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 #else
 258     abort();
 259 #endif
 260
 261 fail:
 262     /* Just put anything nonzero so that the ioctl fails in the guest.  */
 263     stl_p(&req->scsi->errors, 255);
 264     virtio_blk_req_complete(req, status);
 265     g_free(req);
 266 }
 267
 268 typedef struct MultiReqBuffer {
 269     BlockRequest        blkreq[32];
 270     unsigned int        num_writes;
 271 } MultiReqBuffer;
 272
 273 static void virtio_submit_multiwrite(BlockDriverState *bs, MultiReqBuffer *mrb)
 274 {
 275     int i, ret;
 276
 277     if (!mrb->num_writes) {
 278         return;
 279     }
 280
 281     ret = bdrv_aio_multiwrite(bs, mrb->blkreq, mrb->num_writes);
 282     if (ret != 0) {
 283         for (i = 0; i < mrb->num_writes; i++) {
 284             if (mrb->blkreq[i].error) {
 285                 virtio_blk_rw_complete(mrb->blkreq[i].opaque, -EIO);
 286             }
 287         }
 288     }
 289
 290     mrb->num_writes = 0;
 291 }
 292
 293 static void virtio_blk_handle_flush(VirtIOBlockReq *req, MultiReqBuffer *mrb)
 294 {
 295     bdrv_acct_start(req->dev->bs, &req->acct, 0, BDRV_ACCT_FLUSH);
 296
 297     /*
 298      * Make sure all outstanding writes are posted to the backing device.
 299      */
 300     virtio_submit_multiwrite(req->dev->bs, mrb);
 301     bdrv_aio_flush(req->dev->bs, virtio_blk_flush_complete, req);
 302 }
 303
 304 static void virtio_blk_handle_write(VirtIOBlockReq *req, MultiReqBuffer *mrb)
 305 {
 306     BlockRequest *blkreq;
 307     uint64_t sector;
 308
 309     sector = ldq_p(&req->out->sector);
 310
 311     bdrv_acct_start(req->dev->bs, &req->acct, req->qiov.size, BDRV_ACCT_WRITE);
 312
 313     trace_virtio_blk_handle_write(req, sector, req->qiov.size / 512);
 314
 315     if (sector & req->dev->sector_mask) {
 316         virtio_blk_rw_complete(req, -EIO);
 317         return;
 318     }
 319     if (req->qiov.size % req->dev->conf->logical_block_size) {
 320         virtio_blk_rw_complete(req, -EIO);
 321         return;
 322     }
 323
 324     if (mrb->num_writes == 32) {
 325         virtio_submit_multiwrite(req->dev->bs, mrb);
 326     }
 327
 328     blkreq = &mrb->blkreq[mrb->num_writes];
 329     blkreq->sector = sector;
 330     blkreq->nb_sectors = req->qiov.size / BDRV_SECTOR_SIZE;
 331     blkreq->qiov = &req->qiov;
 332     blkreq->cb = virtio_blk_rw_complete;
 333     blkreq->opaque = req;
 334     blkreq->error = 0;
 335
 336     mrb->num_writes++;
 337 }
 338
 339 static void virtio_blk_handle_read(VirtIOBlockReq *req)
 340 {
 341     uint64_t sector;
 342
 343     sector = ldq_p(&req->out->sector);
 344
 345     bdrv_acct_start(req->dev->bs, &req->acct, req->qiov.size, BDRV_ACCT_READ);
 346
 347     trace_virtio_blk_handle_read(req, sector, req->qiov.size / 512);
 348
 349     if (sector & req->dev->sector_mask) {
 350         virtio_blk_rw_complete(req, -EIO);
 351         return;
 352     }
 353     if (req->qiov.size % req->dev->conf->logical_block_size) {
 354         virtio_blk_rw_complete(req, -EIO);
 355         return;
 356     }
 357     bdrv_aio_readv(req->dev->bs, sector, &req->qiov,
 358                    req->qiov.size / BDRV_SECTOR_SIZE,
 359                    virtio_blk_rw_complete, req);
 360 }
 361
 362 static void virtio_blk_handle_request(VirtIOBlockReq *req,
 363     MultiReqBuffer *mrb)
 364 {
 365     uint32_t type;
 366
 367     if (req->elem.out_num < 1 || req->elem.in_num < 1) {
 368         error_report("virtio-blk missing headers");
 369         exit(1);
 370     }
 371
 372     if (req->elem.out_sg[0].iov_len < sizeof(*req->out) ||
 373         req->elem.in_sg[req->elem.in_num - 1].iov_len < sizeof(*req->in)) {
 374         error_report("virtio-blk header not in correct element");
 375         exit(1);
 376     }
 377
 378     req->out = (void *)req->elem.out_sg[0].iov_base;
 379     req->in = (void *)req->elem.in_sg[req->elem.in_num - 1].iov_base;
 380
 381     type = ldl_p(&req->out->type);
 382
 383     if (type & VIRTIO_BLK_T_FLUSH) {
 384         virtio_blk_handle_flush(req, mrb);
 385     } else if (type & VIRTIO_BLK_T_SCSI_CMD) {
 386         virtio_blk_handle_scsi(req);
 387     } else if (type & VIRTIO_BLK_T_GET_ID) {
 388         VirtIOBlock *s = req->dev;
 389
 390         /*
 391          * NB: per existing s/n string convention the string is
 392          * terminated by '\0' only when shorter than buffer.
 393          */
 394         strncpy(req->elem.in_sg[0].iov_base,
 395                 s->blk->serial ? s->blk->serial : "",
 396                 MIN(req->elem.in_sg[0].iov_len, VIRTIO_BLK_ID_BYTES));
 397         virtio_blk_req_complete(req, VIRTIO_BLK_S_OK);
 398         g_free(req);
 399     } else if (type & VIRTIO_BLK_T_OUT) {
 400         qemu_iovec_init_external(&req->qiov, &req->elem.out_sg[1],
 401                                  req->elem.out_num - 1);
 402         virtio_blk_handle_write(req, mrb);
 403     } else {
 404         qemu_iovec_init_external(&req->qiov, &req->elem.in_sg[0],
 405                                  req->elem.in_num - 1);
 406         virtio_blk_handle_read(req);
 407     }
 408 }
 409
 410 static void virtio_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
 411 {
 412     VirtIOBlock *s = to_virtio_blk(vdev);
 413     VirtIOBlockReq *req;
 414     MultiReqBuffer mrb = {
 415         .num_writes = 0,
 416     };
 417
 418     while ((req = virtio_blk_get_request(s))) {
 419         virtio_blk_handle_request(req, &mrb);
 420     }
 421
 422     virtio_submit_multiwrite(s->bs, &mrb);
 423
 424     /*
 425      * FIXME: Want to check for completions before returning to guest mode,
 426      * so cached reads and writes are reported as quickly as possible. But
 427      * that should be done in the generic block layer.
 428      */
 429 }
 430
 431 static void virtio_blk_dma_restart_bh(void *opaque)
 432 {
 433     VirtIOBlock *s = opaque;
 434     VirtIOBlockReq *req = s->rq;
 435     MultiReqBuffer mrb = {
 436         .num_writes = 0,
 437     };
 438
 439     qemu_bh_delete(s->bh);
 440     s->bh = NULL;
 441
 442     s->rq = NULL;
 443
 444     while (req) {
 445         virtio_blk_handle_request(req, &mrb);
 446         req = req->next;
 447     }
 448
 449     virtio_submit_multiwrite(s->bs, &mrb);
 450 }
 451
 452 static void virtio_blk_dma_restart_cb(void *opaque, int running,
 453                                       RunState state)
 454 {
 455     VirtIOBlock *s = opaque;
 456
 457     if (!running)
 458         return;
 459
 460     if (!s->bh) {
 461         s->bh = qemu_bh_new(virtio_blk_dma_restart_bh, s);
 462         qemu_bh_schedule(s->bh);
 463     }
 464 }
 465
 466 static void virtio_blk_reset(VirtIODevice *vdev)
 467 {
 468     /*
 469      * This should cancel pending requests, but can't do nicely until there
 470      * are per-device request lists.
 471      */
 472     bdrv_drain_all();
 473 }
 474
 475 /* coalesce internal state, copy to pci i/o region 0
 476  */
 477 static void virtio_blk_update_config(VirtIODevice *vdev, uint8_t *config)
 478 {
 479     VirtIOBlock *s = to_virtio_blk(vdev);
 480     struct virtio_blk_config blkcfg;
 481     uint64_t capacity;
 482     int blk_size = s->conf->logical_block_size;
 483
 484     bdrv_get_geometry(s->bs, &capacity);
 485     memset(&blkcfg, 0, sizeof(blkcfg));
 486     stq_raw(&blkcfg.capacity, capacity);
 487     stl_raw(&blkcfg.seg_max, 128 - 2);
 488     stw_raw(&blkcfg.cylinders, s->conf->cyls);
 489     stl_raw(&blkcfg.blk_size, blk_size);
 490     stw_raw(&blkcfg.min_io_size, s->conf->min_io_size / blk_size);
 491     stw_raw(&blkcfg.opt_io_size, s->conf->opt_io_size / blk_size);
 492     blkcfg.heads = s->conf->heads;
 493     /*
 494      * We must ensure that the block device capacity is a multiple of
 495      * the logical block size. If that is not the case, lets use
 496      * sector_mask to adopt the geometry to have a correct picture.
 497      * For those devices where the capacity is ok for the given geometry
 498      * we dont touch the sector value of the geometry, since some devices
 499      * (like s390 dasd) need a specific value. Here the capacity is already
 500      * cyls*heads*secs*blk_size and the sector value is not block size
 501      * divided by 512 - instead it is the amount of blk_size blocks
 502      * per track (cylinder).
 503      */
 504     if (bdrv_getlength(s->bs) /  s->conf->heads / s->conf->secs % blk_size) {
 505         blkcfg.sectors = s->conf->secs & ~s->sector_mask;
 506     } else {
 507         blkcfg.sectors = s->conf->secs;
 508     }
 509     blkcfg.size_max = 0;
 510     blkcfg.physical_block_exp = get_physical_block_exp(s->conf);
 511     blkcfg.alignment_offset = 0;
 512     memcpy(config, &blkcfg, sizeof(struct virtio_blk_config));
 513 }
 514
 515 static uint32_t virtio_blk_get_features(VirtIODevice *vdev, uint32_t features)
 516 {
 517     VirtIOBlock *s = to_virtio_blk(vdev);
 518
 519     features |= (1 << VIRTIO_BLK_F_SEG_MAX);
 520     features |= (1 << VIRTIO_BLK_F_GEOMETRY);
 521     features |= (1 << VIRTIO_BLK_F_TOPOLOGY);
 522     features |= (1 << VIRTIO_BLK_F_BLK_SIZE);
 523     features |= (1 << VIRTIO_BLK_F_SCSI);
 524
 525     if (bdrv_enable_write_cache(s->bs))
 526         features |= (1 << VIRTIO_BLK_F_WCACHE);
 527
 528     if (bdrv_is_read_only(s->bs))
 529         features |= 1 << VIRTIO_BLK_F_RO;
 530
 531     return features;
 532 }
 533
 534 static void virtio_blk_save(QEMUFile *f, void *opaque)
 535 {
 536     VirtIOBlock *s = opaque;
 537     VirtIOBlockReq *req = s->rq;
 538
 539     virtio_save(&s->vdev, f);
 540
 541     while (req) {
 542         qemu_put_sbyte(f, 1);
 543         qemu_put_buffer(f, (unsigned char*)&req->elem, sizeof(req->elem));
 544         req = req->next;
 545     }
 546     qemu_put_sbyte(f, 0);
 547 }
 548
 549 static int virtio_blk_load(QEMUFile *f, void *opaque, int version_id)
 550 {
 551     VirtIOBlock *s = opaque;
 552     int ret;
 553
 554     if (version_id != 2)
 555         return -EINVAL;
 556
 557     ret = virtio_load(&s->vdev, f);
 558     if (ret) {
 559         return ret;
 560     }
 561
 562     while (qemu_get_sbyte(f)) {
 563         VirtIOBlockReq *req = virtio_blk_alloc_request(s);
 564         qemu_get_buffer(f, (unsigned char*)&req->elem, sizeof(req->elem));
 565         req->next = s->rq;
 566         s->rq = req;
 567
 568         virtqueue_map_sg(req->elem.in_sg, req->elem.in_addr,
 569             req->elem.in_num, 1);
 570         virtqueue_map_sg(req->elem.out_sg, req->elem.out_addr,
 571             req->elem.out_num, 0);
 572     }
 573
 574     return 0;
 575 }
 576
 577 static void virtio_blk_resize(void *opaque)
 578 {
 579     VirtIOBlock *s = opaque;
 580
 581     virtio_notify_config(&s->vdev);
 582 }
 583
 584 static const BlockDevOps virtio_block_ops = {
 585     .resize_cb = virtio_blk_resize,
 586 };
 587
 588 VirtIODevice *virtio_blk_init(DeviceState *dev, VirtIOBlkConf *blk)
 589 {
 590     VirtIOBlock *s;
 591     static int virtio_blk_id;
 592
 593     if (!blk->conf.bs) {
 594         error_report("drive property not set");
 595         return NULL;
 596     }
 597     if (!bdrv_is_inserted(blk->conf.bs)) {
 598         error_report("Device needs media, but drive is empty");
 599         return NULL;
 600     }
 601
 602     blkconf_serial(&blk->conf, &blk->serial);
 603     if (blkconf_geometry(&blk->conf, NULL, 65535, 255, 255) < 0) {
 604         return NULL;
 605     }
 606
 607     s = (VirtIOBlock *)virtio_common_init("virtio-blk", VIRTIO_ID_BLOCK,
 608                                           sizeof(struct virtio_blk_config),
 609                                           sizeof(VirtIOBlock));
 610
 611     s->vdev.get_config = virtio_blk_update_config;
 612     s->vdev.get_features = virtio_blk_get_features;
 613     s->vdev.reset = virtio_blk_reset;
 614     s->bs = blk->conf.bs;
 615     s->conf = &blk->conf;
 616     s->blk = blk;
 617     s->rq = NULL;
 618     s->sector_mask = (s->conf->logical_block_size / BDRV_SECTOR_SIZE) - 1;
 619
 620     s->vq = virtio_add_queue(&s->vdev, 128, virtio_blk_handle_output);
 621
 622     qemu_add_vm_change_state_handler(virtio_blk_dma_restart_cb, s);
 623     s->qdev = dev;
 624     register_savevm(dev, "virtio-blk", virtio_blk_id++, 2,
 625                     virtio_blk_save, virtio_blk_load, s);
 626     bdrv_set_dev_ops(s->bs, &virtio_block_ops, s);
 627     bdrv_set_buffer_alignment(s->bs, s->conf->logical_block_size);
 628
 629     bdrv_iostatus_enable(s->bs);
 630     add_boot_device_path(s->conf->bootindex, dev, "/disk@0,0");
 631
 632     return &s->vdev;
 633 }
 634
 635 void virtio_blk_exit(VirtIODevice *vdev)
 636 {
 637     VirtIOBlock *s = to_virtio_blk(vdev);
 638     unregister_savevm(s->qdev, "virtio-blk", s);
 639     blockdev_mark_auto_del(s->bs);
 640     virtio_cleanup(vdev);
 641 }