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 <[email protected]> 23 */ 24 #ifndef _LINUX_VRINGH_H 25 #define _LINUX_VRINGH_H 26 #include <uapi/linux/virtio_ring.h> 27 #include <linux/uio.h> 28 #include <linux/slab.h> 29 #include <asm/barrier.h> 30 31 /* virtio_ring with information needed for host access. */ 32 struct vringh { 33 /* Guest publishes used event idx (note: we always do). */ 34 bool event_indices; 35 36 /* Can we get away with weak barriers? */ 37 bool weak_barriers; 38 39 /* Last available index we saw (ie. where we're up to). */ 40 u16 last_avail_idx; 41 42 /* Last index we used. */ 43 u16 last_used_idx; 44 45 /* How many descriptors we've completed since last need_notify(). */ 46 u32 completed; 47 48 /* The vring (note: it may contain user pointers!) */ 49 struct vring vring; 50 }; 51 52 /* The memory the vring can access, and what offset to apply. */ 53 struct vringh_range { 54 u64 start, end_incl; 55 u64 offset; 56 }; 57 58 /** 59 * struct vringh_iov - iovec mangler. 60 * 61 * Mangles iovec in place, and restores it. 62 * Remaining data is iov + i, of used - i elements. 63 */ 64 struct vringh_iov { 65 struct iovec *iov; 66 size_t consumed; /* Within iov[i] */ 67 unsigned i, used, max_num; 68 }; 69 70 /** 71 * struct vringh_iov - kvec mangler. 72 * 73 * Mangles kvec in place, and restores it. 74 * Remaining data is iov + i, of used - i elements. 75 */ 76 struct vringh_kiov { 77 struct kvec *iov; 78 size_t consumed; /* Within iov[i] */ 79 unsigned i, used, max_num; 80 }; 81 82 /* Flag on max_num to indicate we're kmalloced. */ 83 #define VRINGH_IOV_ALLOCATED 0x8000000 84 85 /* Helpers for userspace vrings. */ 86 int vringh_init_user(struct vringh *vrh, u32 features, 87 unsigned int num, bool weak_barriers, 88 struct vring_desc __user *desc, 89 struct vring_avail __user *avail, 90 struct vring_used __user *used); 91 92 static inline void vringh_iov_init(struct vringh_iov *iov, 93 struct iovec *iovec, unsigned num) 94 { 95 iov->used = iov->i = 0; 96 iov->consumed = 0; 97 iov->max_num = num; 98 iov->iov = iovec; 99 } 100 101 static inline void vringh_iov_reset(struct vringh_iov *iov) 102 { 103 iov->iov[iov->i].iov_len += iov->consumed; 104 iov->iov[iov->i].iov_base -= iov->consumed; 105 iov->consumed = 0; 106 iov->i = 0; 107 } 108 109 static inline void vringh_iov_cleanup(struct vringh_iov *iov) 110 { 111 if (iov->max_num & VRINGH_IOV_ALLOCATED) 112 kfree(iov->iov); 113 iov->max_num = iov->used = iov->i = iov->consumed = 0; 114 iov->iov = NULL; 115 } 116 117 /* Convert a descriptor into iovecs. */ 118 int vringh_getdesc_user(struct vringh *vrh, 119 struct vringh_iov *riov, 120 struct vringh_iov *wiov, 121 bool (*getrange)(struct vringh *vrh, 122 u64 addr, struct vringh_range *r), 123 u16 *head); 124 125 /* Copy bytes from readable vsg, consuming it (and incrementing wiov->i). */ 126 ssize_t vringh_iov_pull_user(struct vringh_iov *riov, void *dst, size_t len); 127 128 /* Copy bytes into writable vsg, consuming it (and incrementing wiov->i). */ 129 ssize_t vringh_iov_push_user(struct vringh_iov *wiov, 130 const void *src, size_t len); 131 132 /* Mark a descriptor as used. */ 133 int vringh_complete_user(struct vringh *vrh, u16 head, u32 len); 134 int vringh_complete_multi_user(struct vringh *vrh, 135 const struct vring_used_elem used[], 136 unsigned num_used); 137 138 /* Pretend we've never seen descriptor (for easy error handling). */ 139 void vringh_abandon_user(struct vringh *vrh, unsigned int num); 140 141 /* Do we need to fire the eventfd to notify the other side? */ 142 int vringh_need_notify_user(struct vringh *vrh); 143 144 bool vringh_notify_enable_user(struct vringh *vrh); 145 void vringh_notify_disable_user(struct vringh *vrh); 146 147 /* Helpers for kernelspace vrings. */ 148 int vringh_init_kern(struct vringh *vrh, u32 features, 149 unsigned int num, bool weak_barriers, 150 struct vring_desc *desc, 151 struct vring_avail *avail, 152 struct vring_used *used); 153 154 static inline void vringh_kiov_init(struct vringh_kiov *kiov, 155 struct kvec *kvec, unsigned num) 156 { 157 kiov->used = kiov->i = 0; 158 kiov->consumed = 0; 159 kiov->max_num = num; 160 kiov->iov = kvec; 161 } 162 163 static inline void vringh_kiov_reset(struct vringh_kiov *kiov) 164 { 165 kiov->iov[kiov->i].iov_len += kiov->consumed; 166 kiov->iov[kiov->i].iov_base -= kiov->consumed; 167 kiov->consumed = 0; 168 kiov->i = 0; 169 } 170 171 static inline void vringh_kiov_cleanup(struct vringh_kiov *kiov) 172 { 173 if (kiov->max_num & VRINGH_IOV_ALLOCATED) 174 kfree(kiov->iov); 175 kiov->max_num = kiov->used = kiov->i = kiov->consumed = 0; 176 kiov->iov = NULL; 177 } 178 179 int vringh_getdesc_kern(struct vringh *vrh, 180 struct vringh_kiov *riov, 181 struct vringh_kiov *wiov, 182 u16 *head, 183 gfp_t gfp); 184 185 ssize_t vringh_iov_pull_kern(struct vringh_kiov *riov, void *dst, size_t len); 186 ssize_t vringh_iov_push_kern(struct vringh_kiov *wiov, 187 const void *src, size_t len); 188 void vringh_abandon_kern(struct vringh *vrh, unsigned int num); 189 int vringh_complete_kern(struct vringh *vrh, u16 head, u32 len); 190 191 bool vringh_notify_enable_kern(struct vringh *vrh); 192 void vringh_notify_disable_kern(struct vringh *vrh); 193 194 int vringh_need_notify_kern(struct vringh *vrh); 195 196 #endif /* _LINUX_VRINGH_H */ 197