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	/* 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
60struct virtio_device;
61typedef 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 */
74struct 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. */
81struct 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 */
98struct 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 */
116struct 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. */
126int 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
132static 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
141static 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
149static 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. */
158int 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). */
166ssize_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). */
169ssize_t vringh_iov_push_user(struct vringh_iov *wiov,
170			     const void *src, size_t len);
171
172/* Mark a descriptor as used. */
173int vringh_complete_user(struct vringh *vrh, u16 head, u32 len);
174int 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). */
179void vringh_abandon_user(struct vringh *vrh, unsigned int num);
180
181/* Do we need to fire the eventfd to notify the other side? */
182int vringh_need_notify_user(struct vringh *vrh);
183
184bool vringh_notify_enable_user(struct vringh *vrh);
185void vringh_notify_disable_user(struct vringh *vrh);
186
187/* Helpers for kernelspace vrings. */
188int 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
194static 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
203static 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
211static 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
219static 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
230void vringh_kiov_advance(struct vringh_kiov *kiov, size_t len);
231
232int vringh_getdesc_kern(struct vringh *vrh,
233			struct vringh_kiov *riov,
234			struct vringh_kiov *wiov,
235			u16 *head,
236			gfp_t gfp);
237
238ssize_t vringh_iov_pull_kern(struct vringh_kiov *riov, void *dst, size_t len);
239ssize_t vringh_iov_push_kern(struct vringh_kiov *wiov,
240			     const void *src, size_t len);
241void vringh_abandon_kern(struct vringh *vrh, unsigned int num);
242int vringh_complete_kern(struct vringh *vrh, u16 head, u32 len);
243
244bool vringh_notify_enable_kern(struct vringh *vrh);
245void vringh_notify_disable_kern(struct vringh *vrh);
246
247int vringh_need_notify_kern(struct vringh *vrh);
248
249/* Notify the guest about buffers added to the used ring */
250static inline void vringh_notify(struct vringh *vrh)
251{
252	if (vrh->notify)
253		vrh->notify(vrh);
254}
255
256static inline bool vringh_is_little_endian(const struct vringh *vrh)
257{
258	return vrh->little_endian ||
259		virtio_legacy_is_little_endian();
260}
261
262static 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
267static 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
272static 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
277static 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
282static 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
287static 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
294void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb,
295		      spinlock_t *iotlb_lock);
296
297int 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
303int 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
309int vringh_getdesc_iotlb(struct vringh *vrh,
310			 struct vringh_kiov *riov,
311			 struct vringh_kiov *wiov,
312			 u16 *head,
313			 gfp_t gfp);
314
315ssize_t vringh_iov_pull_iotlb(struct vringh *vrh,
316			      struct vringh_kiov *riov,
317			      void *dst, size_t len);
318ssize_t vringh_iov_push_iotlb(struct vringh *vrh,
319			      struct vringh_kiov *wiov,
320			      const void *src, size_t len);
321
322void vringh_abandon_iotlb(struct vringh *vrh, unsigned int num);
323
324int vringh_complete_iotlb(struct vringh *vrh, u16 head, u32 len);
325
326bool vringh_notify_enable_iotlb(struct vringh *vrh);
327void vringh_notify_disable_iotlb(struct vringh *vrh);
328
329int vringh_need_notify_iotlb(struct vringh *vrh);
330
331#endif /* CONFIG_VHOST_IOTLB */
332
333#endif /* _LINUX_VRINGH_H */
334