netdev - [PATCH net] dpaa2-eth: fix the size of the mapped SGT buffer

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Message-Id: <20201211171607.108034-1-ciorneiioana@gmail.com>
Date:   Fri, 11 Dec 2020 19:16:07 +0200
From:   Ioana Ciornei <ciorneiioana@...il.com>
To:     davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org
Cc:     jon@...id-run.com, Ioana Ciornei <ioana.ciornei@....com>,
        Daniel Thompson <daniel.thompson@...aro.org>
Subject: [PATCH net] dpaa2-eth: fix the size of the mapped SGT buffer

From: Ioana Ciornei <ioana.ciornei@....com>

This patch fixes an error condition triggered when the code path which
transmits a S/G frame descriptor when the skb's headroom is not enough
for DPAA2's needs.

We are greated with a splat like the one below when a SGT structure is
recycled and that is because even though a dma_unmap is performed on the
Tx confirmation path, the unmap is not done with the proper size.

[  714.464927] WARNING: CPU: 13 PID: 0 at drivers/iommu/io-pgtable-arm.c:281 __arm_lpae_map+0x2d4/0x30c
(...)
[  714.465343] Call trace:
[  714.465348]  __arm_lpae_map+0x2d4/0x30c
[  714.465353]  __arm_lpae_map+0x114/0x30c
[  714.465357]  __arm_lpae_map+0x114/0x30c
[  714.465362]  __arm_lpae_map+0x114/0x30c
[  714.465366]  arm_lpae_map+0xf4/0x180
[  714.465373]  arm_smmu_map+0x4c/0xc0
[  714.465379]  __iommu_map+0x100/0x2bc
[  714.465385]  iommu_map_atomic+0x20/0x30
[  714.465391]  __iommu_dma_map+0xb0/0x110
[  714.465397]  iommu_dma_map_page+0xb8/0x120
[  714.465404]  dma_map_page_attrs+0x1a8/0x210
[  714.465413]  __dpaa2_eth_tx+0x384/0xbd0 [fsl_dpaa2_eth]
[  714.465421]  dpaa2_eth_tx+0x84/0x134 [fsl_dpaa2_eth]
[  714.465427]  dev_hard_start_xmit+0x10c/0x2b0
[  714.465433]  sch_direct_xmit+0x1a0/0x550
(...)

The dpaa2-eth driver uses an area of software annotations to transmit
necessary information from the Tx path to the Tx confirmation one. This
SWA structure has a different layout for each kind of frame that we are
dealing with: linear, S/G or XDP.

The commit referenced was incorrectly setting up the 'sgt_size' field
for the S/G type of SWA even though we are dealing with a linear skb
here.

Fixes: d70446ee1f40 ("dpaa2-eth: send a scatter-gather FD instead of realloc-ing")
Reported-by: Daniel Thompson <daniel.thompson@...aro.org>
Tested-by: Daniel Thompson <daniel.thompson@...aro.org>
Signed-off-by: Ioana Ciornei <ioana.ciornei@....com>
---
 drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
index cf9400a9886d..d880ab2a7d96 100644
--- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
+++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
@@ -878,7 +878,7 @@ static int dpaa2_eth_build_sg_fd_single_buf(struct dpaa2_eth_priv *priv,
 	swa = (struct dpaa2_eth_swa *)sgt_buf;
 	swa->type = DPAA2_ETH_SWA_SINGLE;
 	swa->single.skb = skb;
-	swa->sg.sgt_size = sgt_buf_size;
+	swa->single.sgt_size = sgt_buf_size;
 
 	/* Separately map the SGT buffer */
 	sgt_addr = dma_map_single(dev, sgt_buf, sgt_buf_size, DMA_BIDIRECTIONAL);
-- 
2.28.0