qemu/subprojects/libvhost-user/libvhost-user.h

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/*
* Vhost User library
*
* Copyright (c) 2016 Red Hat, Inc.
*
* Authors:
* Victor Kaplansky <victork@redhat.com>
* Marc-André Lureau <mlureau@redhat.com>
*
* This work is licensed under the terms of the GNU GPL, version 2 or
* later. See the COPYING file in the top-level directory.
*/
#ifndef LIBVHOST_USER_H
#define LIBVHOST_USER_H
#include <stdint.h>
#include <stdbool.h>
#include <stddef.h>
#include <sys/poll.h>
#include <linux/vhost.h>
#include <pthread.h>
#include "standard-headers/linux/virtio_ring.h"
/* Based on qemu/hw/virtio/vhost-user.c */
#define VHOST_USER_F_PROTOCOL_FEATURES 30
#define VHOST_LOG_PAGE 4096
#define VIRTQUEUE_MAX_SIZE 1024
#define VHOST_MEMORY_BASELINE_NREGIONS 8
/*
* Set a reasonable maximum number of ram slots, which will be supported by
* any architecture.
*/
#define VHOST_USER_MAX_RAM_SLOTS 32
#define VHOST_USER_HDR_SIZE offsetof(VhostUserMsg, payload.u64)
typedef enum VhostSetConfigType {
VHOST_SET_CONFIG_TYPE_MASTER = 0,
VHOST_SET_CONFIG_TYPE_MIGRATION = 1,
} VhostSetConfigType;
/*
* Maximum size of virtio device config space
*/
#define VHOST_USER_MAX_CONFIG_SIZE 256
enum VhostUserProtocolFeature {
VHOST_USER_PROTOCOL_F_MQ = 0,
VHOST_USER_PROTOCOL_F_LOG_SHMFD = 1,
VHOST_USER_PROTOCOL_F_RARP = 2,
VHOST_USER_PROTOCOL_F_REPLY_ACK = 3,
VHOST_USER_PROTOCOL_F_NET_MTU = 4,
VHOST_USER_PROTOCOL_F_SLAVE_REQ = 5,
VHOST_USER_PROTOCOL_F_CROSS_ENDIAN = 6,
VHOST_USER_PROTOCOL_F_CRYPTO_SESSION = 7,
VHOST_USER_PROTOCOL_F_PAGEFAULT = 8,
VHOST_USER_PROTOCOL_F_CONFIG = 9,
VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD = 10,
VHOST_USER_PROTOCOL_F_HOST_NOTIFIER = 11,
VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD = 12,
VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS = 14,
VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS = 15,
VHOST_USER_PROTOCOL_F_MAX
};
#define VHOST_USER_PROTOCOL_FEATURE_MASK ((1 << VHOST_USER_PROTOCOL_F_MAX) - 1)
typedef enum VhostUserRequest {
VHOST_USER_NONE = 0,
VHOST_USER_GET_FEATURES = 1,
VHOST_USER_SET_FEATURES = 2,
VHOST_USER_SET_OWNER = 3,
VHOST_USER_RESET_OWNER = 4,
VHOST_USER_SET_MEM_TABLE = 5,
VHOST_USER_SET_LOG_BASE = 6,
VHOST_USER_SET_LOG_FD = 7,
VHOST_USER_SET_VRING_NUM = 8,
VHOST_USER_SET_VRING_ADDR = 9,
VHOST_USER_SET_VRING_BASE = 10,
VHOST_USER_GET_VRING_BASE = 11,
VHOST_USER_SET_VRING_KICK = 12,
VHOST_USER_SET_VRING_CALL = 13,
VHOST_USER_SET_VRING_ERR = 14,
VHOST_USER_GET_PROTOCOL_FEATURES = 15,
VHOST_USER_SET_PROTOCOL_FEATURES = 16,
VHOST_USER_GET_QUEUE_NUM = 17,
VHOST_USER_SET_VRING_ENABLE = 18,
VHOST_USER_SEND_RARP = 19,
VHOST_USER_NET_SET_MTU = 20,
VHOST_USER_SET_SLAVE_REQ_FD = 21,
VHOST_USER_IOTLB_MSG = 22,
VHOST_USER_SET_VRING_ENDIAN = 23,
VHOST_USER_GET_CONFIG = 24,
VHOST_USER_SET_CONFIG = 25,
VHOST_USER_CREATE_CRYPTO_SESSION = 26,
VHOST_USER_CLOSE_CRYPTO_SESSION = 27,
VHOST_USER_POSTCOPY_ADVISE = 28,
VHOST_USER_POSTCOPY_LISTEN = 29,
VHOST_USER_POSTCOPY_END = 30,
VHOST_USER_GET_INFLIGHT_FD = 31,
VHOST_USER_SET_INFLIGHT_FD = 32,
VHOST_USER_GPU_SET_SOCKET = 33,
VHOST_USER_VRING_KICK = 35,
VHOST_USER_GET_MAX_MEM_SLOTS = 36,
VHOST_USER_ADD_MEM_REG = 37,
VHOST_USER_REM_MEM_REG = 38,
VHOST_USER_MAX
} VhostUserRequest;
typedef enum VhostUserSlaveRequest {
VHOST_USER_SLAVE_NONE = 0,
VHOST_USER_SLAVE_IOTLB_MSG = 1,
VHOST_USER_SLAVE_CONFIG_CHANGE_MSG = 2,
VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG = 3,
VHOST_USER_SLAVE_VRING_CALL = 4,
VHOST_USER_SLAVE_VRING_ERR = 5,
VHOST_USER_SLAVE_MAX
} VhostUserSlaveRequest;
typedef struct VhostUserMemoryRegion {
uint64_t guest_phys_addr;
uint64_t memory_size;
uint64_t userspace_addr;
uint64_t mmap_offset;
} VhostUserMemoryRegion;
typedef struct VhostUserMemory {
uint32_t nregions;
uint32_t padding;
VhostUserMemoryRegion regions[VHOST_MEMORY_BASELINE_NREGIONS];
} VhostUserMemory;
typedef struct VhostUserMemRegMsg {
vhost-user: fix VHOST_USER_ADD/REM_MEM_REG truncation QEMU currently truncates the mmap_offset field when sending VHOST_USER_ADD_MEM_REG and VHOST_USER_REM_MEM_REG messages. The struct layout looks like this: typedef struct VhostUserMemoryRegion { uint64_t guest_phys_addr; uint64_t memory_size; uint64_t userspace_addr; uint64_t mmap_offset; } VhostUserMemoryRegion; typedef struct VhostUserMemRegMsg { uint32_t padding; /* WARNING: there is a 32-bit hole here! */ VhostUserMemoryRegion region; } VhostUserMemRegMsg; The payload size is calculated as follows when sending the message in hw/virtio/vhost-user.c: msg->hdr.size = sizeof(msg->payload.mem_reg.padding) + sizeof(VhostUserMemoryRegion); This calculation produces an incorrect result of only 36 bytes. sizeof(VhostUserMemRegMsg) is actually 40 bytes. The consequence of this is that the final field, mmap_offset, is truncated. This breaks x86_64 TCG guests on s390 hosts. Other guest/host combinations may get lucky if either of the following holds: 1. The guest memory layout does not need mmap_offset != 0. 2. The host is little-endian and mmap_offset <= 0xffffffff so the truncation has no effect. Fix this by extending the existing 32-bit padding field to 64-bit. Now the padding reflects the actual compiler padding. This can be verified using pahole(1). Also document the layout properly in the vhost-user specification. The vhost-user spec did not document the exact layout. It would be impossible to implement the spec without looking at the QEMU source code. Existing vhost-user frontends and device backends continue to work after this fix has been applied. The only change in the wire protocol is that QEMU now sets hdr.size to 40 instead of 36. If a vhost-user implementation has a hardcoded size check for 36 bytes, then it will fail with new QEMUs. Both QEMU and DPDK/SPDK don't check the exact payload size, so they continue to work. Fixes: f1aeb14b0809e313c74244d838645ed25e85ea63 ("Transmit vhost-user memory regions individually") Cc: Raphael Norwitz <raphael.norwitz@nutanix.com> Cc: Cornelia Huck <cohuck@redhat.com> Cc: Michael S. Tsirkin <mst@redhat.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Message-Id: <20201109174355.1069147-1-stefanha@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Fixes: f1aeb14b0809 ("Transmit vhost-user memory regions individually") Reviewed-by: Cornelia Huck <cohuck@redhat.com> Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
2020-11-09 20:43:55 +03:00
uint64_t padding;
VhostUserMemoryRegion region;
} VhostUserMemRegMsg;
typedef struct VhostUserLog {
uint64_t mmap_size;
uint64_t mmap_offset;
} VhostUserLog;
typedef struct VhostUserConfig {
uint32_t offset;
uint32_t size;
uint32_t flags;
uint8_t region[VHOST_USER_MAX_CONFIG_SIZE];
} VhostUserConfig;
static VhostUserConfig c __attribute__ ((unused));
#define VHOST_USER_CONFIG_HDR_SIZE (sizeof(c.offset) \
+ sizeof(c.size) \
+ sizeof(c.flags))
typedef struct VhostUserVringArea {
uint64_t u64;
uint64_t size;
uint64_t offset;
} VhostUserVringArea;
typedef struct VhostUserInflight {
uint64_t mmap_size;
uint64_t mmap_offset;
uint16_t num_queues;
uint16_t queue_size;
} VhostUserInflight;
#if defined(_WIN32) && (defined(__x86_64__) || defined(__i386__))
# define VU_PACKED __attribute__((gcc_struct, packed))
#else
# define VU_PACKED __attribute__((packed))
#endif
typedef struct VhostUserMsg {
int request;
#define VHOST_USER_VERSION_MASK (0x3)
#define VHOST_USER_REPLY_MASK (0x1 << 2)
#define VHOST_USER_NEED_REPLY_MASK (0x1 << 3)
uint32_t flags;
uint32_t size; /* the following payload size */
union {
#define VHOST_USER_VRING_IDX_MASK (0xff)
#define VHOST_USER_VRING_NOFD_MASK (0x1 << 8)
uint64_t u64;
struct vhost_vring_state state;
struct vhost_vring_addr addr;
VhostUserMemory memory;
VhostUserMemRegMsg memreg;
VhostUserLog log;
VhostUserConfig config;
VhostUserVringArea area;
VhostUserInflight inflight;
} payload;
int fds[VHOST_MEMORY_BASELINE_NREGIONS];
int fd_num;
uint8_t *data;
} VU_PACKED VhostUserMsg;
typedef struct VuDevRegion {
/* Guest Physical address. */
uint64_t gpa;
/* Memory region size. */
uint64_t size;
/* QEMU virtual address (userspace). */
uint64_t qva;
/* Starting offset in our mmaped space. */
uint64_t mmap_offset;
/* Start address of mmaped space. */
uint64_t mmap_addr;
} VuDevRegion;
typedef struct VuDev VuDev;
typedef uint64_t (*vu_get_features_cb) (VuDev *dev);
typedef void (*vu_set_features_cb) (VuDev *dev, uint64_t features);
typedef int (*vu_process_msg_cb) (VuDev *dev, VhostUserMsg *vmsg,
int *do_reply);
typedef bool (*vu_read_msg_cb) (VuDev *dev, int sock, VhostUserMsg *vmsg);
typedef void (*vu_queue_set_started_cb) (VuDev *dev, int qidx, bool started);
typedef bool (*vu_queue_is_processed_in_order_cb) (VuDev *dev, int qidx);
typedef int (*vu_get_config_cb) (VuDev *dev, uint8_t *config, uint32_t len);
typedef int (*vu_set_config_cb) (VuDev *dev, const uint8_t *data,
uint32_t offset, uint32_t size,
uint32_t flags);
typedef struct VuDevIface {
/* called by VHOST_USER_GET_FEATURES to get the features bitmask */
vu_get_features_cb get_features;
/* enable vhost implementation features */
vu_set_features_cb set_features;
/* get the protocol feature bitmask from the underlying vhost
* implementation */
vu_get_features_cb get_protocol_features;
/* enable protocol features in the underlying vhost implementation. */
vu_set_features_cb set_protocol_features;
/* process_msg is called for each vhost-user message received */
/* skip libvhost-user processing if return value != 0 */
vu_process_msg_cb process_msg;
/* tells when queues can be processed */
vu_queue_set_started_cb queue_set_started;
/*
* If the queue is processed in order, in which case it will be
* resumed to vring.used->idx. This can help to support resuming
* on unmanaged exit/crash.
*/
vu_queue_is_processed_in_order_cb queue_is_processed_in_order;
/* get the config space of the device */
vu_get_config_cb get_config;
/* set the config space of the device */
vu_set_config_cb set_config;
} VuDevIface;
typedef void (*vu_queue_handler_cb) (VuDev *dev, int qidx);
typedef struct VuRing {
unsigned int num;
struct vring_desc *desc;
struct vring_avail *avail;
struct vring_used *used;
uint64_t log_guest_addr;
uint32_t flags;
} VuRing;
typedef struct VuDescStateSplit {
/* Indicate whether this descriptor is inflight or not.
* Only available for head-descriptor. */
uint8_t inflight;
/* Padding */
uint8_t padding[5];
/* Maintain a list for the last batch of used descriptors.
* Only available when batching is used for submitting */
uint16_t next;
/* Used to preserve the order of fetching available descriptors.
* Only available for head-descriptor. */
uint64_t counter;
} VuDescStateSplit;
typedef struct VuVirtqInflight {
/* The feature flags of this region. Now it's initialized to 0. */
uint64_t features;
/* The version of this region. It's 1 currently.
* Zero value indicates a vm reset happened. */
uint16_t version;
/* The size of VuDescStateSplit array. It's equal to the virtqueue
* size. Slave could get it from queue size field of VhostUserInflight. */
uint16_t desc_num;
/* The head of list that track the last batch of used descriptors. */
uint16_t last_batch_head;
/* Storing the idx value of used ring */
uint16_t used_idx;
/* Used to track the state of each descriptor in descriptor table */
misc: Replace zero-length arrays with flexible array member (automatic) Description copied from Linux kernel commit from Gustavo A. R. Silva (see [3]): --v-- description start --v-- The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member [1], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being unadvertenly introduced [2] to the Linux codebase from now on. --^-- description end --^-- Do the similar housekeeping in the QEMU codebase (which uses C99 since commit 7be41675f7cb). All these instances of code were found with the help of the following Coccinelle script: @@ identifier s, m, a; type t, T; @@ struct s { ... t m; - T a[0]; + T a[]; }; @@ identifier s, m, a; type t, T; @@ struct s { ... t m; - T a[0]; + T a[]; } QEMU_PACKED; [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=76497732932f [3] https://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux.git/commit/?id=17642a2fbd2c1 Inspired-by: Gustavo A. R. Silva <gustavo@embeddedor.com> Reviewed-by: David Hildenbrand <david@redhat.com> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-03-04 18:38:15 +03:00
VuDescStateSplit desc[];
} VuVirtqInflight;
typedef struct VuVirtqInflightDesc {
uint16_t index;
uint64_t counter;
} VuVirtqInflightDesc;
typedef struct VuVirtq {
VuRing vring;
VuVirtqInflight *inflight;
VuVirtqInflightDesc *resubmit_list;
uint16_t resubmit_num;
uint64_t counter;
/* Next head to pop */
uint16_t last_avail_idx;
/* Last avail_idx read from VQ. */
uint16_t shadow_avail_idx;
uint16_t used_idx;
/* Last used index value we have signalled on */
uint16_t signalled_used;
/* Last used index value we have signalled on */
bool signalled_used_valid;
/* Notification enabled? */
bool notification;
int inuse;
vu_queue_handler_cb handler;
int call_fd;
int kick_fd;
int err_fd;
unsigned int enable;
bool started;
/* Guest addresses of our ring */
struct vhost_vring_addr vra;
} VuVirtq;
enum VuWatchCondtion {
VU_WATCH_IN = POLLIN,
VU_WATCH_OUT = POLLOUT,
VU_WATCH_PRI = POLLPRI,
VU_WATCH_ERR = POLLERR,
VU_WATCH_HUP = POLLHUP,
};
typedef void (*vu_panic_cb) (VuDev *dev, const char *err);
typedef void (*vu_watch_cb) (VuDev *dev, int condition, void *data);
typedef void (*vu_set_watch_cb) (VuDev *dev, int fd, int condition,
vu_watch_cb cb, void *data);
typedef void (*vu_remove_watch_cb) (VuDev *dev, int fd);
typedef struct VuDevInflightInfo {
int fd;
void *addr;
uint64_t size;
} VuDevInflightInfo;
struct VuDev {
int sock;
uint32_t nregions;
VuDevRegion regions[VHOST_USER_MAX_RAM_SLOTS];
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VuVirtq *vq;
VuDevInflightInfo inflight_info;
int log_call_fd;
/* Must be held while using slave_fd */
pthread_mutex_t slave_mutex;
int slave_fd;
uint64_t log_size;
uint8_t *log_table;
uint64_t features;
uint64_t protocol_features;
bool broken;
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uint16_t max_queues;
/*
* @read_msg: custom method to read vhost-user message
*
* Read data from vhost_user socket fd and fill up
* the passed VhostUserMsg *vmsg struct.
*
* If reading fails, it should close the received set of file
* descriptors as socket message's auxiliary data.
*
* For the details, please refer to vu_message_read in libvhost-user.c
* which will be used by default if not custom method is provided when
* calling vu_init
*
* Returns: true if vhost-user message successfully received,
* otherwise return false.
*
*/
vu_read_msg_cb read_msg;
/*
* @set_watch: add or update the given fd to the watch set,
* call cb when condition is met.
*/
vu_set_watch_cb set_watch;
/* @remove_watch: remove the given fd from the watch set */
vu_remove_watch_cb remove_watch;
/*
* @panic: encountered an unrecoverable error, you may try to re-initialize
*/
vu_panic_cb panic;
const VuDevIface *iface;
/* Postcopy data */
int postcopy_ufd;
bool postcopy_listening;
};
typedef struct VuVirtqElement {
unsigned int index;
unsigned int out_num;
unsigned int in_num;
struct iovec *in_sg;
struct iovec *out_sg;
} VuVirtqElement;
/**
* vu_init:
* @dev: a VuDev context
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* @max_queues: maximum number of virtqueues
* @socket: the socket connected to vhost-user master
* @panic: a panic callback
* @set_watch: a set_watch callback
* @remove_watch: a remove_watch callback
* @iface: a VuDevIface structure with vhost-user device callbacks
*
* Initializes a VuDev vhost-user context.
2019-06-26 10:48:13 +03:00
*
* Returns: true on success, false on failure.
**/
2019-06-26 10:48:13 +03:00
bool vu_init(VuDev *dev,
uint16_t max_queues,
int socket,
vu_panic_cb panic,
vu_read_msg_cb read_msg,
vu_set_watch_cb set_watch,
vu_remove_watch_cb remove_watch,
const VuDevIface *iface);
/**
* vu_deinit:
* @dev: a VuDev context
*
* Cleans up the VuDev context
*/
void vu_deinit(VuDev *dev);
/**
* vu_dispatch:
* @dev: a VuDev context
*
* Process one vhost-user message.
*
* Returns: TRUE on success, FALSE on failure.
*/
bool vu_dispatch(VuDev *dev);
/**
* vu_gpa_to_va:
* @dev: a VuDev context
* @plen: guest memory size
* @guest_addr: guest address
*
* Translate a guest address to a pointer. Returns NULL on failure.
*/
void *vu_gpa_to_va(VuDev *dev, uint64_t *plen, uint64_t guest_addr);
/**
* vu_get_queue:
* @dev: a VuDev context
* @qidx: queue index
*
* Returns the queue number @qidx.
*/
VuVirtq *vu_get_queue(VuDev *dev, int qidx);
/**
* vu_set_queue_handler:
* @dev: a VuDev context
* @vq: a VuVirtq queue
* @handler: the queue handler callback
*
* Set the queue handler. This function may be called several times
* for the same queue. If called with NULL @handler, the handler is
* removed.
*/
void vu_set_queue_handler(VuDev *dev, VuVirtq *vq,
vu_queue_handler_cb handler);
/**
* vu_set_queue_host_notifier:
* @dev: a VuDev context
* @vq: a VuVirtq queue
* @fd: a file descriptor
* @size: host page size
* @offset: notifier offset in @fd file
*
* Set queue's host notifier. This function may be called several
* times for the same queue. If called with -1 @fd, the notifier
* is removed.
*/
bool vu_set_queue_host_notifier(VuDev *dev, VuVirtq *vq, int fd,
int size, int offset);
/**
* vu_queue_set_notification:
* @dev: a VuDev context
* @vq: a VuVirtq queue
* @enable: state
*
* Set whether the queue notifies (via event index or interrupt)
*/
void vu_queue_set_notification(VuDev *dev, VuVirtq *vq, int enable);
/**
* vu_queue_enabled:
* @dev: a VuDev context
* @vq: a VuVirtq queue
*
* Returns: whether the queue is enabled.
*/
bool vu_queue_enabled(VuDev *dev, VuVirtq *vq);
/**
* vu_queue_started:
* @dev: a VuDev context
* @vq: a VuVirtq queue
*
* Returns: whether the queue is started.
*/
bool vu_queue_started(const VuDev *dev, const VuVirtq *vq);
/**
* vu_queue_empty:
* @dev: a VuDev context
* @vq: a VuVirtq queue
*
* Returns: true if the queue is empty or not ready.
*/
bool vu_queue_empty(VuDev *dev, VuVirtq *vq);
/**
* vu_queue_notify:
* @dev: a VuDev context
* @vq: a VuVirtq queue
*
* Request to notify the queue via callfd (skipped if unnecessary)
*/
void vu_queue_notify(VuDev *dev, VuVirtq *vq);
/**
* vu_queue_notify_sync:
* @dev: a VuDev context
* @vq: a VuVirtq queue
*
* Request to notify the queue via callfd (skipped if unnecessary)
* or sync message if possible.
*/
void vu_queue_notify_sync(VuDev *dev, VuVirtq *vq);
/**
* vu_queue_pop:
* @dev: a VuDev context
* @vq: a VuVirtq queue
* @sz: the size of struct to return (must be >= VuVirtqElement)
*
* Returns: a VuVirtqElement filled from the queue or NULL. The
* returned element must be free()-d by the caller.
*/
void *vu_queue_pop(VuDev *dev, VuVirtq *vq, size_t sz);
/**
* vu_queue_unpop:
* @dev: a VuDev context
* @vq: a VuVirtq queue
* @elem: The #VuVirtqElement
* @len: number of bytes written
*
* Pretend the most recent element wasn't popped from the virtqueue. The next
* call to vu_queue_pop() will refetch the element.
*/
void vu_queue_unpop(VuDev *dev, VuVirtq *vq, VuVirtqElement *elem,
size_t len);
/**
* vu_queue_rewind:
* @dev: a VuDev context
* @vq: a VuVirtq queue
* @num: number of elements to push back
*
* Pretend that elements weren't popped from the virtqueue. The next
* virtqueue_pop() will refetch the oldest element.
*
* Returns: true on success, false if @num is greater than the number of in use
* elements.
*/
bool vu_queue_rewind(VuDev *dev, VuVirtq *vq, unsigned int num);
/**
* vu_queue_fill:
* @dev: a VuDev context
* @vq: a VuVirtq queue
* @elem: a VuVirtqElement
* @len: length in bytes to write
* @idx: optional offset for the used ring index (0 in general)
*
* Fill the used ring with @elem element.
*/
void vu_queue_fill(VuDev *dev, VuVirtq *vq,
const VuVirtqElement *elem,
unsigned int len, unsigned int idx);
/**
* vu_queue_push:
* @dev: a VuDev context
* @vq: a VuVirtq queue
* @elem: a VuVirtqElement
* @len: length in bytes to write
*
* Helper that combines vu_queue_fill() with a vu_queue_flush().
*/
void vu_queue_push(VuDev *dev, VuVirtq *vq,
const VuVirtqElement *elem, unsigned int len);
/**
* vu_queue_flush:
* @dev: a VuDev context
* @vq: a VuVirtq queue
* @num: number of elements to flush
*
* Mark the last number of elements as done (used.idx is updated by
* num elements).
*/
void vu_queue_flush(VuDev *dev, VuVirtq *vq, unsigned int num);
/**
* vu_queue_get_avail_bytes:
* @dev: a VuDev context
* @vq: a VuVirtq queue
* @in_bytes: in bytes
* @out_bytes: out bytes
* @max_in_bytes: stop counting after max_in_bytes
* @max_out_bytes: stop counting after max_out_bytes
*
* Count the number of available bytes, up to max_in_bytes/max_out_bytes.
*/
void vu_queue_get_avail_bytes(VuDev *vdev, VuVirtq *vq, unsigned int *in_bytes,
unsigned int *out_bytes,
unsigned max_in_bytes, unsigned max_out_bytes);
/**
* vu_queue_avail_bytes:
* @dev: a VuDev context
* @vq: a VuVirtq queue
* @in_bytes: expected in bytes
* @out_bytes: expected out bytes
*
* Returns: true if in_bytes <= in_total && out_bytes <= out_total
*/
bool vu_queue_avail_bytes(VuDev *dev, VuVirtq *vq, unsigned int in_bytes,
unsigned int out_bytes);
#endif /* LIBVHOST_USER_H */