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 bool vringh_is_little_endian(const struct vringh *vrh)
230{
231 return vrh->little_endian ||
232 virtio_legacy_is_little_endian();
233}
234
235static inline u16 vringh16_to_cpu(const struct vringh *vrh, __virtio16 val)
236{
237 return __virtio16_to_cpu(vringh_is_little_endian(vrh), val);
238}
239
240static inline __virtio16 cpu_to_vringh16(const struct vringh *vrh, u16 val)
241{
242 return __cpu_to_virtio16(vringh_is_little_endian(vrh), val);
243}
244
245static inline u32 vringh32_to_cpu(const struct vringh *vrh, __virtio32 val)
246{
247 return __virtio32_to_cpu(vringh_is_little_endian(vrh), val);
248}
249
250static inline __virtio32 cpu_to_vringh32(const struct vringh *vrh, u32 val)
251{
252 return __cpu_to_virtio32(vringh_is_little_endian(vrh), val);
253}
254
255static inline u64 vringh64_to_cpu(const struct vringh *vrh, __virtio64 val)
256{
257 return __virtio64_to_cpu(vringh_is_little_endian(vrh), val);
258}
259
260static inline __virtio64 cpu_to_vringh64(const struct vringh *vrh, u64 val)
261{
262 return __cpu_to_virtio64(vringh_is_little_endian(vrh), val);
263}
264#endif /* _LINUX_VRINGH_H */
265