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    Subject[PATCH 5.4 063/340] ibmvnic: add memory barrier to protect long term buffer
    Date
    From: Lijun Pan <ljp@linux.ibm.com>

    [ Upstream commit 42557dab78edc8235aba5b441f2eb35f725a0ede ]

    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 <ljp@linux.ibm.com>
    Acked-by: Thomas Falcon <tlfalcon@linux.ibm.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    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 5b5d488c2f374..901883a44a320 100644
    --- a/drivers/net/ethernet/ibm/ibmvnic.c
    +++ b/drivers/net/ethernet/ibm/ibmvnic.c
    @@ -1518,6 +1518,9 @@ 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;

    @@ -2340,6 +2343,8 @@ restart_poll:
    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);

    --
    2.27.0


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