LXR linux/include/linux/virtio

   1#ifndef _LINUX_VIRTIO_RING_H
   2#define _LINUX_VIRTIO_RING_H
   3/* An interface for efficient virtio implementation, currently for use by KVM
   4 * and lguest, but hopefully others soon.  Do NOT change this since it will
   5 * break existing servers and clients.
   6 *
   7 * This header is BSD licensed so anyone can use the definitions to implement
   8 * compatible drivers/servers.
   9 *
  10 * Copyright Rusty Russell IBM Corporation 2007. */
  11#include <linux/types.h>
  12
  13/* This marks a buffer as continuing via the next field. */
  14#define VRING_DESC_F_NEXT       1
  15/* This marks a buffer as write-only (otherwise read-only). */
  16#define VRING_DESC_F_WRITE      2
  17/* This means the buffer contains a list of buffer descriptors. */
  18#define VRING_DESC_F_INDIRECT   4
  19
  20/* The Host uses this in used->flags to advise the Guest: don't kick me when
  21 * you add a buffer.  It's unreliable, so it's simply an optimization.  Guest
  22 * will still kick if it's out of buffers. */
  23#define VRING_USED_F_NO_NOTIFY  1
  24/* The Guest uses this in avail->flags to advise the Host: don't interrupt me
  25 * when you consume a buffer.  It's unreliable, so it's simply an
  26 * optimization.  */
  27#define VRING_AVAIL_F_NO_INTERRUPT      1
  28
  29/* We support indirect buffer descriptors */
  30#define VIRTIO_RING_F_INDIRECT_DESC     28
  31
  32/* Virtio ring descriptors: 16 bytes.  These can chain together via "next". */
  33struct vring_desc {
  34        /* Address (guest-physical). */
  35        __u64 addr;
  36        /* Length. */
  37        __u32 len;
  38        /* The flags as indicated above. */
  39        __u16 flags;
  40        /* We chain unused descriptors via this, too */
  41        __u16 next;
  42};
  43
  44struct vring_avail {
  45        __u16 flags;
  46        __u16 idx;
  47        __u16 ring[];
  48};
  49
  50/* u32 is used here for ids for padding reasons. */
  51struct vring_used_elem {
  52        /* Index of start of used descriptor chain. */
  53        __u32 id;
  54        /* Total length of the descriptor chain which was used (written to) */
  55        __u32 len;
  56};
  57
  58struct vring_used {
  59        __u16 flags;
  60        __u16 idx;
  61        struct vring_used_elem ring[];
  62};
  63
  64struct vring {
  65        unsigned int num;
  66
  67        struct vring_desc *desc;
  68
  69        struct vring_avail *avail;
  70
  71        struct vring_used *used;
  72};
  73
  74/* The standard layout for the ring is a continuous chunk of memory which looks
  75 * like this.  We assume num is a power of 2.
  76 *
  77 * struct vring
  78 * {
  79 *      // The actual descriptors (16 bytes each)
  80 *      struct vring_desc desc[num];
  81 *
  82 *      // A ring of available descriptor heads with free-running index.
  83 *      __u16 avail_flags;
  84 *      __u16 avail_idx;
  85 *      __u16 available[num];
  86 *
  87 *      // Padding to the next align boundary.
  88 *      char pad[];
  89 *
  90 *      // A ring of used descriptor heads with free-running index.
  91 *      __u16 used_flags;
  92 *      __u16 used_idx;
  93 *      struct vring_used_elem used[num];
  94 * };
  95 */
  96static inline void vring_init(struct vring *vr, unsigned int num, void *p,
  97                              unsigned long align)
  98{
  99        vr->num = num;
 100        vr->desc = p;
 101        vr->avail = p + num*sizeof(struct vring_desc);
 102        vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + align-1)
 103                            & ~(align - 1));
 104}
 105
 106static inline unsigned vring_size(unsigned int num, unsigned long align)
 107{
 108        return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (2 + num)
 109                 + align - 1) & ~(align - 1))
 110                + sizeof(__u16) * 2 + sizeof(struct vring_used_elem) * num;
 111}
 112
 113#ifdef __KERNEL__
 114#include <linux/irqreturn.h>
 115struct virtio_device;
 116struct virtqueue;
 117
 118struct virtqueue *vring_new_virtqueue(unsigned int num,
 119                                      unsigned int vring_align,
 120                                      struct virtio_device *vdev,
 121                                      void *pages,
 122                                      void (*notify)(struct virtqueue *vq),
 123                                      void (*callback)(struct virtqueue *vq),
 124                                      const char *name);
 125void vring_del_virtqueue(struct virtqueue *vq);
 126/* Filter out transport-specific feature bits. */
 127void vring_transport_features(struct virtio_device *vdev);
 128
 129irqreturn_t vring_interrupt(int irq, void *_vq);
 130#endif /* __KERNEL__ */
 131#endif /* _LINUX_VIRTIO_RING_H */
 132