their notes section should only be
+* used to provide interoperability with legacy implementations.
+*
+* See the XenBus state transition diagram below for details on when XenBus
+* nodes must be published and when they can be queried.
+*
+*****************************************************************************
+* Backend XenBus Nodes
+*****************************************************************************
+*
+*------------------ Backend Device Identification (PRIVATE) ------------------
+*
+* mode
+* Values: "r" (read only), "w" (writable)
+*
+* The read or write access permissions to the backing store to be
+* granted to the frontend.
+*
+* params
+* Values: string
+*
+* A free formatted string providing sufficient information for the
+* hotplug script to attach the device and provide a suitable
+* handler (ie: a block device) for blkback to use.
+*
+* physical-device
+* Values: "MAJOR:MINOR"
+* Notes: 11
+*
+* MAJOR and MINOR are the major number and minor number of the
+* backing device respectively.
+*
+* physical-device-path
+* Values: path string
+*
+* A string that contains the absolute path to the disk image. On
+* NetBSD and Linux this is always a block device, while on FreeBSD
+* it can be either a block device or a regular file.
+*
+* type
+* Values: "file", "phy", "tap"
+*
+* The type of the backing device/object.
+*
+*
+* direct-io-safe
+* Values: 0/1 (boolean)
+* Default Value: 0
+*
+* The underlying storage is not affected by the direct IO memory
+* lifetime bug. See:
+* http://lists.xen.org/archives/html/xen-devel/2012-12/msg01154.html
+*
+* Therefore this option gives the backend permission to use
+* O_DIRECT, notwithstanding that bug.
+*
+* That is, if this option is enabled, use of O_DIRECT is safe,
+* in circumstances where we would normally have avoided it as a
+* workaround for that bug. This option is not relevant for all
+* backends, and even not necessarily supported for those for
+* which it is relevant. A backend which knows that it is not
+* affected by the bug can ignore this option.
+*
+* This option doesn't require a backend to use O_DIRECT, so it
+* should not be used to try to control the caching behaviour.
+*
+*--------------------------------- Features ---------------------------------
+*
+* feature-barrier
+* Values: 0/1 (boolean)
+* Default Value: 0
+*
+* A value of "1" indicates that the backend can process requests
+* containing the BLKIF_OP_WRITE_BARRIER request opcode. Requests
+* of this type may still be returned at any time with the
+* BLKIF_RSP_EOPNOTSUPP result code.
+*
+* feature-flush-cache
+* Values: 0/1 (boolean)
+* Default Value: 0
+*
+* A value of "1" indicates that the backend can process requests
+* containing the BLKIF_OP_FLUSH_DISKCACHE request opcode. Requests
+* of this type may still be returned at any time with the
+* BLKIF_RSP_EOPNOTSUPP result code.
+*
+* feature-discard
+* Values: 0/1 (boolean)
+* Default Value: 0
+*
+* A value of "1" indicates that the backend can process requests
+* containing the BLKIF_OP_DISCARD request opcode. Requests
+* of this type may still be returned at any time with the
+* BLKIF_RSP_EOPNOTSUPP result code.
+*
+* feature-persistent
+* Values: 0/1 (boolean)
+* Default Value: 0
+* Notes: 7
+*
+* A value of "1" indicates that the backend can keep the grants used
+* by the frontend driver mapped, so the same set of grants should be
+* used in all transactions. The maximum number of grants the backend
+* can map persistently depends on the implementation, but ideally it
+* should be RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST. Using this
+* feature the backend doesn't need to unmap each grant, preventing
+* costly TLB flushes. The backend driver should only map grants
+* persistently if the frontend supports it. If a backend driver chooses
+* to use the persistent protocol when the frontend doesn't support it,
+* it will probably hit the maximum number of persistently mapped grants
+* (due to the fact that the frontend won't be reusing the same grants),
+* and fall back to non-persistent mode. Backend implementations may
+* shrink or expand the number of persistently mapped grants without
+* notifying the frontend depending on memory constraints (this might
+* cause a performance degradation).
+*
+* If a backend driver wants to limit the maximum number of persistently
+* mapped grants to a value less than RING_SIZE *
+* BLKIF_MAX_SEGMENTS_PER_REQUEST a LRU strategy should be used to
+* discard the grants that are less commonly used. Using a LRU in the
+* backend driver paired with a LIFO queue in the frontend will
+* allow us to have better performance in this scenario.
+*
+*----------------------- Request Transport Parameters ------------------------
+*
+* max-ring-page-order
+* Values: <uint32_t>
+* Default Value: 0
+* Notes: 1, 3
+*
+* The maximum supported size of the request ring buffer in units of
+* lb(machine pages). (e.g. 0 == 1 page, 1 = 2 pages, 2 == 4 pages,
+* etc.).
+*
+* max-ring-pages
+* Values: <uint32_t>
+* Default Value: 1
+* Notes: DEPRECATED, 2, 3
+*
+* The maximum supported size of the request ring buffer in units of
+* machine pages. The value must be a power of 2.
+*
+*------------------------- Backend Device Properties -------------------------
+*
+* discard-enable
+* Values: 0/1 (boolean)
+* Default Value: 1
+*
+* This optional property, set by the toolstack, instructs the backend
+* to offer (or not to offer) discard to the frontend. If the property
+* is missing the backend should offer discard if the backing storage
+* actually supports it.
+*
+* discard-alignment
+* Values: <uint32_t>
+* Default Value: 0
+* Notes: 4, 5
+*
+* The offset, in bytes from the beginning of the virtual block device,
+* to the first, addressable, discard extent on the underlying device.
+*
+* discard-granularity
+* Values: <uint32_t>
+* Default Value: <"sector-size">
+* Notes: 4
+*
+* The size, in bytes, of the individually addressable discard extents
+* of the underlying device.
+*
+* discard-secure
+* Values: 0/1 (boolean)
+* Default Value: 0
+* Notes: 10
+*
+* A value of "1" indicates that the backend can process BLKIF_OP_DISCARD
+* requests with the BLKIF_DISCARD_SECURE flag set.
+*
+* info
+* Values: <uint32_t> (bitmap)
+*
+* A collection of bit flags describing attributes of the backing
+* device. The VDISK_* macros define the meaning of each bit
+* location.
+*
+* sector-size
+* Values: <uint32_t>
+*
+* The logical sector size, in bytes, of the backend device.
+*
+* physical-sector-size
+* Values: <uint32_t>
+*
+* The physical sector size, in bytes, of the backend device.
+*
+* sectors
+* Values: <uint64_t>
+*
+* The size of the backend device, expressed in units of its logical
+* sector size ("sector-size").
+*
+*****************************************************************************
+* Frontend XenBus Nodes
+*****************************************************************************
+*
+*----------------------- Request Transport Parameters -----------------------
+*
+* event-channel
+* Values: <uint32_t>
+*
+* The identifier of the Xen event channel used to signal activity
+* in the ring buffer.
+*
+* ring-ref
+* Values: <uint32_t>
+* Notes: 6
+*
+* The Xen grant reference granting permission for the backend to map
+* the sole page in a single page sized ring buffer.
+*
+* ring-ref%u
+* Values: <uint32_t>
+* Notes: 6
+*
+* For a frontend providing a multi-page ring, a "number of ring pages"
+* sized list of nodes, each containing a Xen grant reference granting
+* permission for the backend to map the page of the ring located
+* at page index "%u". Page indexes are zero based.
+*
+* protocol
+* Values: string (XEN_IO_PROTO_ABI_*)
+* Default Value: XEN_IO_PROTO_ABI_NATIVE
+*
+* The machine ABI rules governing the format of all ring request and
+* response structures.
+*
+* ring-page-order
+* Values: <uint32_t>
+* Default Value: 0
+* Maximum Value: MAX(ffs(max-ring-pages) - 1, max-ring-page-order)
+* Notes: 1, 3
+*
+* The size of the frontend allocated request ring buffer in units
+* of lb(machine pages). (e.g. 0 == 1 page, 1 = 2 pages, 2 == 4 pages,
+* etc.).
+*
+* num-ring-pages
+* Values: <uint32_t>
+* Default Value: 1
+* Maximum Value: MAX(max-ring-pages,(0x1 << max-ring-page-order))
+* Notes: DEPRECATED, 2, 3
+*
+* The size of the frontend allocated request ring buffer in units of
+* machine pages. The value must be a power of 2.
+*
+* feature-persistent
+* Values: 0/1 (boolean)
+* Default Value: 0
+* Notes: 7, 8, 9
+*
+* A value of "1" indicates that the frontend will reuse the same grants
+* for all transactions, allowing the backend to map them with write
+* access (even when it should be read-only). If the frontend hits the
+* maximum number of allowed persistently mapped grants, it can fallback
+* to non persistent mode. This will cause a performance degradation,
+* since the the backend driver will still try to map those grants
+* persistently. Since the persistent grants protocol is compatible with
+* the previous protocol, a frontend driver can choose to work in
+* persistent mode even when the backend doesn't support it.
+*
+* It is recommended that the frontend driver stores the persistently
+* mapped grants in a LIFO queue, so a subset of all persistently mapped
+* grants gets used commonly. This is done in case the backend driver
+* decides to limit the maximum number of persistently mapped grants
+* to a value less than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST.
+*
+*------------------------- Virtual Device Properties -------------------------
+*
+* device-type
+* Values: "disk", "cdrom", "floppy", etc.
+*
+* virtual-device
+* Values: <uint32_t>
+*
+* A value indicating the physical device to virtualize within the
+* frontend's domain. (e.g. "The first ATA disk", "The third SCSI
+* disk", etc.)
+*
+* See docs/misc/vbd-interface.txt for details on the format of this
+* value.
+*
+* Notes
+* -----
+* (1) Multi-page ring buffer scheme first developed in the Citrix XenServer
+* PV drivers.
+* (2) Multi-page ring buffer scheme first used in some RedHat distributions
+* including a distribution deployed on certain nodes of the Amazon
+* EC2 cluster.
+* (3) Support for multi-page ring buffers was implemented independently,
+* in slightly different forms, by both Citrix and RedHat/Amazon.
+* For full interoperability, block front and backends should publish
+* identical ring parameters, adjusted for unit differences, to the
+* XenStore nodes used in both schemes.
+* (4) Devices that support discard functionality may internally allocate space
+* (discardable extents) in units that are larger than the exported logical
+* block size. If the backing device has such discardable extents the
+* backend should provide both discard-granularity and discard-alignment.
+* Providing just one of the two may be considered an error by the frontend.
+* Backends supporting discard should include discard-granularity and
+* discard-alignment even if it supports discarding individual sectors.
+* Frontends should assume discard-alignment == 0 and discard-granularity
+* == sector size if these keys are missing.
+* (5) The discard-alignment parameter allows a physical device to be
+* partitioned into virtual devices that do not necessarily begin or
+* end on a discardable extent boundary.
+* (6) When there is only a single page allocated to the request ring,
+* 'ring-ref' is used to communicate the grant reference for this
+* page to the backend. When using a multi-page ring, the 'ring-ref'
+* node is not created. Instead 'ring-ref0' - 'ring-refN' are used.
+* (7) When using persistent grants data has to be copied from/to the page
+* where the grant is currently mapped. The overhead of doing this copy
+* however doesn't suppress the speed improvement of not having to unmap
+* the grants.
+* (8) The frontend driver has to allow the backend driver to map all grants
+* with write access, even when they should be mapped read-only, since
+* further requests may reuse these grants and require write permissions.
+* (9) Linux implementation doesn't have a limit on the maximum number of
+* grants that can be persistently mapped in the frontend driver, but
+* due to the frontent driver implementation it should never be bigger
+* than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST.
+*(10) The discard-secure property may be present and will be set to 1 if the
+* backing device supports secure discard.
+*(11) Only used by Linux and NetBSD.
+*/
/*
- * STATE DIAGRAMS
- *
- *****************************************************************************
- * Startup *
- *****************************************************************************
- *
- * Tool stack creates front and back nodes with state XenbusStateInitialising.
- *
- * Front Back
- * ================================= =====================================
- * XenbusStateInitialising XenbusStateInitialising
- * o Query virtual device o Query backend device identification
- * properties. data.
- * o Setup OS device instance. o Open and validate backend device.
- * o Publish backend features and
- * transport parameters.
- * |
- * |
- * V
- * XenbusStateInitWait
- *
- * o Query backend features and
- * transport parameters.
- * o Allocate and initialize the
- * request ring.
- * o Publish transport parameters
- * that will be in effect during
- * this connection.
- * |
- * |
- * V
- * XenbusStateInitialised
- *
- * o Query frontend transport parameters.
- * o Connect to the request ring and
- * event channel.
- * o Publish backend device properties.
- * |
- * |
- * V
- * XenbusStateConnected
- *
- * o Query backend device properties.
- * o Finalize OS virtual device
- * instance.
- * |
- * |
- * V
- * XenbusStateConnected
- *
- * Note: Drivers that do not support any optional features, or the negotiation
- * of transport parameters, can skip certain states in the state machine:
- *
- * o A frontend may transition to XenbusStateInitialised without
- * waiting for the backend to enter XenbusStateInitWait. In this
- * case, default transport parameters are in effect and any
- * transport parameters published by the frontend must contain
- * their default values.
- *
- * o A backend may transition to XenbusStateInitialised, bypassing
- * XenbusStateInitWait, without waiting for the frontend to first
- * enter the XenbusStateInitialised state. In this case, default
- * transport parameters are in effect and any transport parameters
- * published by the backend must contain their default values.
- *
- * Drivers that support optional features and/or transport parameter
- * negotiation must tolerate these additional state transition paths.
- * In general this means performing the work of any skipped state
- * transition, if it has not already been performed, in addition to the
- * work associated with entry into the current state.
- */
+* Multiple hardware queues/rings:
+* If supported, the backend will write the key "multi-queue-max-queues" to
+* the directory for that vbd, and set its value to the maximum supported
+* number of queues.
+* Frontends that are aware of this feature and wish to use it can write the
+* key "multi-queue-num-queues" with the number they wish to use, which must be
+* greater than zero, and no more than the value reported by the backend in
+* "multi-queue-max-queues".
+*
+* For frontends requesting just one queue, the usual event-channel and
+* ring-ref keys are written as before, simplifying the backend processing
+* to avoid distinguishing between a frontend that doesn't understand the
+* multi-queue feature, and one that does, but requested only one queue.
+*
+* Frontends requesting two or more queues must not write the toplevel
+* event-channel and ring-ref keys, instead writing those keys under sub-keys
+* having the name "queue-N" where N is the integer ID of the queue/ring for
+* which those keys belong. Queues are indexed from zero.
+* For example, a frontend with two queues must write the following set of
+* queue-related keys:
+*
+* /local/domain/1/device/vbd/0/multi-queue-num-queues = "2"
+* /local/domain/1/device/vbd/0/queue-0 = ""
+* /local/domain/1/device/vbd/0/queue-0/ring-ref = "<ring-ref#0>"
+* /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn#0>"
+* /local/domain/1/device/vbd/0/queue-1 = ""
+* /local/domain/1/device/vbd/0/queue-1/ring-ref = "<ring-ref#1>"
+* /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn#1>"
+*
+* It is also possible to use multiple queues/rings together with
+* feature multi-page ring buffer.
+* For example, a frontend requests two queues/rings and the size of each ring
+* buffer is two pages must write the following set of related keys:
+*
+* /local/domain/1/device/vbd/0/multi-queue-num-queues = "2"
+* /local/domain/1/device/vbd/0/ring-page-order = "1"
+* /local/domain/1/device/vbd/0/queue-0 = ""
+* /local/domain/1/device/vbd/0/queue-0/ring-ref0 = "<ring-ref#0>"
+* /local/domain/1/device/vbd/0/queue-0/ring-ref1 = "<ring-ref#1>"
+* /local/domain/1/device/vbd/0/queue-0/event-channel = "<evtchn#0>"
+* /local/domain/1/device/vbd/0/queue-1 = ""
+* /local/domain/1/device/vbd/0/queue-1/ring-ref0 = "<ring-ref#2>"
+* /local/domain/1/device/vbd/0/queue-1/ring-ref1 = "<ring-ref#3>"
+* /local/domain/1/device/vbd/0/queue-1/event-channel = "<evtchn#1>"
+*
+*/
/*
- * REQUEST CODES.
- */
+* STATE DIAGRAMS
+*
+*****************************************************************************
+* Startup *
+*****************************************************************************
+*
+* Tool stack creates front and back nodes with state XenbusStateInitialising.
+*
+* Front Back
+* ================================= =====================================
+* XenbusStateInitialising XenbusStateInitialising
+* o Query virtual device o Query backend device identification
+* properties. data.
+* o Setup OS device instance. o Open and validate backend device.
+* o Publish backend features and
+* transport parameters.
+* |
+* |
+* V
+* XenbusStateInitWait
+*
+* o Query backend features and
+* transport parameters.
+* o Allocate and initialize the
+* request ring.
+* o Publish transport parameters
+* that will be in effect during
+* this connection.
+* |
+* |
+* V
+* XenbusStateInitialised
+*
+* o Query frontend transport parameters.
+* o Connect to the request ring and
+* event channel.
+* o Publish backend device properties.
+* |
+* |
+* V
+* XenbusStateConnected
+*
+* o Query backend device properties.
+* o Finalize OS virtual device
+* instance.
+* |
+* |
+* V
+* XenbusStateConnected
+*
+* Note: Drivers that do not support any optional features, or the negotiation
+* of transport parameters, can skip certain states in the state machine:
+*
+* o A frontend may transition to XenbusStateInitialised without
+* waiting for the backend to enter XenbusStateInitWait. In this
+* case, default transport parameters are in effect and any
+* transport parameters published by the frontend must contain
+* their default values.
+*
+* o A backend may transition to XenbusStateInitialised, bypassing
+* XenbusStateInitWait, without waiting for the frontend to first
+* enter the XenbusStateInitialised state. In this case, default
+* transport parameters are in effect and any transport parameters
+* published by the backend must contain their default values.
+*
+* Drivers that support optional features and/or transport parameter
+* negotiation must tolerate these additional state transition paths.
+* In general this means performing the work of any skipped state
+* transition, if it has not already been performed, in addition to the
+* work associated with entry into the current state.
+*/
+
+/*
+* REQUEST CODES.
+*/
#define BLKIF_OP_READ 0
#define BLKIF_OP_WRITE 1
/*
- * All writes issued prior to a request with the BLKIF_OP_WRITE_BARRIER
- * operation code ("barrier request") must be completed prior to the
- * execution of the barrier request. All writes issued after the barrier
- * request must not execute until after the completion of the barrier request.
- *
- * Optional. See "feature-barrier" XenBus node documentation above.
- */
+* All writes issued prior to a request with the BLKIF_OP_WRITE_BARRIER
+* operation code ("barrier request") must be completed prior to the
+* execution of the barrier request. All writes issued after the barrier
+* request must not execute until after the completion of the barrier request.
+*
+* Optional. See "feature-barrier" XenBus node documentation above.
+*/
#define BLKIF_OP_WRITE_BARRIER 2
/*
- * Commit any uncommitted contents of the backing device's volatile cache
- * to stable storage.
- *
- * Optional. See "feature-flush-cache" XenBus node documentation above.
- */
+* Commit any uncommitted contents of the backing device's volatile cache
+* to stable storage.
+*
+* Optional. See "feature-flush-cache" XenBus node documentation above.
+*/
#define BLKIF_OP_FLUSH_DISKCACHE 3
/*
- * Used in SLES sources for device specific command packet
- * contained within the request. Reserved for that purpose.
- */
+* Used in SLES sources for device specific command packet
+* contained within the request. Reserved for that purpose.
+*/
#define BLKIF_OP_RESERVED_1 4
/*
- * Indicate to the backend device that a region of storage is no longer in
- * use, and may be discarded at any time without impact to the client. If
- * the BLKIF_DISCARD_SECURE flag is set on the request, all copies of the
- * discarded region on the device must be rendered unrecoverable before the
- * command returns.
- *
- * This operation is analogous to performing a trim (ATA) or unamp (SCSI),
- * command on a native device.
- *
- * More information about trim/unmap operations can be found 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
- *
- * Optional. See "feature-discard", "discard-alignment",
- * "discard-granularity", and "discard-secure" in the XenBus node
- * documentation above.
- */
+* Indicate to the backend device that a region of storage is no longer in
+* use, and may be discarded at any time without impact to the client. If
+* the BLKIF_DISCARD_SECURE flag is set on the request, all copies of the
+* discarded region on the device must be rendered unrecoverable before the
+* command returns.
+*
+* This operation is analogous to performing a trim (ATA) or unamp (SCSI),
+* command on a native device.
+*
+* More information about trim/unmap operations can be found 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
+*
+* Optional. See "feature-discard", "discard-alignment",
+* "discard-granularity", and "discard-secure" in the XenBus node
+* documentation above.
+*/
#define BLKIF_OP_DISCARD 5
/*
- * Recognized if "feature-max-indirect-segments" in present in the backend
- * xenbus info. The "feature-max-indirect-segments" node contains the maximum
- * number of segments allowed by the backend per request. If the node is
- * present, the frontend might use blkif_request_indirect structs in order to
- * issue requests with more than BLKIF_MAX_SEGMENTS_PER_REQUEST (11). The
- * maximum number of indirect segments is fixed by the backend, but the
- * frontend can issue requests with any number of indirect segments as long as
- * 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!
- */
+* Recognized if "feature-max-indirect-segments" in present in the backend
+* xenbus info. The "feature-max-indirect-segments" node contains the maximum
+* number of segments allowed by the backend per request. If the node is
+* present, the frontend might use blkif_request_indirect structs in order to
+* issue requests with more than BLKIF_MAX_SEGMENTS_PER_REQUEST (11). The
+* maximum number of indirect segments is fixed by the backend, but the
+* frontend can issue requests with any number of indirect segments as long as
+* 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.
- */
+* 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.
- */
+* 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.
- */
+* 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). */
+ /* @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.
- */
+* Starting ring element for any I/O request.
+*/
struct blkif_request {
uint8_t operation; /* BLKIF_OP_??? */
uint8_t nr_segments; /* number of segments */
@@ -541,9 +635,9 @@ struct blkif_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)
- */
+* 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 */
@@ -577,18 +671,18 @@ struct blkif_response {
typedef struct blkif_response blkif_response_t;
/*
- * STATUS RETURN CODES.
- */
- /* Operation not supported (only happens on barrier writes). */
+* STATUS RETURN CODES.
+*/
+/* Operation not supported (only happens on barrier writes). */
#define BLKIF_RSP_EOPNOTSUPP -2
- /* Operation failed for some unspecified reason (-EIO). */
+/* Operation failed for some unspecified reason (-EIO). */
#define BLKIF_RSP_ERROR -1
- /* Operation completed successfully. */
+/* Operation completed successfully. */
#define BLKIF_RSP_OKAY 0
/*
- * Generate blkif ring structures and types.
- */
+* Generate blkif ring structures and types.
+*/
DEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response);
#define VDISK_CDROM 0x1
@@ -598,11 +692,11 @@ DEFINE_RING_TYPES(blkif, struct blkif_request, struct
blkif_response);
#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:
- */
+* Local variables:
+* mode: C
+* c-file-style: "BSD"
+* c-basic-offset: 4
+* tab-width: 4
+* indent-tabs-mode: nil
+* End:
+*/
--
2.16.2.windows.1
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