include/linux/virtio_ring.h

   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
  18 /* This means don't notify other side when buffer added. */
  19 #define VRING_USED_F_NO_NOTIFY  1
  20 /* This means don't interrupt guest when buffer consumed. */
  21 #define VRING_AVAIL_F_NO_INTERRUPT      1
  22
  23 /* Virtio ring descriptors: 16 bytes.  These can chain together via "next". */
  24 struct vring_desc
  25 {
  26         /* Address (guest-physical). */
  27         __u64 addr;
  28         /* Length. */
  29         __u32 len;
  30         /* The flags as indicated above. */
  31         __u16 flags;
  32         /* We chain unused descriptors via this, too */
  33         __u16 next;
  34 };
  35
  36 struct vring_avail
  37 {
  38         __u16 flags;
  39         __u16 idx;
  40         __u16 ring[];
  41 };
  42
  43 /* u32 is used here for ids for padding reasons. */
  44 struct vring_used_elem
  45 {
  46         /* Index of start of used descriptor chain. */
  47         __u32 id;
  48         /* Total length of the descriptor chain which was used (written to) */
  49         __u32 len;
  50 };
  51
  52 struct vring_used
  53 {
  54         __u16 flags;
  55         __u16 idx;
  56         struct vring_used_elem ring[];
  57 };
  58
  59 struct vring {
  60         unsigned int num;
  61
  62         struct vring_desc *desc;
  63
  64         struct vring_avail *avail;
  65
  66         struct vring_used *used;
  67 };
  68
  69 /* The standard layout for the ring is a continuous chunk of memory which looks
  70  * like this.  We assume num is a power of 2.
  71  *
  72  * struct vring
  73  * {
  74  *      // The actual descriptors (16 bytes each)
  75  *      struct vring_desc desc[num];
  76  *
  77  *      // A ring of available descriptor heads with free-running index.
  78  *      __u16 avail_flags;
  79  *      __u16 avail_idx;
  80  *      __u16 available[num];
  81  *
  82  *      // Padding to the next page boundary.
  83  *      char pad[];
  84  *
  85  *      // A ring of used descriptor heads with free-running index.
  86  *      __u16 used_flags;
  87  *      __u16 used_idx;
  88  *      struct vring_used_elem used[num];
  89  * };
  90  */
  91 static inline void vring_init(struct vring *vr, unsigned int num, void *p,
  92                               unsigned int pagesize)
  93 {
  94         vr->num = num;
  95         vr->desc = p;
  96         vr->avail = p + num*sizeof(struct vring_desc);
  97         vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + pagesize-1)
  98                             & ~(pagesize - 1));
  99 }
 100
 101 static inline unsigned vring_size(unsigned int num, unsigned int pagesize)
 102 {
 103         return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (2 + num)
 104                  + pagesize - 1) & ~(pagesize - 1))
 105                 + sizeof(__u16) * 2 + sizeof(struct vring_used_elem) * num;
 106 }
 107
 108 #ifdef __KERNEL__
 109 #include <linux/irqreturn.h>
 110 struct virtio_device;
 111 struct virtqueue;
 112
 113 struct virtqueue *vring_new_virtqueue(unsigned int num,
 114                                       struct virtio_device *vdev,
 115                                       void *pages,
 116                                       void (*notify)(struct virtqueue *vq),
 117                                       bool (*callback)(struct virtqueue *vq));
 118 void vring_del_virtqueue(struct virtqueue *vq);
 119
 120 irqreturn_t vring_interrupt(int irq, void *_vq);
 121 #endif /* __KERNEL__ */
 122 #endif /* _LINUX_VIRTIO_RING_H */