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 */
334
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