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 "hw/block-common.h"
  18 #include "blockdev.h"
  19 #include "virtio-blk.h"
  20 #include "scsi-defs.h"
  21 #ifdef __linux__
  22 # include <scsi/sg.h>
  23 #endif
  24
  25 typedef struct VirtIOBlock
  26 {
  27     VirtIODevice vdev;
  28     BlockDriverState *bs;
  29     VirtQueue *vq;
  30     void *rq;
  31     QEMUBH *bh;
  32     BlockConf *conf;
  33     VirtIOBlkConf *blk;
  34     unsigned short sector_mask;
  35     DeviceState *qdev;
  36 } VirtIOBlock;
  37
  38 static VirtIOBlock *to_virtio_blk(VirtIODevice *vdev)
  39 {
  40     return (VirtIOBlock *)vdev;
  41 }
  42
  43 typedef struct VirtIOBlockReq
  44 {
  45     VirtIOBlock *dev;
  46     VirtQueueElement elem;
  47     struct virtio_blk_inhdr *in;
  48     struct virtio_blk_outhdr *out;
  49     struct virtio_scsi_inhdr *scsi;
  50     QEMUIOVector qiov;
  51     struct VirtIOBlockReq *next;
  52     BlockAcctCookie acct;
  53 } VirtIOBlockReq;
  54
  55 static void virtio_blk_req_complete(VirtIOBlockReq *req, int status)
  56 {
  57     VirtIOBlock *s = req->dev;
  58
  59     trace_virtio_blk_req_complete(req, status);
  60
  61     stb_p(&req->in->status, status);
  62     virtqueue_push(s->vq, &req->elem, req->qiov.size + sizeof(*req->in));
  63     virtio_notify(&s->vdev, s->vq);
  64 }
  65
  66 static int virtio_blk_handle_rw_error(VirtIOBlockReq *req, int error,
  67     int is_read)
  68 {
  69     BlockErrorAction action = bdrv_get_on_error(req->dev->bs, is_read);
  70     VirtIOBlock *s = req->dev;
  71
  72     if (action == BLOCK_ERR_IGNORE) {
  73         bdrv_emit_qmp_error_event(s->bs, BDRV_ACTION_IGNORE, is_read);
  74         return 0;
  75     }
  76
  77     if ((error == ENOSPC && action == BLOCK_ERR_STOP_ENOSPC)
  78             || action == BLOCK_ERR_STOP_ANY) {
  79         req->next = s->rq;
  80         s->rq = req;
  81         bdrv_emit_qmp_error_event(s->bs, BDRV_ACTION_STOP, is_read);
  82         vm_stop(RUN_STATE_IO_ERROR);
  83         bdrv_iostatus_set_err(s->bs, error);
  84     } else {
  85         virtio_blk_req_complete(req, VIRTIO_BLK_S_IOERR);
  86         bdrv_acct_done(s->bs, &req->acct);
  87         g_free(req);
  88         bdrv_emit_qmp_error_event(s->bs, BDRV_ACTION_REPORT, is_read);
  89     }
  90
  91     return 1;
  92 }
  93
  94 static void virtio_blk_rw_complete(void *opaque, int ret)
  95 {
  96     VirtIOBlockReq *req = opaque;
  97
  98     trace_virtio_blk_rw_complete(req, ret);
  99
 100     if (ret) {
 101         int is_read = !(ldl_p(&req->out->type) & VIRTIO_BLK_T_OUT);
 102         if (virtio_blk_handle_rw_error(req, -ret, is_read))
 103             return;
 104     }
 105
 106     virtio_blk_req_complete(req, VIRTIO_BLK_S_OK);
 107     bdrv_acct_done(req->dev->bs, &req->acct);
 108     g_free(req);
 109 }
 110
 111 static void virtio_blk_flush_complete(void *opaque, int ret)
 112 {
 113     VirtIOBlockReq *req = opaque;
 114
 115     if (ret) {
 116         if (virtio_blk_handle_rw_error(req, -ret, 0)) {
 117             return;
 118         }
 119     }
 120
 121     virtio_blk_req_complete(req, VIRTIO_BLK_S_OK);
 122     bdrv_acct_done(req->dev->bs, &req->acct);
 123     g_free(req);
 124 }
 125
 126 static VirtIOBlockReq *virtio_blk_alloc_request(VirtIOBlock *s)
 127 {
 128     VirtIOBlockReq *req = g_malloc(sizeof(*req));
 129     req->dev = s;
 130     req->qiov.size = 0;
 131     req->next = NULL;
 132     return req;
 133 }
 134
 135 static VirtIOBlockReq *virtio_blk_get_request(VirtIOBlock *s)
 136 {
 137     VirtIOBlockReq *req = virtio_blk_alloc_request(s);
 138
 139     if (req != NULL) {
 140         if (!virtqueue_pop(s->vq, &req->elem)) {
 141             g_free(req);
 142             return NULL;
 143         }
 144     }
 145
 146     return req;
 147 }
 148
 149 static void virtio_blk_handle_scsi(VirtIOBlockReq *req)
 150 {
 151 #ifdef __linux__
 152     int ret;
 153     int i;
 154 #endif
 155     int status = VIRTIO_BLK_S_OK;
 156
 157     /*
 158      * We require at least one output segment each for the virtio_blk_outhdr
 159      * and the SCSI command block.
 160      *
 161      * We also at least require the virtio_blk_inhdr, the virtio_scsi_inhdr
 162      * and the sense buffer pointer in the input segments.
 163      */
 164     if (req->elem.out_num < 2 || req->elem.in_num < 3) {
 165         virtio_blk_req_complete(req, VIRTIO_BLK_S_IOERR);
 166         g_free(req);
 167         return;
 168     }
 169
 170     /*
 171      * The scsi inhdr is placed in the second-to-last input segment, just
 172      * before the regular inhdr.
 173      */
 174     req->scsi = (void *)req->elem.in_sg[req->elem.in_num - 2].iov_base;
 175
 176     if (!req->dev->blk->scsi) {
 177         status = VIRTIO_BLK_S_UNSUPP;
 178         goto fail;
 179     }
 180
 181     /*
 182      * No support for bidirection commands yet.
 183      */
 184     if (req->elem.out_num > 2 && req->elem.in_num > 3) {
 185         status = VIRTIO_BLK_S_UNSUPP;
 186         goto fail;
 187     }
 188
 189 #ifdef __linux__
 190     struct sg_io_hdr hdr;
 191     memset(&hdr, 0, sizeof(struct sg_io_hdr));
 192     hdr.interface_id = 'S';
 193     hdr.cmd_len = req->elem.out_sg[1].iov_len;
 194     hdr.cmdp = req->elem.out_sg[1].iov_base;
 195     hdr.dxfer_len = 0;
 196
 197     if (req->elem.out_num > 2) {
 198         /*
 199          * If there are more than the minimally required 2 output segments
 200          * there is write payload starting from the third iovec.
 201          */
 202         hdr.dxfer_direction = SG_DXFER_TO_DEV;
 203         hdr.iovec_count = req->elem.out_num - 2;
 204
 205         for (i = 0; i < hdr.iovec_count; i++)
 206             hdr.dxfer_len += req->elem.out_sg[i + 2].iov_len;
 207
 208         hdr.dxferp = req->elem.out_sg + 2;
 209
 210     } else if (req->elem.in_num > 3) {
 211         /*
 212          * If we have more than 3 input segments the guest wants to actually
 213          * read data.
 214          */
 215         hdr.dxfer_direction = SG_DXFER_FROM_DEV;
 216         hdr.iovec_count = req->elem.in_num - 3;
 217         for (i = 0; i < hdr.iovec_count; i++)
 218             hdr.dxfer_len += req->elem.in_sg[i].iov_len;
 219
 220         hdr.dxferp = req->elem.in_sg;
 221     } else {
 222         /*
 223          * Some SCSI commands don't actually transfer any data.
 224          */
 225         hdr.dxfer_direction = SG_DXFER_NONE;
 226     }
 227
 228     hdr.sbp = req->elem.in_sg[req->elem.in_num - 3].iov_base;
 229     hdr.mx_sb_len = req->elem.in_sg[req->elem.in_num - 3].iov_len;
 230
 231     ret = bdrv_ioctl(req->dev->bs, SG_IO, &hdr);
 232     if (ret) {
 233         status = VIRTIO_BLK_S_UNSUPP;
 234         goto fail;
 235     }
 236
 237     /*
 238      * From SCSI-Generic-HOWTO: "Some lower level drivers (e.g. ide-scsi)
 239      * clear the masked_status field [hence status gets cleared too, see
 240      * block/scsi_ioctl.c] even when a CHECK_CONDITION or COMMAND_TERMINATED
 241      * status has occurred.  However they do set DRIVER_SENSE in driver_status
 242      * field. Also a (sb_len_wr > 0) indicates there is a sense buffer.
 243      */
 244     if (hdr.status == 0 && hdr.sb_len_wr > 0) {
 245         hdr.status = CHECK_CONDITION;
 246     }
 247
 248     stl_p(&req->scsi->errors,
 249           hdr.status | (hdr.msg_status << 8) |
 250           (hdr.host_status << 16) | (hdr.driver_status << 24));
 251     stl_p(&req->scsi->residual, hdr.resid);
 252     stl_p(&req->scsi->sense_len, hdr.sb_len_wr);
 253     stl_p(&req->scsi->data_len, hdr.dxfer_len);
 254
 255     virtio_blk_req_complete(req, status);
 256     g_free(req);
 257     return;
 258 #else
 259     abort();
 260 #endif
 261
 262 fail:
 263     /* Just put anything nonzero so that the ioctl fails in the guest.  */
 264     stl_p(&req->scsi->errors, 255);
 265     virtio_blk_req_complete(req, status);
 266     g_free(req);
 267 }
 268
 269 typedef struct MultiReqBuffer {
 270     BlockRequest        blkreq[32];
 271     unsigned int        num_writes;
 272 } MultiReqBuffer;
 273
 274 static void virtio_submit_multiwrite(BlockDriverState *bs, MultiReqBuffer *mrb)
 275 {
 276     int i, ret;
 277
 278     if (!mrb->num_writes) {
 279         return;
 280     }
 281
 282     ret = bdrv_aio_multiwrite(bs, mrb->blkreq, mrb->num_writes);
 283     if (ret != 0) {
 284         for (i = 0; i < mrb->num_writes; i++) {
 285             if (mrb->blkreq[i].error) {
 286                 virtio_blk_rw_complete(mrb->blkreq[i].opaque, -EIO);
 287             }
 288         }
 289     }
 290
 291     mrb->num_writes = 0;
 292 }
 293
 294 static void virtio_blk_handle_flush(VirtIOBlockReq *req, MultiReqBuffer *mrb)
 295 {
 296     bdrv_acct_start(req->dev->bs, &req->acct, 0, BDRV_ACCT_FLUSH);
 297
 298     /*
 299      * Make sure all outstanding writes are posted to the backing device.
 300      */
 301     virtio_submit_multiwrite(req->dev->bs, mrb);
 302     bdrv_aio_flush(req->dev->bs, virtio_blk_flush_complete, req);
 303 }
 304
 305 static void virtio_blk_handle_write(VirtIOBlockReq *req, MultiReqBuffer *mrb)
 306 {
 307     BlockRequest *blkreq;
 308     uint64_t sector;
 309
 310     sector = ldq_p(&req->out->sector);
 311
 312     bdrv_acct_start(req->dev->bs, &req->acct, req->qiov.size, BDRV_ACCT_WRITE);
 313
 314     trace_virtio_blk_handle_write(req, sector, req->qiov.size / 512);
 315
 316     if (sector & req->dev->sector_mask) {
 317         virtio_blk_rw_complete(req, -EIO);
 318         return;
 319     }
 320     if (req->qiov.size % req->dev->conf->logical_block_size) {
 321         virtio_blk_rw_complete(req, -EIO);
 322         return;
 323     }
 324
 325     if (mrb->num_writes == 32) {
 326         virtio_submit_multiwrite(req->dev->bs, mrb);
 327     }
 328
 329     blkreq = &mrb->blkreq[mrb->num_writes];
 330     blkreq->sector = sector;
 331     blkreq->nb_sectors = req->qiov.size / BDRV_SECTOR_SIZE;
 332     blkreq->qiov = &req->qiov;
 333     blkreq->cb = virtio_blk_rw_complete;
 334     blkreq->opaque = req;
 335     blkreq->error = 0;
 336
 337     mrb->num_writes++;
 338 }
 339
 340 static void virtio_blk_handle_read(VirtIOBlockReq *req)
 341 {
 342     uint64_t sector;
 343
 344     sector = ldq_p(&req->out->sector);
 345
 346     bdrv_acct_start(req->dev->bs, &req->acct, req->qiov.size, BDRV_ACCT_READ);
 347
 348     trace_virtio_blk_handle_read(req, sector, req->qiov.size / 512);
 349
 350     if (sector & req->dev->sector_mask) {
 351         virtio_blk_rw_complete(req, -EIO);
 352         return;
 353     }
 354     if (req->qiov.size % req->dev->conf->logical_block_size) {
 355         virtio_blk_rw_complete(req, -EIO);
 356         return;
 357     }
 358     bdrv_aio_readv(req->dev->bs, sector, &req->qiov,
 359                    req->qiov.size / BDRV_SECTOR_SIZE,
 360                    virtio_blk_rw_complete, req);
 361 }
 362
 363 static void virtio_blk_handle_request(VirtIOBlockReq *req,
 364     MultiReqBuffer *mrb)
 365 {
 366     uint32_t type;
 367
 368     if (req->elem.out_num < 1 || req->elem.in_num < 1) {
 369         error_report("virtio-blk missing headers");
 370         exit(1);
 371     }
 372
 373     if (req->elem.out_sg[0].iov_len < sizeof(*req->out) ||
 374         req->elem.in_sg[req->elem.in_num - 1].iov_len < sizeof(*req->in)) {
 375         error_report("virtio-blk header not in correct element");
 376         exit(1);
 377     }
 378
 379     req->out = (void *)req->elem.out_sg[0].iov_base;
 380     req->in = (void *)req->elem.in_sg[req->elem.in_num - 1].iov_base;
 381
 382     type = ldl_p(&req->out->type);
 383
 384     if (type & VIRTIO_BLK_T_FLUSH) {
 385         virtio_blk_handle_flush(req, mrb);
 386     } else if (type & VIRTIO_BLK_T_SCSI_CMD) {
 387         virtio_blk_handle_scsi(req);
 388     } else if (type & VIRTIO_BLK_T_GET_ID) {
 389         VirtIOBlock *s = req->dev;
 390
 391         /*
 392          * NB: per existing s/n string convention the string is
 393          * terminated by '\0' only when shorter than buffer.
 394          */
 395         strncpy(req->elem.in_sg[0].iov_base,
 396                 s->blk->serial ? s->blk->serial : "",
 397                 MIN(req->elem.in_sg[0].iov_len, VIRTIO_BLK_ID_BYTES));
 398         virtio_blk_req_complete(req, VIRTIO_BLK_S_OK);
 399         g_free(req);
 400     } else if (type & VIRTIO_BLK_T_OUT) {
 401         qemu_iovec_init_external(&req->qiov, &req->elem.out_sg[1],
 402                                  req->elem.out_num - 1);
 403         virtio_blk_handle_write(req, mrb);
 404     } else {
 405         qemu_iovec_init_external(&req->qiov, &req->elem.in_sg[0],
 406                                  req->elem.in_num - 1);
 407         virtio_blk_handle_read(req);
 408     }
 409 }
 410
 411 static void virtio_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
 412 {
 413     VirtIOBlock *s = to_virtio_blk(vdev);
 414     VirtIOBlockReq *req;
 415     MultiReqBuffer mrb = {
 416         .num_writes = 0,
 417     };
 418
 419     while ((req = virtio_blk_get_request(s))) {
 420         virtio_blk_handle_request(req, &mrb);
 421     }
 422
 423     virtio_submit_multiwrite(s->bs, &mrb);
 424
 425     /*
 426      * FIXME: Want to check for completions before returning to guest mode,
 427      * so cached reads and writes are reported as quickly as possible. But
 428      * that should be done in the generic block layer.
 429      */
 430 }
 431
 432 static void virtio_blk_dma_restart_bh(void *opaque)
 433 {
 434     VirtIOBlock *s = opaque;
 435     VirtIOBlockReq *req = s->rq;
 436     MultiReqBuffer mrb = {
 437         .num_writes = 0,
 438     };
 439
 440     qemu_bh_delete(s->bh);
 441     s->bh = NULL;
 442
 443     s->rq = NULL;
 444
 445     while (req) {
 446         virtio_blk_handle_request(req, &mrb);
 447         req = req->next;
 448     }
 449
 450     virtio_submit_multiwrite(s->bs, &mrb);
 451 }
 452
 453 static void virtio_blk_dma_restart_cb(void *opaque, int running,
 454                                       RunState state)
 455 {
 456     VirtIOBlock *s = opaque;
 457
 458     if (!running)
 459         return;
 460
 461     if (!s->bh) {
 462         s->bh = qemu_bh_new(virtio_blk_dma_restart_bh, s);
 463         qemu_bh_schedule(s->bh);
 464     }
 465 }
 466
 467 static void virtio_blk_reset(VirtIODevice *vdev)
 468 {
 469     /*
 470      * This should cancel pending requests, but can't do nicely until there
 471      * are per-device request lists.
 472      */
 473     bdrv_drain_all();
 474 }
 475
 476 /* coalesce internal state, copy to pci i/o region 0
 477  */
 478 static void virtio_blk_update_config(VirtIODevice *vdev, uint8_t *config)
 479 {
 480     VirtIOBlock *s = to_virtio_blk(vdev);
 481     struct virtio_blk_config blkcfg;
 482     uint64_t capacity;
 483     int blk_size = s->conf->logical_block_size;
 484
 485     bdrv_get_geometry(s->bs, &capacity);
 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, s->conf->cyls);
 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 = s->conf->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) /  s->conf->heads / s->conf->secs % blk_size) {
 506         blkcfg.sectors = s->conf->secs & ~s->sector_mask;
 507     } else {
 508         blkcfg.sectors = s->conf->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     static int virtio_blk_id;
 593
 594     if (!blk->conf.bs) {
 595         error_report("drive property not set");
 596         return NULL;
 597     }
 598     if (!bdrv_is_inserted(blk->conf.bs)) {
 599         error_report("Device needs media, but drive is empty");
 600         return NULL;
 601     }
 602
 603     blkconf_serial(&blk->conf, &blk->serial);
 604     if (blkconf_geometry(&blk->conf, NULL, 65535, 255, 255) < 0) {
 605         return NULL;
 606     }
 607
 608     s = (VirtIOBlock *)virtio_common_init("virtio-blk", VIRTIO_ID_BLOCK,
 609                                           sizeof(struct virtio_blk_config),
 610                                           sizeof(VirtIOBlock));
 611
 612     s->vdev.get_config = virtio_blk_update_config;
 613     s->vdev.get_features = virtio_blk_get_features;
 614     s->vdev.reset = virtio_blk_reset;
 615     s->bs = blk->conf.bs;
 616     s->conf = &blk->conf;
 617     s->blk = blk;
 618     s->rq = NULL;
 619     s->sector_mask = (s->conf->logical_block_size / BDRV_SECTOR_SIZE) - 1;
 620
 621     s->vq = virtio_add_queue(&s->vdev, 128, virtio_blk_handle_output);
 622
 623     qemu_add_vm_change_state_handler(virtio_blk_dma_restart_cb, s);
 624     s->qdev = dev;
 625     register_savevm(dev, "virtio-blk", virtio_blk_id++, 2,
 626                     virtio_blk_save, virtio_blk_load, s);
 627     bdrv_set_dev_ops(s->bs, &virtio_block_ops, s);
 628     bdrv_set_buffer_alignment(s->bs, s->conf->logical_block_size);
 629
 630     bdrv_iostatus_enable(s->bs);
 631     add_boot_device_path(s->conf->bootindex, dev, "/disk@0,0");
 632
 633     return &s->vdev;
 634 }
 635
 636 void virtio_blk_exit(VirtIODevice *vdev)
 637 {
 638     VirtIOBlock *s = to_virtio_blk(vdev);
 639     unregister_savevm(s->qdev, "virtio-blk", s);
 640     blockdev_mark_auto_del(s->bs);
 641     virtio_cleanup(vdev);
 642 }