@@ -1151,7 +1285,48 @@ static int coroutine_fn
bdrv_mirror_top_preadv(BlockDriverState *bs,
static int coroutine_fn bdrv_mirror_top_pwritev(BlockDriverState *bs,
uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags)
{
- return bdrv_co_pwritev(bs->backing, offset, bytes, qiov, flags);
+ MirrorOp *op = NULL;
+ MirrorBDSOpaque *s = bs->opaque;
+ QEMUIOVector bounce_qiov;
+ void *bounce_buf;
+ int ret = 0;
+ bool copy_to_target;
+
+ copy_to_target = s->job->ret >= 0 &&
+ s->job->copy_mode == MIRROR_COPY_MODE_WRITE_BLOCKING;
+
+ if (copy_to_target) {
+ /* The guest might concurrently modify the data to write; but
+ * the data on source and destination must match, so we have
+ * to use a bounce buffer if we are going to write to the
+ * target now. */
+ bounce_buf = qemu_blockalign(bs, bytes);
+ iov_to_buf_full(qiov->iov, qiov->niov, 0, bounce_buf, bytes);