[PATCH 4.20 07/52] net: hns3: add dma_rmb() for rx description

[Greg Kroah-Hartman]

4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jian Shen <shenjian15@xxxxxxxxxx>

[ Upstream commit d394d33bee22421b39a0bcdc51ca6d68ba308625 ]

HW can not guarantee complete write desc->rx.size, even though
HNS3_RXD_VLD_B has been set. Driver needs to add dma_rmb()
instruction to make sure desc->rx.size is always valid.

Fixes: e55970950556 ("net: hns3: Add handling of GRO Pkts not fully RX'ed in NAPI poll")
Signed-off-by: Jian Shen <shenjian15@xxxxxxxxxx>
Signed-off-by: Huazhong Tan <tanhuazhong@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/net/ethernet/hisilicon/hns3/hns3_enet.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
+++ b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
@@ -2373,6 +2373,9 @@ static int hns3_handle_rx_bd(struct hns3
 	length = le16_to_cpu(desc->rx.size);
 	bd_base_info = le32_to_cpu(desc->rx.bd_base_info);
 
+	/* make sure HW write desc complete */
+	dma_rmb();
+
 	/* Check valid BD */
 	if (unlikely(!hnae3_get_bit(bd_base_info, HNS3_RXD_VLD_B)))
 		return -EFAULT;