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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Lijun Pan <ljp@linux.ibm.com>,
        Thomas Falcon <tlfalcon@linux.ibm.com>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.19 066/247] ibmvnic: add memory barrier to protect long term buffer
Date:   Mon,  1 Mar 2021 17:11:26 +0100
Message-Id: <20210301161034.904386944@linuxfoundation.org>
In-Reply-To: <20210301161031.684018251@linuxfoundation.org>
References: <20210301161031.684018251@linuxfoundation.org>
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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 5518b56c2a967..788d944b3b51b 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -1521,6 +1521,9 @@ 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;
 
@@ -2186,6 +2189,8 @@ 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