[PATCH 5.18 086/231] nfp: fix issue of skb segments exceeds descriptor limitation

Greg Kroah-Hartman
2022-07-19T12:56:42Z

From: Baowen Zheng <baowen.zheng@corigine.com>

[ Upstream commit 9c840d5f9aaef87e65db900bae21c70b059aba5f ]

TCP packets will be dropped if the segments number in the tx skb
exceeds limitation when sending iperf3 traffic with --zerocopy option.

we make the following changes:

Get nr_frags in nfp_nfdk_tx_maybe_close_block instead of passing from
outside because it will be changed after skb_linearize operation.

Fill maximum dma_len in first tx descriptor to make sure the whole
head is included in the first descriptor.

Fixes: c10d12e3dce8 ("nfp: add support for NFDK data path")
Signed-off-by: Baowen Zheng <baowen.zheng@corigine.com>
Reviewed-by: Louis Peens <louis.peens@corigine.com>
Signed-off-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/ethernet/netronome/nfp/nfdk/dp.c | 33 +++++++++++++++-----
1 file changed, 25 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/netronome/nfp/nfdk/dp.c b/drivers/net/ethernet/netronome/nfp/nfdk/dp.c
index e509d6dcba5c..805071d64a20 100644
--- a/drivers/net/ethernet/netronome/nfp/nfdk/dp.c
+++ b/drivers/net/ethernet/netronome/nfp/nfdk/dp.c
@@ -125,17 +125,18 @@ nfp_nfdk_tx_csum(struct nfp_net_dp *dp, struct nfp_net_r_vector *r_vec,

static int
nfp_nfdk_tx_maybe_close_block(struct nfp_net_tx_ring *tx_ring,
- unsigned int nr_frags, struct sk_buff *skb)
+ struct sk_buff *skb)
{
unsigned int n_descs, wr_p, nop_slots;
const skb_frag_t *frag, *fend;
struct nfp_nfdk_tx_desc *txd;
+ unsigned int nr_frags;
unsigned int wr_idx;
int err;

recount_descs:
n_descs = nfp_nfdk_headlen_to_segs(skb_headlen(skb));
-
+ nr_frags = skb_shinfo(skb)->nr_frags;
frag = skb_shinfo(skb)->frags;
fend = frag + nr_frags;
for (; frag < fend; frag++)
@@ -281,10 +282,13 @@ netdev_tx_t nfp_nfdk_tx(struct sk_buff *skb, struct net_device *netdev)
if (unlikely((int)metadata < 0))
goto err_flush;

- nr_frags = skb_shinfo(skb)->nr_frags;
- if (nfp_nfdk_tx_maybe_close_block(tx_ring, nr_frags, skb))
+ if (nfp_nfdk_tx_maybe_close_block(tx_ring, skb))
goto err_flush;

+ /* nr_frags will change after skb_linearize so we get nr_frags after
+ * nfp_nfdk_tx_maybe_close_block function
+ */
+ nr_frags = skb_shinfo(skb)->nr_frags;
/* DMA map all */
wr_idx = D_IDX(tx_ring, tx_ring->wr_p);
txd = &tx_ring->ktxds[wr_idx];
@@ -310,7 +314,16 @@ netdev_tx_t nfp_nfdk_tx(struct sk_buff *skb, struct net_device *netdev)

/* FIELD_PREP() implicitly truncates to chunk */
dma_len -= 1;
- dlen_type = FIELD_PREP(NFDK_DESC_TX_DMA_LEN_HEAD, dma_len) |
+
+ /* We will do our best to pass as much data as we can in descriptor
+ * and we need to make sure the first descriptor includes whole head
+ * since there is limitation in firmware side. Sometimes the value of
+ * dma_len bitwise and NFDK_DESC_TX_DMA_LEN_HEAD will less than
+ * headlen.
+ */
+ dlen_type = FIELD_PREP(NFDK_DESC_TX_DMA_LEN_HEAD,
+ dma_len > NFDK_DESC_TX_DMA_LEN_HEAD ?
+ NFDK_DESC_TX_DMA_LEN_HEAD : dma_len) |
FIELD_PREP(NFDK_DESC_TX_TYPE_HEAD, type);

txd->dma_len_type = cpu_to_le16(dlen_type);
@@ -925,7 +938,9 @@ nfp_nfdk_tx_xdp_buf(struct nfp_net_dp *dp, struct nfp_net_rx_ring *rx_ring,

/* FIELD_PREP() implicitly truncates to chunk */
dma_len -= 1;
- dlen_type = FIELD_PREP(NFDK_DESC_TX_DMA_LEN_HEAD, dma_len) |
+ dlen_type = FIELD_PREP(NFDK_DESC_TX_DMA_LEN_HEAD,
+ dma_len > NFDK_DESC_TX_DMA_LEN_HEAD ?
+ NFDK_DESC_TX_DMA_LEN_HEAD : dma_len) |
FIELD_PREP(NFDK_DESC_TX_TYPE_HEAD, type);

txd->dma_len_type = cpu_to_le16(dlen_type);
@@ -1303,7 +1318,7 @@ nfp_nfdk_ctrl_tx_one(struct nfp_net *nn, struct nfp_net_r_vector *r_vec,
skb_push(skb, 4));
}

- if (nfp_nfdk_tx_maybe_close_block(tx_ring, 0, skb))
+ if (nfp_nfdk_tx_maybe_close_block(tx_ring, skb))
goto err_free;

/* DMA map all */
@@ -1328,7 +1343,9 @@ nfp_nfdk_ctrl_tx_one(struct nfp_net *nn, struct nfp_net_r_vector *r_vec,
txbuf++;

dma_len -= 1;
- dlen_type = FIELD_PREP(NFDK_DESC_TX_DMA_LEN_HEAD, dma_len) |
+ dlen_type = FIELD_PREP(NFDK_DESC_TX_DMA_LEN_HEAD,
+ dma_len > NFDK_DESC_TX_DMA_LEN_HEAD ?
+ NFDK_DESC_TX_DMA_LEN_HEAD : dma_len) |
FIELD_PREP(NFDK_DESC_TX_TYPE_HEAD, type);

txd->dma_len_type = cpu_to_le16(dlen_type);
--
2.35.1