minix/lib/libvirtio/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  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  * 3. Neither the name of IBM nor the names of its contributors
  19  *    may be used to endorse or promote products derived from this software
  20  *    without specific prior written permission.
  21  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  * Copyright Rusty Russell IBM Corporation 2007. */
  34
  35 /* This marks a buffer as continuing via the next field. */
  36 #define VRING_DESC_F_NEXT       1
  37 /* This marks a buffer as write-only (otherwise read-only). */
  38 #define VRING_DESC_F_WRITE      2
  39 /* This means the buffer contains a list of buffer descriptors. */
  40 #define VRING_DESC_F_INDIRECT   4
  41
  42 /* The Host uses this in used->flags to advise the Guest: don't kick me when
  43  * you add a buffer.  It's unreliable, so it's simply an optimization.  Guest
  44  * will still kick if it's out of buffers. */
  45 #define VRING_USED_F_NO_NOTIFY  1
  46 /* The Guest uses this in avail->flags to advise the Host: don't interrupt me
  47  * when you consume a buffer.  It's unreliable, so it's simply an
  48  * optimization.  */
  49 #define VRING_AVAIL_F_NO_INTERRUPT      1
  50
  51 /* We support indirect buffer descriptors */
  52 #define VIRTIO_RING_F_INDIRECT_DESC     28
  53
  54 /* The Guest publishes the used index for which it expects an interrupt
  55  * at the end of the avail ring. Host should ignore the avail->flags field. */
  56 /* The Host publishes the avail index for which it expects a kick
  57  * at the end of the used ring. Guest should ignore the used->flags field. */
  58 #define VIRTIO_RING_F_EVENT_IDX         29
  59
  60 /* Virtio ring descriptors: 16 bytes.  These can chain together via "next". */
  61 struct vring_desc {
  62         /* Address (guest-physical). */
  63         u64_t addr;
  64         /* Length. */
  65         u32_t len;
  66         /* The flags as indicated above. */
  67         u16_t flags;
  68         /* We chain unused descriptors via this, too */
  69         u16_t next;
  70 };
  71
  72 struct vring_avail {
  73         u16_t flags;
  74         u16_t idx;
  75         u16_t ring[];
  76 };
  77
  78 /* u32 is used here for ids for padding reasons. */
  79 struct vring_used_elem {
  80         /* Index of start of used descriptor chain. */
  81         u32_t id;
  82         /* Total length of the descriptor chain which was used (written to) */
  83         u32_t len;
  84 };
  85
  86 struct vring_used {
  87         u16_t flags;
  88         u16_t idx;
  89         struct vring_used_elem ring[];
  90 };
  91
  92 struct vring {
  93         unsigned int num;
  94
  95         struct vring_desc *desc;
  96
  97         struct vring_avail *avail;
  98
  99         struct vring_used *used;
 100 };
 101
 102 /* The standard layout for the ring is a continuous chunk of memory which looks
 103  * like this.  We assume num is a power of 2.
 104  *
 105  * struct vring
 106  * {
 107  *      // The actual descriptors (16 bytes each)
 108  *      struct vring_desc desc[num];
 109  *
 110  *      // A ring of available descriptor heads with free-running index.
 111  *      u16_t avail_flags;
 112  *      u16_t avail_idx;
 113  *      u16_t available[num];
 114  *      u16_t used_event_idx;
 115  *
 116  *      // Padding to the next align boundary.
 117  *      char pad[];
 118  *
 119  *      // A ring of used descriptor heads with free-running index.
 120  *      u16_t used_flags;
 121  *      u16_t used_idx;
 122  *      struct vring_used_elem used[num];
 123  *      u16_t avail_event_idx;
 124  * };
 125  */
 126 /* We publish the used event index at the end of the available ring, and vice
 127  * versa. They are at the end for backwards compatibility. */
 128 #define vring_used_event(vr) ((vr)->avail->ring[(vr)->num])
 129 #define vring_avail_event(vr) (*(u16_t *)&(vr)->used->ring[(vr)->num])
 130
 131 static inline void vring_init(struct vring *vr, unsigned int num, void *p,
 132                               unsigned long align)
 133 {
 134         vr->num = num;
 135         vr->desc = p;
 136         vr->avail = (void *)((char *)p + num*sizeof(struct vring_desc));
 137         vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + sizeof(u16_t)
 138                 + align-1) & ~(align - 1));
 139 }
 140
 141 static inline unsigned vring_size(unsigned int num, unsigned long align)
 142 {
 143         return ((sizeof(struct vring_desc) * num + sizeof(u16_t) * (3 + num)
 144                  + align - 1) & ~(align - 1))
 145                 + sizeof(u16_t) * 3 + sizeof(struct vring_used_elem) * num;
 146 }
 147
 148 #if 0
 149 /* The following is used with USED_EVENT_IDX and AVAIL_EVENT_IDX */
 150 /* Assuming a given event_idx value from the other size, if
 151  * we have just incremented index from old to new_idx,
 152  * should we trigger an event? */
 153 static inline int vring_need_event(u16_t event_idx, u16_t new_idx, u16_t old)
 154 {
 155         /* Note: Xen has similar logic for notification hold-off
 156          * in include/xen/interface/io/ring.h with req_event and req_prod
 157          * corresponding to event_idx + 1 and new_idx respectively.
 158          * Note also that req_event and req_prod in Xen start at 1,
 159          * event indexes in virtio start at 0. */
 160         return (u16_t)(new_idx - event_idx - 1) < (u16_t)(new_idx - old);
 161 }
 162
 163 #ifdef __KERNEL__
 164 #include <linux/irqreturn.h>
 165 struct virtio_device;
 166 struct virtqueue;
 167
 168 struct virtqueue *vring_new_virtqueue(unsigned int num,
 169                                       unsigned int vring_align,
 170                                       struct virtio_device *vdev,
 171                                       bool weak_barriers,
 172                                       void *pages,
 173                                       void (*notify)(struct virtqueue *vq),
 174                                       void (*callback)(struct virtqueue *vq),
 175                                       const char *name);
 176 void vring_del_virtqueue(struct virtqueue *vq);
 177 /* Filter out transport-specific feature bits. */
 178 void vring_transport_features(struct virtio_device *vdev);
 179
 180 irqreturn_t vring_interrupt(int irq, void *_vq);
 181 #endif /* __KERNEL__ */
 182 #endif /* 0 */
 183 #endif /* _LINUX_VIRTIO_RING_H */