ceph/src/dpdk/drivers/net/virtio/virtio_ring.h

   1 /*-
   2  *   BSD LICENSE
   3  *
   4  *   Copyright(c) 2010-2014 Intel Corporation. All rights reserved.
   5  *   All rights reserved.
   6  *
   7  *   Redistribution and use in source and binary forms, with or without
   8  *   modification, are permitted provided that the following conditions
   9  *   are met:
  10  *
  11  *     * Redistributions of source code must retain the above copyright
  12  *       notice, this list of conditions and the following disclaimer.
  13  *     * Redistributions in binary form must reproduce the above copyright
  14  *       notice, this list of conditions and the following disclaimer in
  15  *       the documentation and/or other materials provided with the
  16  *       distribution.
  17  *     * Neither the name of Intel Corporation nor the names of its
  18  *       contributors may be used to endorse or promote products derived
  19  *       from this software without specific prior written permission.
  20  *
  21  *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  22  *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  23  *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  24  *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  25  *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  26  *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  27  *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  28  *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  29  *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  30  *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  31  *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  32  */
  33
  34 #ifndef _VIRTIO_RING_H_
  35 #define _VIRTIO_RING_H_
  36
  37 #include <stdint.h>
  38
  39 #include <rte_common.h>
  40
  41 /* This marks a buffer as continuing via the next field. */
  42 #define VRING_DESC_F_NEXT       1
  43 /* This marks a buffer as write-only (otherwise read-only). */
  44 #define VRING_DESC_F_WRITE      2
  45 /* This means the buffer contains a list of buffer descriptors. */
  46 #define VRING_DESC_F_INDIRECT   4
  47
  48 /* The Host uses this in used->flags to advise the Guest: don't kick me
  49  * when you add a buffer.  It's unreliable, so it's simply an
  50  * optimization.  Guest will still kick if it's out of buffers. */
  51 #define VRING_USED_F_NO_NOTIFY  1
  52 /* The Guest uses this in avail->flags to advise the Host: don't
  53  * interrupt me when you consume a buffer.  It's unreliable, so it's
  54  * simply an optimization.  */
  55 #define VRING_AVAIL_F_NO_INTERRUPT  1
  56
  57 /* VirtIO ring descriptors: 16 bytes.
  58  * These can chain together via "next". */
  59 struct vring_desc {
  60         uint64_t addr;  /*  Address (guest-physical). */
  61         uint32_t len;   /* Length. */
  62         uint16_t flags; /* The flags as indicated above. */
  63         uint16_t next;  /* We chain unused descriptors via this. */
  64 };
  65
  66 struct vring_avail {
  67         uint16_t flags;
  68         uint16_t idx;
  69         uint16_t ring[0];
  70 };
  71
  72 /* id is a 16bit index. uint32_t is used here for ids for padding reasons. */
  73 struct vring_used_elem {
  74         /* Index of start of used descriptor chain. */
  75         uint32_t id;
  76         /* Total length of the descriptor chain which was written to. */
  77         uint32_t len;
  78 };
  79
  80 struct vring_used {
  81         uint16_t flags;
  82         volatile uint16_t idx;
  83         struct vring_used_elem ring[0];
  84 };
  85
  86 struct vring {
  87         unsigned int num;
  88         struct vring_desc  *desc;
  89         struct vring_avail *avail;
  90         struct vring_used  *used;
  91 };
  92
  93 /* The standard layout for the ring is a continuous chunk of memory which
  94  * looks like this.  We assume num is a power of 2.
  95  *
  96  * struct vring {
  97  *      // The actual descriptors (16 bytes each)
  98  *      struct vring_desc desc[num];
  99  *
 100  *      // A ring of available descriptor heads with free-running index.
 101  *      __u16 avail_flags;
 102  *      __u16 avail_idx;
 103  *      __u16 available[num];
 104  *      __u16 used_event_idx;
 105  *
 106  *      // Padding to the next align boundary.
 107  *      char pad[];
 108  *
 109  *      // A ring of used descriptor heads with free-running index.
 110  *      __u16 used_flags;
 111  *      __u16 used_idx;
 112  *      struct vring_used_elem used[num];
 113  *      __u16 avail_event_idx;
 114  * };
 115  *
 116  * NOTE: for VirtIO PCI, align is 4096.
 117  */
 118
 119 /*
 120  * We publish the used event index at the end of the available ring, and vice
 121  * versa. They are at the end for backwards compatibility.
 122  */
 123 #define vring_used_event(vr)  ((vr)->avail->ring[(vr)->num])
 124 #define vring_avail_event(vr) (*(uint16_t *)&(vr)->used->ring[(vr)->num])
 125
 126 static inline size_t
 127 vring_size(unsigned int num, unsigned long align)
 128 {
 129         size_t size;
 130
 131         size = num * sizeof(struct vring_desc);
 132         size += sizeof(struct vring_avail) + (num * sizeof(uint16_t));
 133         size = RTE_ALIGN_CEIL(size, align);
 134         size += sizeof(struct vring_used) +
 135                 (num * sizeof(struct vring_used_elem));
 136         return size;
 137 }
 138
 139 static inline void
 140 vring_init(struct vring *vr, unsigned int num, uint8_t *p,
 141         unsigned long align)
 142 {
 143         vr->num = num;
 144         vr->desc = (struct vring_desc *) p;
 145         vr->avail = (struct vring_avail *) (p +
 146                 num * sizeof(struct vring_desc));
 147         vr->used = (void *)
 148                 RTE_ALIGN_CEIL((uintptr_t)(&vr->avail->ring[num]), align);
 149 }
 150
 151 /*
 152  * The following is used with VIRTIO_RING_F_EVENT_IDX.
 153  * Assuming a given event_idx value from the other size, if we have
 154  * just incremented index from old to new_idx, should we trigger an
 155  * event?
 156  */
 157 static inline int
 158 vring_need_event(uint16_t event_idx, uint16_t new_idx, uint16_t old)
 159 {
 160         return (uint16_t)(new_idx - event_idx - 1) < (uint16_t)(new_idx - old);
 161 }
 162
 163 #endif /* _VIRTIO_RING_H_ */