src/drivers/bus/virtio-ring.c

   1 /* virtio-pci.c - virtio ring management
   2  *
   3  * (c) Copyright 2008 Bull S.A.S.
   4  *
   5  *  Author: Laurent Vivier <Laurent.Vivier@bull.net>
   6  *
   7  *  some parts from Linux Virtio Ring
   8  *
   9  *  Copyright Rusty Russell IBM Corporation 2007
  10  *
  11  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  12  * See the COPYING file in the top-level directory.
  13  *
  14  *
  15  */
  16
  17 #include "etherboot.h"
  18 #include "gpxe/io.h"
  19 #include "gpxe/virtio-ring.h"
  20 #include "gpxe/virtio-pci.h"
  21
  22 #define BUG() do { \
  23    printf("BUG: failure at %s:%d/%s()!\n", \
  24           __FILE__, __LINE__, __FUNCTION__); \
  25    while(1); \
  26 } while (0)
  27 #define BUG_ON(condition) do { if (condition) BUG(); } while (0)
  28
  29 /*
  30  * vring_free
  31  *
  32  * put at the begin of the free list the current desc[head]
  33  */
  34
  35 void vring_detach(struct vring_virtqueue *vq, unsigned int head)
  36 {
  37    struct vring *vr = &vq->vring;
  38    unsigned int i;
  39
  40    /* find end of given descriptor */
  41
  42    i = head;
  43    while (vr->desc[i].flags & VRING_DESC_F_NEXT)
  44            i = vr->desc[i].next;
  45
  46    /* link it with free list and point to it */
  47
  48    vr->desc[i].next = vq->free_head;
  49    wmb();
  50    vq->free_head = head;
  51 }
  52
  53 /*
  54  * vring_get_buf
  55  *
  56  * get a buffer from the used list
  57  *
  58  */
  59
  60 void *vring_get_buf(struct vring_virtqueue *vq, unsigned int *len)
  61 {
  62    struct vring *vr = &vq->vring;
  63    struct vring_used_elem *elem;
  64    u32 id;
  65    void *opaque;
  66
  67    BUG_ON(!vring_more_used(vq));
  68
  69    elem = &vr->used->ring[vq->last_used_idx % vr->num];
  70    wmb();
  71    id = elem->id;
  72    if (len != NULL)
  73            *len = elem->len;
  74
  75    opaque = vq->vdata[id];
  76
  77    vring_detach(vq, id);
  78
  79    vq->last_used_idx++;
  80
  81    return opaque;
  82 }
  83
  84 void vring_add_buf(struct vring_virtqueue *vq,
  85                    struct vring_list list[],
  86                    unsigned int out, unsigned int in,
  87                    void *opaque, int num_added)
  88 {
  89    struct vring *vr = &vq->vring;
  90    int i, avail, head, prev;
  91
  92    BUG_ON(out + in == 0);
  93
  94    prev = 0;
  95    head = vq->free_head;
  96    for (i = head; out; i = vr->desc[i].next, out--) {
  97
  98            vr->desc[i].flags = VRING_DESC_F_NEXT;
  99            vr->desc[i].addr = (u64)virt_to_phys(list->addr);
 100            vr->desc[i].len = list->length;
 101            prev = i;
 102            list++;
 103    }
 104    for ( ; in; i = vr->desc[i].next, in--) {
 105
 106            vr->desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE;
 107            vr->desc[i].addr = (u64)virt_to_phys(list->addr);
 108            vr->desc[i].len = list->length;
 109            prev = i;
 110            list++;
 111    }
 112    vr->desc[prev].flags &= ~VRING_DESC_F_NEXT;
 113
 114    vq->free_head = i;
 115
 116    vq->vdata[head] = opaque;
 117
 118    avail = (vr->avail->idx + num_added) % vr->num;
 119    vr->avail->ring[avail] = head;
 120    wmb();
 121 }
 122
 123 void vring_kick(unsigned int ioaddr, struct vring_virtqueue *vq, int num_added)
 124 {
 125    struct vring *vr = &vq->vring;
 126
 127    wmb();
 128    vr->avail->idx += num_added;
 129
 130    mb();
 131    if (!(vr->used->flags & VRING_USED_F_NO_NOTIFY))
 132            vp_notify(ioaddr, vq->queue_index);
 133 }
 134