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