virtio_net: disable premapped mode by default

Now, the premapped mode encounters some problem.

    http://lore.kernel.org/all/[email protected]

So we disable the premapped mode by default.
We can re-enable it in the future.

Fixes: f9dac92 ("virtio_ring: enable premapped mode whatever use_dma_api")
Reported-by: "Si-Wei Liu" <[email protected]>
Closes: http://lore.kernel.org/all/[email protected]
Signed-off-by: Xuan Zhuo <[email protected]>
Acked-by: Michael S. Tsirkin <[email protected]>
Tested-by: Takero Funaki <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: fengidri

drivers/net/virtio_net.c

@@ -977,22 +977,6 @@ static void *virtnet_rq_alloc(struct receive_queue *rq, u32 size, gfp_t gfp)
 	return buf;
 }
 
-static void virtnet_rq_set_premapped(struct virtnet_info *vi)
-{
-	int i;
-
-	/* disable for big mode */
-	if (!vi->mergeable_rx_bufs && vi->big_packets)
-		return;
-
-	for (i = 0; i < vi->max_queue_pairs; i++) {
-		if (virtqueue_set_dma_premapped(vi->rq[i].vq))
-			continue;
-
-		vi->rq[i].do_dma = true;
-	}
-}
-
 static void virtnet_rq_unmap_free_buf(struct virtqueue *vq, void *buf)
 {
 	struct virtnet_info *vi = vq->vdev->priv;
@@ -6105,8 +6089,6 @@ static int init_vqs(struct virtnet_info *vi)
 	if (ret)
 		goto err_free;
 
-	virtnet_rq_set_premapped(vi);
-
 	cpus_read_lock();
 	virtnet_set_affinity(vi);
 	cpus_read_unlock();