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 <[email protected]> 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 <asm/barrier.h> 18 19 /* virtio_ring with information needed for host access. */ 20 struct vringh { 21 /* Everything is little endian */ 22 bool little_endian; 23 24 /* Guest publishes used event idx (note: we always do). */ 25 bool event_indices; 26 27 /* Can we get away with weak barriers? */ 28 bool weak_barriers; 29 30 /* Last available index we saw (ie. where we're up to). */ 31 u16 last_avail_idx; 32 33 /* Last index we used. */ 34 u16 last_used_idx; 35 36 /* How many descriptors we've completed since last need_notify(). */ 37 u32 completed; 38 39 /* The vring (note: it may contain user pointers!) */ 40 struct vring vring; 41 42 /* The function to call to notify the guest about added buffers */ 43 void (*notify)(struct vringh *); 44 }; 45 46 /** 47 * struct vringh_config_ops - ops for creating a host vring from a virtio driver 48 * @find_vrhs: find the host vrings and instantiate them 49 * vdev: the virtio_device 50 * nhvrs: the number of host vrings to find 51 * hvrs: on success, includes new host vrings 52 * callbacks: array of driver callbacks, for each host vring 53 * include a NULL entry for vqs that do not need a callback 54 * Returns 0 on success or error status 55 * @del_vrhs: free the host vrings found by find_vrhs(). 56 */ 57 struct virtio_device; 58 typedef void vrh_callback_t(struct virtio_device *, struct vringh *); 59 struct vringh_config_ops { 60 int (*find_vrhs)(struct virtio_device *vdev, unsigned nhvrs, 61 struct vringh *vrhs[], vrh_callback_t *callbacks[]); 62 void (*del_vrhs)(struct virtio_device *vdev); 63 }; 64 65 /* The memory the vring can access, and what offset to apply. */ 66 struct vringh_range { 67 u64 start, end_incl; 68 u64 offset; 69 }; 70 71 /** 72 * struct vringh_iov - iovec mangler. 73 * 74 * Mangles iovec in place, and restores it. 75 * Remaining data is iov + i, of used - i elements. 76 */ 77 struct vringh_iov { 78 struct iovec *iov; 79 size_t consumed; /* Within iov[i] */ 80 unsigned i, used, max_num; 81 }; 82 83 /** 84 * struct vringh_iov - kvec mangler. 85 * 86 * Mangles kvec in place, and restores it. 87 * Remaining data is iov + i, of used - i elements. 88 */ 89 struct vringh_kiov { 90 struct kvec *iov; 91 size_t consumed; /* Within iov[i] */ 92 unsigned i, used, max_num; 93 }; 94 95 /* Flag on max_num to indicate we're kmalloced. */ 96 #define VRINGH_IOV_ALLOCATED 0x8000000 97 98 /* Helpers for userspace vrings. */ 99 int vringh_init_user(struct vringh *vrh, u64 features, 100 unsigned int num, bool weak_barriers, 101 struct vring_desc __user *desc, 102 struct vring_avail __user *avail, 103 struct vring_used __user *used); 104 105 static inline void vringh_iov_init(struct vringh_iov *iov, 106 struct iovec *iovec, unsigned num) 107 { 108 iov->used = iov->i = 0; 109 iov->consumed = 0; 110 iov->max_num = num; 111 iov->iov = iovec; 112 } 113 114 static inline void vringh_iov_reset(struct vringh_iov *iov) 115 { 116 iov->iov[iov->i].iov_len += iov->consumed; 117 iov->iov[iov->i].iov_base -= iov->consumed; 118 iov->consumed = 0; 119 iov->i = 0; 120 } 121 122 static inline void vringh_iov_cleanup(struct vringh_iov *iov) 123 { 124 if (iov->max_num & VRINGH_IOV_ALLOCATED) 125 kfree(iov->iov); 126 iov->max_num = iov->used = iov->i = iov->consumed = 0; 127 iov->iov = NULL; 128 } 129 130 /* Convert a descriptor into iovecs. */ 131 int vringh_getdesc_user(struct vringh *vrh, 132 struct vringh_iov *riov, 133 struct vringh_iov *wiov, 134 bool (*getrange)(struct vringh *vrh, 135 u64 addr, struct vringh_range *r), 136 u16 *head); 137 138 /* Copy bytes from readable vsg, consuming it (and incrementing wiov->i). */ 139 ssize_t vringh_iov_pull_user(struct vringh_iov *riov, void *dst, size_t len); 140 141 /* Copy bytes into writable vsg, consuming it (and incrementing wiov->i). */ 142 ssize_t vringh_iov_push_user(struct vringh_iov *wiov, 143 const void *src, size_t len); 144 145 /* Mark a descriptor as used. */ 146 int vringh_complete_user(struct vringh *vrh, u16 head, u32 len); 147 int vringh_complete_multi_user(struct vringh *vrh, 148 const struct vring_used_elem used[], 149 unsigned num_used); 150 151 /* Pretend we've never seen descriptor (for easy error handling). */ 152 void vringh_abandon_user(struct vringh *vrh, unsigned int num); 153 154 /* Do we need to fire the eventfd to notify the other side? */ 155 int vringh_need_notify_user(struct vringh *vrh); 156 157 bool vringh_notify_enable_user(struct vringh *vrh); 158 void vringh_notify_disable_user(struct vringh *vrh); 159 160 /* Helpers for kernelspace vrings. */ 161 int vringh_init_kern(struct vringh *vrh, u64 features, 162 unsigned int num, bool weak_barriers, 163 struct vring_desc *desc, 164 struct vring_avail *avail, 165 struct vring_used *used); 166 167 static inline void vringh_kiov_init(struct vringh_kiov *kiov, 168 struct kvec *kvec, unsigned num) 169 { 170 kiov->used = kiov->i = 0; 171 kiov->consumed = 0; 172 kiov->max_num = num; 173 kiov->iov = kvec; 174 } 175 176 static inline void vringh_kiov_reset(struct vringh_kiov *kiov) 177 { 178 kiov->iov[kiov->i].iov_len += kiov->consumed; 179 kiov->iov[kiov->i].iov_base -= kiov->consumed; 180 kiov->consumed = 0; 181 kiov->i = 0; 182 } 183 184 static inline void vringh_kiov_cleanup(struct vringh_kiov *kiov) 185 { 186 if (kiov->max_num & VRINGH_IOV_ALLOCATED) 187 kfree(kiov->iov); 188 kiov->max_num = kiov->used = kiov->i = kiov->consumed = 0; 189 kiov->iov = NULL; 190 } 191 192 int vringh_getdesc_kern(struct vringh *vrh, 193 struct vringh_kiov *riov, 194 struct vringh_kiov *wiov, 195 u16 *head, 196 gfp_t gfp); 197 198 ssize_t vringh_iov_pull_kern(struct vringh_kiov *riov, void *dst, size_t len); 199 ssize_t vringh_iov_push_kern(struct vringh_kiov *wiov, 200 const void *src, size_t len); 201 void vringh_abandon_kern(struct vringh *vrh, unsigned int num); 202 int vringh_complete_kern(struct vringh *vrh, u16 head, u32 len); 203 204 bool vringh_notify_enable_kern(struct vringh *vrh); 205 void vringh_notify_disable_kern(struct vringh *vrh); 206 207 int vringh_need_notify_kern(struct vringh *vrh); 208 209 /* Notify the guest about buffers added to the used ring */ 210 static inline void vringh_notify(struct vringh *vrh) 211 { 212 if (vrh->notify) 213 vrh->notify(vrh); 214 } 215 216 static inline bool vringh_is_little_endian(const struct vringh *vrh) 217 { 218 return vrh->little_endian || 219 virtio_legacy_is_little_endian(); 220 } 221 222 static inline u16 vringh16_to_cpu(const struct vringh *vrh, __virtio16 val) 223 { 224 return __virtio16_to_cpu(vringh_is_little_endian(vrh), val); 225 } 226 227 static inline __virtio16 cpu_to_vringh16(const struct vringh *vrh, u16 val) 228 { 229 return __cpu_to_virtio16(vringh_is_little_endian(vrh), val); 230 } 231 232 static inline u32 vringh32_to_cpu(const struct vringh *vrh, __virtio32 val) 233 { 234 return __virtio32_to_cpu(vringh_is_little_endian(vrh), val); 235 } 236 237 static inline __virtio32 cpu_to_vringh32(const struct vringh *vrh, u32 val) 238 { 239 return __cpu_to_virtio32(vringh_is_little_endian(vrh), val); 240 } 241 242 static inline u64 vringh64_to_cpu(const struct vringh *vrh, __virtio64 val) 243 { 244 return __virtio64_to_cpu(vringh_is_little_endian(vrh), val); 245 } 246 247 static inline __virtio64 cpu_to_vringh64(const struct vringh *vrh, u64 val) 248 { 249 return __cpu_to_virtio64(vringh_is_little_endian(vrh), val); 250 } 251 #endif /* _LINUX_VRINGH_H */ 252