include/linux/vringh.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /*
   3  * Linux host-side vring helpers; for when the kernel needs to access
   4  * someone else's vring.
   5  *
   6  * Copyright IBM Corporation, 2013.
   7  * Parts taken from drivers/vhost/vhost.c Copyright 2009 Red Hat, Inc.
   8  *
   9  * Written by: Rusty Russell <rusty@rustcorp.com.au>
  10  */
  11 #ifndef _LINUX_VRINGH_H
  12 #define _LINUX_VRINGH_H
  13 #include <uapi/linux/virtio_ring.h>
  14 #include <linux/virtio_byteorder.h>
  15 #include <linux/uio.h>
  16 #include <linux/slab.h>
  17 #include <asm/barrier.h>
  18
  19 /* virtio_ring with information needed for host access. */
  20 struct vringh {
  21         /* Everything is little endian */
  22         bool little_endian;
  23
  24         /* Guest publishes used event idx (note: we always do). */
  25         bool event_indices;
  26
  27         /* Can we get away with weak barriers? */
  28         bool weak_barriers;
  29
  30         /* Last available index we saw (ie. where we're up to). */
  31         u16 last_avail_idx;
  32
  33         /* Last index we used. */
  34         u16 last_used_idx;
  35
  36         /* How many descriptors we've completed since last need_notify(). */
  37         u32 completed;
  38
  39         /* The vring (note: it may contain user pointers!) */
  40         struct vring vring;
  41
  42         /* The function to call to notify the guest about added buffers */
  43         void (*notify)(struct vringh *);
  44 };
  45
  46 /**
  47  * struct vringh_config_ops - ops for creating a host vring from a virtio driver
  48  * @find_vrhs: find the host vrings and instantiate them
  49  *      vdev: the virtio_device
  50  *      nhvrs: the number of host vrings to find
  51  *      hvrs: on success, includes new host vrings
  52  *      callbacks: array of driver callbacks, for each host vring
  53  *              include a NULL entry for vqs that do not need a callback
  54  *      Returns 0 on success or error status
  55  * @del_vrhs: free the host vrings found by find_vrhs().
  56  */
  57 struct virtio_device;
  58 typedef void vrh_callback_t(struct virtio_device *, struct vringh *);
  59 struct vringh_config_ops {
  60         int (*find_vrhs)(struct virtio_device *vdev, unsigned nhvrs,
  61                          struct vringh *vrhs[], vrh_callback_t *callbacks[]);
  62         void (*del_vrhs)(struct virtio_device *vdev);
  63 };
  64
  65 /* The memory the vring can access, and what offset to apply. */
  66 struct vringh_range {
  67         u64 start, end_incl;
  68         u64 offset;
  69 };
  70
  71 /**
  72  * struct vringh_iov - iovec mangler.
  73  *
  74  * Mangles iovec in place, and restores it.
  75  * Remaining data is iov + i, of used - i elements.
  76  */
  77 struct vringh_iov {
  78         struct iovec *iov;
  79         size_t consumed; /* Within iov[i] */
  80         unsigned i, used, max_num;
  81 };
  82
  83 /**
  84  * struct vringh_iov - kvec mangler.
  85  *
  86  * Mangles kvec in place, and restores it.
  87  * Remaining data is iov + i, of used - i elements.
  88  */
  89 struct vringh_kiov {
  90         struct kvec *iov;
  91         size_t consumed; /* Within iov[i] */
  92         unsigned i, used, max_num;
  93 };
  94
  95 /* Flag on max_num to indicate we're kmalloced. */
  96 #define VRINGH_IOV_ALLOCATED 0x8000000
  97
  98 /* Helpers for userspace vrings. */
  99 int vringh_init_user(struct vringh *vrh, u64 features,
 100                      unsigned int num, bool weak_barriers,
 101                      struct vring_desc __user *desc,
 102                      struct vring_avail __user *avail,
 103                      struct vring_used __user *used);
 104
 105 static inline void vringh_iov_init(struct vringh_iov *iov,
 106                                    struct iovec *iovec, unsigned num)
 107 {
 108         iov->used = iov->i = 0;
 109         iov->consumed = 0;
 110         iov->max_num = num;
 111         iov->iov = iovec;
 112 }
 113
 114 static inline void vringh_iov_reset(struct vringh_iov *iov)
 115 {
 116         iov->iov[iov->i].iov_len += iov->consumed;
 117         iov->iov[iov->i].iov_base -= iov->consumed;
 118         iov->consumed = 0;
 119         iov->i = 0;
 120 }
 121
 122 static inline void vringh_iov_cleanup(struct vringh_iov *iov)
 123 {
 124         if (iov->max_num & VRINGH_IOV_ALLOCATED)
 125                 kfree(iov->iov);
 126         iov->max_num = iov->used = iov->i = iov->consumed = 0;
 127         iov->iov = NULL;
 128 }
 129
 130 /* Convert a descriptor into iovecs. */
 131 int vringh_getdesc_user(struct vringh *vrh,
 132                         struct vringh_iov *riov,
 133                         struct vringh_iov *wiov,
 134                         bool (*getrange)(struct vringh *vrh,
 135                                          u64 addr, struct vringh_range *r),
 136                         u16 *head);
 137
 138 /* Copy bytes from readable vsg, consuming it (and incrementing wiov->i). */
 139 ssize_t vringh_iov_pull_user(struct vringh_iov *riov, void *dst, size_t len);
 140
 141 /* Copy bytes into writable vsg, consuming it (and incrementing wiov->i). */
 142 ssize_t vringh_iov_push_user(struct vringh_iov *wiov,
 143                              const void *src, size_t len);
 144
 145 /* Mark a descriptor as used. */
 146 int vringh_complete_user(struct vringh *vrh, u16 head, u32 len);
 147 int vringh_complete_multi_user(struct vringh *vrh,
 148                                const struct vring_used_elem used[],
 149                                unsigned num_used);
 150
 151 /* Pretend we've never seen descriptor (for easy error handling). */
 152 void vringh_abandon_user(struct vringh *vrh, unsigned int num);
 153
 154 /* Do we need to fire the eventfd to notify the other side? */
 155 int vringh_need_notify_user(struct vringh *vrh);
 156
 157 bool vringh_notify_enable_user(struct vringh *vrh);
 158 void vringh_notify_disable_user(struct vringh *vrh);
 159
 160 /* Helpers for kernelspace vrings. */
 161 int vringh_init_kern(struct vringh *vrh, u64 features,
 162                      unsigned int num, bool weak_barriers,
 163                      struct vring_desc *desc,
 164                      struct vring_avail *avail,
 165                      struct vring_used *used);
 166
 167 static inline void vringh_kiov_init(struct vringh_kiov *kiov,
 168                                     struct kvec *kvec, unsigned num)
 169 {
 170         kiov->used = kiov->i = 0;
 171         kiov->consumed = 0;
 172         kiov->max_num = num;
 173         kiov->iov = kvec;
 174 }
 175
 176 static inline void vringh_kiov_reset(struct vringh_kiov *kiov)
 177 {
 178         kiov->iov[kiov->i].iov_len += kiov->consumed;
 179         kiov->iov[kiov->i].iov_base -= kiov->consumed;
 180         kiov->consumed = 0;
 181         kiov->i = 0;
 182 }
 183
 184 static inline void vringh_kiov_cleanup(struct vringh_kiov *kiov)
 185 {
 186         if (kiov->max_num & VRINGH_IOV_ALLOCATED)
 187                 kfree(kiov->iov);
 188         kiov->max_num = kiov->used = kiov->i = kiov->consumed = 0;
 189         kiov->iov = NULL;
 190 }
 191
 192 int vringh_getdesc_kern(struct vringh *vrh,
 193                         struct vringh_kiov *riov,
 194                         struct vringh_kiov *wiov,
 195                         u16 *head,
 196                         gfp_t gfp);
 197
 198 ssize_t vringh_iov_pull_kern(struct vringh_kiov *riov, void *dst, size_t len);
 199 ssize_t vringh_iov_push_kern(struct vringh_kiov *wiov,
 200                              const void *src, size_t len);
 201 void vringh_abandon_kern(struct vringh *vrh, unsigned int num);
 202 int vringh_complete_kern(struct vringh *vrh, u16 head, u32 len);
 203
 204 bool vringh_notify_enable_kern(struct vringh *vrh);
 205 void vringh_notify_disable_kern(struct vringh *vrh);
 206
 207 int vringh_need_notify_kern(struct vringh *vrh);
 208
 209 /* Notify the guest about buffers added to the used ring */
 210 static inline void vringh_notify(struct vringh *vrh)
 211 {
 212         if (vrh->notify)
 213                 vrh->notify(vrh);
 214 }
 215
 216 static inline bool vringh_is_little_endian(const struct vringh *vrh)
 217 {
 218         return vrh->little_endian ||
 219                 virtio_legacy_is_little_endian();
 220 }
 221
 222 static inline u16 vringh16_to_cpu(const struct vringh *vrh, __virtio16 val)
 223 {
 224         return __virtio16_to_cpu(vringh_is_little_endian(vrh), val);
 225 }
 226
 227 static inline __virtio16 cpu_to_vringh16(const struct vringh *vrh, u16 val)
 228 {
 229         return __cpu_to_virtio16(vringh_is_little_endian(vrh), val);
 230 }
 231
 232 static inline u32 vringh32_to_cpu(const struct vringh *vrh, __virtio32 val)
 233 {
 234         return __virtio32_to_cpu(vringh_is_little_endian(vrh), val);
 235 }
 236
 237 static inline __virtio32 cpu_to_vringh32(const struct vringh *vrh, u32 val)
 238 {
 239         return __cpu_to_virtio32(vringh_is_little_endian(vrh), val);
 240 }
 241
 242 static inline u64 vringh64_to_cpu(const struct vringh *vrh, __virtio64 val)
 243 {
 244         return __virtio64_to_cpu(vringh_is_little_endian(vrh), val);
 245 }
 246
 247 static inline __virtio64 cpu_to_vringh64(const struct vringh *vrh, u64 val)
 248 {
 249         return __cpu_to_virtio64(vringh_is_little_endian(vrh), val);
 250 }
 251 #endif /* _LINUX_VRINGH_H */