1 /****************************************************************************** 2 * blkif.h 3 * 4 * Unified block-device I/O interface for Xen guest OSes. 5 * 6 * Copyright (c) 2003-2004, Keir Fraser 7 */ 8 9 #ifndef __XEN_PUBLIC_IO_BLKIF_H__ 10 #define __XEN_PUBLIC_IO_BLKIF_H__ 11 12 #include "ring.h" 13 #include "../grant_table.h" 14 15 /* 16 * Front->back notifications: When enqueuing a new request, sending a 17 * notification can be made conditional on req_event (i.e., the generic 18 * hold-off mechanism provided by the ring macros). Backends must set 19 * req_event appropriately (e.g., using RING_FINAL_CHECK_FOR_REQUESTS()). 20 * 21 * Back->front notifications: When enqueuing a new response, sending a 22 * notification can be made conditional on rsp_event (i.e., the generic 23 * hold-off mechanism provided by the ring macros). Frontends must set 24 * rsp_event appropriately (e.g., using RING_FINAL_CHECK_FOR_RESPONSES()). 25 */ 26 27 typedef uint16_t blkif_vdev_t; 28 typedef uint64_t blkif_sector_t; 29 30 /* 31 * REQUEST CODES. 32 */ 33 #define BLKIF_OP_READ 0 34 #define BLKIF_OP_WRITE 1 35 /* 36 * Recognised only if "feature-barrier" is present in backend xenbus info. 37 * The "feature_barrier" node contains a boolean indicating whether barrier 38 * requests are likely to succeed or fail. Either way, a barrier request 39 * may fail at any time with BLKIF_RSP_EOPNOTSUPP if it is unsupported by 40 * the underlying block-device hardware. The boolean simply indicates whether 41 * or not it is worthwhile for the frontend to attempt barrier requests. 42 * If a backend does not recognise BLKIF_OP_WRITE_BARRIER, it should *not* 43 * create the "feature-barrier" node! 44 */ 45 #define BLKIF_OP_WRITE_BARRIER 2 46 47 /* 48 * Maximum scatter/gather segments per request. 49 * This is carefully chosen so that sizeof(struct blkif_ring) <= PAGE_SIZE. 50 * NB. This could be 12 if the ring indexes weren't stored in the same page. 51 */ 52 #define BLKIF_MAX_SEGMENTS_PER_REQUEST 11 53 54 struct blkif_request { 55 uint8_t operation; /* BLKIF_OP_??? */ 56 uint8_t nr_segments; /* number of segments */ 57 blkif_vdev_t handle; /* only for read/write requests */ 58 uint64_t id; /* private guest value, echoed in resp */ 59 blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */ 60 struct blkif_request_segment { 61 grant_ref_t gref; /* reference to I/O buffer frame */ 62 /* @first_sect: first sector in frame to transfer (inclusive). */ 63 /* @last_sect: last sector in frame to transfer (inclusive). */ 64 uint8_t first_sect, last_sect; 65 } seg[BLKIF_MAX_SEGMENTS_PER_REQUEST]; 66 }; 67 68 struct blkif_response { 69 uint64_t id; /* copied from request */ 70 uint8_t operation; /* copied from request */ 71 int16_t status; /* BLKIF_RSP_??? */ 72 }; 73 74 /* 75 * STATUS RETURN CODES. 76 */ 77 /* Operation not supported (only happens on barrier writes). */ 78 #define BLKIF_RSP_EOPNOTSUPP -2 79 /* Operation failed for some unspecified reason (-EIO). */ 80 #define BLKIF_RSP_ERROR -1 81 /* Operation completed successfully. */ 82 #define BLKIF_RSP_OKAY 0 83 84 /* 85 * Generate blkif ring structures and types. 86 */ 87 88 DEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response); 89 90 #define VDISK_CDROM 0x1 91 #define VDISK_REMOVABLE 0x2 92 #define VDISK_READONLY 0x4 93 94 #endif /* __XEN_PUBLIC_IO_BLKIF_H__ */ 95