--- /dev/null
+/******************************************************************************
+ * 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-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__ */
Code Review / kvmfornfv.git / blobdiff