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	/* 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/* Do we need to fire the eventfd to notify the other side? */
179int vringh_need_notify_user(struct vringh *vrh);
180
181bool vringh_notify_enable_user(struct vringh *vrh);
182void vringh_notify_disable_user(struct vringh *vrh);
183
184/* Helpers for kernelspace vrings. */
185int vringh_init_kern(struct vringh *vrh, u64 features,
186		     unsigned int num, bool weak_barriers,
187		     struct vring_desc *desc,
188		     struct vring_avail *avail,
189		     struct vring_used *used);
190
191static inline void vringh_kiov_init(struct vringh_kiov *kiov,
192				    struct kvec *kvec, unsigned num)
193{
194	kiov->used = kiov->i = 0;
195	kiov->consumed = 0;
196	kiov->max_num = num;
197	kiov->iov = kvec;
198}
199
200static inline void vringh_kiov_reset(struct vringh_kiov *kiov)
201{
202	kiov->iov[kiov->i].iov_len += kiov->consumed;
203	kiov->iov[kiov->i].iov_base -= kiov->consumed;
204	kiov->consumed = 0;
205	kiov->i = 0;
206}
207
208static inline void vringh_kiov_cleanup(struct vringh_kiov *kiov)
209{
210	if (kiov->max_num & VRINGH_IOV_ALLOCATED)
211		kfree(kiov->iov);
212	kiov->max_num = kiov->used = kiov->i = kiov->consumed = 0;
213	kiov->iov = NULL;
214}
215
216static inline size_t vringh_kiov_length(struct vringh_kiov *kiov)
217{
218	size_t len = 0;
219	int i;
220
221	for (i = kiov->i; i < kiov->used; i++)
222		len += kiov->iov[i].iov_len;
223
224	return len;
225}
226
227void vringh_kiov_advance(struct vringh_kiov *kiov, size_t len);
228
229int vringh_getdesc_kern(struct vringh *vrh,
230			struct vringh_kiov *riov,
231			struct vringh_kiov *wiov,
232			u16 *head,
233			gfp_t gfp);
234
235int vringh_complete_kern(struct vringh *vrh, u16 head, u32 len);
236
237bool vringh_notify_enable_kern(struct vringh *vrh);
238void vringh_notify_disable_kern(struct vringh *vrh);
239
240int vringh_need_notify_kern(struct vringh *vrh);
241
242/* Notify the guest about buffers added to the used ring */
243static inline void vringh_notify(struct vringh *vrh)
244{
245	if (vrh->notify)
246		vrh->notify(vrh);
247}
248
249static inline bool vringh_is_little_endian(const struct vringh *vrh)
250{
251	return vrh->little_endian ||
252		virtio_legacy_is_little_endian();
253}
254
255static inline u16 vringh16_to_cpu(const struct vringh *vrh, __virtio16 val)
256{
257	return __virtio16_to_cpu(vringh_is_little_endian(vrh), val);
258}
259
260static inline __virtio16 cpu_to_vringh16(const struct vringh *vrh, u16 val)
261{
262	return __cpu_to_virtio16(vringh_is_little_endian(vrh), val);
263}
264
265static inline u32 vringh32_to_cpu(const struct vringh *vrh, __virtio32 val)
266{
267	return __virtio32_to_cpu(vringh_is_little_endian(vrh), val);
268}
269
270static inline __virtio32 cpu_to_vringh32(const struct vringh *vrh, u32 val)
271{
272	return __cpu_to_virtio32(vringh_is_little_endian(vrh), val);
273}
274
275static inline u64 vringh64_to_cpu(const struct vringh *vrh, __virtio64 val)
276{
277	return __virtio64_to_cpu(vringh_is_little_endian(vrh), val);
278}
279
280static inline __virtio64 cpu_to_vringh64(const struct vringh *vrh, u64 val)
281{
282	return __cpu_to_virtio64(vringh_is_little_endian(vrh), val);
283}
284
285#if IS_REACHABLE(CONFIG_VHOST_IOTLB)
286
287void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb,
288		      spinlock_t *iotlb_lock);
289
290int vringh_init_iotlb(struct vringh *vrh, u64 features,
291		      unsigned int num, bool weak_barriers,
292		      struct vring_desc *desc,
293		      struct vring_avail *avail,
294		      struct vring_used *used);
295
296int vringh_init_iotlb_va(struct vringh *vrh, u64 features,
297			 unsigned int num, bool weak_barriers,
298			 struct vring_desc *desc,
299			 struct vring_avail *avail,
300			 struct vring_used *used);
301
302int vringh_getdesc_iotlb(struct vringh *vrh,
303			 struct vringh_kiov *riov,
304			 struct vringh_kiov *wiov,
305			 u16 *head,
306			 gfp_t gfp);
307
308ssize_t vringh_iov_pull_iotlb(struct vringh *vrh,
309			      struct vringh_kiov *riov,
310			      void *dst, size_t len);
311ssize_t vringh_iov_push_iotlb(struct vringh *vrh,
312			      struct vringh_kiov *wiov,
313			      const void *src, size_t len);
314
315int vringh_complete_iotlb(struct vringh *vrh, u16 head, u32 len);
316
317int vringh_need_notify_iotlb(struct vringh *vrh);
318
319#endif /* CONFIG_VHOST_IOTLB */
320
321#endif /* _LINUX_VRINGH_H */