Release 4.7 include/xen/interface/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;
/*
* 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.
*/
#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-alignment' - 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
/*
* 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(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
#define BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST 8
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;
};
struct blkif_request_rw {
uint8_t nr_segments; /* number of segments */
blkif_vdev_t handle; /* only for read/write requests */
#ifndef CONFIG_X86_32
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 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 */
#ifndef CONFIG_X86_32
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 */
#ifndef CONFIG_X86_32
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_indirect {
uint8_t indirect_op;
uint16_t nr_segments;
#ifndef CONFIG_X86_32
uint32_t _pad1; /* offsetof(blkif_...,u.indirect.id) == 8 */
#endif
uint64_t id;
blkif_sector_t sector_number;
blkif_vdev_t handle;
uint16_t _pad2;
grant_ref_t indirect_grefs[BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST];
#ifndef CONFIG_X86_32
uint32_t _pad3; /* make it 64 byte aligned */
#else
uint64_t _pad3; /* make it 64 byte aligned */
#endif
} __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;
struct blkif_request_indirect indirect;
}
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__ */
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