palacios/src/devices/lnx_virtio_blk.c

   1 /*
   2  * This file is part of the Palacios Virtual Machine Monitor developed
   3  * by the V3VEE Project with funding from the United States National
   4  * Science Foundation and the Department of Energy.
   5  *
   6  * The V3VEE Project is a joint project between Northwestern University
   7  * and the University of New Mexico.  You can find out more at
   8  * http://www.v3vee.org
   9  *
  10  * Copyright (c) 2008, Jack Lange <jarusl@cs.northwestern.edu>
  11  * Copyright (c) 2008, The V3VEE Project <http://www.v3vee.org>
  12  * All rights reserved.
  13  *
  14  * Author: Jack Lange <jarusl@cs.northwestern.edu>
  15  *
  16  * This is free software.  You are permitted to use,
  17  * redistribute, and modify it as specified in the file "V3VEE_LICENSE".
  18  */
  19
  20 #include <palacios/vmm.h>
  21 #include <palacios/vmm_dev_mgr.h>
  22 #include <devices/lnx_virtio_pci.h>
  23 #include <palacios/vm_guest_mem.h>
  24
  25 #include <devices/pci.h>
  26
  27
  28
  29 #ifndef V3_CONFIG_DEBUG_VIRTIO_BLK
  30 #undef PrintDebug
  31 #define PrintDebug(fmt, args...)
  32 #endif
  33
  34
  35 #define SECTOR_SIZE 512
  36
  37 #define BLK_CAPACITY_PORT     20
  38 #define BLK_MAX_SIZE_PORT     28
  39 #define BLK_MAX_SEG_PORT      32
  40 #define BLK_CYLINDERS_PORT    36
  41 #define BLK_HEADS_PORT        38
  42 #define BLK_SECTS_PORT        39
  43
  44 #define BLK_IN_REQ            0
  45 #define BLK_OUT_REQ           1
  46 #define BLK_SCSI_CMD          2
  47
  48 #define BLK_BARRIER_FLAG     0x80000000
  49
  50 #define BLK_STATUS_OK             0
  51 #define BLK_STATUS_ERR            1
  52 #define BLK_STATUS_NOT_SUPPORTED  2
  53
  54
  55 struct blk_config {
  56     uint64_t capacity;
  57     uint32_t max_size;
  58     uint32_t max_seg;
  59     uint16_t cylinders;
  60     uint8_t heads;
  61     uint8_t sectors;
  62 } __attribute__((packed));
  63
  64
  65
  66 struct blk_op_hdr {
  67     uint32_t type;
  68     uint32_t prior;
  69     uint64_t sector;
  70 } __attribute__((packed));
  71
  72 #define QUEUE_SIZE 128
  73
  74 /* Host Feature flags */
  75 #define VIRTIO_BARRIER       0x01       /* Does host support barriers? */
  76 #define VIRTIO_SIZE_MAX      0x02       /* Indicates maximum segment size */
  77 #define VIRTIO_SEG_MAX       0x04       /* Indicates maximum # of segments */
  78 #define VIRTIO_LEGACY_GEOM   0x10       /* Indicates support of legacy geometry */
  79
  80
  81 struct virtio_dev_state {
  82     struct vm_device * pci_bus;
  83     struct list_head dev_list;
  84 };
  85
  86 struct virtio_blk_state {
  87
  88     struct pci_device * pci_dev;
  89     struct blk_config block_cfg;
  90     struct virtio_config virtio_cfg;
  91
  92
  93     struct virtio_queue queue;
  94
  95     struct v3_dev_blk_ops * ops;
  96
  97     void * backend_data;
  98
  99     int io_range_size;
 100
 101     struct virtio_dev_state * virtio_dev;
 102
 103     struct list_head dev_link;
 104 };
 105
 106
 107
 108
 109 static int blk_reset(struct virtio_blk_state * virtio) {
 110
 111     virtio->queue.ring_desc_addr = 0;
 112     virtio->queue.ring_avail_addr = 0;
 113     virtio->queue.ring_used_addr = 0;
 114     virtio->queue.pfn = 0;
 115     virtio->queue.cur_avail_idx = 0;
 116
 117     virtio->virtio_cfg.status = 0;
 118     virtio->virtio_cfg.pci_isr = 0;
 119     return 0;
 120 }
 121
 122
 123
 124
 125 static int handle_read_op(struct virtio_blk_state * blk_state, uint8_t * buf, uint64_t * sector, uint64_t len) {
 126     int ret = -1;
 127
 128     PrintDebug("Reading Disk\n");
 129     ret = blk_state->ops->read(buf, (*sector) * SECTOR_SIZE, len, (void *)(blk_state->backend_data));
 130     *sector += (len / SECTOR_SIZE);
 131
 132     return ret;
 133 }
 134
 135
 136 static int handle_write_op(struct virtio_blk_state * blk_state, uint8_t * buf, uint64_t * sector, uint64_t len) {
 137     int ret = -1;
 138
 139     PrintDebug("Writing Disk\n");
 140     ret = blk_state->ops->write(buf, (*sector) * SECTOR_SIZE, len, (void *)(blk_state->backend_data));
 141     *sector += (len / SECTOR_SIZE);
 142
 143     return ret;
 144 }
 145
 146
 147
 148 // multiple block operations need to increment the sector
 149
 150 static int handle_block_op(struct guest_info * core, struct virtio_blk_state * blk_state, struct blk_op_hdr * hdr,
 151                            struct vring_desc * buf_desc, uint8_t * status) {
 152     uint8_t * buf = NULL;
 153
 154     PrintDebug("Handling Block op\n");
 155     if (v3_gpa_to_hva(core, buf_desc->addr_gpa, (addr_t *)&(buf)) == -1) {
 156         PrintError("Could not translate buffer address\n");
 157         return -1;
 158     }
 159
 160     PrintDebug("Sector=%p Length=%d\n", (void *)(addr_t)(hdr->sector), buf_desc->length);
 161
 162     if (hdr->type == BLK_IN_REQ) {
 163         if (handle_read_op(blk_state, buf, &(hdr->sector), buf_desc->length) == -1) {
 164             *status = BLK_STATUS_ERR;
 165             return -1;
 166         } else {
 167             *status = BLK_STATUS_OK;
 168         }
 169     } else if (hdr->type == BLK_OUT_REQ) {
 170         if (handle_write_op(blk_state, buf, &(hdr->sector), buf_desc->length) == -1) {
 171             *status = BLK_STATUS_ERR;
 172             return -1;
 173         } else {
 174             *status = BLK_STATUS_OK;
 175         }
 176     } else if (hdr->type == BLK_SCSI_CMD) {
 177         PrintError("VIRTIO: SCSI Command Not supported!!!\n");
 178         *status = BLK_STATUS_NOT_SUPPORTED;
 179         return -1;
 180     }
 181
 182     PrintDebug("Returning Status: %d\n", *status);
 183
 184     return 0;
 185 }
 186
 187 static int get_desc_count(struct virtio_queue * q, int index) {
 188     struct vring_desc * tmp_desc = &(q->desc[index]);
 189     int cnt = 1;
 190
 191     while (tmp_desc->flags & VIRTIO_NEXT_FLAG) {
 192         tmp_desc = &(q->desc[tmp_desc->next]);
 193         cnt++;
 194     }
 195
 196     return cnt;
 197 }
 198
 199
 200
 201 static int handle_kick(struct guest_info * core, struct virtio_blk_state * blk_state) {
 202     struct virtio_queue * q = &(blk_state->queue);
 203
 204     PrintDebug("VIRTIO KICK: cur_index=%d (mod=%d), avail_index=%d\n",
 205                q->cur_avail_idx, q->cur_avail_idx % QUEUE_SIZE, q->avail->index);
 206
 207     while (q->cur_avail_idx != q->avail->index) {
 208         struct vring_desc * hdr_desc = NULL;
 209         struct vring_desc * buf_desc = NULL;
 210         struct vring_desc * status_desc = NULL;
 211         struct blk_op_hdr hdr;
 212         addr_t hdr_addr = 0;
 213         uint16_t desc_idx = q->avail->ring[q->cur_avail_idx % QUEUE_SIZE];
 214         int desc_cnt = get_desc_count(q, desc_idx);
 215         int i = 0;
 216         uint8_t * status_ptr = NULL;
 217         uint8_t status = BLK_STATUS_OK;
 218         uint32_t req_len = 0;
 219
 220         PrintDebug("Descriptor Count=%d, index=%d\n", desc_cnt, q->cur_avail_idx % QUEUE_SIZE);
 221
 222         if (desc_cnt < 3) {
 223             PrintError("Block operations must include at least 3 descriptors\n");
 224             return -1;
 225         }
 226
 227         hdr_desc = &(q->desc[desc_idx]);
 228
 229
 230         PrintDebug("Header Descriptor (ptr=%p) gpa=%p, len=%d, flags=%x, next=%d\n", hdr_desc,
 231                    (void *)(hdr_desc->addr_gpa), hdr_desc->length, hdr_desc->flags, hdr_desc->next);
 232
 233         if (v3_gpa_to_hva(core, hdr_desc->addr_gpa, &(hdr_addr)) == -1) {
 234             PrintError("Could not translate block header address\n");
 235             return -1;
 236         }
 237
 238         // We copy the block op header out because we are going to modify its contents
 239         memcpy(&hdr, (void *)hdr_addr, sizeof(struct blk_op_hdr));
 240
 241         PrintDebug("Blk Op Hdr (ptr=%p) type=%d, sector=%p\n", (void *)hdr_addr, hdr.type, (void *)hdr.sector);
 242
 243         desc_idx = hdr_desc->next;
 244
 245         for (i = 0; i < desc_cnt - 2; i++) {
 246             uint8_t tmp_status = BLK_STATUS_OK;
 247
 248             buf_desc = &(q->desc[desc_idx]);
 249
 250             PrintDebug("Buffer Descriptor (ptr=%p) gpa=%p, len=%d, flags=%x, next=%d\n", buf_desc,
 251                        (void *)(buf_desc->addr_gpa), buf_desc->length, buf_desc->flags, buf_desc->next);
 252
 253             if (handle_block_op(core, blk_state, &hdr, buf_desc, &tmp_status) == -1) {
 254                 PrintError("Error handling block operation\n");
 255                 return -1;
 256             }
 257
 258             if (tmp_status != BLK_STATUS_OK) {
 259                 status = tmp_status;
 260             }
 261
 262             req_len += buf_desc->length;
 263             desc_idx = buf_desc->next;
 264         }
 265
 266         status_desc = &(q->desc[desc_idx]);
 267
 268         PrintDebug("Status Descriptor (ptr=%p) gpa=%p, len=%d, flags=%x, next=%d\n", status_desc,
 269                    (void *)(status_desc->addr_gpa), status_desc->length, status_desc->flags, status_desc->next);
 270
 271         if (v3_gpa_to_hva(core, status_desc->addr_gpa, (addr_t *)&(status_ptr)) == -1) {
 272             PrintError("Could not translate status address\n");
 273             return -1;
 274         }
 275
 276         req_len += status_desc->length;
 277         *status_ptr = status;
 278
 279         q->used->ring[q->used->index % QUEUE_SIZE].id = q->avail->ring[q->cur_avail_idx % QUEUE_SIZE];
 280         q->used->ring[q->used->index % QUEUE_SIZE].length = req_len; // What do we set this to????
 281
 282         q->used->index++;
 283         q->cur_avail_idx++;
 284     }
 285
 286     if (!(q->avail->flags & VIRTIO_NO_IRQ_FLAG)) {
 287         PrintDebug("Raising IRQ %d\n",  blk_state->pci_dev->config_header.intr_line);
 288         v3_pci_raise_irq(blk_state->virtio_dev->pci_bus, 0, blk_state->pci_dev);
 289         blk_state->virtio_cfg.pci_isr = 1;
 290     }
 291
 292     return 0;
 293 }
 294
 295 static int virtio_io_write(struct guest_info * core, uint16_t port, void * src, uint_t length, void * private_data) {
 296     struct virtio_blk_state * blk_state = (struct virtio_blk_state *)private_data;
 297     int port_idx = port % blk_state->io_range_size;
 298
 299
 300     PrintDebug("VIRTIO BLOCK Write for port %d (index=%d) len=%d, value=%x\n",
 301                port, port_idx,  length, *(uint32_t *)src);
 302
 303
 304
 305     switch (port_idx) {
 306         case GUEST_FEATURES_PORT:
 307             if (length != 4) {
 308                 PrintError("Illegal write length for guest features\n");
 309                 return -1;
 310             }
 311
 312             blk_state->virtio_cfg.guest_features = *(uint32_t *)src;
 313             PrintDebug("Setting Guest Features to %x\n", blk_state->virtio_cfg.guest_features);
 314
 315             break;
 316         case VRING_PG_NUM_PORT:
 317             if (length == 4) {
 318                 addr_t pfn = *(uint32_t *)src;
 319                 addr_t page_addr = (pfn << VIRTIO_PAGE_SHIFT);
 320
 321
 322                 blk_state->queue.pfn = pfn;
 323
 324                 blk_state->queue.ring_desc_addr = page_addr ;
 325                 blk_state->queue.ring_avail_addr = page_addr + (QUEUE_SIZE * sizeof(struct vring_desc));
 326                 blk_state->queue.ring_used_addr = ( blk_state->queue.ring_avail_addr + \
 327                                                  sizeof(struct vring_avail)    + \
 328                                                  (QUEUE_SIZE * sizeof(uint16_t)));
 329
 330                 // round up to next page boundary.
 331                 blk_state->queue.ring_used_addr = (blk_state->queue.ring_used_addr + 0xfff) & ~0xfff;
 332
 333                 if (v3_gpa_to_hva(core, blk_state->queue.ring_desc_addr, (addr_t *)&(blk_state->queue.desc)) == -1) {
 334                     PrintError("Could not translate ring descriptor address\n");
 335                     return -1;
 336                 }
 337
 338
 339                 if (v3_gpa_to_hva(core, blk_state->queue.ring_avail_addr, (addr_t *)&(blk_state->queue.avail)) == -1) {
 340                     PrintError("Could not translate ring available address\n");
 341                     return -1;
 342                 }
 343
 344
 345                 if (v3_gpa_to_hva(core, blk_state->queue.ring_used_addr, (addr_t *)&(blk_state->queue.used)) == -1) {
 346                     PrintError("Could not translate ring used address\n");
 347                     return -1;
 348                 }
 349
 350                 PrintDebug("RingDesc_addr=%p, Avail_addr=%p, Used_addr=%p\n",
 351                            (void *)(blk_state->queue.ring_desc_addr),
 352                            (void *)(blk_state->queue.ring_avail_addr),
 353                            (void *)(blk_state->queue.ring_used_addr));
 354
 355                 PrintDebug("RingDesc=%p, Avail=%p, Used=%p\n",
 356                            blk_state->queue.desc, blk_state->queue.avail, blk_state->queue.used);
 357
 358             } else {
 359                 PrintError("Illegal write length for page frame number\n");
 360                 return -1;
 361             }
 362             break;
 363         case VRING_Q_SEL_PORT:
 364             blk_state->virtio_cfg.vring_queue_selector = *(uint16_t *)src;
 365
 366             if (blk_state->virtio_cfg.vring_queue_selector != 0) {
 367                 PrintError("Virtio Block device only uses 1 queue, selected %d\n",
 368                            blk_state->virtio_cfg.vring_queue_selector);
 369                 return -1;
 370             }
 371
 372             break;
 373         case VRING_Q_NOTIFY_PORT:
 374             PrintDebug("Handling Kick\n");
 375             if (handle_kick(core, blk_state) == -1) {
 376                 PrintError("Could not handle Block Notification\n");
 377                 return -1;
 378             }
 379             break;
 380         case VIRTIO_STATUS_PORT:
 381             blk_state->virtio_cfg.status = *(uint8_t *)src;
 382
 383             if (blk_state->virtio_cfg.status == 0) {
 384                 PrintDebug("Resetting device\n");
 385                 blk_reset(blk_state);
 386             }
 387
 388             break;
 389
 390         case VIRTIO_ISR_PORT:
 391             blk_state->virtio_cfg.pci_isr = *(uint8_t *)src;
 392             break;
 393         default:
 394             return -1;
 395             break;
 396     }
 397
 398     return length;
 399 }
 400
 401
 402 static int virtio_io_read(struct guest_info * core, uint16_t port, void * dst, uint_t length, void * private_data) {
 403     struct virtio_blk_state * blk_state = (struct virtio_blk_state *)private_data;
 404     int port_idx = port % blk_state->io_range_size;
 405
 406
 407     PrintDebug("VIRTIO BLOCK Read  for port %d (index =%d), length=%d\n",
 408                port, port_idx, length);
 409
 410     switch (port_idx) {
 411         case HOST_FEATURES_PORT:
 412             if (length != 4) {
 413                 PrintError("Illegal read length for host features\n");
 414                 return -1;
 415             }
 416
 417             *(uint32_t *)dst = blk_state->virtio_cfg.host_features;
 418
 419             break;
 420         case VRING_PG_NUM_PORT:
 421             if (length != 4) {
 422                 PrintError("Illegal read length for page frame number\n");
 423                 return -1;
 424             }
 425
 426             *(uint32_t *)dst = blk_state->queue.pfn;
 427
 428             break;
 429         case VRING_SIZE_PORT:
 430             if (length != 2) {
 431                 PrintError("Illegal read length for vring size\n");
 432                 return -1;
 433             }
 434
 435             *(uint16_t *)dst = blk_state->queue.queue_size;
 436
 437             break;
 438
 439         case VIRTIO_STATUS_PORT:
 440             if (length != 1) {
 441                 PrintError("Illegal read length for status\n");
 442                 return -1;
 443             }
 444
 445             *(uint8_t *)dst = blk_state->virtio_cfg.status;
 446             break;
 447
 448         case VIRTIO_ISR_PORT:
 449             *(uint8_t *)dst = blk_state->virtio_cfg.pci_isr;
 450             blk_state->virtio_cfg.pci_isr = 0;
 451             v3_pci_lower_irq(blk_state->virtio_dev->pci_bus, 0, blk_state->pci_dev);
 452             break;
 453
 454         default:
 455             if ( (port_idx >= sizeof(struct virtio_config)) &&
 456                  (port_idx < (sizeof(struct virtio_config) + sizeof(struct blk_config))) ) {
 457                 int cfg_offset = port_idx - sizeof(struct virtio_config);
 458                 uint8_t * cfg_ptr = (uint8_t *)&(blk_state->block_cfg);
 459
 460                 memcpy(dst, cfg_ptr + cfg_offset, length);
 461
 462             } else {
 463                 PrintError("Read of Unhandled Virtio Read\n");
 464                 return -1;
 465             }
 466
 467             break;
 468     }
 469
 470     return length;
 471 }
 472
 473
 474 static int virtio_free(struct virtio_dev_state * virtio) {
 475     struct virtio_blk_state * blk_state = NULL;
 476     struct virtio_blk_state * tmp = NULL;
 477
 478     list_for_each_entry_safe(blk_state, tmp, &(virtio->dev_list), dev_link) {
 479
 480         // unregister from PCI
 481
 482         list_del(&(blk_state->dev_link));
 483         V3_Free(blk_state);
 484     }
 485
 486
 487     V3_Free(virtio);
 488
 489     return 0;
 490 }
 491
 492
 493
 494 static struct v3_device_ops dev_ops = {
 495     .free = (int (*)(void *))virtio_free,
 496
 497 };
 498
 499
 500
 501
 502
 503 static int register_dev(struct virtio_dev_state * virtio, struct virtio_blk_state * blk_state) {
 504     // initialize PCI
 505     struct pci_device * pci_dev = NULL;
 506     struct v3_pci_bar bars[6];
 507     int num_ports = sizeof(struct virtio_config) + sizeof(struct blk_config);
 508     int tmp_ports = num_ports;
 509     int i;
 510
 511
 512
 513     // This gets the number of ports, rounded up to a power of 2
 514     blk_state->io_range_size = 1; // must be a power of 2
 515
 516     while (tmp_ports > 0) {
 517         tmp_ports >>= 1;
 518         blk_state->io_range_size <<= 1;
 519     }
 520
 521     // this is to account for any low order bits being set in num_ports
 522     // if there are none, then num_ports was already a power of 2 so we shift right to reset it
 523     if ((num_ports & ((blk_state->io_range_size >> 1) - 1)) == 0) {
 524         blk_state->io_range_size >>= 1;
 525     }
 526
 527
 528     for (i = 0; i < 6; i++) {
 529         bars[i].type = PCI_BAR_NONE;
 530     }
 531
 532     PrintDebug("Virtio-BLK io_range_size = %d\n", blk_state->io_range_size);
 533
 534     bars[0].type = PCI_BAR_IO;
 535     bars[0].default_base_port = -1;
 536     bars[0].num_ports = blk_state->io_range_size;
 537
 538     bars[0].io_read = virtio_io_read;
 539     bars[0].io_write = virtio_io_write;
 540     bars[0].private_data = blk_state;
 541
 542     pci_dev = v3_pci_register_device(virtio->pci_bus, PCI_STD_DEVICE,
 543                                      0, PCI_AUTO_DEV_NUM, 0,
 544                                      "LNX_VIRTIO_BLK", bars,
 545                                      NULL, NULL, NULL, blk_state);
 546
 547     if (!pci_dev) {
 548         PrintError("Could not register PCI Device\n");
 549         return -1;
 550     }
 551
 552     pci_dev->config_header.vendor_id = VIRTIO_VENDOR_ID;
 553     pci_dev->config_header.subsystem_vendor_id = VIRTIO_SUBVENDOR_ID;
 554
 555
 556     pci_dev->config_header.device_id = VIRTIO_BLOCK_DEV_ID;
 557     pci_dev->config_header.class = PCI_CLASS_STORAGE;
 558     pci_dev->config_header.subclass = PCI_STORAGE_SUBCLASS_OTHER;
 559
 560     pci_dev->config_header.subsystem_id = VIRTIO_BLOCK_SUBDEVICE_ID;
 561
 562
 563     pci_dev->config_header.intr_pin = 1;
 564
 565     pci_dev->config_header.max_latency = 1; // ?? (qemu does it...)
 566
 567
 568     blk_state->pci_dev = pci_dev;
 569
 570
 571     /* Add backend to list of devices */
 572     list_add(&(blk_state->dev_link), &(virtio->dev_list));
 573
 574     /* Block configuration */
 575     blk_state->virtio_cfg.host_features = VIRTIO_SEG_MAX;
 576     blk_state->block_cfg.max_seg = QUEUE_SIZE - 2;
 577
 578     // Virtio Block only uses one queue
 579     blk_state->queue.queue_size = QUEUE_SIZE;
 580
 581     blk_state->virtio_dev = virtio;
 582
 583     blk_reset(blk_state);
 584
 585
 586     return 0;
 587 }
 588
 589
 590 static int connect_fn(struct v3_vm_info * vm,
 591                       void * frontend_data,
 592                       struct v3_dev_blk_ops * ops,
 593                       v3_cfg_tree_t * cfg,
 594                       void * private_data) {
 595
 596     struct virtio_dev_state * virtio = (struct virtio_dev_state *)frontend_data;
 597
 598     struct virtio_blk_state * blk_state  = (struct virtio_blk_state *)V3_Malloc(sizeof(struct virtio_blk_state));
 599     memset(blk_state, 0, sizeof(struct virtio_blk_state));
 600
 601     register_dev(virtio, blk_state);
 602
 603     blk_state->ops = ops;
 604     blk_state->backend_data = private_data;
 605
 606     blk_state->block_cfg.capacity = ops->get_capacity(private_data) / SECTOR_SIZE;
 607
 608     PrintDebug("Virtio Capacity = %d -- 0x%p\n", (int)(blk_state->block_cfg.capacity),
 609                (void *)(addr_t)(blk_state->block_cfg.capacity));
 610
 611     return 0;
 612 }
 613
 614
 615 static int virtio_init(struct v3_vm_info * vm, v3_cfg_tree_t * cfg) {
 616     struct vm_device * pci_bus = v3_find_dev(vm, v3_cfg_val(cfg, "bus"));
 617     struct virtio_dev_state * virtio_state = NULL;
 618     char * dev_id = v3_cfg_val(cfg, "ID");
 619
 620     PrintDebug("Initializing VIRTIO Block device\n");
 621
 622     if (pci_bus == NULL) {
 623         PrintError("VirtIO devices require a PCI Bus");
 624         return -1;
 625     }
 626
 627
 628     virtio_state  = (struct virtio_dev_state *)V3_Malloc(sizeof(struct virtio_dev_state));
 629     memset(virtio_state, 0, sizeof(struct virtio_dev_state));
 630
 631     INIT_LIST_HEAD(&(virtio_state->dev_list));
 632     virtio_state->pci_bus = pci_bus;
 633
 634
 635     struct vm_device * dev = v3_add_device(vm, dev_id, &dev_ops, virtio_state);
 636
 637     if (dev == NULL) {
 638         PrintError("Could not attach device %s\n", dev_id);
 639         V3_Free(virtio_state);
 640         return -1;
 641     }
 642
 643     if (v3_dev_add_blk_frontend(vm, dev_id, connect_fn, (void *)virtio_state) == -1) {
 644         PrintError("Could not register %s as block frontend\n", dev_id);
 645         v3_remove_device(dev);
 646         return -1;
 647     }
 648
 649     return 0;
 650 }
 651
 652
 653 device_register("LNX_VIRTIO_BLK", virtio_init)