[PATCH net] ibmvnic: add memory barrier to protect long term buffer

[Lijun Pan]

dma_rmb() barrier is added to load the long term buffer before copying
it to socket buffer; and dma_wmb() barrier is added to update the
long term buffer before it being accessed by VIOS (virtual i/o server).

Fixes: 032c5e82847a ("Driver for IBM System i/p VNIC protocol")
Signed-off-by: Lijun Pan <l...@linux.ibm.com>
Acked-by: Thomas Falcon <tlfal...@linux.ibm.com>
---
 drivers/net/ethernet/ibm/ibmvnic.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c 
b/drivers/net/ethernet/ibm/ibmvnic.c
index c8b0d99608d5..cd201f89ce6c 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -1705,6 +1705,9 @@ static netdev_tx_t ibmvnic_xmit(struct sk_buff *skb, 
struct net_device *netdev)
                skb_copy_from_linear_data(skb, dst, skb->len);
        }
 
+       /* post changes to long_term_buff *dst before VIOS accessing it */
+       dma_wmb();
+
        tx_pool->consumer_index =
            (tx_pool->consumer_index + 1) % tx_pool->num_buffers;
 
@@ -2544,6 +2547,8 @@ static int ibmvnic_poll(struct napi_struct *napi, int 
budget)
                offset = be16_to_cpu(next->rx_comp.off_frame_data);
                flags = next->rx_comp.flags;
                skb = rx_buff->skb;
+               /* load long_term_buff before copying to skb */
+               dma_rmb();
                skb_copy_to_linear_data(skb, rx_buff->data + offset,
                                        length);
 
-- 
2.23.0