| Message ID | 20231221-new-gemini-ethernet-regression-v3-1-a96b4374bfe8@linaro.org (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | Fix a regression in the Gemini ethernet controller. | expand |
On Thu, Dec 21, 2023 at 1:02 AM Linus Walleij <linus.walleij@linaro.org> wrote: > > The recent change to allow large frames without hardware checksumming > slotted in software checksumming in the driver if hardware could not > do it. > > This will however upset TSO (TCP Segment Offloading). Typical > error dumps includes this: > > skb len=2961 headroom=222 headlen=66 tailroom=0 > (...) > WARNING: CPU: 0 PID: 956 at net/core/dev.c:3259 skb_warn_bad_offload+0x7c/0x108 > gemini-ethernet-port: caps=(0x0000010000154813, 0x00002007ffdd7889) > > And the packets do not go through. > > After investigating I drilled it down to the introduction of the > software checksumming in the driver. > > Since the segmenting of packets will be done by the hardware this > makes a bit of sense since in that case the hardware also needs to > be keeping track of the checksumming. > > That begs the question why large TCP or UDP packets also have to > bypass the checksumming (like e.g. ICMP does). If the hardware is > splitting it into smaller packets per-MTU setting, and checksumming > them, why is this happening then? I don't know. I know it is needed, > from tests: the OpenWrt webserver uhttpd starts sending big skb:s (up > to 2047 bytes, the max MTU) and above 1514 bytes it starts to fail > and hang unless the bypass bit is set: the frames are not getting > through. > > Drop the size check and the offloading features for now: this > needs to be fixed up properly. > > Suggested-by: Eric Dumazet <edumazet@google.com> > Fixes: d4d0c5b4d279 ("net: ethernet: cortina: Handle large frames") > Signed-off-by: Linus Walleij <linus.walleij@linaro.org> > --- > drivers/net/ethernet/cortina/gemini.c | 21 ++------------------- > 1 file changed, 2 insertions(+), 19 deletions(-) > > diff --git a/drivers/net/ethernet/cortina/gemini.c b/drivers/net/ethernet/cortina/gemini.c > index 78287cfcbf63..ecc247acac39 100644 > --- a/drivers/net/ethernet/cortina/gemini.c > +++ b/drivers/net/ethernet/cortina/gemini.c > @@ -79,8 +79,7 @@ MODULE_PARM_DESC(debug, "Debug level (0=none,...,16=all)"); > #define GMAC0_IRQ4_8 (GMAC0_MIB_INT_BIT | GMAC0_RX_OVERRUN_INT_BIT) > > #define GMAC_OFFLOAD_FEATURES (NETIF_F_SG | NETIF_F_IP_CSUM | \ > - NETIF_F_IPV6_CSUM | NETIF_F_RXCSUM | \ > - NETIF_F_TSO | NETIF_F_TSO_ECN | NETIF_F_TSO6) > + NETIF_F_IPV6_CSUM | NETIF_F_RXCSUM) > > /** > * struct gmac_queue_page - page buffer per-page info > @@ -1145,7 +1144,6 @@ static int gmac_map_tx_bufs(struct net_device *netdev, struct sk_buff *skb, > dma_addr_t mapping; > unsigned short mtu; > void *buffer; > - int ret; > > mtu = ETH_HLEN; > mtu += netdev->mtu; I suggested removing all this business with mtu. A driver is not supposed to double check the upper layer is giving a too big packet. I think this code was 'trying' to implement TSO in a very wrong way. If a patch removes TSO, it should also remove this dead code... > @@ -1160,22 +1158,7 @@ static int gmac_map_tx_bufs(struct net_device *netdev, struct sk_buff *skb, > word3 |= mtu; > } > > - if (skb->len >= ETH_FRAME_LEN) { > - /* Hardware offloaded checksumming isn't working on frames > - * bigger than 1514 bytes. A hypothesis about this is that the > - * checksum buffer is only 1518 bytes, so when the frames get > - * bigger they get truncated, or the last few bytes get > - * overwritten by the FCS. > - * > - * Just use software checksumming and bypass on bigger frames. > - */ > - if (skb->ip_summed == CHECKSUM_PARTIAL) { > - ret = skb_checksum_help(skb); > - if (ret) > - return ret; > - } > - word1 |= TSS_BYPASS_BIT; > - } else if (skb->ip_summed == CHECKSUM_PARTIAL) { > + if (skb->ip_summed == CHECKSUM_PARTIAL) { > int tcp = 0; > > /* We do not switch off the checksumming on non TCP/UDP > > -- > 2.34.1 >
diff --git a/drivers/net/ethernet/cortina/gemini.c b/drivers/net/ethernet/cortina/gemini.c index 78287cfcbf63..ecc247acac39 100644 --- a/drivers/net/ethernet/cortina/gemini.c +++ b/drivers/net/ethernet/cortina/gemini.c @@ -79,8 +79,7 @@ MODULE_PARM_DESC(debug, "Debug level (0=none,...,16=all)"); #define GMAC0_IRQ4_8 (GMAC0_MIB_INT_BIT | GMAC0_RX_OVERRUN_INT_BIT) #define GMAC_OFFLOAD_FEATURES (NETIF_F_SG | NETIF_F_IP_CSUM | \ - NETIF_F_IPV6_CSUM | NETIF_F_RXCSUM | \ - NETIF_F_TSO | NETIF_F_TSO_ECN | NETIF_F_TSO6) + NETIF_F_IPV6_CSUM | NETIF_F_RXCSUM) /** * struct gmac_queue_page - page buffer per-page info @@ -1145,7 +1144,6 @@ static int gmac_map_tx_bufs(struct net_device *netdev, struct sk_buff *skb, dma_addr_t mapping; unsigned short mtu; void *buffer; - int ret; mtu = ETH_HLEN; mtu += netdev->mtu; @@ -1160,22 +1158,7 @@ static int gmac_map_tx_bufs(struct net_device *netdev, struct sk_buff *skb, word3 |= mtu; } - if (skb->len >= ETH_FRAME_LEN) { - /* Hardware offloaded checksumming isn't working on frames - * bigger than 1514 bytes. A hypothesis about this is that the - * checksum buffer is only 1518 bytes, so when the frames get - * bigger they get truncated, or the last few bytes get - * overwritten by the FCS. - * - * Just use software checksumming and bypass on bigger frames. - */ - if (skb->ip_summed == CHECKSUM_PARTIAL) { - ret = skb_checksum_help(skb); - if (ret) - return ret; - } - word1 |= TSS_BYPASS_BIT; - } else if (skb->ip_summed == CHECKSUM_PARTIAL) { + if (skb->ip_summed == CHECKSUM_PARTIAL) { int tcp = 0; /* We do not switch off the checksumming on non TCP/UDP
The recent change to allow large frames without hardware checksumming slotted in software checksumming in the driver if hardware could not do it. This will however upset TSO (TCP Segment Offloading). Typical error dumps includes this: skb len=2961 headroom=222 headlen=66 tailroom=0 (...) WARNING: CPU: 0 PID: 956 at net/core/dev.c:3259 skb_warn_bad_offload+0x7c/0x108 gemini-ethernet-port: caps=(0x0000010000154813, 0x00002007ffdd7889) And the packets do not go through. After investigating I drilled it down to the introduction of the software checksumming in the driver. Since the segmenting of packets will be done by the hardware this makes a bit of sense since in that case the hardware also needs to be keeping track of the checksumming. That begs the question why large TCP or UDP packets also have to bypass the checksumming (like e.g. ICMP does). If the hardware is splitting it into smaller packets per-MTU setting, and checksumming them, why is this happening then? I don't know. I know it is needed, from tests: the OpenWrt webserver uhttpd starts sending big skb:s (up to 2047 bytes, the max MTU) and above 1514 bytes it starts to fail and hang unless the bypass bit is set: the frames are not getting through. Drop the size check and the offloading features for now: this needs to be fixed up properly. Suggested-by: Eric Dumazet <edumazet@google.com> Fixes: d4d0c5b4d279 ("net: ethernet: cortina: Handle large frames") Signed-off-by: Linus Walleij <linus.walleij@linaro.org> --- drivers/net/ethernet/cortina/gemini.c | 21 ++------------------- 1 file changed, 2 insertions(+), 19 deletions(-)