Commit 86e9424d authored by Michael S. Tsirkin's avatar Michael S. Tsirkin

vhost: logging thinko fix

vhost was dong some complex math to get
offset to log at, and got it wrong by a couple of bytes,
while in fact it's simple: get address where we write,
subtract start of buffer, add log base.

Do it this way.
Reviewed-by: default avatarJuan Quintela <>
Signed-off-by: default avatarMichael S. Tsirkin <>
parent 655ffee2
......@@ -1004,10 +1004,14 @@ int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
if (unlikely(vq->log_used)) {
/* Make sure data is seen before log. */
log_write(vq->log_base, vq->log_addr + sizeof *vq->used->ring *
(vq->last_used_idx % vq->num),
sizeof *vq->used->ring);
log_write(vq->log_base, vq->log_addr, sizeof *vq->used->ring);
/* Log used ring entry write. */
vq->log_addr + ((void *)used - (void *)vq->used),
sizeof *used);
/* Log used index update. */
vq->log_addr + offsetof(struct vring_used, idx),
sizeof vq->used->idx);
if (vq->log_ctx)
eventfd_signal(vq->log_ctx, 1);
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