From mboxrd@z Thu Jan 1 00:00:00 1970 From: Prashant Sreedharan Subject: Re: [PATCH] tg3: Work around HW/FW limitations with vlan encapsulated frames Date: Fri, 19 Sep 2014 13:54:53 -0700 Message-ID: <1411160093.6401.30.camel@prashant> References: <1411050677-28147-1-git-send-email-vyasevic@redhat.com> <1411081221.18724.84.camel@prashant> <541C36CC.60405@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Vladislav Yasevich , , Michael Chan To: Return-path: Received: from mail-gw1-out.broadcom.com ([216.31.210.62]:9876 "EHLO mail-gw1-out.broadcom.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757837AbaISVPh (ORCPT ); Fri, 19 Sep 2014 17:15:37 -0400 In-Reply-To: <541C36CC.60405@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, 2014-09-19 at 09:59 -0400, Vlad Yasevich wrote: > On 09/18/2014 07:00 PM, Prashant Sreedharan wrote: > > On Thu, 2014-09-18 at 10:31 -0400, Vladislav Yasevich wrote: > >> TG3 appears to have an issue performing TSO and checksum offloading > >> correclty when the frame has been vlan encapsulated (non-accelrated). > >> In these cases, tcp checksum is not correctly updated. > > > > Yes that is true for inline vlan headers, to clarify was TSO and > > checksum offload working for accelerated 802.1ad packets ? > > We don't accelerate 802.1ad if the driver doesn't claim offload support. > If I had to guess, the TSO would probably work, but the packet would > be encapsulated as 802.1Q by the FW/HW and connection would fail. > In your initial mail you mentioned when you strip the vlan header and set vlan_tci it worked for you. But as you guessed it will not, as the chip does not support 802.1AD. Thanks for clarifying. > > > >> This patch attempts to work around this issue. After the patch, > >> 802.1ad vlans start working correctly over tg3 devices. > >> > >> CC: Prashant Sreedharan > >> CC: Michael Chan > >> Signed-off-by: Vladislav Yasevich > >> --- > >> drivers/net/ethernet/broadcom/tg3.c | 20 ++++++++++++++++++-- > >> 1 file changed, 18 insertions(+), 2 deletions(-) > >> > >> diff --git a/drivers/net/ethernet/broadcom/tg3.c b/drivers/net/ethernet/broadcom/tg3.c > >> index cb77ae9..e7d3a62 100644 > >> --- a/drivers/net/ethernet/broadcom/tg3.c > >> +++ b/drivers/net/ethernet/broadcom/tg3.c > >> @@ -7914,8 +7914,6 @@ static netdev_tx_t tg3_start_xmit(struct sk_buff *skb, struct net_device *dev) > >> > >> entry = tnapi->tx_prod; > >> base_flags = 0; > >> - if (skb->ip_summed == CHECKSUM_PARTIAL) > >> - base_flags |= TXD_FLAG_TCPUDP_CSUM; Check comment below > >> > >> mss = skb_shinfo(skb)->gso_size; > >> if (mss) { > >> @@ -7929,6 +7927,13 @@ static netdev_tx_t tg3_start_xmit(struct sk_buff *skb, struct net_device *dev) > >> > >> hdr_len = skb_transport_offset(skb) + tcp_hdrlen(skb) - ETH_HLEN; > >> > >> + /* HW/FW can not correctly segment packets that have been > >> + * vlan encapsulated. > >> + */ > >> + if (skb->protocol == htons(ETH_P_8021Q) || > >> + skb->protocol == htons(ETH_P_8021AD)) > >> + return tg3_tso_bug(tp, tnapi, txq, skb); > > > > I think skb_gso_segment() would return skbs that would still have > > checksum offloaded to the chip. > > Doesn't appear to. If I don't do this, then netperf throughput drops > to 45.75 Mbps. If I put the above back in, the throughput goes to to 940Mbps. > Two things either the skb is having the "encap_hdr_csum" set forcing skb_segment() to do the checksum calculation OR the second workaround "skb_checksum_help" below will do the checksum for the list of skbs returned by skb_gso_segment(). Also you can move the above workaround further up after skb_cow_head() succeeds. > > > >> + > >> if (!skb_is_gso_v6(skb)) { > >> if (unlikely((ETH_HLEN + hdr_len) > 80) && > >> tg3_flag(tp, TSO_BUG)) > >> @@ -7979,6 +7984,17 @@ static netdev_tx_t tg3_start_xmit(struct sk_buff *skb, struct net_device *dev) > >> base_flags |= tsflags << 12; > >> } > >> } > >> + } else if (skb->ip_summed == CHECKSUM_PARTIAL) { > >> + /* HW/FW can not correctly checksum packets that have been > >> + * vlan encapsulated. > >> + */ > >> + if (skb->protocol == htons(ETH_P_8021Q) || > >> + skb->protocol == htons(ETH_P_8021AD)) { > >> + if (skb_checksum_help(skb)) > >> + goto drop; > >> + } else { > >> + base_flags |= TXD_FLAG_TCPUDP_CSUM; > >> + } tg3 supports various family of chips (around 20+ )I need to check if LSO offload is ok without setting TXD_FLAG_TCPUDP_CSUM for all of them and some of these chips are pretty old too, so instead you can clear the TXD_FLAG_TCPUDP_CSUM flag if skb_checksum_help() succeeds and leave the initial setting of base_flags as it is thus avoiding any regressions. > >> } > >> > >> if (tg3_flag(tp, USE_JUMBO_BDFLAG) && > > > > Instead of the above workarounds since the chips supported by tg3 does > > not support checksum offload and TSO for inline vlan headers, these > > features can be disabled/cleared in dev->vlan_features. Side effect is > > accelerated vlan headers will also have TSO and checksum offload > > disabled. > > I didn't want to impact normal accelerated usage. The non-accelerated > case is rather rare especially since tg3 driver doesn't allow you to > turn off vlan acceleration. One has to put a software device between > tg3 and vlan that allow you to turn off vlan acceleration (ex: bridge) > and turn off acceleration on the bridge to get this to happen for 802.1Q > vlans. People don't normally turn off vlan acceleration though as evidenced > by this bug (and issues in other drivers) being around for a _very_ long time. > Ok, since this is rare we can go with the workaround > > > > Also as part of this review, found a problem with the receive section of > > the driver it was not checking for 802.1ad vlan protocol and dropping > > 802.1ad vlan packets of size > mtu + ETH_HLEN > > Good catch. I should have run the TCP_MAERTS test. :) > > I'll update the patch with the below hunk and resubmit if we can agree > on using the tg3_tso_bug workaround. yes please include. thanks. > > -vlad > > > > > diff --git a/drivers/net/ethernet/broadcom/tg3.c > > b/drivers/net/ethernet/broadcom/tg3.c > > index cb77ae9..620887a 100644 > > --- a/drivers/net/ethernet/broadcom/tg3.c > > +++ b/drivers/net/ethernet/broadcom/tg3.c > > @@ -6918,7 +6918,8 @@ static int tg3_rx(struct tg3_napi *tnapi, int > > budget) > > skb->protocol = eth_type_trans(skb, tp->dev); > > > > if (len > (tp->dev->mtu + ETH_HLEN) && > > - skb->protocol != htons(ETH_P_8021Q)) { > > + skb->protocol != htons(ETH_P_8021Q) && > > + skb->protocol != htons(ETH_P_8021AD)) { > > dev_kfree_skb_any(skb); > > goto drop_it_no_recycle; > > } > > > > >