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. */
  32 struct 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  */
  66 struct virtio_device;
  67 typedef void vrh_callback_t(struct virtio_device *, struct vringh *);
  68 struct 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. */
  75 struct 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  */
  86 struct 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  */
  98 struct 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. */
 108 int 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
 114 static 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
 123 static 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
 131 static 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. */
 140 int 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). */
 148 ssize_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). */
 151 ssize_t vringh_iov_push_user(struct vringh_iov *wiov,
 152                              const void *src, size_t len);
 153
 154 /* Mark a descriptor as used. */
 155 int vringh_complete_user(struct vringh *vrh, u16 head, u32 len);
 156 int 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). */
 161 void vringh_abandon_user(struct vringh *vrh, unsigned int num);
 162
 163 /* Do we need to fire the eventfd to notify the other side? */
 164 int vringh_need_notify_user(struct vringh *vrh);
 165
 166 bool vringh_notify_enable_user(struct vringh *vrh);
 167 void vringh_notify_disable_user(struct vringh *vrh);
 168
 169 /* Helpers for kernelspace vrings. */
 170 int 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
 176 static 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
 185 static 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
 193 static 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
 201 int vringh_getdesc_kern(struct vringh *vrh,
 202                         struct vringh_kiov *riov,
 203                         struct vringh_kiov *wiov,
 204                         u16 *head,
 205                         gfp_t gfp);
 206
 207 ssize_t vringh_iov_pull_kern(struct vringh_kiov *riov, void *dst, size_t len);
 208 ssize_t vringh_iov_push_kern(struct vringh_kiov *wiov,
 209                              const void *src, size_t len);
 210 void vringh_abandon_kern(struct vringh *vrh, unsigned int num);
 211 int vringh_complete_kern(struct vringh *vrh, u16 head, u32 len);
 212
 213 bool vringh_notify_enable_kern(struct vringh *vrh);
 214 void vringh_notify_disable_kern(struct vringh *vrh);
 215
 216 int vringh_need_notify_kern(struct vringh *vrh);
 217
 218 /* Notify the guest about buffers added to the used ring */
 219 static inline void vringh_notify(struct vringh *vrh)
 220 {
 221         if (vrh->notify)
 222                 vrh->notify(vrh);
 223 }
 224
 225 #endif /* _LINUX_VRINGH_H */