@@ -71,9 +71,6 @@ struct vring_virtqueue
/* Number we've added since last sync. */
unsigned int num_added;
- /* Last used index we've seen. */
- u16 last_used_idx;
-
/* How to notify other side. FIXME: commonalize hcalls! */
void (*notify)(struct virtqueue *vq);
@@ -278,12 +275,13 @@ static void detach_buf(struct vring_virt
static inline bool more_used(const struct vring_virtqueue *vq)
{
- return vq->last_used_idx != vq->vring.used->idx;
+ return vring_last_used(&vq->vring) != vq->vring.used->idx;
}
static void *vring_get_buf(struct virtqueue *_vq, unsigned int *len)
{
struct vring_virtqueue *vq = to_vvq(_vq);
+ struct vring_used_elem *u;
void *ret;
unsigned int i;
@@ -300,8 +298,11 @@ static void *vring_get_buf(struct virtqu
return NULL;
}
- i = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].id;
- *len = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].len;
+ u = &vq->vring.used->ring[vring_last_used(&vq->vring) % vq->vring.num];
+ i = u->id;
+ *len = u->len;
+ /* Make sure we don't reload i after doing checks. */
+ rmb();
if (unlikely(i >= vq->vring.num)) {
BAD_RING(vq, "id %u out of range\n", i);
@@ -315,7 +316,8 @@ static void *vring_get_buf(struct virtqu
/* detach_buf clears data, so grab it now. */
ret = vq->data[i];
detach_buf(vq, i);
- vq->last_used_idx++;
+ vring_last_used(&vq->vring)++;
+
END_USE(vq);
return ret;
}
@@ -402,7 +404,6 @@ struct virtqueue *vring_new_virtqueue(un
vq->vq.name = name;
vq->notify = notify;
vq->broken = false;
- vq->last_used_idx = 0;
vq->num_added = 0;
list_add_tail(&vq->vq.list, &vdev->vqs);
#ifdef DEBUG
@@ -413,6 +414,10 @@ struct virtqueue *vring_new_virtqueue(un
vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC);
+ /* We publish indices whether they offer it or not: if not, it's junk
+ * space anyway. But calling this acknowledges the feature. */
+ virtio_has_feature(vdev, VIRTIO_RING_F_PUBLISH_INDICES);
+
/* No callback? Tell other side not to bother us. */
if (!callback)
vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
@@ -443,6 +448,8 @@ void vring_transport_features(struct vir
switch (i) {
case VIRTIO_RING_F_INDIRECT_DESC:
break;
+ case VIRTIO_RING_F_PUBLISH_INDICES:
+ break;
default:
/* We don't understand this bit. */
clear_bit(i, vdev->features);
@@ -29,6 +29,9 @@
/* We support indirect buffer descriptors */
#define VIRTIO_RING_F_INDIRECT_DESC 28
+/* We publish our last-seen used index at the end of the avail ring. */
+#define VIRTIO_RING_F_PUBLISH_INDICES 29
+
/* Virtio ring descriptors: 16 bytes. These can chain together via "next". */
struct vring_desc
{
@@ -87,6 +90,7 @@ struct vring {
* __u16 avail_flags;
* __u16 avail_idx;
* __u16 available[num];
+ * __u16 last_used_idx;
*
* // Padding to the next align boundary.
* char pad[];
@@ -95,6 +99,7 @@ struct vring {
* __u16 used_flags;
* __u16 used_idx;
* struct vring_used_elem used[num];
+ * __u16 last_avail_idx;
* };
*/
static inline void vring_init(struct vring *vr, unsigned int num, void *p,
@@ -111,9 +116,14 @@ static inline unsigned vring_size(unsign
{
return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (2 + num)
+ align - 1) & ~(align - 1))
- + sizeof(__u16) * 2 + sizeof(struct vring_used_elem) * num;
+ + sizeof(__u16) * 2 + sizeof(struct vring_used_elem) * num + 2;
}
+/* We publish the last-seen used index at the end of the available ring, and
+ * vice-versa. These are at the end for backwards compatibility. */
+#define vring_last_used(vr) ((vr)->avail->ring[(vr)->num])
+#define vring_last_avail(vr) (*(__u16 *)&(vr)->used->ring[(vr)->num])
+
#ifdef __KERNEL__
#include <linux/irqreturn.h>
struct virtio_device;