sys/dev/virtio/block/virtio_blk.c

   1 /*-
   2  * Copyright (c) 2011, Bryan Venteicher <bryanv@FreeBSD.org>
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice unmodified, this list of conditions, and the following
  10  *    disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  25  */
  26
  27 /* Driver for VirtIO block devices. */
  28
  29 #include <sys/cdefs.h>
  30 __FBSDID("$FreeBSD$");
  31
  32 #include <sys/param.h>
  33 #include <sys/systm.h>
  34 #include <sys/kernel.h>
  35 #include <sys/bio.h>
  36 #include <sys/malloc.h>
  37 #include <sys/module.h>
  38 #include <sys/sglist.h>
  39 #include <sys/sysctl.h>
  40 #include <sys/lock.h>
  41 #include <sys/mutex.h>
  42 #include <sys/queue.h>
  43
  44 #include <geom/geom_disk.h>
  45
  46 #include <machine/bus.h>
  47 #include <machine/resource.h>
  48 #include <sys/bus.h>
  49 #include <sys/rman.h>
  50
  51 #include <dev/virtio/virtio.h>
  52 #include <dev/virtio/virtqueue.h>
  53 #include <dev/virtio/block/virtio_blk.h>
  54
  55 #include "virtio_if.h"
  56
  57 struct vtblk_request {
  58         struct virtio_blk_outhdr         vbr_hdr;
  59         struct bio                      *vbr_bp;
  60         uint8_t                          vbr_ack;
  61
  62         TAILQ_ENTRY(vtblk_request)       vbr_link;
  63 };
  64
  65 enum vtblk_cache_mode {
  66         VTBLK_CACHE_WRITETHROUGH,
  67         VTBLK_CACHE_WRITEBACK,
  68         VTBLK_CACHE_MAX
  69 };
  70
  71 struct vtblk_softc {
  72         device_t                 vtblk_dev;
  73         struct mtx               vtblk_mtx;
  74         uint64_t                 vtblk_features;
  75         uint32_t                 vtblk_flags;
  76 #define VTBLK_FLAG_INDIRECT     0x0001
  77 #define VTBLK_FLAG_READONLY     0x0002
  78 #define VTBLK_FLAG_DETACH       0x0004
  79 #define VTBLK_FLAG_SUSPEND      0x0008
  80 #define VTBLK_FLAG_DUMPING      0x0010
  81 #define VTBLK_FLAG_BARRIER      0x0020
  82 #define VTBLK_FLAG_WC_CONFIG    0x0040
  83
  84         struct virtqueue        *vtblk_vq;
  85         struct sglist           *vtblk_sglist;
  86         struct disk             *vtblk_disk;
  87
  88         struct bio_queue_head    vtblk_bioq;
  89         TAILQ_HEAD(, vtblk_request)
  90                                  vtblk_req_free;
  91         TAILQ_HEAD(, vtblk_request)
  92                                  vtblk_req_ready;
  93         struct vtblk_request    *vtblk_req_ordered;
  94
  95         int                      vtblk_max_nsegs;
  96         int                      vtblk_request_count;
  97         enum vtblk_cache_mode    vtblk_write_cache;
  98
  99         struct vtblk_request     vtblk_dump_request;
 100 };
 101
 102 static struct virtio_feature_desc vtblk_feature_desc[] = {
 103         { VIRTIO_BLK_F_BARRIER,         "HostBarrier"   },
 104         { VIRTIO_BLK_F_SIZE_MAX,        "MaxSegSize"    },
 105         { VIRTIO_BLK_F_SEG_MAX,         "MaxNumSegs"    },
 106         { VIRTIO_BLK_F_GEOMETRY,        "DiskGeometry"  },
 107         { VIRTIO_BLK_F_RO,              "ReadOnly"      },
 108         { VIRTIO_BLK_F_BLK_SIZE,        "BlockSize"     },
 109         { VIRTIO_BLK_F_SCSI,            "SCSICmds"      },
 110         { VIRTIO_BLK_F_WCE,             "WriteCache"    },
 111         { VIRTIO_BLK_F_TOPOLOGY,        "Topology"      },
 112         { VIRTIO_BLK_F_CONFIG_WCE,      "ConfigWCE"     },
 113
 114         { 0, NULL }
 115 };
 116
 117 static int      vtblk_modevent(module_t, int, void *);
 118
 119 static int      vtblk_probe(device_t);
 120 static int      vtblk_attach(device_t);
 121 static int      vtblk_detach(device_t);
 122 static int      vtblk_suspend(device_t);
 123 static int      vtblk_resume(device_t);
 124 static int      vtblk_shutdown(device_t);
 125 static int      vtblk_config_change(device_t);
 126
 127 static int      vtblk_open(struct disk *);
 128 static int      vtblk_close(struct disk *);
 129 static int      vtblk_ioctl(struct disk *, u_long, void *, int,
 130                     struct thread *);
 131 static int      vtblk_dump(void *, void *, vm_offset_t, off_t, size_t);
 132 static void     vtblk_strategy(struct bio *);
 133
 134 static void     vtblk_negotiate_features(struct vtblk_softc *);
 135 static int      vtblk_maximum_segments(struct vtblk_softc *,
 136                     struct virtio_blk_config *);
 137 static int      vtblk_alloc_virtqueue(struct vtblk_softc *);
 138 static void     vtblk_resize_disk(struct vtblk_softc *, uint64_t);
 139 static void     vtblk_set_write_cache(struct vtblk_softc *, int);
 140 static int      vtblk_write_cache_enabled(struct vtblk_softc *sc,
 141                     struct virtio_blk_config *);
 142 static int      vtblk_write_cache_sysctl(SYSCTL_HANDLER_ARGS);
 143 static void     vtblk_alloc_disk(struct vtblk_softc *,
 144                     struct virtio_blk_config *);
 145 static void     vtblk_create_disk(struct vtblk_softc *);
 146
 147 static int      vtblk_quiesce(struct vtblk_softc *);
 148 static void     vtblk_startio(struct vtblk_softc *);
 149 static struct vtblk_request * vtblk_bio_request(struct vtblk_softc *);
 150 static int      vtblk_execute_request(struct vtblk_softc *,
 151                     struct vtblk_request *);
 152
 153 static void     vtblk_vq_intr(void *);
 154
 155 static void     vtblk_stop(struct vtblk_softc *);
 156
 157 static void     vtblk_read_config(struct vtblk_softc *,
 158                     struct virtio_blk_config *);
 159 static void     vtblk_get_ident(struct vtblk_softc *);
 160 static void     vtblk_prepare_dump(struct vtblk_softc *);
 161 static int      vtblk_write_dump(struct vtblk_softc *, void *, off_t, size_t);
 162 static int      vtblk_flush_dump(struct vtblk_softc *);
 163 static int      vtblk_poll_request(struct vtblk_softc *,
 164                     struct vtblk_request *);
 165
 166 static void     vtblk_finish_completed(struct vtblk_softc *);
 167 static void     vtblk_drain_vq(struct vtblk_softc *, int);
 168 static void     vtblk_drain(struct vtblk_softc *);
 169
 170 static int      vtblk_alloc_requests(struct vtblk_softc *);
 171 static void     vtblk_free_requests(struct vtblk_softc *);
 172 static struct vtblk_request * vtblk_dequeue_request(struct vtblk_softc *);
 173 static void     vtblk_enqueue_request(struct vtblk_softc *,
 174                     struct vtblk_request *);
 175
 176 static struct vtblk_request * vtblk_dequeue_ready(struct vtblk_softc *);
 177 static void     vtblk_enqueue_ready(struct vtblk_softc *,
 178                     struct vtblk_request *);
 179
 180 static int      vtblk_request_error(struct vtblk_request *);
 181 static void     vtblk_finish_bio(struct bio *, int);
 182
 183 static void     vtblk_setup_sysctl(struct vtblk_softc *);
 184 static int      vtblk_tunable_int(struct vtblk_softc *, const char *, int);
 185
 186 /* Tunables. */
 187 static int vtblk_no_ident = 0;
 188 TUNABLE_INT("hw.vtblk.no_ident", &vtblk_no_ident);
 189 static int vtblk_writecache_mode = -1;
 190 TUNABLE_INT("hw.vtblk.writecache_mode", &vtblk_writecache_mode);
 191
 192 /* Features desired/implemented by this driver. */
 193 #define VTBLK_FEATURES \
 194     (VIRTIO_BLK_F_BARRIER               | \
 195      VIRTIO_BLK_F_SIZE_MAX              | \
 196      VIRTIO_BLK_F_SEG_MAX               | \
 197      VIRTIO_BLK_F_GEOMETRY              | \
 198      VIRTIO_BLK_F_RO                    | \
 199      VIRTIO_BLK_F_BLK_SIZE              | \
 200      VIRTIO_BLK_F_WCE                   | \
 201      VIRTIO_BLK_F_CONFIG_WCE            | \
 202      VIRTIO_RING_F_INDIRECT_DESC)
 203
 204 #define VTBLK_MTX(_sc)          &(_sc)->vtblk_mtx
 205 #define VTBLK_LOCK_INIT(_sc, _name) \
 206                                 mtx_init(VTBLK_MTX((_sc)), (_name), \
 207                                     "VirtIO Block Lock", MTX_DEF)
 208 #define VTBLK_LOCK(_sc)         mtx_lock(VTBLK_MTX((_sc)))
 209 #define VTBLK_UNLOCK(_sc)       mtx_unlock(VTBLK_MTX((_sc)))
 210 #define VTBLK_LOCK_DESTROY(_sc) mtx_destroy(VTBLK_MTX((_sc)))
 211 #define VTBLK_LOCK_ASSERT(_sc)  mtx_assert(VTBLK_MTX((_sc)), MA_OWNED)
 212 #define VTBLK_LOCK_ASSERT_NOTOWNED(_sc) \
 213                                 mtx_assert(VTBLK_MTX((_sc)), MA_NOTOWNED)
 214
 215 #define VTBLK_DISK_NAME         "vtbd"
 216 #define VTBLK_QUIESCE_TIMEOUT   (30 * hz)
 217
 218 /*
 219  * Each block request uses at least two segments - one for the header
 220  * and one for the status.
 221  */
 222 #define VTBLK_MIN_SEGMENTS      2
 223
 224 static device_method_t vtblk_methods[] = {
 225         /* Device methods. */
 226         DEVMETHOD(device_probe,         vtblk_probe),
 227         DEVMETHOD(device_attach,        vtblk_attach),
 228         DEVMETHOD(device_detach,        vtblk_detach),
 229         DEVMETHOD(device_suspend,       vtblk_suspend),
 230         DEVMETHOD(device_resume,        vtblk_resume),
 231         DEVMETHOD(device_shutdown,      vtblk_shutdown),
 232
 233         /* VirtIO methods. */
 234         DEVMETHOD(virtio_config_change, vtblk_config_change),
 235
 236         DEVMETHOD_END
 237 };
 238
 239 static driver_t vtblk_driver = {
 240         "vtblk",
 241         vtblk_methods,
 242         sizeof(struct vtblk_softc)
 243 };
 244 static devclass_t vtblk_devclass;
 245
 246 DRIVER_MODULE(virtio_blk, virtio_pci, vtblk_driver, vtblk_devclass,
 247     vtblk_modevent, 0);
 248 MODULE_VERSION(virtio_blk, 1);
 249 MODULE_DEPEND(virtio_blk, virtio, 1, 1, 1);
 250
 251 static int
 252 vtblk_modevent(module_t mod, int type, void *unused)
 253 {
 254         int error;
 255
 256         error = 0;
 257
 258         switch (type) {
 259         case MOD_LOAD:
 260         case MOD_QUIESCE:
 261         case MOD_UNLOAD:
 262         case MOD_SHUTDOWN:
 263                 break;
 264         default:
 265                 error = EOPNOTSUPP;
 266                 break;
 267         }
 268
 269         return (error);
 270 }
 271
 272 static int
 273 vtblk_probe(device_t dev)
 274 {
 275
 276         if (virtio_get_device_type(dev) != VIRTIO_ID_BLOCK)
 277                 return (ENXIO);
 278
 279         device_set_desc(dev, "VirtIO Block Adapter");
 280
 281         return (BUS_PROBE_DEFAULT);
 282 }
 283
 284 static int
 285 vtblk_attach(device_t dev)
 286 {
 287         struct vtblk_softc *sc;
 288         struct virtio_blk_config blkcfg;
 289         int error;
 290
 291         sc = device_get_softc(dev);
 292         sc->vtblk_dev = dev;
 293
 294         VTBLK_LOCK_INIT(sc, device_get_nameunit(dev));
 295
 296         bioq_init(&sc->vtblk_bioq);
 297         TAILQ_INIT(&sc->vtblk_req_free);
 298         TAILQ_INIT(&sc->vtblk_req_ready);
 299
 300         virtio_set_feature_desc(dev, vtblk_feature_desc);
 301         vtblk_negotiate_features(sc);
 302
 303         if (virtio_with_feature(dev, VIRTIO_RING_F_INDIRECT_DESC))
 304                 sc->vtblk_flags |= VTBLK_FLAG_INDIRECT;
 305         if (virtio_with_feature(dev, VIRTIO_BLK_F_RO))
 306                 sc->vtblk_flags |= VTBLK_FLAG_READONLY;
 307         if (virtio_with_feature(dev, VIRTIO_BLK_F_BARRIER))
 308                 sc->vtblk_flags |= VTBLK_FLAG_BARRIER;
 309         if (virtio_with_feature(dev, VIRTIO_BLK_F_CONFIG_WCE))
 310                 sc->vtblk_flags |= VTBLK_FLAG_WC_CONFIG;
 311
 312         vtblk_setup_sysctl(sc);
 313
 314         /* Get local copy of config. */
 315         vtblk_read_config(sc, &blkcfg);
 316
 317         /*
 318          * With the current sglist(9) implementation, it is not easy
 319          * for us to support a maximum segment size as adjacent
 320          * segments are coalesced. For now, just make sure it's larger
 321          * than the maximum supported transfer size.
 322          */
 323         if (virtio_with_feature(dev, VIRTIO_BLK_F_SIZE_MAX)) {
 324                 if (blkcfg.size_max < MAXPHYS) {
 325                         error = ENOTSUP;
 326                         device_printf(dev, "host requires unsupported "
 327                             "maximum segment size feature\n");
 328                         goto fail;
 329                 }
 330         }
 331
 332         sc->vtblk_max_nsegs = vtblk_maximum_segments(sc, &blkcfg);
 333         if (sc->vtblk_max_nsegs <= VTBLK_MIN_SEGMENTS) {
 334                 error = EINVAL;
 335                 device_printf(dev, "fewer than minimum number of segments "
 336                     "allowed: %d\n", sc->vtblk_max_nsegs);
 337                 goto fail;
 338         }
 339
 340         sc->vtblk_sglist = sglist_alloc(sc->vtblk_max_nsegs, M_NOWAIT);
 341         if (sc->vtblk_sglist == NULL) {
 342                 error = ENOMEM;
 343                 device_printf(dev, "cannot allocate sglist\n");
 344                 goto fail;
 345         }
 346
 347         error = vtblk_alloc_virtqueue(sc);
 348         if (error) {
 349                 device_printf(dev, "cannot allocate virtqueue\n");
 350                 goto fail;
 351         }
 352
 353         error = vtblk_alloc_requests(sc);
 354         if (error) {
 355                 device_printf(dev, "cannot preallocate requests\n");
 356                 goto fail;
 357         }
 358
 359         vtblk_alloc_disk(sc, &blkcfg);
 360
 361         error = virtio_setup_intr(dev, INTR_TYPE_BIO | INTR_ENTROPY);
 362         if (error) {
 363                 device_printf(dev, "cannot setup virtqueue interrupt\n");
 364                 goto fail;
 365         }
 366
 367         vtblk_create_disk(sc);
 368
 369         virtqueue_enable_intr(sc->vtblk_vq);
 370
 371 fail:
 372         if (error)
 373                 vtblk_detach(dev);
 374
 375         return (error);
 376 }
 377
 378 static int
 379 vtblk_detach(device_t dev)
 380 {
 381         struct vtblk_softc *sc;
 382
 383         sc = device_get_softc(dev);
 384
 385         VTBLK_LOCK(sc);
 386         sc->vtblk_flags |= VTBLK_FLAG_DETACH;
 387         if (device_is_attached(dev))
 388                 vtblk_stop(sc);
 389         VTBLK_UNLOCK(sc);
 390
 391         vtblk_drain(sc);
 392
 393         if (sc->vtblk_disk != NULL) {
 394                 disk_destroy(sc->vtblk_disk);
 395                 sc->vtblk_disk = NULL;
 396         }
 397
 398         if (sc->vtblk_sglist != NULL) {
 399                 sglist_free(sc->vtblk_sglist);
 400                 sc->vtblk_sglist = NULL;
 401         }
 402
 403         VTBLK_LOCK_DESTROY(sc);
 404
 405         return (0);
 406 }
 407
 408 static int
 409 vtblk_suspend(device_t dev)
 410 {
 411         struct vtblk_softc *sc;
 412         int error;
 413
 414         sc = device_get_softc(dev);
 415
 416         VTBLK_LOCK(sc);
 417         sc->vtblk_flags |= VTBLK_FLAG_SUSPEND;
 418         /* XXX BMV: virtio_stop(), etc needed here? */
 419         error = vtblk_quiesce(sc);
 420         if (error)
 421                 sc->vtblk_flags &= ~VTBLK_FLAG_SUSPEND;
 422         VTBLK_UNLOCK(sc);
 423
 424         return (error);
 425 }
 426
 427 static int
 428 vtblk_resume(device_t dev)
 429 {
 430         struct vtblk_softc *sc;
 431
 432         sc = device_get_softc(dev);
 433
 434         VTBLK_LOCK(sc);
 435         /* XXX BMV: virtio_reinit(), etc needed here? */
 436         sc->vtblk_flags &= ~VTBLK_FLAG_SUSPEND;
 437         vtblk_startio(sc);
 438         VTBLK_UNLOCK(sc);
 439
 440         return (0);
 441 }
 442
 443 static int
 444 vtblk_shutdown(device_t dev)
 445 {
 446
 447         return (0);
 448 }
 449
 450 static int
 451 vtblk_config_change(device_t dev)
 452 {
 453         struct vtblk_softc *sc;
 454         struct virtio_blk_config blkcfg;
 455         uint64_t capacity;
 456
 457         sc = device_get_softc(dev);
 458
 459         vtblk_read_config(sc, &blkcfg);
 460
 461         /* Capacity is always in 512-byte units. */
 462         capacity = blkcfg.capacity * 512;
 463
 464         if (sc->vtblk_disk->d_mediasize != capacity)
 465                 vtblk_resize_disk(sc, capacity);
 466
 467         return (0);
 468 }
 469
 470 static int
 471 vtblk_open(struct disk *dp)
 472 {
 473         struct vtblk_softc *sc;
 474
 475         if ((sc = dp->d_drv1) == NULL)
 476                 return (ENXIO);
 477
 478         return (sc->vtblk_flags & VTBLK_FLAG_DETACH ? ENXIO : 0);
 479 }
 480
 481 static int
 482 vtblk_close(struct disk *dp)
 483 {
 484         struct vtblk_softc *sc;
 485
 486         if ((sc = dp->d_drv1) == NULL)
 487                 return (ENXIO);
 488
 489         return (0);
 490 }
 491
 492 static int
 493 vtblk_ioctl(struct disk *dp, u_long cmd, void *addr, int flag,
 494     struct thread *td)
 495 {
 496         struct vtblk_softc *sc;
 497
 498         if ((sc = dp->d_drv1) == NULL)
 499                 return (ENXIO);
 500
 501         return (ENOTTY);
 502 }
 503
 504 static int
 505 vtblk_dump(void *arg, void *virtual, vm_offset_t physical, off_t offset,
 506     size_t length)
 507 {
 508         struct disk *dp;
 509         struct vtblk_softc *sc;
 510         int error;
 511
 512         dp = arg;
 513
 514         if ((sc = dp->d_drv1) == NULL)
 515                 return (ENXIO);
 516
 517         VTBLK_LOCK(sc);
 518
 519         if ((sc->vtblk_flags & VTBLK_FLAG_DUMPING) == 0) {
 520                 vtblk_prepare_dump(sc);
 521                 sc->vtblk_flags |= VTBLK_FLAG_DUMPING;
 522         }
 523
 524         if (length > 0)
 525                 error = vtblk_write_dump(sc, virtual, offset, length);
 526         else if (virtual == NULL && offset == 0)
 527                 error = vtblk_flush_dump(sc);
 528         else {
 529                 error = EINVAL;
 530                 sc->vtblk_flags &= ~VTBLK_FLAG_DUMPING;
 531         }
 532
 533         VTBLK_UNLOCK(sc);
 534
 535         return (error);
 536 }
 537
 538 static void
 539 vtblk_strategy(struct bio *bp)
 540 {
 541         struct vtblk_softc *sc;
 542
 543         if ((sc = bp->bio_disk->d_drv1) == NULL) {
 544                 vtblk_finish_bio(bp, EINVAL);
 545                 return;
 546         }
 547
 548         /*
 549          * Fail any write if RO. Unfortunately, there does not seem to
 550          * be a better way to report our readonly'ness to GEOM above.
 551          */
 552         if (sc->vtblk_flags & VTBLK_FLAG_READONLY &&
 553             (bp->bio_cmd == BIO_WRITE || bp->bio_cmd == BIO_FLUSH)) {
 554                 vtblk_finish_bio(bp, EROFS);
 555                 return;
 556         }
 557
 558 #ifdef INVARIANTS
 559         /*
 560          * Prevent read/write buffers spanning too many segments from
 561          * getting into the queue. This should only trip if d_maxsize
 562          * was incorrectly set.
 563          */
 564         if (bp->bio_cmd == BIO_READ || bp->bio_cmd == BIO_WRITE) {
 565                 int nsegs, max_nsegs;
 566
 567                 nsegs = sglist_count(bp->bio_data, bp->bio_bcount);
 568                 max_nsegs = sc->vtblk_max_nsegs - VTBLK_MIN_SEGMENTS;
 569
 570                 KASSERT(nsegs <= max_nsegs,
 571                     ("%s: bio %p spanned too many segments: %d, max: %d",
 572                     __func__, bp, nsegs, max_nsegs));
 573         }
 574 #endif
 575
 576         VTBLK_LOCK(sc);
 577         if (sc->vtblk_flags & VTBLK_FLAG_DETACH)
 578                 vtblk_finish_bio(bp, ENXIO);
 579         else {
 580                 bioq_disksort(&sc->vtblk_bioq, bp);
 581
 582                 if ((sc->vtblk_flags & VTBLK_FLAG_SUSPEND) == 0)
 583                         vtblk_startio(sc);
 584         }
 585         VTBLK_UNLOCK(sc);
 586 }
 587
 588 static void
 589 vtblk_negotiate_features(struct vtblk_softc *sc)
 590 {
 591         device_t dev;
 592         uint64_t features;
 593
 594         dev = sc->vtblk_dev;
 595         features = VTBLK_FEATURES;
 596
 597         sc->vtblk_features = virtio_negotiate_features(dev, features);
 598 }
 599
 600 static int
 601 vtblk_maximum_segments(struct vtblk_softc *sc,
 602     struct virtio_blk_config *blkcfg)
 603 {
 604         device_t dev;
 605         int nsegs;
 606
 607         dev = sc->vtblk_dev;
 608         nsegs = VTBLK_MIN_SEGMENTS;
 609
 610         if (virtio_with_feature(dev, VIRTIO_BLK_F_SEG_MAX)) {
 611                 nsegs += MIN(blkcfg->seg_max, MAXPHYS / PAGE_SIZE + 1);
 612                 if (sc->vtblk_flags & VTBLK_FLAG_INDIRECT)
 613                         nsegs = MIN(nsegs, VIRTIO_MAX_INDIRECT);
 614         } else
 615                 nsegs += 1;
 616
 617         return (nsegs);
 618 }
 619
 620 static int
 621 vtblk_alloc_virtqueue(struct vtblk_softc *sc)
 622 {
 623         device_t dev;
 624         struct vq_alloc_info vq_info;
 625
 626         dev = sc->vtblk_dev;
 627
 628         VQ_ALLOC_INFO_INIT(&vq_info, sc->vtblk_max_nsegs,
 629             vtblk_vq_intr, sc, &sc->vtblk_vq,
 630             "%s request", device_get_nameunit(dev));
 631
 632         return (virtio_alloc_virtqueues(dev, 0, 1, &vq_info));
 633 }
 634
 635 static void
 636 vtblk_resize_disk(struct vtblk_softc *sc, uint64_t new_capacity)
 637 {
 638         device_t dev;
 639         struct disk *dp;
 640         int error;
 641
 642         dev = sc->vtblk_dev;
 643         dp = sc->vtblk_disk;
 644
 645         dp->d_mediasize = new_capacity;
 646         if (bootverbose) {
 647                 device_printf(dev, "resized to %juMB (%ju %u byte sectors)\n",
 648                     (uintmax_t) dp->d_mediasize >> 20,
 649                     (uintmax_t) dp->d_mediasize / dp->d_sectorsize,
 650                     dp->d_sectorsize);
 651         }
 652
 653         error = disk_resize(dp, M_NOWAIT);
 654         if (error) {
 655                 device_printf(dev,
 656                     "disk_resize(9) failed, error: %d\n", error);
 657         }
 658 }
 659
 660 static void
 661 vtblk_set_write_cache(struct vtblk_softc *sc, int wc)
 662 {
 663
 664         /* Set either writeback (1) or writethrough (0) mode. */
 665         virtio_write_dev_config_1(sc->vtblk_dev,
 666             offsetof(struct virtio_blk_config, writeback), wc);
 667 }
 668
 669 static int
 670 vtblk_write_cache_enabled(struct vtblk_softc *sc,
 671     struct virtio_blk_config *blkcfg)
 672 {
 673         int wc;
 674
 675         if (sc->vtblk_flags & VTBLK_FLAG_WC_CONFIG) {
 676                 wc = vtblk_tunable_int(sc, "writecache_mode",
 677                     vtblk_writecache_mode);
 678                 if (wc >= 0 && wc < VTBLK_CACHE_MAX)
 679                         vtblk_set_write_cache(sc, wc);
 680                 else
 681                         wc = blkcfg->writeback;
 682         } else
 683                 wc = virtio_with_feature(sc->vtblk_dev, VIRTIO_BLK_F_WCE);
 684
 685         return (wc);
 686 }
 687
 688 static int
 689 vtblk_write_cache_sysctl(SYSCTL_HANDLER_ARGS)
 690 {
 691         struct vtblk_softc *sc;
 692         int wc, error;
 693
 694         sc = oidp->oid_arg1;
 695         wc = sc->vtblk_write_cache;
 696
 697         error = sysctl_handle_int(oidp, &wc, 0, req);
 698         if (error || req->newptr == NULL)
 699                 return (error);
 700         if ((sc->vtblk_flags & VTBLK_FLAG_WC_CONFIG) == 0)
 701                 return (EPERM);
 702         if (wc < 0 || wc >= VTBLK_CACHE_MAX)
 703                 return (EINVAL);
 704
 705         VTBLK_LOCK(sc);
 706         sc->vtblk_write_cache = wc;
 707         vtblk_set_write_cache(sc, sc->vtblk_write_cache);
 708         VTBLK_UNLOCK(sc);
 709
 710         return (0);
 711 }
 712
 713 static void
 714 vtblk_alloc_disk(struct vtblk_softc *sc, struct virtio_blk_config *blkcfg)
 715 {
 716         device_t dev;
 717         struct disk *dp;
 718
 719         dev = sc->vtblk_dev;
 720
 721         sc->vtblk_disk = dp = disk_alloc();
 722         dp->d_open = vtblk_open;
 723         dp->d_close = vtblk_close;
 724         dp->d_ioctl = vtblk_ioctl;
 725         dp->d_strategy = vtblk_strategy;
 726         dp->d_name = VTBLK_DISK_NAME;
 727         dp->d_unit = device_get_unit(dev);
 728         dp->d_drv1 = sc;
 729         dp->d_flags = DISKFLAG_CANFLUSHCACHE;
 730         dp->d_hba_vendor = virtio_get_vendor(dev);
 731         dp->d_hba_device = virtio_get_device(dev);
 732         dp->d_hba_subvendor = virtio_get_subvendor(dev);
 733         dp->d_hba_subdevice = virtio_get_subdevice(dev);
 734
 735         if ((sc->vtblk_flags & VTBLK_FLAG_READONLY) == 0)
 736                 dp->d_dump = vtblk_dump;
 737
 738         /* Capacity is always in 512-byte units. */
 739         dp->d_mediasize = blkcfg->capacity * 512;
 740
 741         if (virtio_with_feature(dev, VIRTIO_BLK_F_BLK_SIZE))
 742                 dp->d_sectorsize = blkcfg->blk_size;
 743         else
 744                 dp->d_sectorsize = 512;
 745
 746         /*
 747          * The VirtIO maximum I/O size is given in terms of segments.
 748          * However, FreeBSD limits I/O size by logical buffer size, not
 749          * by physically contiguous pages. Therefore, we have to assume
 750          * no pages are contiguous. This may impose an artificially low
 751          * maximum I/O size. But in practice, since QEMU advertises 128
 752          * segments, this gives us a maximum IO size of 125 * PAGE_SIZE,
 753          * which is typically greater than MAXPHYS. Eventually we should
 754          * just advertise MAXPHYS and split buffers that are too big.
 755          *
 756          * Note we must subtract one additional segment in case of non
 757          * page aligned buffers.
 758          */
 759         dp->d_maxsize = (sc->vtblk_max_nsegs - VTBLK_MIN_SEGMENTS - 1) *
 760             PAGE_SIZE;
 761         if (dp->d_maxsize < PAGE_SIZE)
 762                 dp->d_maxsize = PAGE_SIZE; /* XXX */
 763
 764         if (virtio_with_feature(dev, VIRTIO_BLK_F_GEOMETRY)) {
 765                 dp->d_fwsectors = blkcfg->geometry.sectors;
 766                 dp->d_fwheads = blkcfg->geometry.heads;
 767         }
 768
 769         if (virtio_with_feature(dev, VIRTIO_BLK_F_TOPOLOGY)) {
 770                 dp->d_stripesize = dp->d_sectorsize *
 771                     (1 << blkcfg->topology.physical_block_exp);
 772                 dp->d_stripeoffset = (dp->d_stripesize -
 773                     blkcfg->topology.alignment_offset * dp->d_sectorsize) %
 774                     dp->d_stripesize;
 775         }
 776
 777         if (vtblk_write_cache_enabled(sc, blkcfg) != 0)
 778                 sc->vtblk_write_cache = VTBLK_CACHE_WRITEBACK;
 779         else
 780                 sc->vtblk_write_cache = VTBLK_CACHE_WRITETHROUGH;
 781 }
 782
 783 static void
 784 vtblk_create_disk(struct vtblk_softc *sc)
 785 {
 786         struct disk *dp;
 787
 788         dp = sc->vtblk_disk;
 789
 790         /*
 791          * Retrieving the identification string must be done after
 792          * the virtqueue interrupt is setup otherwise it will hang.
 793          */
 794         vtblk_get_ident(sc);
 795
 796         device_printf(sc->vtblk_dev, "%juMB (%ju %u byte sectors)\n",
 797             (uintmax_t) dp->d_mediasize >> 20,
 798             (uintmax_t) dp->d_mediasize / dp->d_sectorsize,
 799             dp->d_sectorsize);
 800
 801         disk_create(dp, DISK_VERSION);
 802 }
 803
 804 static int
 805 vtblk_quiesce(struct vtblk_softc *sc)
 806 {
 807         int error;
 808
 809         error = 0;
 810
 811         VTBLK_LOCK_ASSERT(sc);
 812
 813         while (!virtqueue_empty(sc->vtblk_vq)) {
 814                 if (mtx_sleep(&sc->vtblk_vq, VTBLK_MTX(sc), PRIBIO, "vtblkq",
 815                     VTBLK_QUIESCE_TIMEOUT) == EWOULDBLOCK) {
 816                         error = EBUSY;
 817                         break;
 818                 }
 819         }
 820
 821         return (error);
 822 }
 823
 824 static void
 825 vtblk_startio(struct vtblk_softc *sc)
 826 {
 827         struct virtqueue *vq;
 828         struct vtblk_request *req;
 829         int enq;
 830
 831         vq = sc->vtblk_vq;
 832         enq = 0;
 833
 834         VTBLK_LOCK_ASSERT(sc);
 835
 836         while (!virtqueue_full(vq)) {
 837                 if ((req = vtblk_dequeue_ready(sc)) == NULL)
 838                         req = vtblk_bio_request(sc);
 839                 if (req == NULL)
 840                         break;
 841
 842                 if (vtblk_execute_request(sc, req) != 0) {
 843                         vtblk_enqueue_ready(sc, req);
 844                         break;
 845                 }
 846
 847                 enq++;
 848         }
 849
 850         if (enq > 0)
 851                 virtqueue_notify(vq);
 852 }
 853
 854 static struct vtblk_request *
 855 vtblk_bio_request(struct vtblk_softc *sc)
 856 {
 857         struct bio_queue_head *bioq;
 858         struct vtblk_request *req;
 859         struct bio *bp;
 860
 861         bioq = &sc->vtblk_bioq;
 862
 863         if (bioq_first(bioq) == NULL)
 864                 return (NULL);
 865
 866         req = vtblk_dequeue_request(sc);
 867         if (req == NULL)
 868                 return (NULL);
 869
 870         bp = bioq_takefirst(bioq);
 871         req->vbr_bp = bp;
 872         req->vbr_ack = -1;
 873         req->vbr_hdr.ioprio = 1;
 874
 875         switch (bp->bio_cmd) {
 876         case BIO_FLUSH:
 877                 req->vbr_hdr.type = VIRTIO_BLK_T_FLUSH;
 878                 break;
 879         case BIO_READ:
 880                 req->vbr_hdr.type = VIRTIO_BLK_T_IN;
 881                 req->vbr_hdr.sector = bp->bio_offset / 512;
 882                 break;
 883         case BIO_WRITE:
 884                 req->vbr_hdr.type = VIRTIO_BLK_T_OUT;
 885                 req->vbr_hdr.sector = bp->bio_offset / 512;
 886                 break;
 887         default:
 888                 panic("%s: bio with unhandled cmd: %d", __func__, bp->bio_cmd);
 889         }
 890
 891         return (req);
 892 }
 893
 894 static int
 895 vtblk_execute_request(struct vtblk_softc *sc, struct vtblk_request *req)
 896 {
 897         struct virtqueue *vq;
 898         struct sglist *sg;
 899         struct bio *bp;
 900         int ordered, readable, writable, error;
 901
 902         vq = sc->vtblk_vq;
 903         sg = sc->vtblk_sglist;
 904         bp = req->vbr_bp;
 905         ordered = 0;
 906         writable = 0;
 907
 908         VTBLK_LOCK_ASSERT(sc);
 909
 910         /*
 911          * Wait until the ordered request completes before
 912          * executing subsequent requests.
 913          */
 914         if (sc->vtblk_req_ordered != NULL)
 915                 return (EBUSY);
 916
 917         if (bp->bio_flags & BIO_ORDERED) {
 918                 if ((sc->vtblk_flags & VTBLK_FLAG_BARRIER) == 0) {
 919                         /*
 920                          * This request will be executed once all
 921                          * the in-flight requests are completed.
 922                          */
 923                         if (!virtqueue_empty(vq))
 924                                 return (EBUSY);
 925                         ordered = 1;
 926                 } else
 927                         req->vbr_hdr.type |= VIRTIO_BLK_T_BARRIER;
 928         }
 929
 930         sglist_reset(sg);
 931         sglist_append(sg, &req->vbr_hdr, sizeof(struct virtio_blk_outhdr));
 932
 933         if (bp->bio_cmd == BIO_READ || bp->bio_cmd == BIO_WRITE) {
 934                 error = sglist_append(sg, bp->bio_data, bp->bio_bcount);
 935                 if (error || sg->sg_nseg == sg->sg_maxseg)
 936                         panic("%s: data buffer too big bio:%p error:%d",
 937                             __func__, bp, error);
 938
 939                 /* BIO_READ means the host writes into our buffer. */
 940                 if (bp->bio_cmd == BIO_READ)
 941                         writable = sg->sg_nseg - 1;
 942         }
 943
 944         writable++;
 945         sglist_append(sg, &req->vbr_ack, sizeof(uint8_t));
 946         readable = sg->sg_nseg - writable;
 947
 948         error = virtqueue_enqueue(vq, req, sg, readable, writable);
 949         if (error == 0 && ordered)
 950                 sc->vtblk_req_ordered = req;
 951
 952         return (error);
 953 }
 954
 955 static void
 956 vtblk_vq_intr(void *xsc)
 957 {
 958         struct vtblk_softc *sc;
 959         struct virtqueue *vq;
 960
 961         sc = xsc;
 962         vq = sc->vtblk_vq;
 963
 964 again:
 965         VTBLK_LOCK(sc);
 966         if (sc->vtblk_flags & VTBLK_FLAG_DETACH) {
 967                 VTBLK_UNLOCK(sc);
 968                 return;
 969         }
 970
 971         vtblk_finish_completed(sc);
 972
 973         if ((sc->vtblk_flags & VTBLK_FLAG_SUSPEND) == 0)
 974                 vtblk_startio(sc);
 975         else
 976                 wakeup(&sc->vtblk_vq);
 977
 978         if (virtqueue_enable_intr(vq) != 0) {
 979                 virtqueue_disable_intr(vq);
 980                 VTBLK_UNLOCK(sc);
 981                 goto again;
 982         }
 983
 984         VTBLK_UNLOCK(sc);
 985 }
 986
 987 static void
 988 vtblk_stop(struct vtblk_softc *sc)
 989 {
 990
 991         virtqueue_disable_intr(sc->vtblk_vq);
 992         virtio_stop(sc->vtblk_dev);
 993 }
 994
 995 #define VTBLK_GET_CONFIG(_dev, _feature, _field, _cfg)                  \
 996         if (virtio_with_feature(_dev, _feature)) {                      \
 997                 virtio_read_device_config(_dev,                         \
 998                     offsetof(struct virtio_blk_config, _field),         \
 999                     &(_cfg)->_field, sizeof((_cfg)->_field));           \
1000         }
1001
1002 static void
1003 vtblk_read_config(struct vtblk_softc *sc, struct virtio_blk_config *blkcfg)
1004 {
1005         device_t dev;
1006
1007         dev = sc->vtblk_dev;
1008
1009         bzero(blkcfg, sizeof(struct virtio_blk_config));
1010
1011         /* The capacity is always available. */
1012         virtio_read_device_config(dev, offsetof(struct virtio_blk_config,
1013             capacity), &blkcfg->capacity, sizeof(blkcfg->capacity));
1014
1015         /* Read the configuration if the feature was negotiated. */
1016         VTBLK_GET_CONFIG(dev, VIRTIO_BLK_F_SIZE_MAX, size_max, blkcfg);
1017         VTBLK_GET_CONFIG(dev, VIRTIO_BLK_F_SEG_MAX, seg_max, blkcfg);
1018         VTBLK_GET_CONFIG(dev, VIRTIO_BLK_F_GEOMETRY, geometry, blkcfg);
1019         VTBLK_GET_CONFIG(dev, VIRTIO_BLK_F_BLK_SIZE, blk_size, blkcfg);
1020         VTBLK_GET_CONFIG(dev, VIRTIO_BLK_F_TOPOLOGY, topology, blkcfg);
1021         VTBLK_GET_CONFIG(dev, VIRTIO_BLK_F_CONFIG_WCE, writeback, blkcfg);
1022 }
1023
1024 #undef VTBLK_GET_CONFIG
1025
1026 static void
1027 vtblk_get_ident(struct vtblk_softc *sc)
1028 {
1029         struct bio buf;
1030         struct disk *dp;
1031         struct vtblk_request *req;
1032         int len, error;
1033
1034         dp = sc->vtblk_disk;
1035         len = MIN(VIRTIO_BLK_ID_BYTES, DISK_IDENT_SIZE);
1036
1037         if (vtblk_tunable_int(sc, "no_ident", vtblk_no_ident) != 0)
1038                 return;
1039
1040         req = vtblk_dequeue_request(sc);
1041         if (req == NULL)
1042                 return;
1043
1044         req->vbr_ack = -1;
1045         req->vbr_hdr.type = VIRTIO_BLK_T_GET_ID;
1046         req->vbr_hdr.ioprio = 1;
1047         req->vbr_hdr.sector = 0;
1048
1049         req->vbr_bp = &buf;
1050         bzero(&buf, sizeof(struct bio));
1051
1052         buf.bio_cmd = BIO_READ;
1053         buf.bio_data = dp->d_ident;
1054         buf.bio_bcount = len;
1055
1056         VTBLK_LOCK(sc);
1057         error = vtblk_poll_request(sc, req);
1058         VTBLK_UNLOCK(sc);
1059
1060         vtblk_enqueue_request(sc, req);
1061
1062         if (error) {
1063                 device_printf(sc->vtblk_dev,
1064                     "error getting device identifier: %d\n", error);
1065         }
1066 }
1067
1068 static void
1069 vtblk_prepare_dump(struct vtblk_softc *sc)
1070 {
1071         device_t dev;
1072         struct virtqueue *vq;
1073
1074         dev = sc->vtblk_dev;
1075         vq = sc->vtblk_vq;
1076
1077         vtblk_stop(sc);
1078
1079         /*
1080          * Drain all requests caught in-flight in the virtqueue,
1081          * skipping biodone(). When dumping, only one request is
1082          * outstanding at a time, and we just poll the virtqueue
1083          * for the response.
1084          */
1085         vtblk_drain_vq(sc, 1);
1086
1087         if (virtio_reinit(dev, sc->vtblk_features) != 0) {
1088                 panic("%s: cannot reinit VirtIO block device during dump",
1089                     device_get_nameunit(dev));
1090         }
1091
1092         virtqueue_disable_intr(vq);
1093         virtio_reinit_complete(dev);
1094 }
1095
1096 static int
1097 vtblk_write_dump(struct vtblk_softc *sc, void *virtual, off_t offset,
1098     size_t length)
1099 {
1100         struct bio buf;
1101         struct vtblk_request *req;
1102
1103         req = &sc->vtblk_dump_request;
1104         req->vbr_ack = -1;
1105         req->vbr_hdr.type = VIRTIO_BLK_T_OUT;
1106         req->vbr_hdr.ioprio = 1;
1107         req->vbr_hdr.sector = offset / 512;
1108
1109         req->vbr_bp = &buf;
1110         bzero(&buf, sizeof(struct bio));
1111
1112         buf.bio_cmd = BIO_WRITE;
1113         buf.bio_data = virtual;
1114         buf.bio_bcount = length;
1115
1116         return (vtblk_poll_request(sc, req));
1117 }
1118
1119 static int
1120 vtblk_flush_dump(struct vtblk_softc *sc)
1121 {
1122         struct bio buf;
1123         struct vtblk_request *req;
1124
1125         req = &sc->vtblk_dump_request;
1126         req->vbr_ack = -1;
1127         req->vbr_hdr.type = VIRTIO_BLK_T_FLUSH;
1128         req->vbr_hdr.ioprio = 1;
1129         req->vbr_hdr.sector = 0;
1130
1131         req->vbr_bp = &buf;
1132         bzero(&buf, sizeof(struct bio));
1133
1134         buf.bio_cmd = BIO_FLUSH;
1135
1136         return (vtblk_poll_request(sc, req));
1137 }
1138
1139 static int
1140 vtblk_poll_request(struct vtblk_softc *sc, struct vtblk_request *req)
1141 {
1142         struct virtqueue *vq;
1143         int error;
1144
1145         vq = sc->vtblk_vq;
1146
1147         if (!virtqueue_empty(vq))
1148                 return (EBUSY);
1149
1150         error = vtblk_execute_request(sc, req);
1151         if (error)
1152                 return (error);
1153
1154         virtqueue_notify(vq);
1155         virtqueue_poll(vq, NULL);
1156
1157         error = vtblk_request_error(req);
1158         if (error && bootverbose) {
1159                 device_printf(sc->vtblk_dev,
1160                     "%s: IO error: %d\n", __func__, error);
1161         }
1162
1163         return (error);
1164 }
1165
1166 static void
1167 vtblk_finish_completed(struct vtblk_softc *sc)
1168 {
1169         struct vtblk_request *req;
1170         struct bio *bp;
1171         int error;
1172
1173         while ((req = virtqueue_dequeue(sc->vtblk_vq, NULL)) != NULL) {
1174                 bp = req->vbr_bp;
1175
1176                 if (sc->vtblk_req_ordered != NULL) {
1177                         /* This should be the only outstanding request. */
1178                         MPASS(sc->vtblk_req_ordered == req);
1179                         sc->vtblk_req_ordered = NULL;
1180                 }
1181
1182                 error = vtblk_request_error(req);
1183                 if (error)
1184                         disk_err(bp, "hard error", -1, 1);
1185
1186                 vtblk_finish_bio(bp, error);
1187                 vtblk_enqueue_request(sc, req);
1188         }
1189 }
1190
1191 static void
1192 vtblk_drain_vq(struct vtblk_softc *sc, int skip_done)
1193 {
1194         struct virtqueue *vq;
1195         struct vtblk_request *req;
1196         int last;
1197
1198         vq = sc->vtblk_vq;
1199         last = 0;
1200
1201         while ((req = virtqueue_drain(vq, &last)) != NULL) {
1202                 if (!skip_done)
1203                         vtblk_finish_bio(req->vbr_bp, ENXIO);
1204
1205                 vtblk_enqueue_request(sc, req);
1206         }
1207
1208         sc->vtblk_req_ordered = NULL;
1209         KASSERT(virtqueue_empty(vq), ("virtqueue not empty"));
1210 }
1211
1212 static void
1213 vtblk_drain(struct vtblk_softc *sc)
1214 {
1215         struct bio_queue_head *bioq;
1216         struct vtblk_request *req;
1217         struct bio *bp;
1218
1219         bioq = &sc->vtblk_bioq;
1220
1221         if (sc->vtblk_vq != NULL) {
1222                 vtblk_finish_completed(sc);
1223                 vtblk_drain_vq(sc, 0);
1224         }
1225
1226         while ((req = vtblk_dequeue_ready(sc)) != NULL) {
1227                 vtblk_finish_bio(req->vbr_bp, ENXIO);
1228                 vtblk_enqueue_request(sc, req);
1229         }
1230
1231         while (bioq_first(bioq) != NULL) {
1232                 bp = bioq_takefirst(bioq);
1233                 vtblk_finish_bio(bp, ENXIO);
1234         }
1235
1236         vtblk_free_requests(sc);
1237 }
1238
1239 #ifdef INVARIANTS
1240 static void
1241 vtblk_request_invariants(struct vtblk_request *req)
1242 {
1243         int hdr_nsegs, ack_nsegs;
1244
1245         hdr_nsegs = sglist_count(&req->vbr_hdr, sizeof(req->vbr_hdr));
1246         ack_nsegs = sglist_count(&req->vbr_ack, sizeof(req->vbr_ack));
1247
1248         KASSERT(hdr_nsegs == 1, ("request header crossed page boundary"));
1249         KASSERT(ack_nsegs == 1, ("request ack crossed page boundary"));
1250 }
1251 #endif
1252
1253 static int
1254 vtblk_alloc_requests(struct vtblk_softc *sc)
1255 {
1256         struct vtblk_request *req;
1257         int i, nreqs;
1258
1259         nreqs = virtqueue_size(sc->vtblk_vq);
1260
1261         /*
1262          * Preallocate sufficient requests to keep the virtqueue full. Each
1263          * request consumes VTBLK_MIN_SEGMENTS or more descriptors so reduce
1264          * the number allocated when indirect descriptors are not available.
1265          */
1266         if ((sc->vtblk_flags & VTBLK_FLAG_INDIRECT) == 0)
1267                 nreqs /= VTBLK_MIN_SEGMENTS;
1268
1269         for (i = 0; i < nreqs; i++) {
1270                 req = malloc(sizeof(struct vtblk_request), M_DEVBUF, M_NOWAIT);
1271                 if (req == NULL)
1272                         return (ENOMEM);
1273
1274 #ifdef INVARIANTS
1275                 vtblk_request_invariants(req);
1276 #endif
1277
1278                 sc->vtblk_request_count++;
1279                 vtblk_enqueue_request(sc, req);
1280         }
1281
1282         return (0);
1283 }
1284
1285 static void
1286 vtblk_free_requests(struct vtblk_softc *sc)
1287 {
1288         struct vtblk_request *req;
1289
1290         KASSERT(TAILQ_EMPTY(&sc->vtblk_req_ready),
1291             ("%s: ready requests left on queue", __func__));
1292
1293         while ((req = vtblk_dequeue_request(sc)) != NULL) {
1294                 sc->vtblk_request_count--;
1295                 free(req, M_DEVBUF);
1296         }
1297
1298         KASSERT(sc->vtblk_request_count == 0,
1299             ("%s: leaked %d requests", __func__, sc->vtblk_request_count));
1300 }
1301
1302 static struct vtblk_request *
1303 vtblk_dequeue_request(struct vtblk_softc *sc)
1304 {
1305         struct vtblk_request *req;
1306
1307         req = TAILQ_FIRST(&sc->vtblk_req_free);
1308         if (req != NULL)
1309                 TAILQ_REMOVE(&sc->vtblk_req_free, req, vbr_link);
1310
1311         return (req);
1312 }
1313
1314 static void
1315 vtblk_enqueue_request(struct vtblk_softc *sc, struct vtblk_request *req)
1316 {
1317
1318         bzero(req, sizeof(struct vtblk_request));
1319         TAILQ_INSERT_HEAD(&sc->vtblk_req_free, req, vbr_link);
1320 }
1321
1322 static struct vtblk_request *
1323 vtblk_dequeue_ready(struct vtblk_softc *sc)
1324 {
1325         struct vtblk_request *req;
1326
1327         req = TAILQ_FIRST(&sc->vtblk_req_ready);
1328         if (req != NULL)
1329                 TAILQ_REMOVE(&sc->vtblk_req_ready, req, vbr_link);
1330
1331         return (req);
1332 }
1333
1334 static void
1335 vtblk_enqueue_ready(struct vtblk_softc *sc, struct vtblk_request *req)
1336 {
1337
1338         TAILQ_INSERT_HEAD(&sc->vtblk_req_ready, req, vbr_link);
1339 }
1340
1341 static int
1342 vtblk_request_error(struct vtblk_request *req)
1343 {
1344         int error;
1345
1346         switch (req->vbr_ack) {
1347         case VIRTIO_BLK_S_OK:
1348                 error = 0;
1349                 break;
1350         case VIRTIO_BLK_S_UNSUPP:
1351                 error = ENOTSUP;
1352                 break;
1353         default:
1354                 error = EIO;
1355                 break;
1356         }
1357
1358         return (error);
1359 }
1360
1361 static void
1362 vtblk_finish_bio(struct bio *bp, int error)
1363 {
1364
1365         if (error) {
1366                 bp->bio_resid = bp->bio_bcount;
1367                 bp->bio_error = error;
1368                 bp->bio_flags |= BIO_ERROR;
1369         }
1370
1371         biodone(bp);
1372 }
1373
1374 static void
1375 vtblk_setup_sysctl(struct vtblk_softc *sc)
1376 {
1377         device_t dev;
1378         struct sysctl_ctx_list *ctx;
1379         struct sysctl_oid *tree;
1380         struct sysctl_oid_list *child;
1381
1382         dev = sc->vtblk_dev;
1383         ctx = device_get_sysctl_ctx(dev);
1384         tree = device_get_sysctl_tree(dev);
1385         child = SYSCTL_CHILDREN(tree);
1386
1387         SYSCTL_ADD_PROC(ctx, child, OID_AUTO, "writecache_mode",
1388             CTLTYPE_INT | CTLFLAG_RW, sc, 0, vtblk_write_cache_sysctl,
1389             "I", "Write cache mode (writethrough (0) or writeback (1))");
1390 }
1391
1392 static int
1393 vtblk_tunable_int(struct vtblk_softc *sc, const char *knob, int def)
1394 {
1395         char path[64];
1396
1397         snprintf(path, sizeof(path),
1398             "hw.vtblk.%d.%s", device_get_unit(sc->vtblk_dev), knob);
1399         TUNABLE_INT_FETCH(path, &def);
1400
1401         return (def);
1402 }