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 #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 */
691