Arınç reports that on his MT7621AT Unielec U7621-06 board and MT7623NI
Bananapi BPI-R2, packets received by the CPU over mt7530 switch port 0
(of which this driver acts as the DSA master) are not processed
correctly by software. More precisely, they arrive without a DSA tag
(in packet or in the hwaccel area - skb_metadata_dst()), so DSA cannot
demux them towards the switch's interface for port 0. Traffic from other
ports receives a skb_metadata_dst() with the correct port and is demuxed
properly.
Looking at mtk_poll_rx(), it becomes apparent that this driver uses the
skb vlan hwaccel area:
union {
u32 vlan_all;
struct {
__be16 vlan_proto;
__u16 vlan_tci;
};
};
as a temporary storage for the VLAN hwaccel tag, or the DSA hwaccel tag.
If this is a DSA master it's a DSA hwaccel tag, and finally clears up
the skb VLAN hwaccel header.
I'm guessing that the problem is the (mis)use of API.
skb_vlan_tag_present() looks like this:
#define skb_vlan_tag_present(__skb) (!!(__skb)->vlan_all)
So if both vlan_proto and vlan_tci are zeroes, skb_vlan_tag_present()
returns precisely false. I don't know for sure what is the format of the
DSA hwaccel tag, but I surely know that lowermost 3 bits of vlan_proto
are 0 when receiving from port 0:
unsigned int port = vlan_proto & GENMASK(2, 0);
If the RX descriptor has no other bits set to non-zero values in
RX_DMA_VTAG, then the call to __vlan_hwaccel_put_tag() will not, in
fact, make the subsequent skb_vlan_tag_present() return true, because
it's implemented like this:
static inline void __vlan_hwaccel_put_tag(struct sk_buff *skb,
__be16 vlan_proto, u16 vlan_tci)
{
skb->vlan_proto = vlan_proto;
skb->vlan_tci = vlan_tci;
}
What we need to do to fix this problem (assuming this is the problem) is
to stop using skb->vlan_all as temporary storage for driver affairs, and
just create some local variables that serve the same purpose, but
hopefully better. Instead of calling skb_vlan_tag_present(), let's look
at a boolean has_hwaccel_tag which we set to true when the RX DMA
descriptors have something. Disambiguate based on netdev_uses_dsa()
whether this is a VLAN or DSA hwaccel tag, and only call
__vlan_hwaccel_put_tag() if we're certain it's a VLAN tag.
Arınç confirms that the treatment works, so this validates the
assumption.
Link: https://lore.kernel.org/netdev/[email protected]/
Fixes: 2d7605a72906 ("net: ethernet: mtk_eth_soc: enable hardware DSA untagging")
Reported-by: Arınç ÜNAL <[email protected]>
Tested-by: Arınç ÜNAL <[email protected]>
Signed-off-by: Vladimir Oltean <[email protected]>
---
drivers/net/ethernet/mediatek/mtk_eth_soc.c | 24 ++++++++++++---------
1 file changed, 14 insertions(+), 10 deletions(-)
diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
index f1cb1efc94cf..64b575fbe317 100644
--- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
+++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
@@ -1921,7 +1921,9 @@ static int mtk_poll_rx(struct napi_struct *napi, int budget,
while (done < budget) {
unsigned int pktlen, *rxdcsum;
+ bool has_hwaccel_tag = false;
struct net_device *netdev;
+ u16 vlan_proto, vlan_tci;
dma_addr_t dma_addr;
u32 hash, reason;
int mac = 0;
@@ -2061,27 +2063,29 @@ static int mtk_poll_rx(struct napi_struct *napi, int budget,
if (netdev->features & NETIF_F_HW_VLAN_CTAG_RX) {
if (MTK_HAS_CAPS(eth->soc->caps, MTK_NETSYS_V2)) {
- if (trxd.rxd3 & RX_DMA_VTAG_V2)
- __vlan_hwaccel_put_tag(skb,
- htons(RX_DMA_VPID(trxd.rxd4)),
- RX_DMA_VID(trxd.rxd4));
+ if (trxd.rxd3 & RX_DMA_VTAG_V2) {
+ vlan_proto = RX_DMA_VPID(trxd.rxd4);
+ vlan_tci = RX_DMA_VID(trxd.rxd4);
+ has_hwaccel_tag = true;
+ }
} else if (trxd.rxd2 & RX_DMA_VTAG) {
- __vlan_hwaccel_put_tag(skb, htons(RX_DMA_VPID(trxd.rxd3)),
- RX_DMA_VID(trxd.rxd3));
+ vlan_proto = RX_DMA_VPID(trxd.rxd3);
+ vlan_tci = RX_DMA_VID(trxd.rxd3);
+ has_hwaccel_tag = true;
}
}
/* When using VLAN untagging in combination with DSA, the
* hardware treats the MTK special tag as a VLAN and untags it.
*/
- if (skb_vlan_tag_present(skb) && netdev_uses_dsa(netdev)) {
- unsigned int port = ntohs(skb->vlan_proto) & GENMASK(2, 0);
+ if (has_hwaccel_tag && netdev_uses_dsa(netdev)) {
+ unsigned int port = vlan_proto & GENMASK(2, 0);
if (port < ARRAY_SIZE(eth->dsa_meta) &&
eth->dsa_meta[port])
skb_dst_set_noref(skb, ð->dsa_meta[port]->dst);
-
- __vlan_hwaccel_clear_tag(skb);
+ } else if (has_hwaccel_tag) {
+ __vlan_hwaccel_put_tag(skb, htons(vlan_proto), vlan_tci);
}
skb_record_rx_queue(skb, 0);
--
2.34.1
On 07.02.23 11:30, Vladimir Oltean wrote:
> Arınç reports that on his MT7621AT Unielec U7621-06 board and MT7623NI
> Bananapi BPI-R2, packets received by the CPU over mt7530 switch port 0
> (of which this driver acts as the DSA master) are not processed
> correctly by software. More precisely, they arrive without a DSA tag
> (in packet or in the hwaccel area - skb_metadata_dst()), so DSA cannot
> demux them towards the switch's interface for port 0. Traffic from other
> ports receives a skb_metadata_dst() with the correct port and is demuxed
> properly.
>
> Looking at mtk_poll_rx(), it becomes apparent that this driver uses the
> skb vlan hwaccel area:
>
> union {
> u32 vlan_all;
> struct {
> __be16 vlan_proto;
> __u16 vlan_tci;
> };
> };
>
> as a temporary storage for the VLAN hwaccel tag, or the DSA hwaccel tag.
> If this is a DSA master it's a DSA hwaccel tag, and finally clears up
> the skb VLAN hwaccel header.
>
> I'm guessing that the problem is the (mis)use of API.
> skb_vlan_tag_present() looks like this:
>
> #define skb_vlan_tag_present(__skb) (!!(__skb)->vlan_all)
>
> So if both vlan_proto and vlan_tci are zeroes, skb_vlan_tag_present()
> returns precisely false. I don't know for sure what is the format of the
> DSA hwaccel tag, but I surely know that lowermost 3 bits of vlan_proto
> are 0 when receiving from port 0:
>
> unsigned int port = vlan_proto & GENMASK(2, 0);
>
> If the RX descriptor has no other bits set to non-zero values in
> RX_DMA_VTAG, then the call to __vlan_hwaccel_put_tag() will not, in
> fact, make the subsequent skb_vlan_tag_present() return true, because
> it's implemented like this:
>
> static inline void __vlan_hwaccel_put_tag(struct sk_buff *skb,
> __be16 vlan_proto, u16 vlan_tci)
> {
> skb->vlan_proto = vlan_proto;
> skb->vlan_tci = vlan_tci;
> }
>
> What we need to do to fix this problem (assuming this is the problem) is
> to stop using skb->vlan_all as temporary storage for driver affairs, and
> just create some local variables that serve the same purpose, but
> hopefully better. Instead of calling skb_vlan_tag_present(), let's look
> at a boolean has_hwaccel_tag which we set to true when the RX DMA
> descriptors have something. Disambiguate based on netdev_uses_dsa()
> whether this is a VLAN or DSA hwaccel tag, and only call
> __vlan_hwaccel_put_tag() if we're certain it's a VLAN tag.
>
> Arınç confirms that the treatment works, so this validates the
> assumption.
>
> Link: https://lore.kernel.org/netdev/[email protected]/
> Fixes: 2d7605a72906 ("net: ethernet: mtk_eth_soc: enable hardware DSA untagging")
> Reported-by: Arınç ÜNAL <[email protected]>
> Tested-by: Arınç ÜNAL <[email protected]>
> Signed-off-by: Vladimir Oltean <[email protected]>
Reviewed-by: Felix Fietkau <[email protected]>
Hello:
This patch was applied to netdev/net.git (master)
by David S. Miller <[email protected]>:
On Tue, 7 Feb 2023 12:30:27 +0200 you wrote:
> Arınç reports that on his MT7621AT Unielec U7621-06 board and MT7623NI
> Bananapi BPI-R2, packets received by the CPU over mt7530 switch port 0
> (of which this driver acts as the DSA master) are not processed
> correctly by software. More precisely, they arrive without a DSA tag
> (in packet or in the hwaccel area - skb_metadata_dst()), so DSA cannot
> demux them towards the switch's interface for port 0. Traffic from other
> ports receives a skb_metadata_dst() with the correct port and is demuxed
> properly.
>
> [...]
Here is the summary with links:
- [net] net: ethernet: mtk_eth_soc: fix DSA TX tag hwaccel for switch port 0
https://git.kernel.org/netdev/net/c/1a3245fe0cf8
You are awesome, thank you!
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