[PATCH][SRU Bionic] net: hns3: add dma_rmb() for rx description

[dann frazier]

From: Jian Shen <shenjian15 at huawei.com>

BugLink: https://bugs.launchpad.net/bugs/1821064

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 at huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong at huawei.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
(backported from commit d394d33bee22421b39a0bcdc51ca6d68ba308625)
[ dannf: trivial context fix ]
Signed-off-by: dann frazier <dann.frazier at canonical.com>
---
 drivers/net/ethernet/hisilicon/hns3/hns3_enet.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
index 15d9de4c0575a..08718f9093dc5 100644
--- a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
+++ b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
@@ -2466,6 +2466,8 @@ static int hns3_add_frag(struct hns3_enet_ring *ring, struct hns3_desc *desc,
 		desc = &ring->desc[ring->next_to_clean];
 		desc_cb = &ring->desc_cb[ring->next_to_clean];
 		bd_base_info = le32_to_cpu(desc->rx.bd_base_info);
+		/* make sure HW write desc complete */
+		dma_rmb();
 		if (!hnae3_get_bit(bd_base_info, HNS3_RXD_VLD_B))
 			return -ENXIO;
 
-- 
2.20.1