hw/virtio-blk.c

   1 /*
   2  * Virtio Block Device
   3  *
   4  * Copyright IBM, Corp. 2007
   5  *
   6  * Authors:
   7  *  Anthony Liguori   <aliguori@us.ibm.com>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2.  See
  10  * the COPYING file in the top-level directory.
  11  *
  12  */
  13
  14 #include "qemu-common.h"
  15 #include "qemu-error.h"
  16 #include "trace.h"
  17 #include "blockdev.h"
  18 #include "virtio-blk.h"
  19 #include "scsi-defs.h"
  20 #ifdef __linux__
  21 # include <scsi/sg.h>
  22 #endif
  23
  24 typedef struct VirtIOBlock
  25 {
  26     VirtIODevice vdev;
  27     BlockDriverState *bs;
  28     VirtQueue *vq;
  29     void *rq;
  30     QEMUBH *bh;
  31     BlockConf *conf;
  32     VirtIOBlkConf *blk;
  33     unsigned short sector_mask;
  34     DeviceState *qdev;
  35 } VirtIOBlock;
  36
  37 static VirtIOBlock *to_virtio_blk(VirtIODevice *vdev)
  38 {
  39     return (VirtIOBlock *)vdev;
  40 }
  41
  42 typedef struct VirtIOBlockReq
  43 {
  44     VirtIOBlock *dev;
  45     VirtQueueElement elem;
  46     struct virtio_blk_inhdr *in;
  47     struct virtio_blk_outhdr *out;
  48     struct virtio_scsi_inhdr *scsi;
  49     QEMUIOVector qiov;
  50     struct VirtIOBlockReq *next;
  51     BlockAcctCookie acct;
  52 } VirtIOBlockReq;
  53
  54 static void virtio_blk_req_complete(VirtIOBlockReq *req, int status)
  55 {
  56     VirtIOBlock *s = req->dev;
  57
  58     trace_virtio_blk_req_complete(req, status);
  59
  60     stb_p(&req->in->status, status);
  61     virtqueue_push(s->vq, &req->elem, req->qiov.size + sizeof(*req->in));
  62     virtio_notify(&s->vdev, s->vq);
  63 }
  64
  65 static int virtio_blk_handle_rw_error(VirtIOBlockReq *req, int error,
  66     int is_read)
  67 {
  68     BlockErrorAction action = bdrv_get_on_error(req->dev->bs, is_read);
  69     VirtIOBlock *s = req->dev;
  70
  71     if (action == BLOCK_ERR_IGNORE) {
  72         bdrv_emit_qmp_error_event(s->bs, BDRV_ACTION_IGNORE, is_read);
  73         return 0;
  74     }
  75
  76     if ((error == ENOSPC && action == BLOCK_ERR_STOP_ENOSPC)
  77             || action == BLOCK_ERR_STOP_ANY) {
  78         req->next = s->rq;
  79         s->rq = req;
  80         bdrv_emit_qmp_error_event(s->bs, BDRV_ACTION_STOP, is_read);
  81         vm_stop(RUN_STATE_IO_ERROR);
  82         bdrv_iostatus_set_err(s->bs, error);
  83     } else {
  84         virtio_blk_req_complete(req, VIRTIO_BLK_S_IOERR);
  85         bdrv_acct_done(s->bs, &req->acct);
  86         g_free(req);
  87         bdrv_emit_qmp_error_event(s->bs, BDRV_ACTION_REPORT, is_read);
  88     }
  89
  90     return 1;
  91 }
  92
  93 static void virtio_blk_rw_complete(void *opaque, int ret)
  94 {
  95     VirtIOBlockReq *req = opaque;
  96
  97     trace_virtio_blk_rw_complete(req, ret);
  98
  99     if (ret) {
 100         int is_read = !(ldl_p(&req->out->type) & VIRTIO_BLK_T_OUT);
 101         if (virtio_blk_handle_rw_error(req, -ret, is_read))
 102             return;
 103     }
 104
 105     virtio_blk_req_complete(req, VIRTIO_BLK_S_OK);
 106     bdrv_acct_done(req->dev->bs, &req->acct);
 107     g_free(req);
 108 }
 109
 110 static void virtio_blk_flush_complete(void *opaque, int ret)
 111 {
 112     VirtIOBlockReq *req = opaque;
 113
 114     if (ret) {
 115         if (virtio_blk_handle_rw_error(req, -ret, 0)) {
 116             return;
 117         }
 118     }
 119
 120     virtio_blk_req_complete(req, VIRTIO_BLK_S_OK);
 121     bdrv_acct_done(req->dev->bs, &req->acct);
 122     g_free(req);
 123 }
 124
 125 static VirtIOBlockReq *virtio_blk_alloc_request(VirtIOBlock *s)
 126 {
 127     VirtIOBlockReq *req = g_malloc(sizeof(*req));
 128     req->dev = s;
 129     req->qiov.size = 0;
 130     req->next = NULL;
 131     return req;
 132 }
 133
 134 static VirtIOBlockReq *virtio_blk_get_request(VirtIOBlock *s)
 135 {
 136     VirtIOBlockReq *req = virtio_blk_alloc_request(s);
 137
 138     if (req != NULL) {
 139         if (!virtqueue_pop(s->vq, &req->elem)) {
 140             g_free(req);
 141             return NULL;
 142         }
 143     }
 144
 145     return req;
 146 }
 147
 148 static void virtio_blk_handle_scsi(VirtIOBlockReq *req)
 149 {
 150 #ifdef __linux__
 151     int ret;
 152     int i;
 153 #endif
 154     int status = VIRTIO_BLK_S_OK;
 155
 156     /*
 157      * We require at least one output segment each for the virtio_blk_outhdr
 158      * and the SCSI command block.
 159      *
 160      * We also at least require the virtio_blk_inhdr, the virtio_scsi_inhdr
 161      * and the sense buffer pointer in the input segments.
 162      */
 163     if (req->elem.out_num < 2 || req->elem.in_num < 3) {
 164         virtio_blk_req_complete(req, VIRTIO_BLK_S_IOERR);
 165         g_free(req);
 166         return;
 167     }
 168
 169     /*
 170      * The scsi inhdr is placed in the second-to-last input segment, just
 171      * before the regular inhdr.
 172      */
 173     req->scsi = (void *)req->elem.in_sg[req->elem.in_num - 2].iov_base;
 174
 175     if (!req->dev->blk->scsi) {
 176         status = VIRTIO_BLK_S_UNSUPP;
 177         goto fail;
 178     }
 179
 180     /*
 181      * No support for bidirection commands yet.
 182      */
 183     if (req->elem.out_num > 2 && req->elem.in_num > 3) {
 184         status = VIRTIO_BLK_S_UNSUPP;
 185         goto fail;
 186     }
 187
 188 #ifdef __linux__
 189     struct sg_io_hdr hdr;
 190     memset(&hdr, 0, sizeof(struct sg_io_hdr));
 191     hdr.interface_id = 'S';
 192     hdr.cmd_len = req->elem.out_sg[1].iov_len;
 193     hdr.cmdp = req->elem.out_sg[1].iov_base;
 194     hdr.dxfer_len = 0;
 195
 196     if (req->elem.out_num > 2) {
 197         /*
 198          * If there are more than the minimally required 2 output segments
 199          * there is write payload starting from the third iovec.
 200          */
 201         hdr.dxfer_direction = SG_DXFER_TO_DEV;
 202         hdr.iovec_count = req->elem.out_num - 2;
 203
 204         for (i = 0; i < hdr.iovec_count; i++)
 205             hdr.dxfer_len += req->elem.out_sg[i + 2].iov_len;
 206
 207         hdr.dxferp = req->elem.out_sg + 2;
 208
 209     } else if (req->elem.in_num > 3) {
 210         /*
 211          * If we have more than 3 input segments the guest wants to actually
 212          * read data.
 213          */
 214         hdr.dxfer_direction = SG_DXFER_FROM_DEV;
 215         hdr.iovec_count = req->elem.in_num - 3;
 216         for (i = 0; i < hdr.iovec_count; i++)
 217             hdr.dxfer_len += req->elem.in_sg[i].iov_len;
 218
 219         hdr.dxferp = req->elem.in_sg;
 220     } else {
 221         /*
 222          * Some SCSI commands don't actually transfer any data.
 223          */
 224         hdr.dxfer_direction = SG_DXFER_NONE;
 225     }
 226
 227     hdr.sbp = req->elem.in_sg[req->elem.in_num - 3].iov_base;
 228     hdr.mx_sb_len = req->elem.in_sg[req->elem.in_num - 3].iov_len;
 229
 230     ret = bdrv_ioctl(req->dev->bs, SG_IO, &hdr);
 231     if (ret) {
 232         status = VIRTIO_BLK_S_UNSUPP;
 233         goto fail;
 234     }
 235
 236     /*
 237      * From SCSI-Generic-HOWTO: "Some lower level drivers (e.g. ide-scsi)
 238      * clear the masked_status field [hence status gets cleared too, see
 239      * block/scsi_ioctl.c] even when a CHECK_CONDITION or COMMAND_TERMINATED
 240      * status has occurred.  However they do set DRIVER_SENSE in driver_status
 241      * field. Also a (sb_len_wr > 0) indicates there is a sense buffer.
 242      */
 243     if (hdr.status == 0 && hdr.sb_len_wr > 0) {
 244         hdr.status = CHECK_CONDITION;
 245     }
 246
 247     stl_p(&req->scsi->errors,
 248           hdr.status | (hdr.msg_status << 8) |
 249           (hdr.host_status << 16) | (hdr.driver_status << 24));
 250     stl_p(&req->scsi->residual, hdr.resid);
 251     stl_p(&req->scsi->sense_len, hdr.sb_len_wr);
 252     stl_p(&req->scsi->data_len, hdr.dxfer_len);
 253
 254     virtio_blk_req_complete(req, status);
 255     g_free(req);
 256 #else
 257     abort();
 258 #endif
 259
 260 fail:
 261     /* Just put anything nonzero so that the ioctl fails in the guest.  */
 262     stl_p(&req->scsi->errors, 255);
 263     virtio_blk_req_complete(req, status);
 264     g_free(req);
 265 }
 266
 267 typedef struct MultiReqBuffer {
 268     BlockRequest        blkreq[32];
 269     unsigned int        num_writes;
 270 } MultiReqBuffer;
 271
 272 static void virtio_submit_multiwrite(BlockDriverState *bs, MultiReqBuffer *mrb)
 273 {
 274     int i, ret;
 275
 276     if (!mrb->num_writes) {
 277         return;
 278     }
 279
 280     ret = bdrv_aio_multiwrite(bs, mrb->blkreq, mrb->num_writes);
 281     if (ret != 0) {
 282         for (i = 0; i < mrb->num_writes; i++) {
 283             if (mrb->blkreq[i].error) {
 284                 virtio_blk_rw_complete(mrb->blkreq[i].opaque, -EIO);
 285             }
 286         }
 287     }
 288
 289     mrb->num_writes = 0;
 290 }
 291
 292 static void virtio_blk_handle_flush(VirtIOBlockReq *req, MultiReqBuffer *mrb)
 293 {
 294     bdrv_acct_start(req->dev->bs, &req->acct, 0, BDRV_ACCT_FLUSH);
 295
 296     /*
 297      * Make sure all outstanding writes are posted to the backing device.
 298      */
 299     virtio_submit_multiwrite(req->dev->bs, mrb);
 300     bdrv_aio_flush(req->dev->bs, virtio_blk_flush_complete, req);
 301 }
 302
 303 static void virtio_blk_handle_write(VirtIOBlockReq *req, MultiReqBuffer *mrb)
 304 {
 305     BlockRequest *blkreq;
 306     uint64_t sector;
 307
 308     sector = ldq_p(&req->out->sector);
 309
 310     bdrv_acct_start(req->dev->bs, &req->acct, req->qiov.size, BDRV_ACCT_WRITE);
 311
 312     trace_virtio_blk_handle_write(req, sector, req->qiov.size / 512);
 313
 314     if (sector & req->dev->sector_mask) {
 315         virtio_blk_rw_complete(req, -EIO);
 316         return;
 317     }
 318     if (req->qiov.size % req->dev->conf->logical_block_size) {
 319         virtio_blk_rw_complete(req, -EIO);
 320         return;
 321     }
 322
 323     if (mrb->num_writes == 32) {
 324         virtio_submit_multiwrite(req->dev->bs, mrb);
 325     }
 326
 327     blkreq = &mrb->blkreq[mrb->num_writes];
 328     blkreq->sector = sector;
 329     blkreq->nb_sectors = req->qiov.size / BDRV_SECTOR_SIZE;
 330     blkreq->qiov = &req->qiov;
 331     blkreq->cb = virtio_blk_rw_complete;
 332     blkreq->opaque = req;
 333     blkreq->error = 0;
 334
 335     mrb->num_writes++;
 336 }
 337
 338 static void virtio_blk_handle_read(VirtIOBlockReq *req)
 339 {
 340     uint64_t sector;
 341
 342     sector = ldq_p(&req->out->sector);
 343
 344     bdrv_acct_start(req->dev->bs, &req->acct, req->qiov.size, BDRV_ACCT_READ);
 345
 346     trace_virtio_blk_handle_read(req, sector, req->qiov.size / 512);
 347
 348     if (sector & req->dev->sector_mask) {
 349         virtio_blk_rw_complete(req, -EIO);
 350         return;
 351     }
 352     if (req->qiov.size % req->dev->conf->logical_block_size) {
 353         virtio_blk_rw_complete(req, -EIO);
 354         return;
 355     }
 356     bdrv_aio_readv(req->dev->bs, sector, &req->qiov,
 357                    req->qiov.size / BDRV_SECTOR_SIZE,
 358                    virtio_blk_rw_complete, req);
 359 }
 360
 361 static void virtio_blk_handle_request(VirtIOBlockReq *req,
 362     MultiReqBuffer *mrb)
 363 {
 364     uint32_t type;
 365
 366     if (req->elem.out_num < 1 || req->elem.in_num < 1) {
 367         error_report("virtio-blk missing headers");
 368         exit(1);
 369     }
 370
 371     if (req->elem.out_sg[0].iov_len < sizeof(*req->out) ||
 372         req->elem.in_sg[req->elem.in_num - 1].iov_len < sizeof(*req->in)) {
 373         error_report("virtio-blk header not in correct element");
 374         exit(1);
 375     }
 376
 377     req->out = (void *)req->elem.out_sg[0].iov_base;
 378     req->in = (void *)req->elem.in_sg[req->elem.in_num - 1].iov_base;
 379
 380     type = ldl_p(&req->out->type);
 381
 382     if (type & VIRTIO_BLK_T_FLUSH) {
 383         virtio_blk_handle_flush(req, mrb);
 384     } else if (type & VIRTIO_BLK_T_SCSI_CMD) {
 385         virtio_blk_handle_scsi(req);
 386     } else if (type & VIRTIO_BLK_T_GET_ID) {
 387         VirtIOBlock *s = req->dev;
 388
 389         /*
 390          * NB: per existing s/n string convention the string is
 391          * terminated by '\0' only when shorter than buffer.
 392          */
 393         strncpy(req->elem.in_sg[0].iov_base,
 394                 s->blk->serial ? s->blk->serial : "",
 395                 MIN(req->elem.in_sg[0].iov_len, VIRTIO_BLK_ID_BYTES));
 396         virtio_blk_req_complete(req, VIRTIO_BLK_S_OK);
 397         g_free(req);
 398     } else if (type & VIRTIO_BLK_T_OUT) {
 399         qemu_iovec_init_external(&req->qiov, &req->elem.out_sg[1],
 400                                  req->elem.out_num - 1);
 401         virtio_blk_handle_write(req, mrb);
 402     } else {
 403         qemu_iovec_init_external(&req->qiov, &req->elem.in_sg[0],
 404                                  req->elem.in_num - 1);
 405         virtio_blk_handle_read(req);
 406     }
 407 }
 408
 409 static void virtio_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
 410 {
 411     VirtIOBlock *s = to_virtio_blk(vdev);
 412     VirtIOBlockReq *req;
 413     MultiReqBuffer mrb = {
 414         .num_writes = 0,
 415     };
 416
 417     while ((req = virtio_blk_get_request(s))) {
 418         virtio_blk_handle_request(req, &mrb);
 419     }
 420
 421     virtio_submit_multiwrite(s->bs, &mrb);
 422
 423     /*
 424      * FIXME: Want to check for completions before returning to guest mode,
 425      * so cached reads and writes are reported as quickly as possible. But
 426      * that should be done in the generic block layer.
 427      */
 428 }
 429
 430 static void virtio_blk_dma_restart_bh(void *opaque)
 431 {
 432     VirtIOBlock *s = opaque;
 433     VirtIOBlockReq *req = s->rq;
 434     MultiReqBuffer mrb = {
 435         .num_writes = 0,
 436     };
 437
 438     qemu_bh_delete(s->bh);
 439     s->bh = NULL;
 440
 441     s->rq = NULL;
 442
 443     while (req) {
 444         virtio_blk_handle_request(req, &mrb);
 445         req = req->next;
 446     }
 447
 448     virtio_submit_multiwrite(s->bs, &mrb);
 449 }
 450
 451 static void virtio_blk_dma_restart_cb(void *opaque, int running,
 452                                       RunState state)
 453 {
 454     VirtIOBlock *s = opaque;
 455
 456     if (!running)
 457         return;
 458
 459     if (!s->bh) {
 460         s->bh = qemu_bh_new(virtio_blk_dma_restart_bh, s);
 461         qemu_bh_schedule(s->bh);
 462     }
 463 }
 464
 465 static void virtio_blk_reset(VirtIODevice *vdev)
 466 {
 467     /*
 468      * This should cancel pending requests, but can't do nicely until there
 469      * are per-device request lists.
 470      */
 471     bdrv_drain_all();
 472 }
 473
 474 /* coalesce internal state, copy to pci i/o region 0
 475  */
 476 static void virtio_blk_update_config(VirtIODevice *vdev, uint8_t *config)
 477 {
 478     VirtIOBlock *s = to_virtio_blk(vdev);
 479     struct virtio_blk_config blkcfg;
 480     uint64_t capacity;
 481     int cylinders, heads, secs;
 482     int blk_size = s->conf->logical_block_size;
 483
 484     bdrv_get_geometry(s->bs, &capacity);
 485     bdrv_get_geometry_hint(s->bs, &cylinders, &heads, &secs);
 486     memset(&blkcfg, 0, sizeof(blkcfg));
 487     stq_raw(&blkcfg.capacity, capacity);
 488     stl_raw(&blkcfg.seg_max, 128 - 2);
 489     stw_raw(&blkcfg.cylinders, cylinders);
 490     stl_raw(&blkcfg.blk_size, blk_size);
 491     stw_raw(&blkcfg.min_io_size, s->conf->min_io_size / blk_size);
 492     stw_raw(&blkcfg.opt_io_size, s->conf->opt_io_size / blk_size);
 493     blkcfg.heads = heads;
 494     /*
 495      * We must ensure that the block device capacity is a multiple of
 496      * the logical block size. If that is not the case, lets use
 497      * sector_mask to adopt the geometry to have a correct picture.
 498      * For those devices where the capacity is ok for the given geometry
 499      * we dont touch the sector value of the geometry, since some devices
 500      * (like s390 dasd) need a specific value. Here the capacity is already
 501      * cyls*heads*secs*blk_size and the sector value is not block size
 502      * divided by 512 - instead it is the amount of blk_size blocks
 503      * per track (cylinder).
 504      */
 505     if (bdrv_getlength(s->bs) /  heads / secs % blk_size) {
 506         blkcfg.sectors = secs & ~s->sector_mask;
 507     } else {
 508         blkcfg.sectors = secs;
 509     }
 510     blkcfg.size_max = 0;
 511     blkcfg.physical_block_exp = get_physical_block_exp(s->conf);
 512     blkcfg.alignment_offset = 0;
 513     memcpy(config, &blkcfg, sizeof(struct virtio_blk_config));
 514 }
 515
 516 static uint32_t virtio_blk_get_features(VirtIODevice *vdev, uint32_t features)
 517 {
 518     VirtIOBlock *s = to_virtio_blk(vdev);
 519
 520     features |= (1 << VIRTIO_BLK_F_SEG_MAX);
 521     features |= (1 << VIRTIO_BLK_F_GEOMETRY);
 522     features |= (1 << VIRTIO_BLK_F_TOPOLOGY);
 523     features |= (1 << VIRTIO_BLK_F_BLK_SIZE);
 524     features |= (1 << VIRTIO_BLK_F_SCSI);
 525
 526     if (bdrv_enable_write_cache(s->bs))
 527         features |= (1 << VIRTIO_BLK_F_WCACHE);
 528
 529     if (bdrv_is_read_only(s->bs))
 530         features |= 1 << VIRTIO_BLK_F_RO;
 531
 532     return features;
 533 }
 534
 535 static void virtio_blk_save(QEMUFile *f, void *opaque)
 536 {
 537     VirtIOBlock *s = opaque;
 538     VirtIOBlockReq *req = s->rq;
 539
 540     virtio_save(&s->vdev, f);
 541
 542     while (req) {
 543         qemu_put_sbyte(f, 1);
 544         qemu_put_buffer(f, (unsigned char*)&req->elem, sizeof(req->elem));
 545         req = req->next;
 546     }
 547     qemu_put_sbyte(f, 0);
 548 }
 549
 550 static int virtio_blk_load(QEMUFile *f, void *opaque, int version_id)
 551 {
 552     VirtIOBlock *s = opaque;
 553     int ret;
 554
 555     if (version_id != 2)
 556         return -EINVAL;
 557
 558     ret = virtio_load(&s->vdev, f);
 559     if (ret) {
 560         return ret;
 561     }
 562
 563     while (qemu_get_sbyte(f)) {
 564         VirtIOBlockReq *req = virtio_blk_alloc_request(s);
 565         qemu_get_buffer(f, (unsigned char*)&req->elem, sizeof(req->elem));
 566         req->next = s->rq;
 567         s->rq = req;
 568
 569         virtqueue_map_sg(req->elem.in_sg, req->elem.in_addr,
 570             req->elem.in_num, 1);
 571         virtqueue_map_sg(req->elem.out_sg, req->elem.out_addr,
 572             req->elem.out_num, 0);
 573     }
 574
 575     return 0;
 576 }
 577
 578 static void virtio_blk_resize(void *opaque)
 579 {
 580     VirtIOBlock *s = opaque;
 581
 582     virtio_notify_config(&s->vdev);
 583 }
 584
 585 static const BlockDevOps virtio_block_ops = {
 586     .resize_cb = virtio_blk_resize,
 587 };
 588
 589 VirtIODevice *virtio_blk_init(DeviceState *dev, VirtIOBlkConf *blk)
 590 {
 591     VirtIOBlock *s;
 592     int cylinders, heads, secs;
 593     static int virtio_blk_id;
 594     DriveInfo *dinfo;
 595
 596     if (!blk->conf.bs) {
 597         error_report("drive property not set");
 598         return NULL;
 599     }
 600     if (!bdrv_is_inserted(blk->conf.bs)) {
 601         error_report("Device needs media, but drive is empty");
 602         return NULL;
 603     }
 604
 605     if (!blk->serial) {
 606         /* try to fall back to value set with legacy -drive serial=... */
 607         dinfo = drive_get_by_blockdev(blk->conf.bs);
 608         if (*dinfo->serial) {
 609             blk->serial = strdup(dinfo->serial);
 610         }
 611     }
 612
 613     s = (VirtIOBlock *)virtio_common_init("virtio-blk", VIRTIO_ID_BLOCK,
 614                                           sizeof(struct virtio_blk_config),
 615                                           sizeof(VirtIOBlock));
 616
 617     s->vdev.get_config = virtio_blk_update_config;
 618     s->vdev.get_features = virtio_blk_get_features;
 619     s->vdev.reset = virtio_blk_reset;
 620     s->bs = blk->conf.bs;
 621     s->conf = &blk->conf;
 622     s->blk = blk;
 623     s->rq = NULL;
 624     s->sector_mask = (s->conf->logical_block_size / BDRV_SECTOR_SIZE) - 1;
 625     bdrv_guess_geometry(s->bs, &cylinders, &heads, &secs);
 626
 627     s->vq = virtio_add_queue(&s->vdev, 128, virtio_blk_handle_output);
 628
 629     qemu_add_vm_change_state_handler(virtio_blk_dma_restart_cb, s);
 630     s->qdev = dev;
 631     register_savevm(dev, "virtio-blk", virtio_blk_id++, 2,
 632                     virtio_blk_save, virtio_blk_load, s);
 633     bdrv_set_dev_ops(s->bs, &virtio_block_ops, s);
 634     bdrv_set_buffer_alignment(s->bs, s->conf->logical_block_size);
 635
 636     bdrv_iostatus_enable(s->bs);
 637     add_boot_device_path(s->conf->bootindex, dev, "/disk@0,0");
 638
 639     return &s->vdev;
 640 }
 641
 642 void virtio_blk_exit(VirtIODevice *vdev)
 643 {
 644     VirtIOBlock *s = to_virtio_blk(vdev);
 645     unregister_savevm(s->qdev, "virtio-blk", s);
 646     blockdev_mark_auto_del(s->bs);
 647     virtio_cleanup(vdev);
 648 }