include/virtio_ring.h

   1 /* SPDX-License-Identifier: BSD-3-Clause */
   2 /*
   3  * Copyright (C) 2018, Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
   4  * Copyright (C) 2018, Bin Meng <bmeng.cn@gmail.com>
   5  *
   6  * From Linux kernel include/uapi/linux/virtio_ring.h
   7  */
   8
   9 #ifndef _LINUX_VIRTIO_RING_H
  10 #define _LINUX_VIRTIO_RING_H
  11
  12 #include <virtio_types.h>
  13
  14 /* This marks a buffer as continuing via the next field */
  15 #define VRING_DESC_F_NEXT               1
  16 /* This marks a buffer as write-only (otherwise read-only) */
  17 #define VRING_DESC_F_WRITE              2
  18 /* This means the buffer contains a list of buffer descriptors */
  19 #define VRING_DESC_F_INDIRECT           4
  20
  21 /*
  22  * The Host uses this in used->flags to advise the Guest: don't kick me when
  23  * you add a buffer. It's unreliable, so it's simply an optimization. Guest
  24  * will still kick if it's out of buffers.
  25  */
  26 #define VRING_USED_F_NO_NOTIFY          1
  27
  28 /*
  29  * The Guest uses this in avail->flags to advise the Host: don't interrupt me
  30  * when you consume a buffer. It's unreliable, so it's simply an optimization.
  31  */
  32 #define VRING_AVAIL_F_NO_INTERRUPT      1
  33
  34 /* We support indirect buffer descriptors */
  35 #define VIRTIO_RING_F_INDIRECT_DESC     28
  36
  37 /*
  38  * The Guest publishes the used index for which it expects an interrupt
  39  * at the end of the avail ring. Host should ignore the avail->flags field.
  40  *
  41  * The Host publishes the avail index for which it expects a kick
  42  * at the end of the used ring. Guest should ignore the used->flags field.
  43  */
  44 #define VIRTIO_RING_F_EVENT_IDX         29
  45
  46 /* Virtio ring descriptors: 16 bytes. These can chain together via "next". */
  47 struct vring_desc {
  48         /* Address (guest-physical) */
  49         __virtio64 addr;
  50         /* Length */
  51         __virtio32 len;
  52         /* The flags as indicated above */
  53         __virtio16 flags;
  54         /* We chain unused descriptors via this, too */
  55         __virtio16 next;
  56 };
  57
  58 /* Shadow of struct vring_desc in guest byte order. */
  59 struct vring_desc_shadow {
  60         u64 addr;
  61         u32 len;
  62         u16 flags;
  63         u16 next;
  64         /* Metadata about the descriptor. */
  65         bool chain_head;
  66 };
  67
  68 struct vring_avail {
  69         __virtio16 flags;
  70         __virtio16 idx;
  71         __virtio16 ring[];
  72 };
  73
  74 struct vring_used_elem {
  75         /* Index of start of used descriptor chain */
  76         __virtio32 id;
  77         /* Total length of the descriptor chain which was used (written to) */
  78         __virtio32 len;
  79 };
  80
  81 struct vring_used {
  82         __virtio16 flags;
  83         __virtio16 idx;
  84         struct vring_used_elem ring[];
  85 };
  86
  87 struct vring {
  88         unsigned int num;
  89         size_t size;
  90         struct bounce_buffer *bouncebufs;
  91         struct vring_desc *desc;
  92         struct vring_avail *avail;
  93         struct vring_used *used;
  94 };
  95
  96 /**
  97  * virtqueue - a queue to register buffers for sending or receiving.
  98  *
  99  * @list: the chain of virtqueues for this device
 100  * @vdev: the virtio device this queue was created for
 101  * @index: the zero-based ordinal number for this queue
 102  * @num_free: number of elements we expect to be able to fit
 103  * @vring: actual memory layout for this queue
 104  * @vring_desc_shadow: guest-only copy of descriptors
 105  * @event: host publishes avail event idx
 106  * @free_head: head of free buffer list
 107  * @num_added: number we've added since last sync
 108  * @last_used_idx: last used index we've seen
 109  * @avail_flags_shadow: last written value to avail->flags
 110  * @avail_idx_shadow: last written value to avail->idx in guest byte order
 111  */
 112 struct virtqueue {
 113         struct list_head list;
 114         struct udevice *vdev;
 115         unsigned int index;
 116         unsigned int num_free;
 117         struct vring vring;
 118         struct vring_desc_shadow *vring_desc_shadow;
 119         bool event;
 120         unsigned int free_head;
 121         unsigned int num_added;
 122         u16 last_used_idx;
 123         u16 avail_flags_shadow;
 124         u16 avail_idx_shadow;
 125 };
 126
 127 /*
 128  * Alignment requirements for vring elements.
 129  * When using pre-virtio 1.0 layout, these fall out naturally.
 130  */
 131 #define VRING_AVAIL_ALIGN_SIZE          2
 132 #define VRING_USED_ALIGN_SIZE           4
 133 #define VRING_DESC_ALIGN_SIZE           16
 134
 135 /*
 136  * We publish the used event index at the end of the available ring,
 137  * and vice versa. They are at the end for backwards compatibility.
 138  */
 139 #define vring_used_event(vr)    ((vr)->avail->ring[(vr)->num])
 140 #define vring_avail_event(vr)   (*(__virtio16 *)&(vr)->used->ring[(vr)->num])
 141
 142 static inline unsigned int vring_size(unsigned int num, unsigned long align)
 143 {
 144         return ((sizeof(struct vring_desc) * num +
 145                 sizeof(__virtio16) * (3 + num)  + align - 1) & ~(align - 1)) +
 146                 sizeof(__virtio16) * 3 + sizeof(struct vring_used_elem) * num;
 147 }
 148
 149 static inline void vring_init(struct vring *vr, unsigned int num, void *p,
 150                               unsigned long align,
 151                               struct bounce_buffer *bouncebufs)
 152 {
 153         vr->num = num;
 154         vr->size = vring_size(num, align);
 155         vr->bouncebufs = bouncebufs;
 156         vr->desc = p;
 157         vr->avail = p + num * sizeof(struct vring_desc);
 158         vr->used = (void *)(((uintptr_t)&vr->avail->ring[num] +
 159                    sizeof(__virtio16) + align - 1) & ~(align - 1));
 160 }
 161
 162 /*
 163  * The following is used with USED_EVENT_IDX and AVAIL_EVENT_IDX.
 164  * Assuming a given event_idx value from the other side, if we have just
 165  * incremented index from old to new_idx, should we trigger an event?
 166  */
 167 static inline int vring_need_event(__u16 event_idx, __u16 new_idx, __u16 old)
 168 {
 169         /*
 170          * Note: Xen has similar logic for notification hold-off
 171          * in include/xen/interface/io/ring.h with req_event and req_prod
 172          * corresponding to event_idx + 1 and new_idx respectively.
 173          * Note also that req_event and req_prod in Xen start at 1,
 174          * event indexes in virtio start at 0.
 175          */
 176         return (__u16)(new_idx - event_idx - 1) < (__u16)(new_idx - old);
 177 }
 178
 179 struct virtio_sg;
 180
 181 /**
 182  * virtqueue_add - expose buffers to other end
 183  *
 184  * @vq:         the struct virtqueue we're talking about
 185  * @sgs:        array of terminated scatterlists
 186  * @out_sgs:    the number of scatterlists readable by other side
 187  * @in_sgs:     the number of scatterlists which are writable
 188  *              (after readable ones)
 189  *
 190  * Caller must ensure we don't call this with other virtqueue operations
 191  * at the same time (except where noted).
 192  *
 193  * Returns zero or a negative error (ie. ENOSPC, ENOMEM, EIO).
 194  */
 195 int virtqueue_add(struct virtqueue *vq, struct virtio_sg *sgs[],
 196                   unsigned int out_sgs, unsigned int in_sgs);
 197
 198 /**
 199  * virtqueue_kick - update after add_buf
 200  *
 201  * @vq:         the struct virtqueue
 202  *
 203  * After one or more virtqueue_add() calls, invoke this to kick
 204  * the other side.
 205  *
 206  * Caller must ensure we don't call this with other virtqueue
 207  * operations at the same time (except where noted).
 208  */
 209 void virtqueue_kick(struct virtqueue *vq);
 210
 211 /**
 212  * virtqueue_get_buf - get the next used buffer
 213  *
 214  * @vq:         the struct virtqueue we're talking about
 215  * @len:        the length written into the buffer
 216  *
 217  * If the device wrote data into the buffer, @len will be set to the
 218  * amount written. This means you don't need to clear the buffer
 219  * beforehand to ensure there's no data leakage in the case of short
 220  * writes.
 221  *
 222  * Caller must ensure we don't call this with other virtqueue
 223  * operations at the same time (except where noted).
 224  *
 225  * Returns NULL if there are no used buffers, or the memory buffer
 226  * handed to virtqueue_add_*().
 227  */
 228 void *virtqueue_get_buf(struct virtqueue *vq, unsigned int *len);
 229
 230 /**
 231  * vring_create_virtqueue - create a virtqueue for a virtio device
 232  *
 233  * @index:      the index of the queue
 234  * @num:        number of elements of the queue
 235  * @vring_align:the alignment requirement of the descriptor ring
 236  * @udev:       the virtio transport udevice
 237  * @return: the virtqueue pointer or NULL if failed
 238  *
 239  * This creates a virtqueue and allocates the descriptor ring for a virtio
 240  * device. The caller should query virtqueue_get_ring_size() to learn the
 241  * actual size of the ring.
 242  *
 243  * This API is supposed to be called by the virtio transport driver in the
 244  * virtio find_vqs() uclass method.
 245  */
 246 struct virtqueue *vring_create_virtqueue(unsigned int index, unsigned int num,
 247                                          unsigned int vring_align,
 248                                          struct udevice *udev);
 249
 250 /**
 251  * vring_del_virtqueue - destroy a virtqueue
 252  *
 253  * @vq:         the struct virtqueue we're talking about
 254  *
 255  * This destroys a virtqueue. If created with vring_create_virtqueue(),
 256  * this also frees the descriptor ring.
 257  *
 258  * This API is supposed to be called by the virtio transport driver in the
 259  * virtio del_vqs() uclass method.
 260  */
 261 void vring_del_virtqueue(struct virtqueue *vq);
 262
 263 /**
 264  * virtqueue_get_vring_size - get the size of the virtqueue's vring
 265  *
 266  * @vq:         the struct virtqueue containing the vring of interest
 267  * @return: the size of the vring in a virtqueue.
 268  */
 269 unsigned int virtqueue_get_vring_size(struct virtqueue *vq);
 270
 271 /**
 272  * virtqueue_get_desc_addr - get the vring descriptor table address
 273  *
 274  * @vq:         the struct virtqueue containing the vring of interest
 275  * @return: the descriptor table address of the vring in a virtqueue.
 276  */
 277 ulong virtqueue_get_desc_addr(struct virtqueue *vq);
 278
 279 /**
 280  * virtqueue_get_avail_addr - get the vring available ring address
 281  *
 282  * @vq:         the struct virtqueue containing the vring of interest
 283  * @return: the available ring address of the vring in a virtqueue.
 284  */
 285 ulong virtqueue_get_avail_addr(struct virtqueue *vq);
 286
 287 /**
 288  * virtqueue_get_used_addr - get the vring used ring address
 289  *
 290  * @vq:         the struct virtqueue containing the vring of interest
 291  * @return: the used ring address of the vring in a virtqueue.
 292  */
 293 ulong virtqueue_get_used_addr(struct virtqueue *vq);
 294
 295 /**
 296  * virtqueue_poll - query pending used buffers
 297  *
 298  * @vq:                 the struct virtqueue we're talking about
 299  * @last_used_idx:      virtqueue last used index
 300  *
 301  * Returns "true" if there are pending used buffers in the queue.
 302  */
 303 bool virtqueue_poll(struct virtqueue *vq, u16 last_used_idx);
 304
 305 /**
 306  * virtqueue_dump - dump the virtqueue for debugging
 307  *
 308  * @vq:         the struct virtqueue we're talking about
 309  *
 310  * Caller must ensure we don't call this with other virtqueue operations
 311  * at the same time (except where noted).
 312  */
 313 void virtqueue_dump(struct virtqueue *vq);
 314
 315 /*
 316  * Barriers in virtio are tricky. Since we are not in a hyperviosr/guest
 317  * scenario, having these as nops is enough to work as expected.
 318  */
 319
 320 static inline void virtio_mb(void)
 321 {
 322 }
 323
 324 static inline void virtio_rmb(void)
 325 {
 326 }
 327
 328 static inline void virtio_wmb(void)
 329 {
 330 }
 331
 332 static inline void virtio_store_mb(__virtio16 *p, __virtio16 v)
 333 {
 334         WRITE_ONCE(*p, v);
 335 }
 336
 337 #endif /* _LINUX_VIRTIO_RING_H */