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. */
33 struct 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  */
70 struct virtio_device;
71 typedef void vrh_callback_t(struct virtio_device *, struct vringh *);
72 struct 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. */
79 struct 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  */
90 struct 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  */
102 struct 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. */
112 int 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 
vringh_iov_init(struct vringh_iov * iov,struct iovec * iovec,unsigned num)118 static 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 
vringh_iov_reset(struct vringh_iov * iov)127 static 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 
vringh_iov_cleanup(struct vringh_iov * iov)135 static 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. */
144 int 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). */
152 ssize_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). */
155 ssize_t vringh_iov_push_user(struct vringh_iov *wiov,
156 			     const void *src, size_t len);
157 
158 /* Mark a descriptor as used. */
159 int vringh_complete_user(struct vringh *vrh, u16 head, u32 len);
160 int 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). */
165 void vringh_abandon_user(struct vringh *vrh, unsigned int num);
166 
167 /* Do we need to fire the eventfd to notify the other side? */
168 int vringh_need_notify_user(struct vringh *vrh);
169 
170 bool vringh_notify_enable_user(struct vringh *vrh);
171 void vringh_notify_disable_user(struct vringh *vrh);
172 
173 /* Helpers for kernelspace vrings. */
174 int 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 
vringh_kiov_init(struct vringh_kiov * kiov,struct kvec * kvec,unsigned num)180 static 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 
vringh_kiov_reset(struct vringh_kiov * kiov)189 static 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 
vringh_kiov_cleanup(struct vringh_kiov * kiov)197 static 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 
205 int vringh_getdesc_kern(struct vringh *vrh,
206 			struct vringh_kiov *riov,
207 			struct vringh_kiov *wiov,
208 			u16 *head,
209 			gfp_t gfp);
210 
211 ssize_t vringh_iov_pull_kern(struct vringh_kiov *riov, void *dst, size_t len);
212 ssize_t vringh_iov_push_kern(struct vringh_kiov *wiov,
213 			     const void *src, size_t len);
214 void vringh_abandon_kern(struct vringh *vrh, unsigned int num);
215 int vringh_complete_kern(struct vringh *vrh, u16 head, u32 len);
216 
217 bool vringh_notify_enable_kern(struct vringh *vrh);
218 void vringh_notify_disable_kern(struct vringh *vrh);
219 
220 int vringh_need_notify_kern(struct vringh *vrh);
221 
222 /* Notify the guest about buffers added to the used ring */
vringh_notify(struct vringh * vrh)223 static inline void vringh_notify(struct vringh *vrh)
224 {
225 	if (vrh->notify)
226 		vrh->notify(vrh);
227 }
228 
vringh_is_little_endian(const struct vringh * vrh)229 static inline bool vringh_is_little_endian(const struct vringh *vrh)
230 {
231 	return vrh->little_endian ||
232 		virtio_legacy_is_little_endian();
233 }
234 
vringh16_to_cpu(const struct vringh * vrh,__virtio16 val)235 static 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 
cpu_to_vringh16(const struct vringh * vrh,u16 val)240 static 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 
vringh32_to_cpu(const struct vringh * vrh,__virtio32 val)245 static 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 
cpu_to_vringh32(const struct vringh * vrh,u32 val)250 static 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 
vringh64_to_cpu(const struct vringh * vrh,__virtio64 val)255 static 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 
cpu_to_vringh64(const struct vringh * vrh,u64 val)260 static 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