| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <CALs4sv2PWbijor=7aU4oh=yipYo2OMD79wMqEGfj3c4Lw9uycA@mail.gmail.com>
Date: Fri, 29 Oct 2021 10:34:50 +0530
From: Pavan Chebbi <pavan.chebbi@...adcom.com>
To: Vitaly Bursov <vitaly@...sov.com>
Cc: Siva Reddy Kallam <siva.kallam@...adcom.com>,
Prashant Sreedharan <prashant@...adcom.com>,
Michael Chan <mchan@...adcom.com>,
Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: tg3 RX packet re-order in queue 0 with RSS
90On Thu, Oct 28, 2021 at 9:11 PM Vitaly Bursov <vitaly@...sov.com> wrote:
>
>
> 28.10.2021 10:33, Pavan Chebbi wrote:
> > On Wed, Oct 27, 2021 at 4:02 PM Vitaly Bursov <vitaly@...sov.com> wrote:
> >>
> >>
> >> 27.10.2021 12:30, Pavan Chebbi wrote:
> >>> On Wed, Sep 22, 2021 at 12:10 PM Siva Reddy Kallam
> >>> <siva.kallam@...adcom.com> wrote:
> >>>>
> >>>> Thank you for reporting this. Pavan(cc'd) from Broadcom looking into this issue.
> >>>> We will provide our feedback very soon on this.
> >>>>
> >>>> On Mon, Sep 20, 2021 at 6:59 PM Vitaly Bursov <vitaly@...sov.com> wrote:
> >>>>>
> >>>>> Hi,
> >>>>>
> >>>>> We found a occassional and random (sometimes happens, sometimes not)
> >>>>> packet re-order when NIC is involved in UDP multicast reception, which
> >>>>> is sensitive to a packet re-order. Network capture with tcpdump
> >>>>> sometimes shows the packet re-order, sometimes not (e.g. no re-order on
> >>>>> a host, re-order in a container at the same time). In a pcap file
> >>>>> re-ordered packets have a correct timestamp - delayed packet had a more
> >>>>> earlier timestamp compared to a previous packet:
> >>>>> 1.00s packet1
> >>>>> 1.20s packet3
> >>>>> 1.10s packet2
> >>>>> 1.30s packet4
> >>>>>
> >>>>> There's about 300Mbps of traffic on this NIC, and server is busy
> >>>>> (hyper-threading enabled, about 50% overall idle) with its
> >>>>> computational application work.
> >>>>>
> >>>>> NIC is HPE's 4-port 331i adapter - BCM5719, in a default ring and
> >>>>> coalescing configuration, 1 TX queue, 4 RX queues.
> >>>>>
> >>>>> After further investigation, I believe that there are two separate
> >>>>> issues in tg3.c driver. Issues can be reproduced with iperf3, and
> >>>>> unicast UDP.
> >>>>>
> >>>>> Here are the details of how I understand this behavior.
> >>>>>
> >>>>> 1. Packet re-order.
> >>>>>
> >>>>> Driver calls napi_schedule(&tnapi->napi) when handling the interrupt,
> >>>>> however, sometimes it calls napi_schedule(&tp->napi[1].napi), which
> >>>>> handles RX queue 0 too:
> >>>>>
> >>>>> https://github.com/torvalds/linux/blob/master/drivers/net/ethernet/broadcom/tg3.c#L6802-L7007
> >>>>>
> >>>>> static int tg3_rx(struct tg3_napi *tnapi, int budget)
> >>>>> {
> >>>>> struct tg3 *tp = tnapi->tp;
> >>>>>
> >>>>> ...
> >>>>>
> >>>>> /* Refill RX ring(s). */
> >>>>> if (!tg3_flag(tp, ENABLE_RSS)) {
> >>>>> ....
> >>>>> } else if (work_mask) {
> >>>>> ...
> >>>>>
> >>>>> if (tnapi != &tp->napi[1]) {
> >>>>> tp->rx_refill = true;
> >>>>> napi_schedule(&tp->napi[1].napi);
> >>>>> }
> >>>>> }
> >>>>> ...
> >>>>> }
> >>>>>
> >>>>> From napi_schedule() code, it should schedure RX 0 traffic handling on
> >>>>> a current CPU, which handles queues RX1-3 right now.
> >>>>>
> >>>>> At least two traffic flows are required - one on RX queue 0, and the
> >>>>> other on any other queue (1-3). Re-ordering may happend only on flow
> >>>>> from queue 0, the second flow will work fine.
> >>>>>
> >>>>> No idea how to fix this.
> >>>
> >>> In the case of RSS the actual rings for RX are from 1 to 4.
> >>> The napi of those rings are indeed processing the packets.
> >>> The explicit napi_schedule of napi[1] is only re-filling rx BD
> >>> producer ring because it is shared with return rings for 1-4.
> >>> I tried to repro this but I am not seeing the issue. If you are
> >>> receiving packets on RX 0 then the RSS must have been disabled.
> >>> Can you please check?
> >>>
> >>
> >> # ethtool -i enp2s0f0
> >> driver: tg3
> >> version: 3.137
> >> firmware-version: 5719-v1.46 NCSI v1.5.18.0
> >> expansion-rom-version:
> >> bus-info: 0000:02:00.0
> >> supports-statistics: yes
> >> supports-test: yes
> >> supports-eeprom-access: yes
> >> supports-register-dump: yes
> >> supports-priv-flags: no
> >>
> >> # ethtool -l enp2s0f0
> >> Channel parameters for enp2s0f0:
> >> Pre-set maximums:
> >> RX: 4
> >> TX: 4
> >> Other: 0
> >> Combined: 0
> >> Current hardware settings:
> >> RX: 4
> >> TX: 1
> >> Other: 0
> >> Combined: 0
> >>
> >> # ethtool -x enp2s0f0
> >> RX flow hash indirection table for enp2s0f0 with 4 RX ring(s):
> >> 0: 0 1 2 3 0 1 2 3
> >> 8: 0 1 2 3 0 1 2 3
> >> 16: 0 1 2 3 0 1 2 3
> >> 24: 0 1 2 3 0 1 2 3
> >> 32: 0 1 2 3 0 1 2 3
> >> 40: 0 1 2 3 0 1 2 3
> >> 48: 0 1 2 3 0 1 2 3
> >> 56: 0 1 2 3 0 1 2 3
> >> 64: 0 1 2 3 0 1 2 3
> >> 72: 0 1 2 3 0 1 2 3
> >> 80: 0 1 2 3 0 1 2 3
> >> 88: 0 1 2 3 0 1 2 3
> >> 96: 0 1 2 3 0 1 2 3
> >> 104: 0 1 2 3 0 1 2 3
> >> 112: 0 1 2 3 0 1 2 3
> >> 120: 0 1 2 3 0 1 2 3
> >> RSS hash key:
> >> Operation not supported
> >> RSS hash function:
> >> toeplitz: on
> >> xor: off
> >> crc32: off
> >>
> >> In /proc/interrupts there are enp2s0f0-tx-0, enp2s0f0-rx-1,
> >> enp2s0f0-rx-2, enp2s0f0-rx-3, enp2s0f0-rx-4 interrupts, all on
> >> different CPU cores. Kernel also has "threadirqs" enabled in
> >> command line, I didn't check if this parameter affects the issue.
> >>
> >> Yes, some things start with 0, and others with 1, sorry for a confusion
> >> in terminology, what I meant:
> >> - There are 4 RX rings/queues, I counted starting from 0, so: 0..3.
> >> RX0 is the first queue/ring that actually receives the traffic.
> >> RX0 is handled by enp2s0f0-rx-1 interrupt.
> >> - These are related to (tp->napi[i]), but i is in 1..4, so the first
> >> receiving queue relates to tp->napi[1], the second relates to
> >> tp->napi[2], and so on. Correct?
> >>
> >> Suppose, tg3_rx() is called for tp->napi[2], this function most likely
> >> calls napi_gro_receive(&tnapi->napi, skb) to further process packets in
> >> tp->napi[2]. And, under some conditions (RSS and work_mask), it calls
> >> napi_schedule(&tp->napi[1].napi), which schedules tp->napi[1] work
> >> on a currect CPU, which is designated for tp->napi[2], but not for
> >> tp->napi[1]. Correct?
> >>
> >> I don't understand what napi_schedule(&tp->napi[1].napi) does for the
> >> NIC or driver, "re-filling rx BD producer ring" sounds important. I
> >> suspect something will break badly if I simply remove it without
> >> replacing with something more elaborate. I guess along with re-filling
> >> rx BD producer ring it also can process incoming packets. Is it possible?
> >>
> >
> > Yes, napi[1] work may be called on the napi[2]'s CPU but it generally
> > won't process
> > any rx packets because the producer index of napi[1] has not changed. If the
> > producer count did change, then we get a poll from the ISR for napi[1]
> > to process
> > packets. So it is mostly used to re-fill rx buffers when called
> > explicitly. However
> > there could be a small window where the prod index is incremented but the ISR
> > is not fired yet. It may process some small no of packets. But I don't
> > think this
> > should lead to a reorder problem.
> >
>
> I tried to reproduce without using bridge and veth interfaces, and it seems
> like it's not reproducible, so traffic forwarding via a bridge interface may
> be necessary. It also does not happen if traffic load is low, but moderate
> load is enough - e.g. two 100 Mbps streams with 130-byte packets. It's easier
> to reproduce with a higher load.
>
> With about the same setup as in an original message (bridge + veth 2
> network namespaces), irqbalance daemon stopped, if traffic flows via
> enp2s0f0-rx-2 and enp2s0f0-rx-4, there's no reordering. enp2s0f0-rx-1
> still gets some interrupts, but at a much lower rate compared to 2 and
> 4.
>
> namespace 1:
> # iperf3 -u -c server_ip -p 5000 -R -b 300M -t 300 -l 130
> - - - - - - - - - - - - - - - - - - - - - - - - -
> [ ID] Interval Transfer Bandwidth Jitter Lost/Total Datagrams
> [ 4] 0.00-300.00 sec 6.72 GBytes 192 Mbits/sec 0.008 ms 3805/55508325 (0.0069%)
> [ 4] Sent 55508325 datagrams
>
> iperf Done.
>
> namespace 2:
> # iperf3 -u -c server_ip -p 5001 -R -b 300M -t 300 -l 130
> - - - - - - - - - - - - - - - - - - - - - - - - -
> [ ID] Interval Transfer Bandwidth Jitter Lost/Total Datagrams
> [ 4] 0.00-300.00 sec 6.83 GBytes 196 Mbits/sec 0.005 ms 3873/56414001 (0.0069%)
> [ 4] Sent 56414001 datagrams
>
> iperf Done.
>
>
> With the same configuration but different IP address so that instead of
> enp2s0f0-rx-4 enp2s0f0-rx-1 would be used, there is a reordering.
>
>
> namespace 1 (client IP was changed):
> # iperf3 -u -c server_ip -p 5000 -R -b 300M -t 300 -l 130
> - - - - - - - - - - - - - - - - - - - - - - - - -
> [ ID] Interval Transfer Bandwidth Jitter Lost/Total Datagrams
> [ 4] 0.00-300.00 sec 6.32 GBytes 181 Mbits/sec 0.007 ms 8506/52172059 (0.016%)
> [ 4] Sent 52172059 datagrams
> [SUM] 0.0-300.0 sec 2452 datagrams received out-of-order
>
> iperf Done.
>
> namespace 2:
> # iperf3 -u -c server_ip -p 5001 -R -b 300M -t 300 -l 130
> - - - - - - - - - - - - - - - - - - - - - - - - -
> [ ID] Interval Transfer Bandwidth Jitter Lost/Total Datagrams
> [ 4] 0.00-300.00 sec 6.59 GBytes 189 Mbits/sec 0.006 ms 6302/54463973 (0.012%)
> [ 4] Sent 54463973 datagrams
>
> iperf Done.
>
> Swapping IP addresses in these namespaces also changes the namespace exhibiting the issue,
> it's following the IP address.
>
>
> Is there something I could check to confirm that this behavior is or is not
> related to napi_schedule(&tp->napi[1].napi) call?
in the function tg3_msi_1shot() you could store the cpu assigned to
tnapi1 (inside the struct tg3_napi)
and then in tg3_poll_work() you can add another check after
if (*(tnapi->rx_rcb_prod_idx) != tnapi->rx_rcb_ptr)
something like
if (tnapi == &tp->napi[1] && tnapi->assigned_cpu == smp_processor_id())
only then execute tg3_rx()
This may stop tnapi 1 from reading rx pkts on the current CPU from
which refill is called.
>
> --
> Thanks
> Vitalii
Powered by blists - more mailing lists