1/*
2 * Linux host-side vring helpers; for when the kernel needs to access
3 * someone else's vring.
4 *
5 * Copyright IBM Corporation, 2013.
6 * Parts taken from drivers/vhost/vhost.c Copyright 2009 Red Hat, Inc.
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
12 *
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16 * GNU General Public License for more details.
17 *
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
21 *
22 * Written by: Rusty Russell <rusty@rustcorp.com.au>
23 */
24#ifndef _LINUX_VRINGH_H
25#define _LINUX_VRINGH_H
26#include <uapi/linux/virtio_ring.h>
27#include <linux/virtio_byteorder.h>
28#include <linux/uio.h>
29#include <linux/slab.h>
30#include <asm/barrier.h>
31
32/* virtio_ring with information needed for host access. */
33struct vringh {
34	/* Everything is little endian */
35	bool little_endian;
36
37	/* Guest publishes used event idx (note: we always do). */
38	bool event_indices;
39
40	/* Can we get away with weak barriers? */
41	bool weak_barriers;
42
43	/* Last available index we saw (ie. where we're up to). */
44	u16 last_avail_idx;
45
46	/* Last index we used. */
47	u16 last_used_idx;
48
49	/* How many descriptors we've completed since last need_notify(). */
50	u32 completed;
51
52	/* The vring (note: it may contain user pointers!) */
53	struct vring vring;
54
55	/* The function to call to notify the guest about added buffers */
56	void (*notify)(struct vringh *);
57};
58
59/**
60 * struct vringh_config_ops - ops for creating a host vring from a virtio driver
61 * @find_vrhs: find the host vrings and instantiate them
62 *	vdev: the virtio_device
63 *	nhvrs: the number of host vrings to find
64 *	hvrs: on success, includes new host vrings
65 *	callbacks: array of driver callbacks, for each host vring
66 *		include a NULL entry for vqs that do not need a callback
67 *	Returns 0 on success or error status
68 * @del_vrhs: free the host vrings found by find_vrhs().
69 */
70struct virtio_device;
71typedef void vrh_callback_t(struct virtio_device *, struct vringh *);
72struct vringh_config_ops {
73	int (*find_vrhs)(struct virtio_device *vdev, unsigned nhvrs,
74			 struct vringh *vrhs[], vrh_callback_t *callbacks[]);
75	void (*del_vrhs)(struct virtio_device *vdev);
76};
77
78/* The memory the vring can access, and what offset to apply. */
79struct vringh_range {
80	u64 start, end_incl;
81	u64 offset;
82};
83
84/**
85 * struct vringh_iov - iovec mangler.
86 *
87 * Mangles iovec in place, and restores it.
88 * Remaining data is iov + i, of used - i elements.
89 */
90struct vringh_iov {
91	struct iovec *iov;
92	size_t consumed; /* Within iov[i] */
93	unsigned i, used, max_num;
94};
95
96/**
97 * struct vringh_iov - kvec mangler.
98 *
99 * Mangles kvec in place, and restores it.
100 * Remaining data is iov + i, of used - i elements.
101 */
102struct vringh_kiov {
103	struct kvec *iov;
104	size_t consumed; /* Within iov[i] */
105	unsigned i, used, max_num;
106};
107
108/* Flag on max_num to indicate we're kmalloced. */
109#define VRINGH_IOV_ALLOCATED 0x8000000
110
111/* Helpers for userspace vrings. */
112int vringh_init_user(struct vringh *vrh, u64 features,
113		     unsigned int num, bool weak_barriers,
114		     struct vring_desc __user *desc,
115		     struct vring_avail __user *avail,
116		     struct vring_used __user *used);
117
118static inline void vringh_iov_init(struct vringh_iov *iov,
119				   struct iovec *iovec, unsigned num)
120{
121	iov->used = iov->i = 0;
122	iov->consumed = 0;
123	iov->max_num = num;
124	iov->iov = iovec;
125}
126
127static inline void vringh_iov_reset(struct vringh_iov *iov)
128{
129	iov->iov[iov->i].iov_len += iov->consumed;
130	iov->iov[iov->i].iov_base -= iov->consumed;
131	iov->consumed = 0;
132	iov->i = 0;
133}
134
135static inline void vringh_iov_cleanup(struct vringh_iov *iov)
136{
137	if (iov->max_num & VRINGH_IOV_ALLOCATED)
138		kfree(iov->iov);
139	iov->max_num = iov->used = iov->i = iov->consumed = 0;
140	iov->iov = NULL;
141}
142
143/* Convert a descriptor into iovecs. */
144int vringh_getdesc_user(struct vringh *vrh,
145			struct vringh_iov *riov,
146			struct vringh_iov *wiov,
147			bool (*getrange)(struct vringh *vrh,
148					 u64 addr, struct vringh_range *r),
149			u16 *head);
150
151/* Copy bytes from readable vsg, consuming it (and incrementing wiov->i). */
152ssize_t vringh_iov_pull_user(struct vringh_iov *riov, void *dst, size_t len);
153
154/* Copy bytes into writable vsg, consuming it (and incrementing wiov->i). */
155ssize_t vringh_iov_push_user(struct vringh_iov *wiov,
156			     const void *src, size_t len);
157
158/* Mark a descriptor as used. */
159int vringh_complete_user(struct vringh *vrh, u16 head, u32 len);
160int vringh_complete_multi_user(struct vringh *vrh,
161			       const struct vring_used_elem used[],
162			       unsigned num_used);
163
164/* Pretend we've never seen descriptor (for easy error handling). */
165void vringh_abandon_user(struct vringh *vrh, unsigned int num);
166
167/* Do we need to fire the eventfd to notify the other side? */
168int vringh_need_notify_user(struct vringh *vrh);
169
170bool vringh_notify_enable_user(struct vringh *vrh);
171void vringh_notify_disable_user(struct vringh *vrh);
172
173/* Helpers for kernelspace vrings. */
174int vringh_init_kern(struct vringh *vrh, u64 features,
175		     unsigned int num, bool weak_barriers,
176		     struct vring_desc *desc,
177		     struct vring_avail *avail,
178		     struct vring_used *used);
179
180static inline void vringh_kiov_init(struct vringh_kiov *kiov,
181				    struct kvec *kvec, unsigned num)
182{
183	kiov->used = kiov->i = 0;
184	kiov->consumed = 0;
185	kiov->max_num = num;
186	kiov->iov = kvec;
187}
188
189static inline void vringh_kiov_reset(struct vringh_kiov *kiov)
190{
191	kiov->iov[kiov->i].iov_len += kiov->consumed;
192	kiov->iov[kiov->i].iov_base -= kiov->consumed;
193	kiov->consumed = 0;
194	kiov->i = 0;
195}
196
197static inline void vringh_kiov_cleanup(struct vringh_kiov *kiov)
198{
199	if (kiov->max_num & VRINGH_IOV_ALLOCATED)
200		kfree(kiov->iov);
201	kiov->max_num = kiov->used = kiov->i = kiov->consumed = 0;
202	kiov->iov = NULL;
203}
204
205int vringh_getdesc_kern(struct vringh *vrh,
206			struct vringh_kiov *riov,
207			struct vringh_kiov *wiov,
208			u16 *head,
209			gfp_t gfp);
210
211ssize_t vringh_iov_pull_kern(struct vringh_kiov *riov, void *dst, size_t len);
212ssize_t vringh_iov_push_kern(struct vringh_kiov *wiov,
213			     const void *src, size_t len);
214void vringh_abandon_kern(struct vringh *vrh, unsigned int num);
215int vringh_complete_kern(struct vringh *vrh, u16 head, u32 len);
216
217bool vringh_notify_enable_kern(struct vringh *vrh);
218void vringh_notify_disable_kern(struct vringh *vrh);
219
220int vringh_need_notify_kern(struct vringh *vrh);
221
222/* Notify the guest about buffers added to the used ring */
223static inline void vringh_notify(struct vringh *vrh)
224{
225	if (vrh->notify)
226		vrh->notify(vrh);
227}
228
229static inline u16 vringh16_to_cpu(const struct vringh *vrh, __virtio16 val)
230{
231	return __virtio16_to_cpu(vrh->little_endian, val);
232}
233
234static inline __virtio16 cpu_to_vringh16(const struct vringh *vrh, u16 val)
235{
236	return __cpu_to_virtio16(vrh->little_endian, val);
237}
238
239static inline u32 vringh32_to_cpu(const struct vringh *vrh, __virtio32 val)
240{
241	return __virtio32_to_cpu(vrh->little_endian, val);
242}
243
244static inline __virtio32 cpu_to_vringh32(const struct vringh *vrh, u32 val)
245{
246	return __cpu_to_virtio32(vrh->little_endian, val);
247}
248
249static inline u64 vringh64_to_cpu(const struct vringh *vrh, __virtio64 val)
250{
251	return __virtio64_to_cpu(vrh->little_endian, val);
252}
253
254static inline __virtio64 cpu_to_vringh64(const struct vringh *vrh, u64 val)
255{
256	return __cpu_to_virtio64(vrh->little_endian, val);
257}
258#endif /* _LINUX_VRINGH_H */
259