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. */
  33 struct 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  */
  70 struct virtio_device;
  71 typedef void vrh_callback_t(struct virtio_device *, struct vringh *);
  72 struct 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. */
  79 struct 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  */
  90 struct 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  */
 102 struct 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. */
 112 int 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
 118 static 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
 127 static 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
 135 static 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. */
 144 int 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). */
 152 ssize_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). */
 155 ssize_t vringh_iov_push_user(struct vringh_iov *wiov,
 156                              const void *src, size_t len);
 157
 158 /* Mark a descriptor as used. */
 159 int vringh_complete_user(struct vringh *vrh, u16 head, u32 len);
 160 int 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). */
 165 void vringh_abandon_user(struct vringh *vrh, unsigned int num);
 166
 167 /* Do we need to fire the eventfd to notify the other side? */
 168 int vringh_need_notify_user(struct vringh *vrh);
 169
 170 bool vringh_notify_enable_user(struct vringh *vrh);
 171 void vringh_notify_disable_user(struct vringh *vrh);
 172
 173 /* Helpers for kernelspace vrings. */
 174 int 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
 180 static 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
 189 static 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
 197 static 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
 205 int vringh_getdesc_kern(struct vringh *vrh,
 206                         struct vringh_kiov *riov,
 207                         struct vringh_kiov *wiov,
 208                         u16 *head,
 209                         gfp_t gfp);
 210
 211 ssize_t vringh_iov_pull_kern(struct vringh_kiov *riov, void *dst, size_t len);
 212 ssize_t vringh_iov_push_kern(struct vringh_kiov *wiov,
 213                              const void *src, size_t len);
 214 void vringh_abandon_kern(struct vringh *vrh, unsigned int num);
 215 int vringh_complete_kern(struct vringh *vrh, u16 head, u32 len);
 216
 217 bool vringh_notify_enable_kern(struct vringh *vrh);
 218 void vringh_notify_disable_kern(struct vringh *vrh);
 219
 220 int vringh_need_notify_kern(struct vringh *vrh);
 221
 222 /* Notify the guest about buffers added to the used ring */
 223 static inline void vringh_notify(struct vringh *vrh)
 224 {
 225         if (vrh->notify)
 226                 vrh->notify(vrh);
 227 }
 228
 229 static inline bool vringh_is_little_endian(const struct vringh *vrh)
 230 {
 231         return vrh->little_endian ||
 232                 virtio_legacy_is_little_endian();
 233 }
 234
 235 static 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
 240 static 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
 245 static 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
 250 static 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
 255 static 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
 260 static 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 */