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/******************************************************************************
* 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__
#include <xen/interface/io/ring.h>
#include <xen/interface/grant_table.h>
/*
* Front->back notifications: When enqueuing a new request, sending a
* notification can be made conditional on req_event (i.e., the generic
* hold-off mechanism provided by the ring macros). Backends must set
* req_event appropriately (e.g., using RING_FINAL_CHECK_FOR_REQUESTS()).
*
* Back->front notifications: When enqueuing a new response, sending a
* notification can be made conditional on rsp_event (i.e., the generic
* hold-off mechanism provided by the ring macros). Frontends must set
* rsp_event appropriately (e.g., using RING_FINAL_CHECK_FOR_RESPONSES()).
*/
#ifndef blkif_vdev_t
#define blkif_vdev_t uint16_t
#endif
#define blkif_sector_t uint64_t
/*
* 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.
*
* 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.
*
*----------------------- 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: 2, 3
*
* The maximum supported size of the request ring buffer in units of
* machine pages. The value must be a power of 2.
*
* max-requests <uint32_t>
* Default Value: BLKIF_MAX_RING_REQUESTS(PAGE_SIZE)
* Maximum Value: BLKIF_MAX_RING_REQUESTS(PAGE_SIZE * max-ring-pages)
*
* The maximum number of concurrent, logical requests that will be
* issued by the backend.
*
* Note: A logical request may span multiple ring entries.
*
* max-request-segments
* Values: <uint8_t>
* Default Value: BLKIF_MAX_SEGMENTS_PER_HEADER_BLOCK
* Maximum Value: BLKIF_MAX_SEGMENTS_PER_REQUEST
*
* The maximum value of blkif_request.nr_segments supported by
* the backend.
*
* max-request-size
* Values: <uint32_t>
* Default Value: BLKIF_MAX_SEGMENTS_PER_HEADER_BLOCK * PAGE_SIZE
* Maximum Value: BLKIF_MAX_SEGMENTS_PER_REQUEST * PAGE_SIZE
*
* The maximum amount of data, in bytes, that can be referenced by a
* request type that accesses frontend memory (currently BLKIF_OP_READ,
* BLKIF_OP_WRITE, or BLKIF_OP_WRITE_BARRIER).
*
*------------------------- Backend Device Properties -------------------------
*
* discard-aligment
* 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
*
* 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 native sector size, in bytes, of the backend device.
*
* sectors
* Values: <uint64_t>
*
* The size of the backend device, expressed in units of its native
* 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 "num-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: 2, 3
*
* The size of the frontend allocated request ring buffer in units of
* machine pages. The value must be a power of 2.
*
* max-requests
* Values: <uint32_t>
* Default Value: BLKIF_MAX_RING_REQUESTS(PAGE_SIZE)
* Maximum Value: BLKIF_MAX_RING_REQUESTS(PAGE_SIZE * max-ring_pages)
*
* The maximum number of concurrent, logical requests that will be
* issued by the frontend.
*
* Note: A logical request may span multiple ring entries.
*
* max-request-segments
* Values: <uint8_t>
* Default Value: BLKIF_MAX_SEGMENTS_PER_HEADER_BLOCK
* Maximum Value: MIN(255, backend/max-request-segments)
*
* The maximum value the frontend will set in the
* blkif_request.nr_segments field.
*
* max-request-size
* Values: <uint32_t>
* Default Value: BLKIF_MAX_SEGMENTS_PER_HEADER_BLOCK * PAGE_SIZE
* Maximum Value: max-request-segments * PAGE_SIZE
*
* The maximum amount of data, in bytes, that can be referenced by
* a request type that accesses frontend memory (currently BLKIF_OP_READ,
* BLKIF_OP_WRITE, or BLKIF_OP_WRITE_BARRIER).
*
*------------------------- 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.
* (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.
*/
/*
* 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.
*/
#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.
*/
#define BLKIF_OP_FLUSH_DISKCACHE 3
/*
* Used in SLES sources for device specific command packet
* contained within the request. Reserved for that purpose.
*/
#define BLKIF_OP_RESERVED_1 4
/*
* 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
/*
* Maximum scatter/gather segments associated with a request header block.
* 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_HEADER_BLOCK 11
/*
* Maximum scatter/gather segments associated with a segment block.
*/
#define BLKIF_MAX_SEGMENTS_PER_SEGMENT_BLOCK 14
/*
* Maximum scatter/gather segments per request (header + segment blocks).
*/
#define BLKIF_MAX_SEGMENTS_PER_REQUEST 255
/*
* NB. first_sect and last_sect in blkif_request_segment, as well as
* sector_number in blkif_request, are always expressed in 512-byte units.
* However they must be properly aligned to the real sector size of the
* physical disk, which is reported in the "sector-size" node in the backend
* xenbus info. Also the xenbus "sectors" node is expressed in 512-byte units.
*/
struct blkif_request_segment {
grant_ref_t gref; /* reference to I/O buffer frame */
/* @first_sect: first sector in frame to transfer (inclusive). */
/* @last_sect: last sector in frame to transfer (inclusive). */
uint8_t first_sect, last_sect;
};
typedef struct blkif_request_segment blkif_request_segment_t;
/*
* Starting ring element for any I/O request.
*
* One or more segment blocks can be inserted into the request ring
* just after a blkif_request_t, allowing requests to operate on
* up to BLKIF_MAX_SEGMENTS_PER_REQUEST.
*
* BLKIF_SEGS_TO_BLOCKS() can be used on blkif_requst.nr_segments
* to determine the number of contiguous ring entries associated
* with this request.
*
* Note: Due to the way Xen request rings operate, the producer and
* consumer indices of the ring must be incremented by the
* BLKIF_SEGS_TO_BLOCKS() value of the associated request.
* (e.g. a response to a 3 ring entry request must also consume
* 3 entries in the ring, even though only the first ring entry
* in the response has any data.)
*/
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) */
blkif_request_segment_t seg[BLKIF_MAX_SEGMENTS_PER_HEADER_BLOCK];
};
typedef struct blkif_request blkif_request_t;
/*
* A segment block is a ring request structure that contains only
* segment data.
*
* sizeof(struct blkif_segment_block) <= sizeof(struct blkif_request)
*/
struct blkif_segment_block {
blkif_request_segment_t seg[BLKIF_MAX_SEGMENTS_PER_SEGMENT_BLOCK];
};
typedef struct blkif_segment_block blkif_segment_block_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_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);
/*
* Index to, and treat as a segment block, an entry in the ring.
*/
#define BLKRING_GET_SEG_BLOCK(_r, _idx) \
(((blkif_segment_block_t *)RING_GET_REQUEST(_r, _idx))->seg)
/*
* The number of ring request blocks required to handle an I/O
* request containing _segs segments.
*/
#define BLKIF_SEGS_TO_BLOCKS(_segs) \
((((_segs - BLKIF_MAX_SEGMENTS_PER_HEADER_BLOCK) \
+ (BLKIF_MAX_SEGMENTS_PER_SEGMENT_BLOCK - 1)) \
/ BLKIF_MAX_SEGMENTS_PER_SEGMENT_BLOCK) + /*header_block*/1)
#define VDISK_CDROM 0x1
#define VDISK_REMOVABLE 0x2
#define VDISK_READONLY 0x4
#endif /* __XEN_PUBLIC_IO_BLKIF_H__ */
/*
* Local variables:
* mode: C
* c-set-style: "BSD"
* c-basic-offset: 4
* tab-width: 4
* indent-tabs-mode: nil
* End:
*/