subprojects/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 <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 #define VHOST_USER_HDR_SIZE offsetof(VhostUserMsg, payload.u64)
  40
  41 typedef enum VhostSetConfigType {
  42     VHOST_SET_CONFIG_TYPE_MASTER = 0,
  43     VHOST_SET_CONFIG_TYPE_MIGRATION = 1,
  44 } VhostSetConfigType;
  45
  46 /*
  47  * Maximum size of virtio device config space
  48  */
  49 #define VHOST_USER_MAX_CONFIG_SIZE 256
  50
  51 enum VhostUserProtocolFeature {
  52     VHOST_USER_PROTOCOL_F_MQ = 0,
  53     VHOST_USER_PROTOCOL_F_LOG_SHMFD = 1,
  54     VHOST_USER_PROTOCOL_F_RARP = 2,
  55     VHOST_USER_PROTOCOL_F_REPLY_ACK = 3,
  56     VHOST_USER_PROTOCOL_F_NET_MTU = 4,
  57     VHOST_USER_PROTOCOL_F_SLAVE_REQ = 5,
  58     VHOST_USER_PROTOCOL_F_CROSS_ENDIAN = 6,
  59     VHOST_USER_PROTOCOL_F_CRYPTO_SESSION = 7,
  60     VHOST_USER_PROTOCOL_F_PAGEFAULT = 8,
  61     VHOST_USER_PROTOCOL_F_CONFIG = 9,
  62     VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD = 10,
  63     VHOST_USER_PROTOCOL_F_HOST_NOTIFIER = 11,
  64     VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD = 12,
  65     VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS = 14,
  66     VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS = 15,
  67
  68     VHOST_USER_PROTOCOL_F_MAX
  69 };
  70
  71 #define VHOST_USER_PROTOCOL_FEATURE_MASK ((1 << VHOST_USER_PROTOCOL_F_MAX) - 1)
  72
  73 typedef enum VhostUserRequest {
  74     VHOST_USER_NONE = 0,
  75     VHOST_USER_GET_FEATURES = 1,
  76     VHOST_USER_SET_FEATURES = 2,
  77     VHOST_USER_SET_OWNER = 3,
  78     VHOST_USER_RESET_OWNER = 4,
  79     VHOST_USER_SET_MEM_TABLE = 5,
  80     VHOST_USER_SET_LOG_BASE = 6,
  81     VHOST_USER_SET_LOG_FD = 7,
  82     VHOST_USER_SET_VRING_NUM = 8,
  83     VHOST_USER_SET_VRING_ADDR = 9,
  84     VHOST_USER_SET_VRING_BASE = 10,
  85     VHOST_USER_GET_VRING_BASE = 11,
  86     VHOST_USER_SET_VRING_KICK = 12,
  87     VHOST_USER_SET_VRING_CALL = 13,
  88     VHOST_USER_SET_VRING_ERR = 14,
  89     VHOST_USER_GET_PROTOCOL_FEATURES = 15,
  90     VHOST_USER_SET_PROTOCOL_FEATURES = 16,
  91     VHOST_USER_GET_QUEUE_NUM = 17,
  92     VHOST_USER_SET_VRING_ENABLE = 18,
  93     VHOST_USER_SEND_RARP = 19,
  94     VHOST_USER_NET_SET_MTU = 20,
  95     VHOST_USER_SET_SLAVE_REQ_FD = 21,
  96     VHOST_USER_IOTLB_MSG = 22,
  97     VHOST_USER_SET_VRING_ENDIAN = 23,
  98     VHOST_USER_GET_CONFIG = 24,
  99     VHOST_USER_SET_CONFIG = 25,
 100     VHOST_USER_CREATE_CRYPTO_SESSION = 26,
 101     VHOST_USER_CLOSE_CRYPTO_SESSION = 27,
 102     VHOST_USER_POSTCOPY_ADVISE  = 28,
 103     VHOST_USER_POSTCOPY_LISTEN  = 29,
 104     VHOST_USER_POSTCOPY_END     = 30,
 105     VHOST_USER_GET_INFLIGHT_FD = 31,
 106     VHOST_USER_SET_INFLIGHT_FD = 32,
 107     VHOST_USER_GPU_SET_SOCKET = 33,
 108     VHOST_USER_VRING_KICK = 35,
 109     VHOST_USER_GET_MAX_MEM_SLOTS = 36,
 110     VHOST_USER_ADD_MEM_REG = 37,
 111     VHOST_USER_REM_MEM_REG = 38,
 112     VHOST_USER_MAX
 113 } VhostUserRequest;
 114
 115 typedef enum VhostUserSlaveRequest {
 116     VHOST_USER_SLAVE_NONE = 0,
 117     VHOST_USER_SLAVE_IOTLB_MSG = 1,
 118     VHOST_USER_SLAVE_CONFIG_CHANGE_MSG = 2,
 119     VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG = 3,
 120     VHOST_USER_SLAVE_VRING_CALL = 4,
 121     VHOST_USER_SLAVE_VRING_ERR = 5,
 122     VHOST_USER_SLAVE_MAX
 123 }  VhostUserSlaveRequest;
 124
 125 typedef struct VhostUserMemoryRegion {
 126     uint64_t guest_phys_addr;
 127     uint64_t memory_size;
 128     uint64_t userspace_addr;
 129     uint64_t mmap_offset;
 130 } VhostUserMemoryRegion;
 131
 132 typedef struct VhostUserMemory {
 133     uint32_t nregions;
 134     uint32_t padding;
 135     VhostUserMemoryRegion regions[VHOST_MEMORY_BASELINE_NREGIONS];
 136 } VhostUserMemory;
 137
 138 typedef struct VhostUserMemRegMsg {
 139     uint64_t padding;
 140     VhostUserMemoryRegion region;
 141 } VhostUserMemRegMsg;
 142
 143 typedef struct VhostUserLog {
 144     uint64_t mmap_size;
 145     uint64_t mmap_offset;
 146 } VhostUserLog;
 147
 148 typedef struct VhostUserConfig {
 149     uint32_t offset;
 150     uint32_t size;
 151     uint32_t flags;
 152     uint8_t region[VHOST_USER_MAX_CONFIG_SIZE];
 153 } VhostUserConfig;
 154
 155 static VhostUserConfig c __attribute__ ((unused));
 156 #define VHOST_USER_CONFIG_HDR_SIZE (sizeof(c.offset) \
 157                                    + sizeof(c.size) \
 158                                    + sizeof(c.flags))
 159
 160 typedef struct VhostUserVringArea {
 161     uint64_t u64;
 162     uint64_t size;
 163     uint64_t offset;
 164 } VhostUserVringArea;
 165
 166 typedef struct VhostUserInflight {
 167     uint64_t mmap_size;
 168     uint64_t mmap_offset;
 169     uint16_t num_queues;
 170     uint16_t queue_size;
 171 } VhostUserInflight;
 172
 173 #if defined(_WIN32) && (defined(__x86_64__) || defined(__i386__))
 174 # define VU_PACKED __attribute__((gcc_struct, packed))
 175 #else
 176 # define VU_PACKED __attribute__((packed))
 177 #endif
 178
 179 typedef struct VhostUserMsg {
 180     int request;
 181
 182 #define VHOST_USER_VERSION_MASK     (0x3)
 183 #define VHOST_USER_REPLY_MASK       (0x1 << 2)
 184 #define VHOST_USER_NEED_REPLY_MASK  (0x1 << 3)
 185     uint32_t flags;
 186     uint32_t size; /* the following payload size */
 187
 188     union {
 189 #define VHOST_USER_VRING_IDX_MASK   (0xff)
 190 #define VHOST_USER_VRING_NOFD_MASK  (0x1 << 8)
 191         uint64_t u64;
 192         struct vhost_vring_state state;
 193         struct vhost_vring_addr addr;
 194         VhostUserMemory memory;
 195         VhostUserMemRegMsg memreg;
 196         VhostUserLog log;
 197         VhostUserConfig config;
 198         VhostUserVringArea area;
 199         VhostUserInflight inflight;
 200     } payload;
 201
 202     int fds[VHOST_MEMORY_BASELINE_NREGIONS];
 203     int fd_num;
 204     uint8_t *data;
 205 } VU_PACKED VhostUserMsg;
 206
 207 typedef struct VuDevRegion {
 208     /* Guest Physical address. */
 209     uint64_t gpa;
 210     /* Memory region size. */
 211     uint64_t size;
 212     /* QEMU virtual address (userspace). */
 213     uint64_t qva;
 214     /* Starting offset in our mmaped space. */
 215     uint64_t mmap_offset;
 216     /* Start address of mmaped space. */
 217     uint64_t mmap_addr;
 218 } VuDevRegion;
 219
 220 typedef struct VuDev VuDev;
 221
 222 typedef uint64_t (*vu_get_features_cb) (VuDev *dev);
 223 typedef void (*vu_set_features_cb) (VuDev *dev, uint64_t features);
 224 typedef int (*vu_process_msg_cb) (VuDev *dev, VhostUserMsg *vmsg,
 225                                   int *do_reply);
 226 typedef bool (*vu_read_msg_cb) (VuDev *dev, int sock, VhostUserMsg *vmsg);
 227 typedef void (*vu_queue_set_started_cb) (VuDev *dev, int qidx, bool started);
 228 typedef bool (*vu_queue_is_processed_in_order_cb) (VuDev *dev, int qidx);
 229 typedef int (*vu_get_config_cb) (VuDev *dev, uint8_t *config, uint32_t len);
 230 typedef int (*vu_set_config_cb) (VuDev *dev, const uint8_t *data,
 231                                  uint32_t offset, uint32_t size,
 232                                  uint32_t flags);
 233
 234 typedef struct VuDevIface {
 235     /* called by VHOST_USER_GET_FEATURES to get the features bitmask */
 236     vu_get_features_cb get_features;
 237     /* enable vhost implementation features */
 238     vu_set_features_cb set_features;
 239     /* get the protocol feature bitmask from the underlying vhost
 240      * implementation */
 241     vu_get_features_cb get_protocol_features;
 242     /* enable protocol features in the underlying vhost implementation. */
 243     vu_set_features_cb set_protocol_features;
 244     /* process_msg is called for each vhost-user message received */
 245     /* skip libvhost-user processing if return value != 0 */
 246     vu_process_msg_cb process_msg;
 247     /* tells when queues can be processed */
 248     vu_queue_set_started_cb queue_set_started;
 249     /*
 250      * If the queue is processed in order, in which case it will be
 251      * resumed to vring.used->idx. This can help to support resuming
 252      * on unmanaged exit/crash.
 253      */
 254     vu_queue_is_processed_in_order_cb queue_is_processed_in_order;
 255     /* get the config space of the device */
 256     vu_get_config_cb get_config;
 257     /* set the config space of the device */
 258     vu_set_config_cb set_config;
 259 } VuDevIface;
 260
 261 typedef void (*vu_queue_handler_cb) (VuDev *dev, int qidx);
 262
 263 typedef struct VuRing {
 264     unsigned int num;
 265     struct vring_desc *desc;
 266     struct vring_avail *avail;
 267     struct vring_used *used;
 268     uint64_t log_guest_addr;
 269     uint32_t flags;
 270 } VuRing;
 271
 272 typedef struct VuDescStateSplit {
 273     /* Indicate whether this descriptor is inflight or not.
 274      * Only available for head-descriptor. */
 275     uint8_t inflight;
 276
 277     /* Padding */
 278     uint8_t padding[5];
 279
 280     /* Maintain a list for the last batch of used descriptors.
 281      * Only available when batching is used for submitting */
 282     uint16_t next;
 283
 284     /* Used to preserve the order of fetching available descriptors.
 285      * Only available for head-descriptor. */
 286     uint64_t counter;
 287 } VuDescStateSplit;
 288
 289 typedef struct VuVirtqInflight {
 290     /* The feature flags of this region. Now it's initialized to 0. */
 291     uint64_t features;
 292
 293     /* The version of this region. It's 1 currently.
 294      * Zero value indicates a vm reset happened. */
 295     uint16_t version;
 296
 297     /* The size of VuDescStateSplit array. It's equal to the virtqueue
 298      * size. Slave could get it from queue size field of VhostUserInflight. */
 299     uint16_t desc_num;
 300
 301     /* The head of list that track the last batch of used descriptors. */
 302     uint16_t last_batch_head;
 303
 304     /* Storing the idx value of used ring */
 305     uint16_t used_idx;
 306
 307     /* Used to track the state of each descriptor in descriptor table */
 308     VuDescStateSplit desc[];
 309 } VuVirtqInflight;
 310
 311 typedef struct VuVirtqInflightDesc {
 312     uint16_t index;
 313     uint64_t counter;
 314 } VuVirtqInflightDesc;
 315
 316 typedef struct VuVirtq {
 317     VuRing vring;
 318
 319     VuVirtqInflight *inflight;
 320
 321     VuVirtqInflightDesc *resubmit_list;
 322
 323     uint16_t resubmit_num;
 324
 325     uint64_t counter;
 326
 327     /* Next head to pop */
 328     uint16_t last_avail_idx;
 329
 330     /* Last avail_idx read from VQ. */
 331     uint16_t shadow_avail_idx;
 332
 333     uint16_t used_idx;
 334
 335     /* Last used index value we have signalled on */
 336     uint16_t signalled_used;
 337
 338     /* Last used index value we have signalled on */
 339     bool signalled_used_valid;
 340
 341     /* Notification enabled? */
 342     bool notification;
 343
 344     int inuse;
 345
 346     vu_queue_handler_cb handler;
 347
 348     int call_fd;
 349     int kick_fd;
 350     int err_fd;
 351     unsigned int enable;
 352     bool started;
 353
 354     /* Guest addresses of our ring */
 355     struct vhost_vring_addr vra;
 356 } VuVirtq;
 357
 358 enum VuWatchCondtion {
 359     VU_WATCH_IN = POLLIN,
 360     VU_WATCH_OUT = POLLOUT,
 361     VU_WATCH_PRI = POLLPRI,
 362     VU_WATCH_ERR = POLLERR,
 363     VU_WATCH_HUP = POLLHUP,
 364 };
 365
 366 typedef void (*vu_panic_cb) (VuDev *dev, const char *err);
 367 typedef void (*vu_watch_cb) (VuDev *dev, int condition, void *data);
 368 typedef void (*vu_set_watch_cb) (VuDev *dev, int fd, int condition,
 369                                  vu_watch_cb cb, void *data);
 370 typedef void (*vu_remove_watch_cb) (VuDev *dev, int fd);
 371
 372 typedef struct VuDevInflightInfo {
 373     int fd;
 374     void *addr;
 375     uint64_t size;
 376 } VuDevInflightInfo;
 377
 378 struct VuDev {
 379     int sock;
 380     uint32_t nregions;
 381     VuDevRegion regions[VHOST_USER_MAX_RAM_SLOTS];
 382     VuVirtq *vq;
 383     VuDevInflightInfo inflight_info;
 384     int log_call_fd;
 385     /* Must be held while using slave_fd */
 386     pthread_mutex_t slave_mutex;
 387     int slave_fd;
 388     uint64_t log_size;
 389     uint8_t *log_table;
 390     uint64_t features;
 391     uint64_t protocol_features;
 392     bool broken;
 393     uint16_t max_queues;
 394
 395     /*
 396      * @read_msg: custom method to read vhost-user message
 397      *
 398      * Read data from vhost_user socket fd and fill up
 399      * the passed VhostUserMsg *vmsg struct.
 400      *
 401      * If reading fails, it should close the received set of file
 402      * descriptors as socket message's auxiliary data.
 403      *
 404      * For the details, please refer to vu_message_read in libvhost-user.c
 405      * which will be used by default if not custom method is provided when
 406      * calling vu_init
 407      *
 408      * Returns: true if vhost-user message successfully received,
 409      *          otherwise return false.
 410      *
 411      */
 412     vu_read_msg_cb read_msg;
 413
 414     /*
 415      * @set_watch: add or update the given fd to the watch set,
 416      * call cb when condition is met.
 417      */
 418     vu_set_watch_cb set_watch;
 419
 420     /* @remove_watch: remove the given fd from the watch set */
 421     vu_remove_watch_cb remove_watch;
 422
 423     /*
 424      * @panic: encountered an unrecoverable error, you may try to re-initialize
 425      */
 426     vu_panic_cb panic;
 427     const VuDevIface *iface;
 428
 429     /* Postcopy data */
 430     int postcopy_ufd;
 431     bool postcopy_listening;
 432 };
 433
 434 typedef struct VuVirtqElement {
 435     unsigned int index;
 436     unsigned int out_num;
 437     unsigned int in_num;
 438     struct iovec *in_sg;
 439     struct iovec *out_sg;
 440 } VuVirtqElement;
 441
 442 /**
 443  * vu_init:
 444  * @dev: a VuDev context
 445  * @max_queues: maximum number of virtqueues
 446  * @socket: the socket connected to vhost-user master
 447  * @panic: a panic callback
 448  * @set_watch: a set_watch callback
 449  * @remove_watch: a remove_watch callback
 450  * @iface: a VuDevIface structure with vhost-user device callbacks
 451  *
 452  * Initializes a VuDev vhost-user context.
 453  *
 454  * Returns: true on success, false on failure.
 455  **/
 456 bool vu_init(VuDev *dev,
 457              uint16_t max_queues,
 458              int socket,
 459              vu_panic_cb panic,
 460              vu_read_msg_cb read_msg,
 461              vu_set_watch_cb set_watch,
 462              vu_remove_watch_cb remove_watch,
 463              const VuDevIface *iface);
 464
 465
 466 /**
 467  * vu_deinit:
 468  * @dev: a VuDev context
 469  *
 470  * Cleans up the VuDev context
 471  */
 472 void vu_deinit(VuDev *dev);
 473
 474 /**
 475  * vu_dispatch:
 476  * @dev: a VuDev context
 477  *
 478  * Process one vhost-user message.
 479  *
 480  * Returns: TRUE on success, FALSE on failure.
 481  */
 482 bool vu_dispatch(VuDev *dev);
 483
 484 /**
 485  * vu_gpa_to_va:
 486  * @dev: a VuDev context
 487  * @plen: guest memory size
 488  * @guest_addr: guest address
 489  *
 490  * Translate a guest address to a pointer. Returns NULL on failure.
 491  */
 492 void *vu_gpa_to_va(VuDev *dev, uint64_t *plen, uint64_t guest_addr);
 493
 494 /**
 495  * vu_get_queue:
 496  * @dev: a VuDev context
 497  * @qidx: queue index
 498  *
 499  * Returns the queue number @qidx.
 500  */
 501 VuVirtq *vu_get_queue(VuDev *dev, int qidx);
 502
 503 /**
 504  * vu_set_queue_handler:
 505  * @dev: a VuDev context
 506  * @vq: a VuVirtq queue
 507  * @handler: the queue handler callback
 508  *
 509  * Set the queue handler. This function may be called several times
 510  * for the same queue. If called with NULL @handler, the handler is
 511  * removed.
 512  */
 513 void vu_set_queue_handler(VuDev *dev, VuVirtq *vq,
 514                           vu_queue_handler_cb handler);
 515
 516 /**
 517  * vu_set_queue_host_notifier:
 518  * @dev: a VuDev context
 519  * @vq: a VuVirtq queue
 520  * @fd: a file descriptor
 521  * @size: host page size
 522  * @offset: notifier offset in @fd file
 523  *
 524  * Set queue's host notifier. This function may be called several
 525  * times for the same queue. If called with -1 @fd, the notifier
 526  * is removed.
 527  */
 528 bool vu_set_queue_host_notifier(VuDev *dev, VuVirtq *vq, int fd,
 529                                 int size, int offset);
 530
 531 /**
 532  * vu_queue_set_notification:
 533  * @dev: a VuDev context
 534  * @vq: a VuVirtq queue
 535  * @enable: state
 536  *
 537  * Set whether the queue notifies (via event index or interrupt)
 538  */
 539 void vu_queue_set_notification(VuDev *dev, VuVirtq *vq, int enable);
 540
 541 /**
 542  * vu_queue_enabled:
 543  * @dev: a VuDev context
 544  * @vq: a VuVirtq queue
 545  *
 546  * Returns: whether the queue is enabled.
 547  */
 548 bool vu_queue_enabled(VuDev *dev, VuVirtq *vq);
 549
 550 /**
 551  * vu_queue_started:
 552  * @dev: a VuDev context
 553  * @vq: a VuVirtq queue
 554  *
 555  * Returns: whether the queue is started.
 556  */
 557 bool vu_queue_started(const VuDev *dev, const VuVirtq *vq);
 558
 559 /**
 560  * vu_queue_empty:
 561  * @dev: a VuDev context
 562  * @vq: a VuVirtq queue
 563  *
 564  * Returns: true if the queue is empty or not ready.
 565  */
 566 bool vu_queue_empty(VuDev *dev, VuVirtq *vq);
 567
 568 /**
 569  * vu_queue_notify:
 570  * @dev: a VuDev context
 571  * @vq: a VuVirtq queue
 572  *
 573  * Request to notify the queue via callfd (skipped if unnecessary)
 574  */
 575 void vu_queue_notify(VuDev *dev, VuVirtq *vq);
 576
 577 /**
 578  * vu_queue_notify_sync:
 579  * @dev: a VuDev context
 580  * @vq: a VuVirtq queue
 581  *
 582  * Request to notify the queue via callfd (skipped if unnecessary)
 583  * or sync message if possible.
 584  */
 585 void vu_queue_notify_sync(VuDev *dev, VuVirtq *vq);
 586
 587 /**
 588  * vu_queue_pop:
 589  * @dev: a VuDev context
 590  * @vq: a VuVirtq queue
 591  * @sz: the size of struct to return (must be >= VuVirtqElement)
 592  *
 593  * Returns: a VuVirtqElement filled from the queue or NULL. The
 594  * returned element must be free()-d by the caller.
 595  */
 596 void *vu_queue_pop(VuDev *dev, VuVirtq *vq, size_t sz);
 597
 598
 599 /**
 600  * vu_queue_unpop:
 601  * @dev: a VuDev context
 602  * @vq: a VuVirtq queue
 603  * @elem: The #VuVirtqElement
 604  * @len: number of bytes written
 605  *
 606  * Pretend the most recent element wasn't popped from the virtqueue.  The next
 607  * call to vu_queue_pop() will refetch the element.
 608  */
 609 void vu_queue_unpop(VuDev *dev, VuVirtq *vq, VuVirtqElement *elem,
 610                     size_t len);
 611
 612 /**
 613  * vu_queue_rewind:
 614  * @dev: a VuDev context
 615  * @vq: a VuVirtq queue
 616  * @num: number of elements to push back
 617  *
 618  * Pretend that elements weren't popped from the virtqueue.  The next
 619  * virtqueue_pop() will refetch the oldest element.
 620  *
 621  * Returns: true on success, false if @num is greater than the number of in use
 622  * elements.
 623  */
 624 bool vu_queue_rewind(VuDev *dev, VuVirtq *vq, unsigned int num);
 625
 626 /**
 627  * vu_queue_fill:
 628  * @dev: a VuDev context
 629  * @vq: a VuVirtq queue
 630  * @elem: a VuVirtqElement
 631  * @len: length in bytes to write
 632  * @idx: optional offset for the used ring index (0 in general)
 633  *
 634  * Fill the used ring with @elem element.
 635  */
 636 void vu_queue_fill(VuDev *dev, VuVirtq *vq,
 637                    const VuVirtqElement *elem,
 638                    unsigned int len, unsigned int idx);
 639
 640 /**
 641  * vu_queue_push:
 642  * @dev: a VuDev context
 643  * @vq: a VuVirtq queue
 644  * @elem: a VuVirtqElement
 645  * @len: length in bytes to write
 646  *
 647  * Helper that combines vu_queue_fill() with a vu_queue_flush().
 648  */
 649 void vu_queue_push(VuDev *dev, VuVirtq *vq,
 650                    const VuVirtqElement *elem, unsigned int len);
 651
 652 /**
 653  * vu_queue_flush:
 654  * @dev: a VuDev context
 655  * @vq: a VuVirtq queue
 656  * @num: number of elements to flush
 657  *
 658  * Mark the last number of elements as done (used.idx is updated by
 659  * num elements).
 660 */
 661 void vu_queue_flush(VuDev *dev, VuVirtq *vq, unsigned int num);
 662
 663 /**
 664  * vu_queue_get_avail_bytes:
 665  * @dev: a VuDev context
 666  * @vq: a VuVirtq queue
 667  * @in_bytes: in bytes
 668  * @out_bytes: out bytes
 669  * @max_in_bytes: stop counting after max_in_bytes
 670  * @max_out_bytes: stop counting after max_out_bytes
 671  *
 672  * Count the number of available bytes, up to max_in_bytes/max_out_bytes.
 673  */
 674 void vu_queue_get_avail_bytes(VuDev *vdev, VuVirtq *vq, unsigned int *in_bytes,
 675                               unsigned int *out_bytes,
 676                               unsigned max_in_bytes, unsigned max_out_bytes);
 677
 678 /**
 679  * vu_queue_avail_bytes:
 680  * @dev: a VuDev context
 681  * @vq: a VuVirtq queue
 682  * @in_bytes: expected in bytes
 683  * @out_bytes: expected out bytes
 684  *
 685  * Returns: true if in_bytes <= in_total && out_bytes <= out_total
 686  */
 687 bool vu_queue_avail_bytes(VuDev *dev, VuVirtq *vq, unsigned int in_bytes,
 688                           unsigned int out_bytes);
 689
 690 #endif /* LIBVHOST_USER_H */