hw/virtio/vhost-user.c

   1 /*
   2  * vhost-user
   3  *
   4  * Copyright (c) 2013 Virtual Open Systems Sarl.
   5  *
   6  * This work is licensed under the terms of the GNU GPL, version 2 or later.
   7  * See the COPYING file in the top-level directory.
   8  *
   9  */
  10
  11 #include "qemu/osdep.h"
  12 #include "qapi/error.h"
  13 #include "hw/virtio/vhost.h"
  14 #include "hw/virtio/vhost-backend.h"
  15 #include "hw/virtio/virtio-net.h"
  16 #include "sysemu/char.h"
  17 #include "sysemu/kvm.h"
  18 #include "qemu/error-report.h"
  19 #include "qemu/sockets.h"
  20 #include "migration/migration.h"
  21
  22 #include <sys/ioctl.h>
  23 #include <sys/socket.h>
  24 #include <sys/un.h>
  25 #include <linux/vhost.h>
  26
  27 #define VHOST_MEMORY_MAX_NREGIONS    8
  28 #define VHOST_USER_F_PROTOCOL_FEATURES 30
  29
  30 enum VhostUserProtocolFeature {
  31     VHOST_USER_PROTOCOL_F_MQ = 0,
  32     VHOST_USER_PROTOCOL_F_LOG_SHMFD = 1,
  33     VHOST_USER_PROTOCOL_F_RARP = 2,
  34
  35     VHOST_USER_PROTOCOL_F_MAX
  36 };
  37
  38 #define VHOST_USER_PROTOCOL_FEATURE_MASK ((1 << VHOST_USER_PROTOCOL_F_MAX) - 1)
  39
  40 typedef enum VhostUserRequest {
  41     VHOST_USER_NONE = 0,
  42     VHOST_USER_GET_FEATURES = 1,
  43     VHOST_USER_SET_FEATURES = 2,
  44     VHOST_USER_SET_OWNER = 3,
  45     VHOST_USER_RESET_OWNER = 4,
  46     VHOST_USER_SET_MEM_TABLE = 5,
  47     VHOST_USER_SET_LOG_BASE = 6,
  48     VHOST_USER_SET_LOG_FD = 7,
  49     VHOST_USER_SET_VRING_NUM = 8,
  50     VHOST_USER_SET_VRING_ADDR = 9,
  51     VHOST_USER_SET_VRING_BASE = 10,
  52     VHOST_USER_GET_VRING_BASE = 11,
  53     VHOST_USER_SET_VRING_KICK = 12,
  54     VHOST_USER_SET_VRING_CALL = 13,
  55     VHOST_USER_SET_VRING_ERR = 14,
  56     VHOST_USER_GET_PROTOCOL_FEATURES = 15,
  57     VHOST_USER_SET_PROTOCOL_FEATURES = 16,
  58     VHOST_USER_GET_QUEUE_NUM = 17,
  59     VHOST_USER_SET_VRING_ENABLE = 18,
  60     VHOST_USER_SEND_RARP = 19,
  61     VHOST_USER_MAX
  62 } VhostUserRequest;
  63
  64 typedef struct VhostUserMemoryRegion {
  65     uint64_t guest_phys_addr;
  66     uint64_t memory_size;
  67     uint64_t userspace_addr;
  68     uint64_t mmap_offset;
  69 } VhostUserMemoryRegion;
  70
  71 typedef struct VhostUserMemory {
  72     uint32_t nregions;
  73     uint32_t padding;
  74     VhostUserMemoryRegion regions[VHOST_MEMORY_MAX_NREGIONS];
  75 } VhostUserMemory;
  76
  77 typedef struct VhostUserLog {
  78     uint64_t mmap_size;
  79     uint64_t mmap_offset;
  80 } VhostUserLog;
  81
  82 typedef struct VhostUserMsg {
  83     VhostUserRequest request;
  84
  85 #define VHOST_USER_VERSION_MASK     (0x3)
  86 #define VHOST_USER_REPLY_MASK       (0x1<<2)
  87     uint32_t flags;
  88     uint32_t size; /* the following payload size */
  89     union {
  90 #define VHOST_USER_VRING_IDX_MASK   (0xff)
  91 #define VHOST_USER_VRING_NOFD_MASK  (0x1<<8)
  92         uint64_t u64;
  93         struct vhost_vring_state state;
  94         struct vhost_vring_addr addr;
  95         VhostUserMemory memory;
  96         VhostUserLog log;
  97     } payload;
  98 } QEMU_PACKED VhostUserMsg;
  99
 100 static VhostUserMsg m __attribute__ ((unused));
 101 #define VHOST_USER_HDR_SIZE (sizeof(m.request) \
 102                             + sizeof(m.flags) \
 103                             + sizeof(m.size))
 104
 105 #define VHOST_USER_PAYLOAD_SIZE (sizeof(m) - VHOST_USER_HDR_SIZE)
 106
 107 /* The version of the protocol we support */
 108 #define VHOST_USER_VERSION    (0x1)
 109
 110 static bool ioeventfd_enabled(void)
 111 {
 112     return kvm_enabled() && kvm_eventfds_enabled();
 113 }
 114
 115 static int vhost_user_read(struct vhost_dev *dev, VhostUserMsg *msg)
 116 {
 117     CharDriverState *chr = dev->opaque;
 118     uint8_t *p = (uint8_t *) msg;
 119     int r, size = VHOST_USER_HDR_SIZE;
 120
 121     r = qemu_chr_fe_read_all(chr, p, size);
 122     if (r != size) {
 123         error_report("Failed to read msg header. Read %d instead of %d."
 124                      " Original request %d.", r, size, msg->request);
 125         goto fail;
 126     }
 127
 128     /* validate received flags */
 129     if (msg->flags != (VHOST_USER_REPLY_MASK | VHOST_USER_VERSION)) {
 130         error_report("Failed to read msg header."
 131                 " Flags 0x%x instead of 0x%x.", msg->flags,
 132                 VHOST_USER_REPLY_MASK | VHOST_USER_VERSION);
 133         goto fail;
 134     }
 135
 136     /* validate message size is sane */
 137     if (msg->size > VHOST_USER_PAYLOAD_SIZE) {
 138         error_report("Failed to read msg header."
 139                 " Size %d exceeds the maximum %zu.", msg->size,
 140                 VHOST_USER_PAYLOAD_SIZE);
 141         goto fail;
 142     }
 143
 144     if (msg->size) {
 145         p += VHOST_USER_HDR_SIZE;
 146         size = msg->size;
 147         r = qemu_chr_fe_read_all(chr, p, size);
 148         if (r != size) {
 149             error_report("Failed to read msg payload."
 150                          " Read %d instead of %d.", r, msg->size);
 151             goto fail;
 152         }
 153     }
 154
 155     return 0;
 156
 157 fail:
 158     return -1;
 159 }
 160
 161 static bool vhost_user_one_time_request(VhostUserRequest request)
 162 {
 163     switch (request) {
 164     case VHOST_USER_SET_OWNER:
 165     case VHOST_USER_RESET_OWNER:
 166     case VHOST_USER_SET_MEM_TABLE:
 167     case VHOST_USER_GET_QUEUE_NUM:
 168         return true;
 169     default:
 170         return false;
 171     }
 172 }
 173
 174 /* most non-init callers ignore the error */
 175 static int vhost_user_write(struct vhost_dev *dev, VhostUserMsg *msg,
 176                             int *fds, int fd_num)
 177 {
 178     CharDriverState *chr = dev->opaque;
 179     int size = VHOST_USER_HDR_SIZE + msg->size;
 180
 181     /*
 182      * For non-vring specific requests, like VHOST_USER_SET_MEM_TABLE,
 183      * we just need send it once in the first time. For later such
 184      * request, we just ignore it.
 185      */
 186     if (vhost_user_one_time_request(msg->request) && dev->vq_index != 0) {
 187         return 0;
 188     }
 189
 190     qemu_chr_fe_set_msgfds(chr, fds, fd_num);
 191
 192     return qemu_chr_fe_write_all(chr, (const uint8_t *) msg, size) == size ?
 193             0 : -1;
 194 }
 195
 196 static int vhost_user_set_log_base(struct vhost_dev *dev, uint64_t base,
 197                                    struct vhost_log *log)
 198 {
 199     int fds[VHOST_MEMORY_MAX_NREGIONS];
 200     size_t fd_num = 0;
 201     bool shmfd = virtio_has_feature(dev->protocol_features,
 202                                     VHOST_USER_PROTOCOL_F_LOG_SHMFD);
 203     VhostUserMsg msg = {
 204         .request = VHOST_USER_SET_LOG_BASE,
 205         .flags = VHOST_USER_VERSION,
 206         .payload.log.mmap_size = log->size * sizeof(*(log->log)),
 207         .payload.log.mmap_offset = 0,
 208         .size = sizeof(msg.payload.log),
 209     };
 210
 211     if (shmfd && log->fd != -1) {
 212         fds[fd_num++] = log->fd;
 213     }
 214
 215     vhost_user_write(dev, &msg, fds, fd_num);
 216
 217     if (shmfd) {
 218         msg.size = 0;
 219         if (vhost_user_read(dev, &msg) < 0) {
 220             return 0;
 221         }
 222
 223         if (msg.request != VHOST_USER_SET_LOG_BASE) {
 224             error_report("Received unexpected msg type. "
 225                          "Expected %d received %d",
 226                          VHOST_USER_SET_LOG_BASE, msg.request);
 227             return -1;
 228         }
 229     }
 230
 231     return 0;
 232 }
 233
 234 static int vhost_user_set_mem_table(struct vhost_dev *dev,
 235                                     struct vhost_memory *mem)
 236 {
 237     int fds[VHOST_MEMORY_MAX_NREGIONS];
 238     int i, fd;
 239     size_t fd_num = 0;
 240     VhostUserMsg msg = {
 241         .request = VHOST_USER_SET_MEM_TABLE,
 242         .flags = VHOST_USER_VERSION,
 243     };
 244
 245     for (i = 0; i < dev->mem->nregions; ++i) {
 246         struct vhost_memory_region *reg = dev->mem->regions + i;
 247         ram_addr_t offset;
 248         MemoryRegion *mr;
 249
 250         assert((uintptr_t)reg->userspace_addr == reg->userspace_addr);
 251         mr = memory_region_from_host((void *)(uintptr_t)reg->userspace_addr,
 252                                      &offset);
 253         fd = memory_region_get_fd(mr);
 254         if (fd > 0) {
 255             msg.payload.memory.regions[fd_num].userspace_addr = reg->userspace_addr;
 256             msg.payload.memory.regions[fd_num].memory_size  = reg->memory_size;
 257             msg.payload.memory.regions[fd_num].guest_phys_addr = reg->guest_phys_addr;
 258             msg.payload.memory.regions[fd_num].mmap_offset = offset;
 259             assert(fd_num < VHOST_MEMORY_MAX_NREGIONS);
 260             fds[fd_num++] = fd;
 261         }
 262     }
 263
 264     msg.payload.memory.nregions = fd_num;
 265
 266     if (!fd_num) {
 267         error_report("Failed initializing vhost-user memory map, "
 268                      "consider using -object memory-backend-file share=on");
 269         return -1;
 270     }
 271
 272     msg.size = sizeof(msg.payload.memory.nregions);
 273     msg.size += sizeof(msg.payload.memory.padding);
 274     msg.size += fd_num * sizeof(VhostUserMemoryRegion);
 275
 276     vhost_user_write(dev, &msg, fds, fd_num);
 277
 278     return 0;
 279 }
 280
 281 static int vhost_user_set_vring_addr(struct vhost_dev *dev,
 282                                      struct vhost_vring_addr *addr)
 283 {
 284     VhostUserMsg msg = {
 285         .request = VHOST_USER_SET_VRING_ADDR,
 286         .flags = VHOST_USER_VERSION,
 287         .payload.addr = *addr,
 288         .size = sizeof(msg.payload.addr),
 289     };
 290
 291     vhost_user_write(dev, &msg, NULL, 0);
 292
 293     return 0;
 294 }
 295
 296 static int vhost_user_set_vring_endian(struct vhost_dev *dev,
 297                                        struct vhost_vring_state *ring)
 298 {
 299     error_report("vhost-user trying to send unhandled ioctl");
 300     return -1;
 301 }
 302
 303 static int vhost_set_vring(struct vhost_dev *dev,
 304                            unsigned long int request,
 305                            struct vhost_vring_state *ring)
 306 {
 307     VhostUserMsg msg = {
 308         .request = request,
 309         .flags = VHOST_USER_VERSION,
 310         .payload.state = *ring,
 311         .size = sizeof(msg.payload.state),
 312     };
 313
 314     vhost_user_write(dev, &msg, NULL, 0);
 315
 316     return 0;
 317 }
 318
 319 static int vhost_user_set_vring_num(struct vhost_dev *dev,
 320                                     struct vhost_vring_state *ring)
 321 {
 322     return vhost_set_vring(dev, VHOST_USER_SET_VRING_NUM, ring);
 323 }
 324
 325 static int vhost_user_set_vring_base(struct vhost_dev *dev,
 326                                      struct vhost_vring_state *ring)
 327 {
 328     return vhost_set_vring(dev, VHOST_USER_SET_VRING_BASE, ring);
 329 }
 330
 331 static int vhost_user_set_vring_enable(struct vhost_dev *dev, int enable)
 332 {
 333     int i;
 334
 335     if (!virtio_has_feature(dev->features, VHOST_USER_F_PROTOCOL_FEATURES)) {
 336         return -1;
 337     }
 338
 339     for (i = 0; i < dev->nvqs; ++i) {
 340         struct vhost_vring_state state = {
 341             .index = dev->vq_index + i,
 342             .num   = enable,
 343         };
 344
 345         vhost_set_vring(dev, VHOST_USER_SET_VRING_ENABLE, &state);
 346     }
 347
 348     return 0;
 349 }
 350
 351 static int vhost_user_get_vring_base(struct vhost_dev *dev,
 352                                      struct vhost_vring_state *ring)
 353 {
 354     VhostUserMsg msg = {
 355         .request = VHOST_USER_GET_VRING_BASE,
 356         .flags = VHOST_USER_VERSION,
 357         .payload.state = *ring,
 358         .size = sizeof(msg.payload.state),
 359     };
 360
 361     vhost_user_write(dev, &msg, NULL, 0);
 362
 363     if (vhost_user_read(dev, &msg) < 0) {
 364         return 0;
 365     }
 366
 367     if (msg.request != VHOST_USER_GET_VRING_BASE) {
 368         error_report("Received unexpected msg type. Expected %d received %d",
 369                      VHOST_USER_GET_VRING_BASE, msg.request);
 370         return -1;
 371     }
 372
 373     if (msg.size != sizeof(msg.payload.state)) {
 374         error_report("Received bad msg size.");
 375         return -1;
 376     }
 377
 378     *ring = msg.payload.state;
 379
 380     return 0;
 381 }
 382
 383 static int vhost_set_vring_file(struct vhost_dev *dev,
 384                                 VhostUserRequest request,
 385                                 struct vhost_vring_file *file)
 386 {
 387     int fds[VHOST_MEMORY_MAX_NREGIONS];
 388     size_t fd_num = 0;
 389     VhostUserMsg msg = {
 390         .request = request,
 391         .flags = VHOST_USER_VERSION,
 392         .payload.u64 = file->index & VHOST_USER_VRING_IDX_MASK,
 393         .size = sizeof(msg.payload.u64),
 394     };
 395
 396     if (ioeventfd_enabled() && file->fd > 0) {
 397         fds[fd_num++] = file->fd;
 398     } else {
 399         msg.payload.u64 |= VHOST_USER_VRING_NOFD_MASK;
 400     }
 401
 402     vhost_user_write(dev, &msg, fds, fd_num);
 403
 404     return 0;
 405 }
 406
 407 static int vhost_user_set_vring_kick(struct vhost_dev *dev,
 408                                      struct vhost_vring_file *file)
 409 {
 410     return vhost_set_vring_file(dev, VHOST_USER_SET_VRING_KICK, file);
 411 }
 412
 413 static int vhost_user_set_vring_call(struct vhost_dev *dev,
 414                                      struct vhost_vring_file *file)
 415 {
 416     return vhost_set_vring_file(dev, VHOST_USER_SET_VRING_CALL, file);
 417 }
 418
 419 static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64)
 420 {
 421     VhostUserMsg msg = {
 422         .request = request,
 423         .flags = VHOST_USER_VERSION,
 424         .payload.u64 = u64,
 425         .size = sizeof(msg.payload.u64),
 426     };
 427
 428     vhost_user_write(dev, &msg, NULL, 0);
 429
 430     return 0;
 431 }
 432
 433 static int vhost_user_set_features(struct vhost_dev *dev,
 434                                    uint64_t features)
 435 {
 436     return vhost_user_set_u64(dev, VHOST_USER_SET_FEATURES, features);
 437 }
 438
 439 static int vhost_user_set_protocol_features(struct vhost_dev *dev,
 440                                             uint64_t features)
 441 {
 442     return vhost_user_set_u64(dev, VHOST_USER_SET_PROTOCOL_FEATURES, features);
 443 }
 444
 445 static int vhost_user_get_u64(struct vhost_dev *dev, int request, uint64_t *u64)
 446 {
 447     VhostUserMsg msg = {
 448         .request = request,
 449         .flags = VHOST_USER_VERSION,
 450     };
 451
 452     if (vhost_user_one_time_request(request) && dev->vq_index != 0) {
 453         return 0;
 454     }
 455
 456     vhost_user_write(dev, &msg, NULL, 0);
 457
 458     if (vhost_user_read(dev, &msg) < 0) {
 459         return 0;
 460     }
 461
 462     if (msg.request != request) {
 463         error_report("Received unexpected msg type. Expected %d received %d",
 464                      request, msg.request);
 465         return -1;
 466     }
 467
 468     if (msg.size != sizeof(msg.payload.u64)) {
 469         error_report("Received bad msg size.");
 470         return -1;
 471     }
 472
 473     *u64 = msg.payload.u64;
 474
 475     return 0;
 476 }
 477
 478 static int vhost_user_get_features(struct vhost_dev *dev, uint64_t *features)
 479 {
 480     return vhost_user_get_u64(dev, VHOST_USER_GET_FEATURES, features);
 481 }
 482
 483 static int vhost_user_set_owner(struct vhost_dev *dev)
 484 {
 485     VhostUserMsg msg = {
 486         .request = VHOST_USER_SET_OWNER,
 487         .flags = VHOST_USER_VERSION,
 488     };
 489
 490     vhost_user_write(dev, &msg, NULL, 0);
 491
 492     return 0;
 493 }
 494
 495 static int vhost_user_reset_device(struct vhost_dev *dev)
 496 {
 497     VhostUserMsg msg = {
 498         .request = VHOST_USER_RESET_OWNER,
 499         .flags = VHOST_USER_VERSION,
 500     };
 501
 502     vhost_user_write(dev, &msg, NULL, 0);
 503
 504     return 0;
 505 }
 506
 507 static int vhost_user_init(struct vhost_dev *dev, void *opaque)
 508 {
 509     uint64_t features;
 510     int err;
 511
 512     assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER);
 513
 514     dev->opaque = opaque;
 515
 516     err = vhost_user_get_features(dev, &features);
 517     if (err < 0) {
 518         return err;
 519     }
 520
 521     if (virtio_has_feature(features, VHOST_USER_F_PROTOCOL_FEATURES)) {
 522         dev->backend_features |= 1ULL << VHOST_USER_F_PROTOCOL_FEATURES;
 523
 524         err = vhost_user_get_u64(dev, VHOST_USER_GET_PROTOCOL_FEATURES,
 525                                  &features);
 526         if (err < 0) {
 527             return err;
 528         }
 529
 530         dev->protocol_features = features & VHOST_USER_PROTOCOL_FEATURE_MASK;
 531         err = vhost_user_set_protocol_features(dev, dev->protocol_features);
 532         if (err < 0) {
 533             return err;
 534         }
 535
 536         /* query the max queues we support if backend supports Multiple Queue */
 537         if (dev->protocol_features & (1ULL << VHOST_USER_PROTOCOL_F_MQ)) {
 538             err = vhost_user_get_u64(dev, VHOST_USER_GET_QUEUE_NUM,
 539                                      &dev->max_queues);
 540             if (err < 0) {
 541                 return err;
 542             }
 543         }
 544     }
 545
 546     if (dev->migration_blocker == NULL &&
 547         !virtio_has_feature(dev->protocol_features,
 548                             VHOST_USER_PROTOCOL_F_LOG_SHMFD)) {
 549         error_setg(&dev->migration_blocker,
 550                    "Migration disabled: vhost-user backend lacks "
 551                    "VHOST_USER_PROTOCOL_F_LOG_SHMFD feature.");
 552     }
 553
 554     return 0;
 555 }
 556
 557 static int vhost_user_cleanup(struct vhost_dev *dev)
 558 {
 559     assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER);
 560
 561     dev->opaque = 0;
 562
 563     return 0;
 564 }
 565
 566 static int vhost_user_get_vq_index(struct vhost_dev *dev, int idx)
 567 {
 568     assert(idx >= dev->vq_index && idx < dev->vq_index + dev->nvqs);
 569
 570     return idx;
 571 }
 572
 573 static int vhost_user_memslots_limit(struct vhost_dev *dev)
 574 {
 575     return VHOST_MEMORY_MAX_NREGIONS;
 576 }
 577
 578 static bool vhost_user_requires_shm_log(struct vhost_dev *dev)
 579 {
 580     assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER);
 581
 582     return virtio_has_feature(dev->protocol_features,
 583                               VHOST_USER_PROTOCOL_F_LOG_SHMFD);
 584 }
 585
 586 static int vhost_user_migration_done(struct vhost_dev *dev, char* mac_addr)
 587 {
 588     VhostUserMsg msg = { 0 };
 589     int err;
 590
 591     assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER);
 592
 593     /* If guest supports GUEST_ANNOUNCE do nothing */
 594     if (virtio_has_feature(dev->acked_features, VIRTIO_NET_F_GUEST_ANNOUNCE)) {
 595         return 0;
 596     }
 597
 598     /* if backend supports VHOST_USER_PROTOCOL_F_RARP ask it to send the RARP */
 599     if (virtio_has_feature(dev->protocol_features,
 600                            VHOST_USER_PROTOCOL_F_RARP)) {
 601         msg.request = VHOST_USER_SEND_RARP;
 602         msg.flags = VHOST_USER_VERSION;
 603         memcpy((char *)&msg.payload.u64, mac_addr, 6);
 604         msg.size = sizeof(msg.payload.u64);
 605
 606         err = vhost_user_write(dev, &msg, NULL, 0);
 607         return err;
 608     }
 609     return -1;
 610 }
 611
 612 static bool vhost_user_can_merge(struct vhost_dev *dev,
 613                                  uint64_t start1, uint64_t size1,
 614                                  uint64_t start2, uint64_t size2)
 615 {
 616     ram_addr_t offset;
 617     int mfd, rfd;
 618     MemoryRegion *mr;
 619
 620     mr = memory_region_from_host((void *)(uintptr_t)start1, &offset);
 621     mfd = memory_region_get_fd(mr);
 622
 623     mr = memory_region_from_host((void *)(uintptr_t)start2, &offset);
 624     rfd = memory_region_get_fd(mr);
 625
 626     return mfd == rfd;
 627 }
 628
 629 const VhostOps user_ops = {
 630         .backend_type = VHOST_BACKEND_TYPE_USER,
 631         .vhost_backend_init = vhost_user_init,
 632         .vhost_backend_cleanup = vhost_user_cleanup,
 633         .vhost_backend_memslots_limit = vhost_user_memslots_limit,
 634         .vhost_set_log_base = vhost_user_set_log_base,
 635         .vhost_set_mem_table = vhost_user_set_mem_table,
 636         .vhost_set_vring_addr = vhost_user_set_vring_addr,
 637         .vhost_set_vring_endian = vhost_user_set_vring_endian,
 638         .vhost_set_vring_num = vhost_user_set_vring_num,
 639         .vhost_set_vring_base = vhost_user_set_vring_base,
 640         .vhost_get_vring_base = vhost_user_get_vring_base,
 641         .vhost_set_vring_kick = vhost_user_set_vring_kick,
 642         .vhost_set_vring_call = vhost_user_set_vring_call,
 643         .vhost_set_features = vhost_user_set_features,
 644         .vhost_get_features = vhost_user_get_features,
 645         .vhost_set_owner = vhost_user_set_owner,
 646         .vhost_reset_device = vhost_user_reset_device,
 647         .vhost_get_vq_index = vhost_user_get_vq_index,
 648         .vhost_set_vring_enable = vhost_user_set_vring_enable,
 649         .vhost_requires_shm_log = vhost_user_requires_shm_log,
 650         .vhost_migration_done = vhost_user_migration_done,
 651         .vhost_backend_can_merge = vhost_user_can_merge,
 652 };