contrib/libvhost-user/libvhost-user.h

   1 /*
   2  * Vhost User library
   3  *
   4  * Copyright (c) 2016 Red Hat, Inc.
   5  *
   6  * Authors:
   7  *  Victor Kaplansky <victork@redhat.com>
   8  *  Marc-André Lureau <mlureau@redhat.com>
   9  *
  10  * This work is licensed under the terms of the GNU GPL, version 2 or
  11  * later.  See the COPYING file in the top-level directory.
  12  */
  13
  14 #ifndef LIBVHOST_USER_H
  15 #define LIBVHOST_USER_H
  16
  17 #include <stdint.h>
  18 #include <stdbool.h>
  19 #include <stddef.h>
  20 #include <sys/poll.h>
  21 #include <linux/vhost.h>
  22 #include <pthread.h>
  23 #include "standard-headers/linux/virtio_ring.h"
  24
  25 /* Based on qemu/hw/virtio/vhost-user.c */
  26 #define VHOST_USER_F_PROTOCOL_FEATURES 30
  27 #define VHOST_LOG_PAGE 4096
  28
  29 #define VIRTQUEUE_MAX_SIZE 1024
  30
  31 #define VHOST_MEMORY_BASELINE_NREGIONS 8
  32
  33 /*
  34  * Set a reasonable maximum number of ram slots, which will be supported by
  35  * any architecture.
  36  */
  37 #define VHOST_USER_MAX_RAM_SLOTS 32
  38
  39 typedef enum VhostSetConfigType {
  40     VHOST_SET_CONFIG_TYPE_MASTER = 0,
  41     VHOST_SET_CONFIG_TYPE_MIGRATION = 1,
  42 } VhostSetConfigType;
  43
  44 /*
  45  * Maximum size of virtio device config space
  46  */
  47 #define VHOST_USER_MAX_CONFIG_SIZE 256
  48
  49 enum VhostUserProtocolFeature {
  50     VHOST_USER_PROTOCOL_F_MQ = 0,
  51     VHOST_USER_PROTOCOL_F_LOG_SHMFD = 1,
  52     VHOST_USER_PROTOCOL_F_RARP = 2,
  53     VHOST_USER_PROTOCOL_F_REPLY_ACK = 3,
  54     VHOST_USER_PROTOCOL_F_NET_MTU = 4,
  55     VHOST_USER_PROTOCOL_F_SLAVE_REQ = 5,
  56     VHOST_USER_PROTOCOL_F_CROSS_ENDIAN = 6,
  57     VHOST_USER_PROTOCOL_F_CRYPTO_SESSION = 7,
  58     VHOST_USER_PROTOCOL_F_PAGEFAULT = 8,
  59     VHOST_USER_PROTOCOL_F_CONFIG = 9,
  60     VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD = 10,
  61     VHOST_USER_PROTOCOL_F_HOST_NOTIFIER = 11,
  62     VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD = 12,
  63     VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS = 14,
  64     VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS = 15,
  65
  66     VHOST_USER_PROTOCOL_F_MAX
  67 };
  68
  69 #define VHOST_USER_PROTOCOL_FEATURE_MASK ((1 << VHOST_USER_PROTOCOL_F_MAX) - 1)
  70
  71 typedef enum VhostUserRequest {
  72     VHOST_USER_NONE = 0,
  73     VHOST_USER_GET_FEATURES = 1,
  74     VHOST_USER_SET_FEATURES = 2,
  75     VHOST_USER_SET_OWNER = 3,
  76     VHOST_USER_RESET_OWNER = 4,
  77     VHOST_USER_SET_MEM_TABLE = 5,
  78     VHOST_USER_SET_LOG_BASE = 6,
  79     VHOST_USER_SET_LOG_FD = 7,
  80     VHOST_USER_SET_VRING_NUM = 8,
  81     VHOST_USER_SET_VRING_ADDR = 9,
  82     VHOST_USER_SET_VRING_BASE = 10,
  83     VHOST_USER_GET_VRING_BASE = 11,
  84     VHOST_USER_SET_VRING_KICK = 12,
  85     VHOST_USER_SET_VRING_CALL = 13,
  86     VHOST_USER_SET_VRING_ERR = 14,
  87     VHOST_USER_GET_PROTOCOL_FEATURES = 15,
  88     VHOST_USER_SET_PROTOCOL_FEATURES = 16,
  89     VHOST_USER_GET_QUEUE_NUM = 17,
  90     VHOST_USER_SET_VRING_ENABLE = 18,
  91     VHOST_USER_SEND_RARP = 19,
  92     VHOST_USER_NET_SET_MTU = 20,
  93     VHOST_USER_SET_SLAVE_REQ_FD = 21,
  94     VHOST_USER_IOTLB_MSG = 22,
  95     VHOST_USER_SET_VRING_ENDIAN = 23,
  96     VHOST_USER_GET_CONFIG = 24,
  97     VHOST_USER_SET_CONFIG = 25,
  98     VHOST_USER_CREATE_CRYPTO_SESSION = 26,
  99     VHOST_USER_CLOSE_CRYPTO_SESSION = 27,
 100     VHOST_USER_POSTCOPY_ADVISE  = 28,
 101     VHOST_USER_POSTCOPY_LISTEN  = 29,
 102     VHOST_USER_POSTCOPY_END     = 30,
 103     VHOST_USER_GET_INFLIGHT_FD = 31,
 104     VHOST_USER_SET_INFLIGHT_FD = 32,
 105     VHOST_USER_GPU_SET_SOCKET = 33,
 106     VHOST_USER_VRING_KICK = 35,
 107     VHOST_USER_GET_MAX_MEM_SLOTS = 36,
 108     VHOST_USER_ADD_MEM_REG = 37,
 109     VHOST_USER_REM_MEM_REG = 38,
 110     VHOST_USER_MAX
 111 } VhostUserRequest;
 112
 113 typedef enum VhostUserSlaveRequest {
 114     VHOST_USER_SLAVE_NONE = 0,
 115     VHOST_USER_SLAVE_IOTLB_MSG = 1,
 116     VHOST_USER_SLAVE_CONFIG_CHANGE_MSG = 2,
 117     VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG = 3,
 118     VHOST_USER_SLAVE_VRING_CALL = 4,
 119     VHOST_USER_SLAVE_VRING_ERR = 5,
 120     VHOST_USER_SLAVE_MAX
 121 }  VhostUserSlaveRequest;
 122
 123 typedef struct VhostUserMemoryRegion {
 124     uint64_t guest_phys_addr;
 125     uint64_t memory_size;
 126     uint64_t userspace_addr;
 127     uint64_t mmap_offset;
 128 } VhostUserMemoryRegion;
 129
 130 typedef struct VhostUserMemory {
 131     uint32_t nregions;
 132     uint32_t padding;
 133     VhostUserMemoryRegion regions[VHOST_MEMORY_BASELINE_NREGIONS];
 134 } VhostUserMemory;
 135
 136 typedef struct VhostUserMemRegMsg {
 137     uint32_t padding;
 138     VhostUserMemoryRegion region;
 139 } VhostUserMemRegMsg;
 140
 141 typedef struct VhostUserLog {
 142     uint64_t mmap_size;
 143     uint64_t mmap_offset;
 144 } VhostUserLog;
 145
 146 typedef struct VhostUserConfig {
 147     uint32_t offset;
 148     uint32_t size;
 149     uint32_t flags;
 150     uint8_t region[VHOST_USER_MAX_CONFIG_SIZE];
 151 } VhostUserConfig;
 152
 153 static VhostUserConfig c __attribute__ ((unused));
 154 #define VHOST_USER_CONFIG_HDR_SIZE (sizeof(c.offset) \
 155                                    + sizeof(c.size) \
 156                                    + sizeof(c.flags))
 157
 158 typedef struct VhostUserVringArea {
 159     uint64_t u64;
 160     uint64_t size;
 161     uint64_t offset;
 162 } VhostUserVringArea;
 163
 164 typedef struct VhostUserInflight {
 165     uint64_t mmap_size;
 166     uint64_t mmap_offset;
 167     uint16_t num_queues;
 168     uint16_t queue_size;
 169 } VhostUserInflight;
 170
 171 #if defined(_WIN32) && (defined(__x86_64__) || defined(__i386__))
 172 # define VU_PACKED __attribute__((gcc_struct, packed))
 173 #else
 174 # define VU_PACKED __attribute__((packed))
 175 #endif
 176
 177 typedef struct VhostUserMsg {
 178     int request;
 179
 180 #define VHOST_USER_VERSION_MASK     (0x3)
 181 #define VHOST_USER_REPLY_MASK       (0x1 << 2)
 182 #define VHOST_USER_NEED_REPLY_MASK  (0x1 << 3)
 183     uint32_t flags;
 184     uint32_t size; /* the following payload size */
 185
 186     union {
 187 #define VHOST_USER_VRING_IDX_MASK   (0xff)
 188 #define VHOST_USER_VRING_NOFD_MASK  (0x1 << 8)
 189         uint64_t u64;
 190         struct vhost_vring_state state;
 191         struct vhost_vring_addr addr;
 192         VhostUserMemory memory;
 193         VhostUserMemRegMsg memreg;
 194         VhostUserLog log;
 195         VhostUserConfig config;
 196         VhostUserVringArea area;
 197         VhostUserInflight inflight;
 198     } payload;
 199
 200     int fds[VHOST_MEMORY_BASELINE_NREGIONS];
 201     int fd_num;
 202     uint8_t *data;
 203 } VU_PACKED VhostUserMsg;
 204
 205 typedef struct VuDevRegion {
 206     /* Guest Physical address. */
 207     uint64_t gpa;
 208     /* Memory region size. */
 209     uint64_t size;
 210     /* QEMU virtual address (userspace). */
 211     uint64_t qva;
 212     /* Starting offset in our mmaped space. */
 213     uint64_t mmap_offset;
 214     /* Start address of mmaped space. */
 215     uint64_t mmap_addr;
 216 } VuDevRegion;
 217
 218 typedef struct VuDev VuDev;
 219
 220 typedef uint64_t (*vu_get_features_cb) (VuDev *dev);
 221 typedef void (*vu_set_features_cb) (VuDev *dev, uint64_t features);
 222 typedef int (*vu_process_msg_cb) (VuDev *dev, VhostUserMsg *vmsg,
 223                                   int *do_reply);
 224 typedef void (*vu_queue_set_started_cb) (VuDev *dev, int qidx, bool started);
 225 typedef bool (*vu_queue_is_processed_in_order_cb) (VuDev *dev, int qidx);
 226 typedef int (*vu_get_config_cb) (VuDev *dev, uint8_t *config, uint32_t len);
 227 typedef int (*vu_set_config_cb) (VuDev *dev, const uint8_t *data,
 228                                  uint32_t offset, uint32_t size,
 229                                  uint32_t flags);
 230
 231 typedef struct VuDevIface {
 232     /* called by VHOST_USER_GET_FEATURES to get the features bitmask */
 233     vu_get_features_cb get_features;
 234     /* enable vhost implementation features */
 235     vu_set_features_cb set_features;
 236     /* get the protocol feature bitmask from the underlying vhost
 237      * implementation */
 238     vu_get_features_cb get_protocol_features;
 239     /* enable protocol features in the underlying vhost implementation. */
 240     vu_set_features_cb set_protocol_features;
 241     /* process_msg is called for each vhost-user message received */
 242     /* skip libvhost-user processing if return value != 0 */
 243     vu_process_msg_cb process_msg;
 244     /* tells when queues can be processed */
 245     vu_queue_set_started_cb queue_set_started;
 246     /*
 247      * If the queue is processed in order, in which case it will be
 248      * resumed to vring.used->idx. This can help to support resuming
 249      * on unmanaged exit/crash.
 250      */
 251     vu_queue_is_processed_in_order_cb queue_is_processed_in_order;
 252     /* get the config space of the device */
 253     vu_get_config_cb get_config;
 254     /* set the config space of the device */
 255     vu_set_config_cb set_config;
 256 } VuDevIface;
 257
 258 typedef void (*vu_queue_handler_cb) (VuDev *dev, int qidx);
 259
 260 typedef struct VuRing {
 261     unsigned int num;
 262     struct vring_desc *desc;
 263     struct vring_avail *avail;
 264     struct vring_used *used;
 265     uint64_t log_guest_addr;
 266     uint32_t flags;
 267 } VuRing;
 268
 269 typedef struct VuDescStateSplit {
 270     /* Indicate whether this descriptor is inflight or not.
 271      * Only available for head-descriptor. */
 272     uint8_t inflight;
 273
 274     /* Padding */
 275     uint8_t padding[5];
 276
 277     /* Maintain a list for the last batch of used descriptors.
 278      * Only available when batching is used for submitting */
 279     uint16_t next;
 280
 281     /* Used to preserve the order of fetching available descriptors.
 282      * Only available for head-descriptor. */
 283     uint64_t counter;
 284 } VuDescStateSplit;
 285
 286 typedef struct VuVirtqInflight {
 287     /* The feature flags of this region. Now it's initialized to 0. */
 288     uint64_t features;
 289
 290     /* The version of this region. It's 1 currently.
 291      * Zero value indicates a vm reset happened. */
 292     uint16_t version;
 293
 294     /* The size of VuDescStateSplit array. It's equal to the virtqueue
 295      * size. Slave could get it from queue size field of VhostUserInflight. */
 296     uint16_t desc_num;
 297
 298     /* The head of list that track the last batch of used descriptors. */
 299     uint16_t last_batch_head;
 300
 301     /* Storing the idx value of used ring */
 302     uint16_t used_idx;
 303
 304     /* Used to track the state of each descriptor in descriptor table */
 305     VuDescStateSplit desc[];
 306 } VuVirtqInflight;
 307
 308 typedef struct VuVirtqInflightDesc {
 309     uint16_t index;
 310     uint64_t counter;
 311 } VuVirtqInflightDesc;
 312
 313 typedef struct VuVirtq {
 314     VuRing vring;
 315
 316     VuVirtqInflight *inflight;
 317
 318     VuVirtqInflightDesc *resubmit_list;
 319
 320     uint16_t resubmit_num;
 321
 322     uint64_t counter;
 323
 324     /* Next head to pop */
 325     uint16_t last_avail_idx;
 326
 327     /* Last avail_idx read from VQ. */
 328     uint16_t shadow_avail_idx;
 329
 330     uint16_t used_idx;
 331
 332     /* Last used index value we have signalled on */
 333     uint16_t signalled_used;
 334
 335     /* Last used index value we have signalled on */
 336     bool signalled_used_valid;
 337
 338     /* Notification enabled? */
 339     bool notification;
 340
 341     int inuse;
 342
 343     vu_queue_handler_cb handler;
 344
 345     int call_fd;
 346     int kick_fd;
 347     int err_fd;
 348     unsigned int enable;
 349     bool started;
 350
 351     /* Guest addresses of our ring */
 352     struct vhost_vring_addr vra;
 353 } VuVirtq;
 354
 355 enum VuWatchCondtion {
 356     VU_WATCH_IN = POLLIN,
 357     VU_WATCH_OUT = POLLOUT,
 358     VU_WATCH_PRI = POLLPRI,
 359     VU_WATCH_ERR = POLLERR,
 360     VU_WATCH_HUP = POLLHUP,
 361 };
 362
 363 typedef void (*vu_panic_cb) (VuDev *dev, const char *err);
 364 typedef void (*vu_watch_cb) (VuDev *dev, int condition, void *data);
 365 typedef void (*vu_set_watch_cb) (VuDev *dev, int fd, int condition,
 366                                  vu_watch_cb cb, void *data);
 367 typedef void (*vu_remove_watch_cb) (VuDev *dev, int fd);
 368
 369 typedef struct VuDevInflightInfo {
 370     int fd;
 371     void *addr;
 372     uint64_t size;
 373 } VuDevInflightInfo;
 374
 375 struct VuDev {
 376     int sock;
 377     uint32_t nregions;
 378     VuDevRegion regions[VHOST_USER_MAX_RAM_SLOTS];
 379     VuVirtq *vq;
 380     VuDevInflightInfo inflight_info;
 381     int log_call_fd;
 382     /* Must be held while using slave_fd */
 383     pthread_mutex_t slave_mutex;
 384     int slave_fd;
 385     uint64_t log_size;
 386     uint8_t *log_table;
 387     uint64_t features;
 388     uint64_t protocol_features;
 389     bool broken;
 390     uint16_t max_queues;
 391
 392     /* @set_watch: add or update the given fd to the watch set,
 393      * call cb when condition is met */
 394     vu_set_watch_cb set_watch;
 395
 396     /* @remove_watch: remove the given fd from the watch set */
 397     vu_remove_watch_cb remove_watch;
 398
 399     /* @panic: encountered an unrecoverable error, you may try to
 400      * re-initialize */
 401     vu_panic_cb panic;
 402     const VuDevIface *iface;
 403
 404     /* Postcopy data */
 405     int postcopy_ufd;
 406     bool postcopy_listening;
 407 };
 408
 409 typedef struct VuVirtqElement {
 410     unsigned int index;
 411     unsigned int out_num;
 412     unsigned int in_num;
 413     struct iovec *in_sg;
 414     struct iovec *out_sg;
 415 } VuVirtqElement;
 416
 417 /**
 418  * vu_init:
 419  * @dev: a VuDev context
 420  * @max_queues: maximum number of virtqueues
 421  * @socket: the socket connected to vhost-user master
 422  * @panic: a panic callback
 423  * @set_watch: a set_watch callback
 424  * @remove_watch: a remove_watch callback
 425  * @iface: a VuDevIface structure with vhost-user device callbacks
 426  *
 427  * Initializes a VuDev vhost-user context.
 428  *
 429  * Returns: true on success, false on failure.
 430  **/
 431 bool vu_init(VuDev *dev,
 432              uint16_t max_queues,
 433              int socket,
 434              vu_panic_cb panic,
 435              vu_set_watch_cb set_watch,
 436              vu_remove_watch_cb remove_watch,
 437              const VuDevIface *iface);
 438
 439
 440 /**
 441  * vu_deinit:
 442  * @dev: a VuDev context
 443  *
 444  * Cleans up the VuDev context
 445  */
 446 void vu_deinit(VuDev *dev);
 447
 448 /**
 449  * vu_dispatch:
 450  * @dev: a VuDev context
 451  *
 452  * Process one vhost-user message.
 453  *
 454  * Returns: TRUE on success, FALSE on failure.
 455  */
 456 bool vu_dispatch(VuDev *dev);
 457
 458 /**
 459  * vu_gpa_to_va:
 460  * @dev: a VuDev context
 461  * @plen: guest memory size
 462  * @guest_addr: guest address
 463  *
 464  * Translate a guest address to a pointer. Returns NULL on failure.
 465  */
 466 void *vu_gpa_to_va(VuDev *dev, uint64_t *plen, uint64_t guest_addr);
 467
 468 /**
 469  * vu_get_queue:
 470  * @dev: a VuDev context
 471  * @qidx: queue index
 472  *
 473  * Returns the queue number @qidx.
 474  */
 475 VuVirtq *vu_get_queue(VuDev *dev, int qidx);
 476
 477 /**
 478  * vu_set_queue_handler:
 479  * @dev: a VuDev context
 480  * @vq: a VuVirtq queue
 481  * @handler: the queue handler callback
 482  *
 483  * Set the queue handler. This function may be called several times
 484  * for the same queue. If called with NULL @handler, the handler is
 485  * removed.
 486  */
 487 void vu_set_queue_handler(VuDev *dev, VuVirtq *vq,
 488                           vu_queue_handler_cb handler);
 489
 490 /**
 491  * vu_set_queue_host_notifier:
 492  * @dev: a VuDev context
 493  * @vq: a VuVirtq queue
 494  * @fd: a file descriptor
 495  * @size: host page size
 496  * @offset: notifier offset in @fd file
 497  *
 498  * Set queue's host notifier. This function may be called several
 499  * times for the same queue. If called with -1 @fd, the notifier
 500  * is removed.
 501  */
 502 bool vu_set_queue_host_notifier(VuDev *dev, VuVirtq *vq, int fd,
 503                                 int size, int offset);
 504
 505 /**
 506  * vu_queue_set_notification:
 507  * @dev: a VuDev context
 508  * @vq: a VuVirtq queue
 509  * @enable: state
 510  *
 511  * Set whether the queue notifies (via event index or interrupt)
 512  */
 513 void vu_queue_set_notification(VuDev *dev, VuVirtq *vq, int enable);
 514
 515 /**
 516  * vu_queue_enabled:
 517  * @dev: a VuDev context
 518  * @vq: a VuVirtq queue
 519  *
 520  * Returns: whether the queue is enabled.
 521  */
 522 bool vu_queue_enabled(VuDev *dev, VuVirtq *vq);
 523
 524 /**
 525  * vu_queue_started:
 526  * @dev: a VuDev context
 527  * @vq: a VuVirtq queue
 528  *
 529  * Returns: whether the queue is started.
 530  */
 531 bool vu_queue_started(const VuDev *dev, const VuVirtq *vq);
 532
 533 /**
 534  * vu_queue_empty:
 535  * @dev: a VuDev context
 536  * @vq: a VuVirtq queue
 537  *
 538  * Returns: true if the queue is empty or not ready.
 539  */
 540 bool vu_queue_empty(VuDev *dev, VuVirtq *vq);
 541
 542 /**
 543  * vu_queue_notify:
 544  * @dev: a VuDev context
 545  * @vq: a VuVirtq queue
 546  *
 547  * Request to notify the queue via callfd (skipped if unnecessary)
 548  */
 549 void vu_queue_notify(VuDev *dev, VuVirtq *vq);
 550
 551 /**
 552  * vu_queue_notify_sync:
 553  * @dev: a VuDev context
 554  * @vq: a VuVirtq queue
 555  *
 556  * Request to notify the queue via callfd (skipped if unnecessary)
 557  * or sync message if possible.
 558  */
 559 void vu_queue_notify_sync(VuDev *dev, VuVirtq *vq);
 560
 561 /**
 562  * vu_queue_pop:
 563  * @dev: a VuDev context
 564  * @vq: a VuVirtq queue
 565  * @sz: the size of struct to return (must be >= VuVirtqElement)
 566  *
 567  * Returns: a VuVirtqElement filled from the queue or NULL. The
 568  * returned element must be free()-d by the caller.
 569  */
 570 void *vu_queue_pop(VuDev *dev, VuVirtq *vq, size_t sz);
 571
 572
 573 /**
 574  * vu_queue_unpop:
 575  * @dev: a VuDev context
 576  * @vq: a VuVirtq queue
 577  * @elem: The #VuVirtqElement
 578  * @len: number of bytes written
 579  *
 580  * Pretend the most recent element wasn't popped from the virtqueue.  The next
 581  * call to vu_queue_pop() will refetch the element.
 582  */
 583 void vu_queue_unpop(VuDev *dev, VuVirtq *vq, VuVirtqElement *elem,
 584                     size_t len);
 585
 586 /**
 587  * vu_queue_rewind:
 588  * @dev: a VuDev context
 589  * @vq: a VuVirtq queue
 590  * @num: number of elements to push back
 591  *
 592  * Pretend that elements weren't popped from the virtqueue.  The next
 593  * virtqueue_pop() will refetch the oldest element.
 594  *
 595  * Returns: true on success, false if @num is greater than the number of in use
 596  * elements.
 597  */
 598 bool vu_queue_rewind(VuDev *dev, VuVirtq *vq, unsigned int num);
 599
 600 /**
 601  * vu_queue_fill:
 602  * @dev: a VuDev context
 603  * @vq: a VuVirtq queue
 604  * @elem: a VuVirtqElement
 605  * @len: length in bytes to write
 606  * @idx: optional offset for the used ring index (0 in general)
 607  *
 608  * Fill the used ring with @elem element.
 609  */
 610 void vu_queue_fill(VuDev *dev, VuVirtq *vq,
 611                    const VuVirtqElement *elem,
 612                    unsigned int len, unsigned int idx);
 613
 614 /**
 615  * vu_queue_push:
 616  * @dev: a VuDev context
 617  * @vq: a VuVirtq queue
 618  * @elem: a VuVirtqElement
 619  * @len: length in bytes to write
 620  *
 621  * Helper that combines vu_queue_fill() with a vu_queue_flush().
 622  */
 623 void vu_queue_push(VuDev *dev, VuVirtq *vq,
 624                    const VuVirtqElement *elem, unsigned int len);
 625
 626 /**
 627  * vu_queue_flush:
 628  * @dev: a VuDev context
 629  * @vq: a VuVirtq queue
 630  * @num: number of elements to flush
 631  *
 632  * Mark the last number of elements as done (used.idx is updated by
 633  * num elements).
 634 */
 635 void vu_queue_flush(VuDev *dev, VuVirtq *vq, unsigned int num);
 636
 637 /**
 638  * vu_queue_get_avail_bytes:
 639  * @dev: a VuDev context
 640  * @vq: a VuVirtq queue
 641  * @in_bytes: in bytes
 642  * @out_bytes: out bytes
 643  * @max_in_bytes: stop counting after max_in_bytes
 644  * @max_out_bytes: stop counting after max_out_bytes
 645  *
 646  * Count the number of available bytes, up to max_in_bytes/max_out_bytes.
 647  */
 648 void vu_queue_get_avail_bytes(VuDev *vdev, VuVirtq *vq, unsigned int *in_bytes,
 649                               unsigned int *out_bytes,
 650                               unsigned max_in_bytes, unsigned max_out_bytes);
 651
 652 /**
 653  * vu_queue_avail_bytes:
 654  * @dev: a VuDev context
 655  * @vq: a VuVirtq queue
 656  * @in_bytes: expected in bytes
 657  * @out_bytes: expected out bytes
 658  *
 659  * Returns: true if in_bytes <= in_total && out_bytes <= out_total
 660  */
 661 bool vu_queue_avail_bytes(VuDev *dev, VuVirtq *vq, unsigned int in_bytes,
 662                           unsigned int out_bytes);
 663
 664 #endif /* LIBVHOST_USER_H */