* [PATCH v3 net] net: fec: add dma_wmb to ensure correct descriptor values
@ 2023-05-18 15:02 Shenwei Wang
2023-05-19 1:33 ` Wei Fang
2023-05-20 4:51 ` Jakub Kicinski
0 siblings, 2 replies; 3+ messages in thread
From: Shenwei Wang @ 2023-05-18 15:02 UTC (permalink / raw
To: Wei Fang, David S. Miller, Eric Dumazet, Jakub Kicinski,
Paolo Abeni, Simon Horman, Horatiu Vultur, Heiner Kallweit
Cc: Shenwei Wang, Clark Wang, NXP Linux Team, netdev, imx
Two dma_wmb() are added in the XDP TX path to ensure proper ordering of
descriptor and buffer updates:
1. A dma_wmb() is added after updating the last BD to make sure
the updates to rest of the descriptor are visible before
transferring ownership to FEC.
2. A dma_wmb() is also added after updating the bdp to ensure these
updates are visible before updating txq->bd.cur.
3. Start the xmit of the frame immediately right after configuring the
tx descriptor.
Fixes: 6d6b39f180b8 ("net: fec: add initial XDP support")
Signed-off-by: Shenwei Wang <shenwei.wang@nxp.com>
---
v3:
- use the lightweight memory barrier dma_wmb.
v2:
- update the inline comments for 2nd wmb per Wei Fang's review.
drivers/net/ethernet/freescale/fec_main.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)
diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index 6d0b46c76924..a5096c3cac01 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -3834,6 +3834,11 @@ static int fec_enet_txq_xmit_frame(struct fec_enet_private *fep,
index = fec_enet_get_bd_index(last_bdp, &txq->bd);
txq->tx_skbuff[index] = NULL;
+ /* Make sure the updates to rest of the descriptor are performed before
+ * transferring ownership.
+ */
+ dma_wmb();
+
/* Send it on its way. Tell FEC it's ready, interrupt when done,
* it's the last BD of the frame, and to put the CRC on the end.
*/
@@ -3843,8 +3848,14 @@ static int fec_enet_txq_xmit_frame(struct fec_enet_private *fep,
/* If this was the last BD in the ring, start at the beginning again. */
bdp = fec_enet_get_nextdesc(last_bdp, &txq->bd);
+ /* Make sure the update to bdp are performed before txq->bd.cur. */
+ dma_wmb();
+
txq->bd.cur = bdp;
+ /* Trigger transmission start */
+ writel(0, txq->bd.reg_desc_active);
+
return 0;
}
@@ -3873,12 +3884,6 @@ static int fec_enet_xdp_xmit(struct net_device *dev,
sent_frames++;
}
- /* Make sure the update to bdp and tx_skbuff are performed. */
- wmb();
-
- /* Trigger transmission start */
- writel(0, txq->bd.reg_desc_active);
-
__netif_tx_unlock(nq);
return sent_frames;
--
2.34.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* RE: [PATCH v3 net] net: fec: add dma_wmb to ensure correct descriptor values
2023-05-18 15:02 [PATCH v3 net] net: fec: add dma_wmb to ensure correct descriptor values Shenwei Wang
@ 2023-05-19 1:33 ` Wei Fang
2023-05-20 4:51 ` Jakub Kicinski
1 sibling, 0 replies; 3+ messages in thread
From: Wei Fang @ 2023-05-19 1:33 UTC (permalink / raw
To: Shenwei Wang, David S. Miller, Eric Dumazet, Jakub Kicinski,
Paolo Abeni, Simon Horman, Horatiu Vultur, Heiner Kallweit
Cc: Clark Wang, dl-linux-imx, netdev@vger.kernel.org,
imx@lists.linux.dev
> -----Original Message-----
> From: Shenwei Wang <shenwei.wang@nxp.com>
> Sent: 2023年5月18日 23:02
> To: Wei Fang <wei.fang@nxp.com>; David S. Miller <davem@davemloft.net>;
> Eric Dumazet <edumazet@google.com>; Jakub Kicinski <kuba@kernel.org>;
> Paolo Abeni <pabeni@redhat.com>; Simon Horman <horms@kernel.org>;
> Horatiu Vultur <horatiu.vultur@microchip.com>; Heiner Kallweit
> <hkallweit1@gmail.com>
> Cc: Shenwei Wang <shenwei.wang@nxp.com>; Clark Wang
> <xiaoning.wang@nxp.com>; dl-linux-imx <linux-imx@nxp.com>;
> netdev@vger.kernel.org; imx@lists.linux.dev
> Subject: [PATCH v3 net] net: fec: add dma_wmb to ensure correct descriptor
> values
>
> Two dma_wmb() are added in the XDP TX path to ensure proper ordering of
> descriptor and buffer updates:
> 1. A dma_wmb() is added after updating the last BD to make sure
> the updates to rest of the descriptor are visible before
> transferring ownership to FEC.
> 2. A dma_wmb() is also added after updating the bdp to ensure these
> updates are visible before updating txq->bd.cur.
> 3. Start the xmit of the frame immediately right after configuring the
> tx descriptor.
>
> Fixes: 6d6b39f180b8 ("net: fec: add initial XDP support")
> Signed-off-by: Shenwei Wang <shenwei.wang@nxp.com>
> ---
> v3:
> - use the lightweight memory barrier dma_wmb.
>
> v2:
> - update the inline comments for 2nd wmb per Wei Fang's review.
>
> drivers/net/ethernet/freescale/fec_main.c | 17 +++++++++++------
> 1 file changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/ethernet/freescale/fec_main.c
> b/drivers/net/ethernet/freescale/fec_main.c
> index 6d0b46c76924..a5096c3cac01 100644
> --- a/drivers/net/ethernet/freescale/fec_main.c
> +++ b/drivers/net/ethernet/freescale/fec_main.c
> @@ -3834,6 +3834,11 @@ static int fec_enet_txq_xmit_frame(struct
> fec_enet_private *fep,
> index = fec_enet_get_bd_index(last_bdp, &txq->bd);
> txq->tx_skbuff[index] = NULL;
>
> + /* Make sure the updates to rest of the descriptor are performed before
> + * transferring ownership.
> + */
> + dma_wmb();
> +
> /* Send it on its way. Tell FEC it's ready, interrupt when done,
> * it's the last BD of the frame, and to put the CRC on the end.
> */
> @@ -3843,8 +3848,14 @@ static int fec_enet_txq_xmit_frame(struct
> fec_enet_private *fep,
> /* If this was the last BD in the ring, start at the beginning again. */
> bdp = fec_enet_get_nextdesc(last_bdp, &txq->bd);
>
> + /* Make sure the update to bdp are performed before txq->bd.cur. */
> + dma_wmb();
> +
> txq->bd.cur = bdp;
>
> + /* Trigger transmission start */
> + writel(0, txq->bd.reg_desc_active);
> +
> return 0;
> }
>
> @@ -3873,12 +3884,6 @@ static int fec_enet_xdp_xmit(struct net_device
> *dev,
> sent_frames++;
> }
>
> - /* Make sure the update to bdp and tx_skbuff are performed. */
> - wmb();
> -
> - /* Trigger transmission start */
> - writel(0, txq->bd.reg_desc_active);
> -
> __netif_tx_unlock(nq);
>
> return sent_frames;
> --
> 2.34.1
Reviewed-by: Wei Fang <wei.fang@nxp.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v3 net] net: fec: add dma_wmb to ensure correct descriptor values
2023-05-18 15:02 [PATCH v3 net] net: fec: add dma_wmb to ensure correct descriptor values Shenwei Wang
2023-05-19 1:33 ` Wei Fang
@ 2023-05-20 4:51 ` Jakub Kicinski
1 sibling, 0 replies; 3+ messages in thread
From: Jakub Kicinski @ 2023-05-20 4:51 UTC (permalink / raw
To: Shenwei Wang
Cc: Wei Fang, David S. Miller, Eric Dumazet, Paolo Abeni,
Simon Horman, Horatiu Vultur, Heiner Kallweit, Clark Wang,
NXP Linux Team, netdev, imx
On Thu, 18 May 2023 10:02:02 -0500 Shenwei Wang wrote:
> Two dma_wmb() are added in the XDP TX path to ensure proper ordering of
> descriptor and buffer updates:
> 1. A dma_wmb() is added after updating the last BD to make sure
> the updates to rest of the descriptor are visible before
> transferring ownership to FEC.
> 2. A dma_wmb() is also added after updating the bdp to ensure these
> updates are visible before updating txq->bd.cur.
> 3. Start the xmit of the frame immediately right after configuring the
> tx descriptor.
>
> Fixes: 6d6b39f180b8 ("net: fec: add initial XDP support")
> Signed-off-by: Shenwei Wang <shenwei.wang@nxp.com>
Applied, thanks (commit 9025944fddfed).
^ permalink raw reply [flat|nested] 3+ messages in thread
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