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