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/virtio_byteorder.h>
  28#include <linux/uio.h>
  29#include <linux/slab.h>
  30#include <asm/barrier.h>
  31
  32/* virtio_ring with information needed for host access. */
  33struct vringh {
  34        /* Everything is little endian */
  35        bool little_endian;
  36
  37        /* Guest publishes used event idx (note: we always do). */
  38        bool event_indices;
  39
  40        /* Can we get away with weak barriers? */
  41        bool weak_barriers;
  42
  43        /* Last available index we saw (ie. where we're up to). */
  44        u16 last_avail_idx;
  45
  46        /* Last index we used. */
  47        u16 last_used_idx;
  48
  49        /* How many descriptors we've completed since last need_notify(). */
  50        u32 completed;
  51
  52        /* The vring (note: it may contain user pointers!) */
  53        struct vring vring;
  54
  55        /* The function to call to notify the guest about added buffers */
  56        void (*notify)(struct vringh *);
  57};
  58
  59/**
  60 * struct vringh_config_ops - ops for creating a host vring from a virtio driver
  61 * @find_vrhs: find the host vrings and instantiate them
  62 *      vdev: the virtio_device
  63 *      nhvrs: the number of host vrings to find
  64 *      hvrs: on success, includes new host vrings
  65 *      callbacks: array of driver callbacks, for each host vring
  66 *              include a NULL entry for vqs that do not need a callback
  67 *      Returns 0 on success or error status
  68 * @del_vrhs: free the host vrings found by find_vrhs().
  69 */
  70struct virtio_device;
  71typedef void vrh_callback_t(struct virtio_device *, struct vringh *);
  72struct vringh_config_ops {
  73        int (*find_vrhs)(struct virtio_device *vdev, unsigned nhvrs,
  74                         struct vringh *vrhs[], vrh_callback_t *callbacks[]);
  75        void (*del_vrhs)(struct virtio_device *vdev);
  76};
  77
  78/* The memory the vring can access, and what offset to apply. */
  79struct vringh_range {
  80        u64 start, end_incl;
  81        u64 offset;
  82};
  83
  84/**
  85 * struct vringh_iov - iovec mangler.
  86 *
  87 * Mangles iovec in place, and restores it.
  88 * Remaining data is iov + i, of used - i elements.
  89 */
  90struct vringh_iov {
  91        struct iovec *iov;
  92        size_t consumed; /* Within iov[i] */
  93        unsigned i, used, max_num;
  94};
  95
  96/**
  97 * struct vringh_iov - kvec mangler.
  98 *
  99 * Mangles kvec in place, and restores it.
 100 * Remaining data is iov + i, of used - i elements.
 101 */
 102struct vringh_kiov {
 103        struct kvec *iov;
 104        size_t consumed; /* Within iov[i] */
 105        unsigned i, used, max_num;
 106};
 107
 108/* Flag on max_num to indicate we're kmalloced. */
 109#define VRINGH_IOV_ALLOCATED 0x8000000
 110
 111/* Helpers for userspace vrings. */
 112int vringh_init_user(struct vringh *vrh, u64 features,
 113                     unsigned int num, bool weak_barriers,
 114                     struct vring_desc __user *desc,
 115                     struct vring_avail __user *avail,
 116                     struct vring_used __user *used);
 117
 118static inline void vringh_iov_init(struct vringh_iov *iov,
 119                                   struct iovec *iovec, unsigned num)
 120{
 121        iov->used = iov->i = 0;
 122        iov->consumed = 0;
 123        iov->max_num = num;
 124        iov->iov = iovec;
 125}
 126
 127static inline void vringh_iov_reset(struct vringh_iov *iov)
 128{
 129        iov->iov[iov->i].iov_len += iov->consumed;
 130        iov->iov[iov->i].iov_base -= iov->consumed;
 131        iov->consumed = 0;
 132        iov->i = 0;
 133}
 134
 135static inline void vringh_iov_cleanup(struct vringh_iov *iov)
 136{
 137        if (iov->max_num & VRINGH_IOV_ALLOCATED)
 138                kfree(iov->iov);
 139        iov->max_num = iov->used = iov->i = iov->consumed = 0;
 140        iov->iov = NULL;
 141}
 142
 143/* Convert a descriptor into iovecs. */
 144int vringh_getdesc_user(struct vringh *vrh,
 145                        struct vringh_iov *riov,
 146                        struct vringh_iov *wiov,
 147                        bool (*getrange)(struct vringh *vrh,
 148                                         u64 addr, struct vringh_range *r),
 149                        u16 *head);
 150
 151/* Copy bytes from readable vsg, consuming it (and incrementing wiov->i). */
 152ssize_t vringh_iov_pull_user(struct vringh_iov *riov, void *dst, size_t len);
 153
 154/* Copy bytes into writable vsg, consuming it (and incrementing wiov->i). */
 155ssize_t vringh_iov_push_user(struct vringh_iov *wiov,
 156                             const void *src, size_t len);
 157
 158/* Mark a descriptor as used. */
 159int vringh_complete_user(struct vringh *vrh, u16 head, u32 len);
 160int vringh_complete_multi_user(struct vringh *vrh,
 161                               const struct vring_used_elem used[],
 162                               unsigned num_used);
 163
 164/* Pretend we've never seen descriptor (for easy error handling). */
 165void vringh_abandon_user(struct vringh *vrh, unsigned int num);
 166
 167/* Do we need to fire the eventfd to notify the other side? */
 168int vringh_need_notify_user(struct vringh *vrh);
 169
 170bool vringh_notify_enable_user(struct vringh *vrh);
 171void vringh_notify_disable_user(struct vringh *vrh);
 172
 173/* Helpers for kernelspace vrings. */
 174int vringh_init_kern(struct vringh *vrh, u64 features,
 175                     unsigned int num, bool weak_barriers,
 176                     struct vring_desc *desc,
 177                     struct vring_avail *avail,
 178                     struct vring_used *used);
 179
 180static inline void vringh_kiov_init(struct vringh_kiov *kiov,
 181                                    struct kvec *kvec, unsigned num)
 182{
 183        kiov->used = kiov->i = 0;
 184        kiov->consumed = 0;
 185        kiov->max_num = num;
 186        kiov->iov = kvec;
 187}
 188
 189static inline void vringh_kiov_reset(struct vringh_kiov *kiov)
 190{
 191        kiov->iov[kiov->i].iov_len += kiov->consumed;
 192        kiov->iov[kiov->i].iov_base -= kiov->consumed;
 193        kiov->consumed = 0;
 194        kiov->i = 0;
 195}
 196
 197static inline void vringh_kiov_cleanup(struct vringh_kiov *kiov)
 198{
 199        if (kiov->max_num & VRINGH_IOV_ALLOCATED)
 200                kfree(kiov->iov);
 201        kiov->max_num = kiov->used = kiov->i = kiov->consumed = 0;
 202        kiov->iov = NULL;
 203}
 204
 205int vringh_getdesc_kern(struct vringh *vrh,
 206                        struct vringh_kiov *riov,
 207                        struct vringh_kiov *wiov,
 208                        u16 *head,
 209                        gfp_t gfp);
 210
 211ssize_t vringh_iov_pull_kern(struct vringh_kiov *riov, void *dst, size_t len);
 212ssize_t vringh_iov_push_kern(struct vringh_kiov *wiov,
 213                             const void *src, size_t len);
 214void vringh_abandon_kern(struct vringh *vrh, unsigned int num);
 215int vringh_complete_kern(struct vringh *vrh, u16 head, u32 len);
 216
 217bool vringh_notify_enable_kern(struct vringh *vrh);
 218void vringh_notify_disable_kern(struct vringh *vrh);
 219
 220int vringh_need_notify_kern(struct vringh *vrh);
 221
 222/* Notify the guest about buffers added to the used ring */
 223static inline void vringh_notify(struct vringh *vrh)
 224{
 225        if (vrh->notify)
 226                vrh->notify(vrh);
 227}
 228
 229static inline bool vringh_is_little_endian(const struct vringh *vrh)
 230{
 231        return vrh->little_endian ||
 232                virtio_legacy_is_little_endian();
 233}
 234
 235static inline u16 vringh16_to_cpu(const struct vringh *vrh, __virtio16 val)
 236{
 237        return __virtio16_to_cpu(vringh_is_little_endian(vrh), val);
 238}
 239
 240static inline __virtio16 cpu_to_vringh16(const struct vringh *vrh, u16 val)
 241{
 242        return __cpu_to_virtio16(vringh_is_little_endian(vrh), val);
 243}
 244
 245static inline u32 vringh32_to_cpu(const struct vringh *vrh, __virtio32 val)
 246{
 247        return __virtio32_to_cpu(vringh_is_little_endian(vrh), val);
 248}
 249
 250static inline __virtio32 cpu_to_vringh32(const struct vringh *vrh, u32 val)
 251{
 252        return __cpu_to_virtio32(vringh_is_little_endian(vrh), val);
 253}
 254
 255static inline u64 vringh64_to_cpu(const struct vringh *vrh, __virtio64 val)
 256{
 257        return __virtio64_to_cpu(vringh_is_little_endian(vrh), val);
 258}
 259
 260static inline __virtio64 cpu_to_vringh64(const struct vringh *vrh, u64 val)
 261{
 262        return __cpu_to_virtio64(vringh_is_little_endian(vrh), val);
 263}
 264#endif /* _LINUX_VRINGH_H */
 265