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 <linux/spinlock.h>
  18 #if IS_REACHABLE(CONFIG_VHOST_IOTLB)
  19 #include <linux/dma-direction.h>
  20 #include <linux/vhost_iotlb.h>
  21 #endif
  22 #include <asm/barrier.h>
  23
  24 /* virtio_ring with information needed for host access. */
  25 struct vringh {
  26         /* Everything is little endian */
  27         bool little_endian;
  28
  29         /* Guest publishes used event idx (note: we always do). */
  30         bool event_indices;
  31
  32         /* Can we get away with weak barriers? */
  33         bool weak_barriers;
  34
  35         /* Use user's VA */
  36         bool use_va;
  37
  38         /* Last available index we saw (ie. where we're up to). */
  39         u16 last_avail_idx;
  40
  41         /* Last index we used. */
  42         u16 last_used_idx;
  43
  44         /* How many descriptors we've completed since last need_notify(). */
  45         u32 completed;
  46
  47         /* The vring (note: it may contain user pointers!) */
  48         struct vring vring;
  49
  50         /* IOTLB for this vring */
  51         struct vhost_iotlb *iotlb;
  52
  53         /* spinlock to synchronize IOTLB accesses */
  54         spinlock_t *iotlb_lock;
  55
  56         /* The function to call to notify the guest about added buffers */
  57         void (*notify)(struct vringh *);
  58 };
  59
  60 struct virtio_device;
  61 typedef void vrh_callback_t(struct virtio_device *, struct vringh *);
  62
  63 /**
  64  * struct vringh_config_ops - ops for creating a host vring from a virtio driver
  65  * @find_vrhs: find the host vrings and instantiate them
  66  *      vdev: the virtio_device
  67  *      nhvrs: the number of host vrings to find
  68  *      hvrs: on success, includes new host vrings
  69  *      callbacks: array of driver callbacks, for each host vring
  70  *              include a NULL entry for vqs that do not need a callback
  71  *      Returns 0 on success or error status
  72  * @del_vrhs: free the host vrings found by find_vrhs().
  73  */
  74 struct vringh_config_ops {
  75         int (*find_vrhs)(struct virtio_device *vdev, unsigned nhvrs,
  76                          struct vringh *vrhs[], vrh_callback_t *callbacks[]);
  77         void (*del_vrhs)(struct virtio_device *vdev);
  78 };
  79
  80 /* The memory the vring can access, and what offset to apply. */
  81 struct vringh_range {
  82         u64 start, end_incl;
  83         u64 offset;
  84 };
  85
  86 /**
  87  * struct vringh_iov - iovec mangler.
  88  * @iov: array of iovecs to operate on
  89  * @consumed: number of bytes consumed within iov[i]
  90  * @i: index of current iovec
  91  * @used: number of iovecs present in @iov
  92  * @max_num: maximum number of iovecs.
  93  *           corresponds to allocated memory of @iov
  94  *
  95  * Mangles iovec in place, and restores it.
  96  * Remaining data is iov + i, of used - i elements.
  97  */
  98 struct vringh_iov {
  99         struct iovec *iov;
 100         size_t consumed; /* Within iov[i] */
 101         unsigned i, used, max_num;
 102 };
 103
 104 /**
 105  * struct vringh_kiov - kvec mangler.
 106  * @iov: array of iovecs to operate on
 107  * @consumed: number of bytes consumed within iov[i]
 108  * @i: index of current iovec
 109  * @used: number of iovecs present in @iov
 110  * @max_num: maximum number of iovecs.
 111  *           corresponds to allocated memory of @iov
 112  *
 113  * Mangles kvec in place, and restores it.
 114  * Remaining data is iov + i, of used - i elements.
 115  */
 116 struct vringh_kiov {
 117         struct kvec *iov;
 118         size_t consumed; /* Within iov[i] */
 119         unsigned i, used, max_num;
 120 };
 121
 122 /* Flag on max_num to indicate we're kmalloced. */
 123 #define VRINGH_IOV_ALLOCATED 0x8000000
 124
 125 /* Helpers for userspace vrings. */
 126 int vringh_init_user(struct vringh *vrh, u64 features,
 127                      unsigned int num, bool weak_barriers,
 128                      vring_desc_t __user *desc,
 129                      vring_avail_t __user *avail,
 130                      vring_used_t __user *used);
 131
 132 static inline void vringh_iov_init(struct vringh_iov *iov,
 133                                    struct iovec *iovec, unsigned num)
 134 {
 135         iov->used = iov->i = 0;
 136         iov->consumed = 0;
 137         iov->max_num = num;
 138         iov->iov = iovec;
 139 }
 140
 141 static inline void vringh_iov_reset(struct vringh_iov *iov)
 142 {
 143         iov->iov[iov->i].iov_len += iov->consumed;
 144         iov->iov[iov->i].iov_base -= iov->consumed;
 145         iov->consumed = 0;
 146         iov->i = 0;
 147 }
 148
 149 static inline void vringh_iov_cleanup(struct vringh_iov *iov)
 150 {
 151         if (iov->max_num & VRINGH_IOV_ALLOCATED)
 152                 kfree(iov->iov);
 153         iov->max_num = iov->used = iov->i = iov->consumed = 0;
 154         iov->iov = NULL;
 155 }
 156
 157 /* Convert a descriptor into iovecs. */
 158 int vringh_getdesc_user(struct vringh *vrh,
 159                         struct vringh_iov *riov,
 160                         struct vringh_iov *wiov,
 161                         bool (*getrange)(struct vringh *vrh,
 162                                          u64 addr, struct vringh_range *r),
 163                         u16 *head);
 164
 165 /* Copy bytes from readable vsg, consuming it (and incrementing wiov->i). */
 166 ssize_t vringh_iov_pull_user(struct vringh_iov *riov, void *dst, size_t len);
 167
 168 /* Copy bytes into writable vsg, consuming it (and incrementing wiov->i). */
 169 ssize_t vringh_iov_push_user(struct vringh_iov *wiov,
 170                              const void *src, size_t len);
 171
 172 /* Mark a descriptor as used. */
 173 int vringh_complete_user(struct vringh *vrh, u16 head, u32 len);
 174 int vringh_complete_multi_user(struct vringh *vrh,
 175                                const struct vring_used_elem used[],
 176                                unsigned num_used);
 177
 178 /* Pretend we've never seen descriptor (for easy error handling). */
 179 void vringh_abandon_user(struct vringh *vrh, unsigned int num);
 180
 181 /* Do we need to fire the eventfd to notify the other side? */
 182 int vringh_need_notify_user(struct vringh *vrh);
 183
 184 bool vringh_notify_enable_user(struct vringh *vrh);
 185 void vringh_notify_disable_user(struct vringh *vrh);
 186
 187 /* Helpers for kernelspace vrings. */
 188 int vringh_init_kern(struct vringh *vrh, u64 features,
 189                      unsigned int num, bool weak_barriers,
 190                      struct vring_desc *desc,
 191                      struct vring_avail *avail,
 192                      struct vring_used *used);
 193
 194 static inline void vringh_kiov_init(struct vringh_kiov *kiov,
 195                                     struct kvec *kvec, unsigned num)
 196 {
 197         kiov->used = kiov->i = 0;
 198         kiov->consumed = 0;
 199         kiov->max_num = num;
 200         kiov->iov = kvec;
 201 }
 202
 203 static inline void vringh_kiov_reset(struct vringh_kiov *kiov)
 204 {
 205         kiov->iov[kiov->i].iov_len += kiov->consumed;
 206         kiov->iov[kiov->i].iov_base -= kiov->consumed;
 207         kiov->consumed = 0;
 208         kiov->i = 0;
 209 }
 210
 211 static inline void vringh_kiov_cleanup(struct vringh_kiov *kiov)
 212 {
 213         if (kiov->max_num & VRINGH_IOV_ALLOCATED)
 214                 kfree(kiov->iov);
 215         kiov->max_num = kiov->used = kiov->i = kiov->consumed = 0;
 216         kiov->iov = NULL;
 217 }
 218
 219 static inline size_t vringh_kiov_length(struct vringh_kiov *kiov)
 220 {
 221         size_t len = 0;
 222         int i;
 223
 224         for (i = kiov->i; i < kiov->used; i++)
 225                 len += kiov->iov[i].iov_len;
 226
 227         return len;
 228 }
 229
 230 void vringh_kiov_advance(struct vringh_kiov *kiov, size_t len);
 231
 232 int vringh_getdesc_kern(struct vringh *vrh,
 233                         struct vringh_kiov *riov,
 234                         struct vringh_kiov *wiov,
 235                         u16 *head,
 236                         gfp_t gfp);
 237
 238 ssize_t vringh_iov_pull_kern(struct vringh_kiov *riov, void *dst, size_t len);
 239 ssize_t vringh_iov_push_kern(struct vringh_kiov *wiov,
 240                              const void *src, size_t len);
 241 void vringh_abandon_kern(struct vringh *vrh, unsigned int num);
 242 int vringh_complete_kern(struct vringh *vrh, u16 head, u32 len);
 243
 244 bool vringh_notify_enable_kern(struct vringh *vrh);
 245 void vringh_notify_disable_kern(struct vringh *vrh);
 246
 247 int vringh_need_notify_kern(struct vringh *vrh);
 248
 249 /* Notify the guest about buffers added to the used ring */
 250 static inline void vringh_notify(struct vringh *vrh)
 251 {
 252         if (vrh->notify)
 253                 vrh->notify(vrh);
 254 }
 255
 256 static inline bool vringh_is_little_endian(const struct vringh *vrh)
 257 {
 258         return vrh->little_endian ||
 259                 virtio_legacy_is_little_endian();
 260 }
 261
 262 static inline u16 vringh16_to_cpu(const struct vringh *vrh, __virtio16 val)
 263 {
 264         return __virtio16_to_cpu(vringh_is_little_endian(vrh), val);
 265 }
 266
 267 static inline __virtio16 cpu_to_vringh16(const struct vringh *vrh, u16 val)
 268 {
 269         return __cpu_to_virtio16(vringh_is_little_endian(vrh), val);
 270 }
 271
 272 static inline u32 vringh32_to_cpu(const struct vringh *vrh, __virtio32 val)
 273 {
 274         return __virtio32_to_cpu(vringh_is_little_endian(vrh), val);
 275 }
 276
 277 static inline __virtio32 cpu_to_vringh32(const struct vringh *vrh, u32 val)
 278 {
 279         return __cpu_to_virtio32(vringh_is_little_endian(vrh), val);
 280 }
 281
 282 static inline u64 vringh64_to_cpu(const struct vringh *vrh, __virtio64 val)
 283 {
 284         return __virtio64_to_cpu(vringh_is_little_endian(vrh), val);
 285 }
 286
 287 static inline __virtio64 cpu_to_vringh64(const struct vringh *vrh, u64 val)
 288 {
 289         return __cpu_to_virtio64(vringh_is_little_endian(vrh), val);
 290 }
 291
 292 #if IS_REACHABLE(CONFIG_VHOST_IOTLB)
 293
 294 void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb,
 295                       spinlock_t *iotlb_lock);
 296
 297 int vringh_init_iotlb(struct vringh *vrh, u64 features,
 298                       unsigned int num, bool weak_barriers,
 299                       struct vring_desc *desc,
 300                       struct vring_avail *avail,
 301                       struct vring_used *used);
 302
 303 int vringh_init_iotlb_va(struct vringh *vrh, u64 features,
 304                          unsigned int num, bool weak_barriers,
 305                          struct vring_desc *desc,
 306                          struct vring_avail *avail,
 307                          struct vring_used *used);
 308
 309 int vringh_getdesc_iotlb(struct vringh *vrh,
 310                          struct vringh_kiov *riov,
 311                          struct vringh_kiov *wiov,
 312                          u16 *head,
 313                          gfp_t gfp);
 314
 315 ssize_t vringh_iov_pull_iotlb(struct vringh *vrh,
 316                               struct vringh_kiov *riov,
 317                               void *dst, size_t len);
 318 ssize_t vringh_iov_push_iotlb(struct vringh *vrh,
 319                               struct vringh_kiov *wiov,
 320                               const void *src, size_t len);
 321
 322 void vringh_abandon_iotlb(struct vringh *vrh, unsigned int num);
 323
 324 int vringh_complete_iotlb(struct vringh *vrh, u16 head, u32 len);
 325
 326 bool vringh_notify_enable_iotlb(struct vringh *vrh);
 327 void vringh_notify_disable_iotlb(struct vringh *vrh);
 328
 329 int vringh_need_notify_iotlb(struct vringh *vrh);
 330
 331 #endif /* CONFIG_VHOST_IOTLB */
 332
 333 #endif /* _LINUX_VRINGH_H */