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