include/xen/interface/io/blkif.h - maze/linux - Git at Google

 /******************************************************************************
  * blkif.h
  *
  * Unified block-device I/O interface for Xen guest OSes.
  *
  * Copyright (c) 2003-2004, Keir Fraser
  */

 #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()).
  */

 typedef uint16_t blkif_vdev_t;
 typedef uint64_t blkif_sector_t;

 /*
  * REQUEST CODES.
  */
 #define BLKIF_OP_READ              0
 #define BLKIF_OP_WRITE             1
 /*
  * Recognised only if "feature-barrier" is present in backend xenbus info.
  * The "feature_barrier" node contains a boolean indicating whether barrier
  * requests are likely to succeed or fail. Either way, a barrier request
  * may fail at any time with BLKIF_RSP_EOPNOTSUPP if it is unsupported by
  * the underlying block-device hardware. The boolean simply indicates whether
  * or not it is worthwhile for the frontend to attempt barrier requests.
  * If a backend does not recognise BLKIF_OP_WRITE_BARRIER, it should *not*
  * create the "feature-barrier" node!
  */
 #define BLKIF_OP_WRITE_BARRIER     2

 /*
  * Recognised if "feature-flush-cache" is present in backend xenbus
  * info.  A flush will ask the underlying storage hardware to flush its
  * non-volatile caches as appropriate.  The "feature-flush-cache" node
  * contains a boolean indicating whether flush requests are likely to
  * succeed or fail. Either way, a flush request may fail at any time
  * with BLKIF_RSP_EOPNOTSUPP if it is unsupported by the underlying
  * block-device hardware. The boolean simply indicates whether or not it
  * is worthwhile for the frontend to attempt flushes.  If a backend does
  * not recognise BLKIF_OP_WRITE_FLUSH_CACHE, it should *not* create the
  * "feature-flush-cache" node!
  */
 #define BLKIF_OP_FLUSH_DISKCACHE   3

 /*
  * Recognised only if "feature-discard" is present in backend xenbus info.
  * The "feature-discard" node contains a boolean indicating whether trim
  * (ATA) or unmap (SCSI) - conviently called discard requests are likely
  * to succeed or fail. Either way, a discard request
  * may fail at any time with BLKIF_RSP_EOPNOTSUPP if it is unsupported by
  * the underlying block-device hardware. The boolean simply indicates whether
  * or not it is worthwhile for the frontend to attempt discard requests.
  * If a backend does not recognise BLKIF_OP_DISCARD, it should *not*
  * create the "feature-discard" node!
  *
  * Discard operation is a request for the underlying block device to mark
  * extents to be erased. However, discard does not guarantee that the blocks
  * will be erased from the device - it is just a hint to the device
  * controller that these blocks are no longer in use. What the device
  * controller does with that information is left to the controller.
  * Discard operations are passed with sector_number as the
  * sector index to begin discard operations at and nr_sectors as the number of
  * sectors to be discarded. The specified sectors should be discarded if the
  * underlying block device supports trim (ATA) or unmap (SCSI) operations,
  * or a BLKIF_RSP_EOPNOTSUPP  should be returned.
  * More information about trim/unmap operations 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
  * The backend can optionally provide three extra XenBus attributes to
  * further optimize the discard functionality:
  * 'discard-aligment' - Devices that support discard functionality may
  * internally allocate space in units that are bigger than the exported
  * logical block size. The discard-alignment parameter indicates how many bytes
  * the beginning of the partition is offset from the internal allocation unit's
  * natural alignment.
  * 'discard-granularity'  - Devices that support discard functionality may
  * internally allocate space using units that are bigger than the logical block
  * size. The discard-granularity parameter indicates the size of the internal
  * allocation unit in bytes if reported by the device. Otherwise the
  * discard-granularity will be set to match the device's physical block size.
  * 'discard-secure' - All copies of the discarded sectors (potentially created
  * by garbage collection) must also be erased.  To use this feature, the flag
  * BLKIF_DISCARD_SECURE must be set in the blkif_request_trim.
  */
 #define BLKIF_OP_DISCARD           5

 /*
  * Maximum scatter/gather segments per request.
  * This is carefully chosen so that sizeof(struct blkif_ring) <= 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

 struct blkif_request_rw {
 	uint8_t        nr_segments;  /* number of segments                   */
 	blkif_vdev_t   handle;       /* only for read/write requests         */
 #ifdef CONFIG_X86_64
 	uint32_t       _pad1;	     /* offsetof(blkif_request,u.rw.id) == 8 */
 #endif
 	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 {
 		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;
 	} seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 } __attribute__((__packed__));

 struct blkif_request_discard {
 	uint8_t        flag;         /* BLKIF_DISCARD_SECURE or zero.        */
 #define BLKIF_DISCARD_SECURE (1<<0)  /* ignored if discard-secure=0          */
 	blkif_vdev_t   _pad1;        /* only for read/write requests         */
 #ifdef CONFIG_X86_64
 	uint32_t       _pad2;        /* offsetof(blkif_req..,u.discard.id)==8*/
 #endif
 	uint64_t       id;           /* private guest value, echoed in resp  */
 	blkif_sector_t sector_number;
 	uint64_t       nr_sectors;
 	uint8_t        _pad3;
 } __attribute__((__packed__));

 struct blkif_request_other {
 	uint8_t      _pad1;
 	blkif_vdev_t _pad2;        /* only for read/write requests         */
 #ifdef CONFIG_X86_64
 	uint32_t     _pad3;        /* offsetof(blkif_req..,u.other.id)==8*/
 #endif
 	uint64_t     id;           /* private guest value, echoed in resp  */
 } __attribute__((__packed__));

 struct blkif_request {
 	uint8_t        operation;    /* BLKIF_OP_???                         */
 	union {
 		struct blkif_request_rw rw;
 		struct blkif_request_discard discard;
 		struct blkif_request_other other;
 	} u;
 } __attribute__((__packed__));

 struct blkif_response {
 	uint64_t        id;              /* copied from request */
 	uint8_t         operation;       /* copied from request */
 	int16_t         status;          /* BLKIF_RSP_???       */
 };

 /*
  * 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

 /* Xen-defined major numbers for virtual disks, they look strangely
  * familiar */
 #define XEN_IDE0_MAJOR	3
 #define XEN_IDE1_MAJOR	22
 #define XEN_SCSI_DISK0_MAJOR	8
 #define XEN_SCSI_DISK1_MAJOR	65
 #define XEN_SCSI_DISK2_MAJOR	66
 #define XEN_SCSI_DISK3_MAJOR	67
 #define XEN_SCSI_DISK4_MAJOR	68
 #define XEN_SCSI_DISK5_MAJOR	69
 #define XEN_SCSI_DISK6_MAJOR	70
 #define XEN_SCSI_DISK7_MAJOR	71
 #define XEN_SCSI_DISK8_MAJOR	128
 #define XEN_SCSI_DISK9_MAJOR	129
 #define XEN_SCSI_DISK10_MAJOR	130
 #define XEN_SCSI_DISK11_MAJOR	131
 #define XEN_SCSI_DISK12_MAJOR	132
 #define XEN_SCSI_DISK13_MAJOR	133
 #define XEN_SCSI_DISK14_MAJOR	134
 #define XEN_SCSI_DISK15_MAJOR	135

 #endif /* __XEN_PUBLIC_IO_BLKIF_H__ */
	/******************************************************************************
	* blkif.h
	*
	* Unified block-device I/O interface for Xen guest OSes.
	*
	* Copyright (c) 2003-2004, Keir Fraser
	*/

	#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()).
	*/

	typedef uint16_t blkif_vdev_t;
	typedef uint64_t blkif_sector_t;

	/*
	* REQUEST CODES.
	*/
	#define BLKIF_OP_READ 0
	#define BLKIF_OP_WRITE 1
	/*
	* Recognised only if "feature-barrier" is present in backend xenbus info.
	* The "feature_barrier" node contains a boolean indicating whether barrier
	* requests are likely to succeed or fail. Either way, a barrier request
	* may fail at any time with BLKIF_RSP_EOPNOTSUPP if it is unsupported by
	* the underlying block-device hardware. The boolean simply indicates whether
	* or not it is worthwhile for the frontend to attempt barrier requests.
	* If a backend does not recognise BLKIF_OP_WRITE_BARRIER, it should not
	* create the "feature-barrier" node!
	*/
	#define BLKIF_OP_WRITE_BARRIER 2

	/*
	* Recognised if "feature-flush-cache" is present in backend xenbus
	* info. A flush will ask the underlying storage hardware to flush its
	* non-volatile caches as appropriate. The "feature-flush-cache" node
	* contains a boolean indicating whether flush requests are likely to
	* succeed or fail. Either way, a flush request may fail at any time
	* with BLKIF_RSP_EOPNOTSUPP if it is unsupported by the underlying
	* block-device hardware. The boolean simply indicates whether or not it
	* is worthwhile for the frontend to attempt flushes. If a backend does
	* not recognise BLKIF_OP_WRITE_FLUSH_CACHE, it should not create the
	* "feature-flush-cache" node!
	*/
	#define BLKIF_OP_FLUSH_DISKCACHE 3

	/*
	* Recognised only if "feature-discard" is present in backend xenbus info.
	* The "feature-discard" node contains a boolean indicating whether trim
	* (ATA) or unmap (SCSI) - conviently called discard requests are likely
	* to succeed or fail. Either way, a discard request
	* may fail at any time with BLKIF_RSP_EOPNOTSUPP if it is unsupported by
	* the underlying block-device hardware. The boolean simply indicates whether
	* or not it is worthwhile for the frontend to attempt discard requests.
	* If a backend does not recognise BLKIF_OP_DISCARD, it should not
	* create the "feature-discard" node!
	*
	* Discard operation is a request for the underlying block device to mark
	* extents to be erased. However, discard does not guarantee that the blocks
	* will be erased from the device - it is just a hint to the device
	* controller that these blocks are no longer in use. What the device
	* controller does with that information is left to the controller.
	* Discard operations are passed with sector_number as the
	* sector index to begin discard operations at and nr_sectors as the number of
	* sectors to be discarded. The specified sectors should be discarded if the
	* underlying block device supports trim (ATA) or unmap (SCSI) operations,
	* or a BLKIF_RSP_EOPNOTSUPP should be returned.
	* More information about trim/unmap operations 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
	* The backend can optionally provide three extra XenBus attributes to
	* further optimize the discard functionality:
	* 'discard-aligment' - Devices that support discard functionality may
	* internally allocate space in units that are bigger than the exported
	* logical block size. The discard-alignment parameter indicates how many bytes
	* the beginning of the partition is offset from the internal allocation unit's
	* natural alignment.
	* 'discard-granularity' - Devices that support discard functionality may
	* internally allocate space using units that are bigger than the logical block
	* size. The discard-granularity parameter indicates the size of the internal
	* allocation unit in bytes if reported by the device. Otherwise the
	* discard-granularity will be set to match the device's physical block size.
	* 'discard-secure' - All copies of the discarded sectors (potentially created
	* by garbage collection) must also be erased. To use this feature, the flag
	* BLKIF_DISCARD_SECURE must be set in the blkif_request_trim.
	*/
	#define BLKIF_OP_DISCARD 5

	/*
	* Maximum scatter/gather segments per request.
	* This is carefully chosen so that sizeof(struct blkif_ring) <= 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

	struct blkif_request_rw {
	uint8_t nr_segments; /* number of segments */
	blkif_vdev_t handle; /* only for read/write requests */
	#ifdef CONFIG_X86_64
	uint32_t _pad1; /* offsetof(blkif_request,u.rw.id) == 8 */
	#endif
	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 {
	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;
	} seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
	} __attribute__((__packed__));

	struct blkif_request_discard {
	uint8_t flag; /* BLKIF_DISCARD_SECURE or zero. */
	#define BLKIF_DISCARD_SECURE (1<<0) /* ignored if discard-secure=0 */
	blkif_vdev_t _pad1; /* only for read/write requests */
	#ifdef CONFIG_X86_64
	uint32_t _pad2; /* offsetof(blkif_req..,u.discard.id)==8*/
	#endif
	uint64_t id; /* private guest value, echoed in resp */
	blkif_sector_t sector_number;
	uint64_t nr_sectors;
	uint8_t _pad3;
	} __attribute__((__packed__));

	struct blkif_request_other {
	uint8_t _pad1;
	blkif_vdev_t _pad2; /* only for read/write requests */
	#ifdef CONFIG_X86_64
	uint32_t _pad3; /* offsetof(blkif_req..,u.other.id)==8*/
	#endif
	uint64_t id; /* private guest value, echoed in resp */
	} __attribute__((__packed__));

	struct blkif_request {
	uint8_t operation; /* BLKIF_OP_??? */
	union {
	struct blkif_request_rw rw;
	struct blkif_request_discard discard;
	struct blkif_request_other other;
	} u;
	} __attribute__((__packed__));

	struct blkif_response {
	uint64_t id; /* copied from request */
	uint8_t operation; /* copied from request */
	int16_t status; /* BLKIF_RSP_??? */
	};

	/*
	* 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

	/* Xen-defined major numbers for virtual disks, they look strangely
	* familiar */
	#define XEN_IDE0_MAJOR 3
	#define XEN_IDE1_MAJOR 22
	#define XEN_SCSI_DISK0_MAJOR 8
	#define XEN_SCSI_DISK1_MAJOR 65
	#define XEN_SCSI_DISK2_MAJOR 66
	#define XEN_SCSI_DISK3_MAJOR 67
	#define XEN_SCSI_DISK4_MAJOR 68
	#define XEN_SCSI_DISK5_MAJOR 69
	#define XEN_SCSI_DISK6_MAJOR 70
	#define XEN_SCSI_DISK7_MAJOR 71
	#define XEN_SCSI_DISK8_MAJOR 128
	#define XEN_SCSI_DISK9_MAJOR 129
	#define XEN_SCSI_DISK10_MAJOR 130
	#define XEN_SCSI_DISK11_MAJOR 131
	#define XEN_SCSI_DISK12_MAJOR 132
	#define XEN_SCSI_DISK13_MAJOR 133
	#define XEN_SCSI_DISK14_MAJOR 134
	#define XEN_SCSI_DISK15_MAJOR 135

	#endif /* __XEN_PUBLIC_IO_BLKIF_H__ */