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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. */
20struct 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 */
57struct virtio_device;
58typedef void vrh_callback_t(struct virtio_device *, struct vringh *);
59struct 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. */
66struct 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 */
77struct 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 */
89struct 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. */
99int 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
105static 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
114static 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
122static 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. */
131int 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). */
139ssize_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). */
142ssize_t vringh_iov_push_user(struct vringh_iov *wiov,
143 const void *src, size_t len);
144
145/* Mark a descriptor as used. */
146int vringh_complete_user(struct vringh *vrh, u16 head, u32 len);
147int 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). */
152void vringh_abandon_user(struct vringh *vrh, unsigned int num);
153
154/* Do we need to fire the eventfd to notify the other side? */
155int vringh_need_notify_user(struct vringh *vrh);
156
157bool vringh_notify_enable_user(struct vringh *vrh);
158void vringh_notify_disable_user(struct vringh *vrh);
159
160/* Helpers for kernelspace vrings. */
161int 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
167static 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
176static 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
184static 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
192int vringh_getdesc_kern(struct vringh *vrh,
193 struct vringh_kiov *riov,
194 struct vringh_kiov *wiov,
195 u16 *head,
196 gfp_t gfp);
197
198ssize_t vringh_iov_pull_kern(struct vringh_kiov *riov, void *dst, size_t len);
199ssize_t vringh_iov_push_kern(struct vringh_kiov *wiov,
200 const void *src, size_t len);
201void vringh_abandon_kern(struct vringh *vrh, unsigned int num);
202int vringh_complete_kern(struct vringh *vrh, u16 head, u32 len);
203
204bool vringh_notify_enable_kern(struct vringh *vrh);
205void vringh_notify_disable_kern(struct vringh *vrh);
206
207int vringh_need_notify_kern(struct vringh *vrh);
208
209/* Notify the guest about buffers added to the used ring */
210static inline void vringh_notify(struct vringh *vrh)
211{
212 if (vrh->notify)
213 vrh->notify(vrh);
214}
215
216static inline bool vringh_is_little_endian(const struct vringh *vrh)
217{
218 return vrh->little_endian ||
219 virtio_legacy_is_little_endian();
220}
221
222static 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
227static 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
232static 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
237static 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
242static 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
247static 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 */