LXR linux/include/linux/vringh.h

   1/*
   2 * Linux host-side vring helpers; for when the kernel needs to access
   3 * someone else's vring.
   4 *
   5 * Copyright IBM Corporation, 2013.
   6 * Parts taken from drivers/vhost/vhost.c Copyright 2009 Red Hat, Inc.
   7 *
   8 * This program is free software; you can redistribute it and/or modify
   9 * it under the terms of the GNU General Public License as published by
  10 * the Free Software Foundation; either version 2 of the License, or
  11 * (at your option) any later version.
  12 *
  13 * This program is distributed in the hope that it will be useful,
  14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 * GNU General Public License for more details.
  17 *
  18 * You should have received a copy of the GNU General Public License
  19 * along with this program; if not, write to the Free Software
  20 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  21 *
  22 * Written by: Rusty Russell <rusty@rustcorp.com.au>
  23 */
  24#ifndef _LINUX_VRINGH_H
  25#define _LINUX_VRINGH_H
  26#include <uapi/linux/virtio_ring.h>
  27#include <linux/uio.h>
  28#include <linux/slab.h>
  29#include <asm/barrier.h>
  30
  31/* virtio_ring with information needed for host access. */
  32struct vringh {
  33        /* Guest publishes used event idx (note: we always do). */
  34        bool event_indices;
  35
  36        /* Can we get away with weak barriers? */
  37        bool weak_barriers;
  38
  39        /* Last available index we saw (ie. where we're up to). */
  40        u16 last_avail_idx;
  41
  42        /* Last index we used. */
  43        u16 last_used_idx;
  44
  45        /* How many descriptors we've completed since last need_notify(). */
  46        u32 completed;
  47
  48        /* The vring (note: it may contain user pointers!) */
  49        struct vring vring;
  50
  51        /* The function to call to notify the guest about added buffers */
  52        void (*notify)(struct vringh *);
  53};
  54
  55/**
  56 * struct vringh_config_ops - ops for creating a host vring from a virtio driver
  57 * @find_vrhs: find the host vrings and instantiate them
  58 *      vdev: the virtio_device
  59 *      nhvrs: the number of host vrings to find
  60 *      hvrs: on success, includes new host vrings
  61 *      callbacks: array of driver callbacks, for each host vring
  62 *              include a NULL entry for vqs that do not need a callback
  63 *      Returns 0 on success or error status
  64 * @del_vrhs: free the host vrings found by find_vrhs().
  65 */
  66struct virtio_device;
  67typedef void vrh_callback_t(struct virtio_device *, struct vringh *);
  68struct vringh_config_ops {
  69        int (*find_vrhs)(struct virtio_device *vdev, unsigned nhvrs,
  70                         struct vringh *vrhs[], vrh_callback_t *callbacks[]);
  71        void (*del_vrhs)(struct virtio_device *vdev);
  72};
  73
  74/* The memory the vring can access, and what offset to apply. */
  75struct vringh_range {
  76        u64 start, end_incl;
  77        u64 offset;
  78};
  79
  80/**
  81 * struct vringh_iov - iovec mangler.
  82 *
  83 * Mangles iovec in place, and restores it.
  84 * Remaining data is iov + i, of used - i elements.
  85 */
  86struct vringh_iov {
  87        struct iovec *iov;
  88        size_t consumed; /* Within iov[i] */
  89        unsigned i, used, max_num;
  90};
  91
  92/**
  93 * struct vringh_iov - kvec mangler.
  94 *
  95 * Mangles kvec in place, and restores it.
  96 * Remaining data is iov + i, of used - i elements.
  97 */
  98struct vringh_kiov {
  99        struct kvec *iov;
 100        size_t consumed; /* Within iov[i] */
 101        unsigned i, used, max_num;
 102};
 103
 104/* Flag on max_num to indicate we're kmalloced. */
 105#define VRINGH_IOV_ALLOCATED 0x8000000
 106
 107/* Helpers for userspace vrings. */
 108int vringh_init_user(struct vringh *vrh, u32 features,
 109                     unsigned int num, bool weak_barriers,
 110                     struct vring_desc __user *desc,
 111                     struct vring_avail __user *avail,
 112                     struct vring_used __user *used);
 113
 114static inline void vringh_iov_init(struct vringh_iov *iov,
 115                                   struct iovec *iovec, unsigned num)
 116{
 117        iov->used = iov->i = 0;
 118        iov->consumed = 0;
 119        iov->max_num = num;
 120        iov->iov = iovec;
 121}
 122
 123static inline void vringh_iov_reset(struct vringh_iov *iov)
 124{
 125        iov->iov[iov->i].iov_len += iov->consumed;
 126        iov->iov[iov->i].iov_base -= iov->consumed;
 127        iov->consumed = 0;
 128        iov->i = 0;
 129}
 130
 131static inline void vringh_iov_cleanup(struct vringh_iov *iov)
 132{
 133        if (iov->max_num & VRINGH_IOV_ALLOCATED)
 134                kfree(iov->iov);
 135        iov->max_num = iov->used = iov->i = iov->consumed = 0;
 136        iov->iov = NULL;
 137}
 138
 139/* Convert a descriptor into iovecs. */
 140int vringh_getdesc_user(struct vringh *vrh,
 141                        struct vringh_iov *riov,
 142                        struct vringh_iov *wiov,
 143                        bool (*getrange)(struct vringh *vrh,
 144                                         u64 addr, struct vringh_range *r),
 145                        u16 *head);
 146
 147/* Copy bytes from readable vsg, consuming it (and incrementing wiov->i). */
 148ssize_t vringh_iov_pull_user(struct vringh_iov *riov, void *dst, size_t len);
 149
 150/* Copy bytes into writable vsg, consuming it (and incrementing wiov->i). */
 151ssize_t vringh_iov_push_user(struct vringh_iov *wiov,
 152                             const void *src, size_t len);
 153
 154/* Mark a descriptor as used. */
 155int vringh_complete_user(struct vringh *vrh, u16 head, u32 len);
 156int vringh_complete_multi_user(struct vringh *vrh,
 157                               const struct vring_used_elem used[],
 158                               unsigned num_used);
 159
 160/* Pretend we've never seen descriptor (for easy error handling). */
 161void vringh_abandon_user(struct vringh *vrh, unsigned int num);
 162
 163/* Do we need to fire the eventfd to notify the other side? */
 164int vringh_need_notify_user(struct vringh *vrh);
 165
 166bool vringh_notify_enable_user(struct vringh *vrh);
 167void vringh_notify_disable_user(struct vringh *vrh);
 168
 169/* Helpers for kernelspace vrings. */
 170int vringh_init_kern(struct vringh *vrh, u32 features,
 171                     unsigned int num, bool weak_barriers,
 172                     struct vring_desc *desc,
 173                     struct vring_avail *avail,
 174                     struct vring_used *used);
 175
 176static inline void vringh_kiov_init(struct vringh_kiov *kiov,
 177                                    struct kvec *kvec, unsigned num)
 178{
 179        kiov->used = kiov->i = 0;
 180        kiov->consumed = 0;
 181        kiov->max_num = num;
 182        kiov->iov = kvec;
 183}
 184
 185static inline void vringh_kiov_reset(struct vringh_kiov *kiov)
 186{
 187        kiov->iov[kiov->i].iov_len += kiov->consumed;
 188        kiov->iov[kiov->i].iov_base -= kiov->consumed;
 189        kiov->consumed = 0;
 190        kiov->i = 0;
 191}
 192
 193static inline void vringh_kiov_cleanup(struct vringh_kiov *kiov)
 194{
 195        if (kiov->max_num & VRINGH_IOV_ALLOCATED)
 196                kfree(kiov->iov);
 197        kiov->max_num = kiov->used = kiov->i = kiov->consumed = 0;
 198        kiov->iov = NULL;
 199}
 200
 201int vringh_getdesc_kern(struct vringh *vrh,
 202                        struct vringh_kiov *riov,
 203                        struct vringh_kiov *wiov,
 204                        u16 *head,
 205                        gfp_t gfp);
 206
 207ssize_t vringh_iov_pull_kern(struct vringh_kiov *riov, void *dst, size_t len);
 208ssize_t vringh_iov_push_kern(struct vringh_kiov *wiov,
 209                             const void *src, size_t len);
 210void vringh_abandon_kern(struct vringh *vrh, unsigned int num);
 211int vringh_complete_kern(struct vringh *vrh, u16 head, u32 len);
 212
 213bool vringh_notify_enable_kern(struct vringh *vrh);
 214void vringh_notify_disable_kern(struct vringh *vrh);
 215
 216int vringh_need_notify_kern(struct vringh *vrh);
 217
 218/* Notify the guest about buffers added to the used ring */
 219static inline void vringh_notify(struct vringh *vrh)
 220{
 221        if (vrh->notify)
 222                vrh->notify(vrh);
 223}
 224
 225#endif /* _LINUX_VRINGH_H */
 226