[dpdk-stable] [18.11] net/virtio: add barriers for extra descriptors on Rx split

[Kevin Traynor]

From: Ilya Maximets <i.maximets at samsung.com>

[ upstream commit 23d25f1a40175343c8a27d539d47fecef477ecf5 ]

There should be read barrier between checking VIRTQUEUE_NUSED (reading
the used->idx) and reading these descriptors. It's done for the first
checks at the beginning of these functions but missed while checking
for extra required descriptors.

Fixes: e5f456a98d3c ("net/virtio: support in-order Rx and Tx")
Fixes: 13ce5e7eb94f ("virtio: mergeable buffers")

Signed-off-by: Ilya Maximets <i.maximets at samsung.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin at redhat.com>
Signed-off-by: Kevin Traynor <ktraynor at redhat.com>
---
 drivers/net/virtio/virtio_rxtx.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
index 7e035130f..606706e94 100644
--- a/drivers/net/virtio/virtio_rxtx.c
+++ b/drivers/net/virtio/virtio_rxtx.c
@@ -1100,4 +1100,5 @@ virtio_recv_mergeable_pkts_inorder(void *rx_queue,
 		prev = rcv_pkts[nb_rx];
 		if (likely(VIRTQUEUE_NUSED(vq) >= rcv_cnt)) {
+			virtio_rmb();
 			num = virtqueue_dequeue_rx_inorder(vq, rcv_pkts, len,
 							   rcv_cnt);
@@ -1264,4 +1265,5 @@ virtio_recv_mergeable_pkts(void *rx_queue,
 				RTE_MIN(seg_res, RTE_DIM(rcv_pkts));
 			if (likely(VIRTQUEUE_NUSED(vq) >= rcv_cnt)) {
+				virtio_rmb();
 				uint32_t rx_num =
 					virtqueue_dequeue_burst_rx(vq,
-- 
2.20.1