Message-ID: <OS0PR01MB592261426615D281CD598DF086B79@OS0PR01MB5922.jpnprd01.prod.outlook.com>
Date:   Wed, 13 Oct 2021 06:41:45 +0000
From:   Biju Das <biju.das.jz@...renesas.com>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     "David S. Miller" <davem@...emloft.net>,
        Sergey Shtylyov <s.shtylyov@....ru>,
        Sergei Shtylyov <sergei.shtylyov@...il.com>,
        Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@...renesas.com>,
        Andrew Lunn <andrew@...n.ch>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Adam Ford <aford173@...il.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-renesas-soc@...r.kernel.org>, Chris Paterson
        <Chris.Paterson2@...esas.com>, Biju Das <biju.das@...renesas.com" 
        <linux-renesas-soc@...r.kernel.org>
Subject: RE: [PATCH net-next v3 00/14] Add functional support for Gigabit
 Ethernet driver

Hi Jakub Kicinski,

Thanks for the feedback.

> Subject: Re: [PATCH net-next v3 00/14] Add functional support for Gigabit
> Ethernet driver
> 
> On Tue, 12 Oct 2021 18:53:50 +0000 Biju Das wrote:
> > > > Yes, you are correct. Sergey, suggested use R-Car RX-HW checksum
> > > > with RCSC/RCPT and But the TOE gives either 0x0 or 0xffff as csum
> > > > output and feeding this value to skb->csum lead to kernel crash.
> > >
> > > That's quite concerning. Do you have any of the
> > >
> > > /proc/sys/kernel/panic_on_io_nmi
> > > /proc/sys/kernel/panic_on_oops
> > > /proc/sys/kernel/panic_on_rcu_stall
> > > /proc/sys/kernel/panic_on_unrecovered_nmi
> > > /proc/sys/kernel/panic_on_warn
> > >
> > > knobs set? I'm guessing we hit do_netdev_rx_csum_fault() when the
> > > checksum is incorrect, but I'm surprised that causes a panic.
> >
> > I tested this last week, if I remember correctly It was not panic,
> > rather do_netdev_rx_csum_fault. I will recheck and will send you the
> > stack trace next time.
> 
> Ah, when you say crash you mean a stack trace appears. The machine does
> not crash? That's fine, we don't need to see the trace.

I have rechecked today. It does crash, if you pass bad checksum to skb->csum. Please find the logs.

root@...rc-rzg2l:~# ethtool -K eth0 rx on
Actual changes:
rx-checksum: on
[   34.391956] eth0: hw csum failure
[   34.396044] skb len=168 headroom=142 headlen=168 tailroom=15754
[   34.396044] mac=(128,14) net=(142,20) trans=162
[   34.396044] shinfo(txflags=0 nr_frags=0 gso(size=0 type=0 segs=0))
[   34.396044] csum(0x0 ip_summed=2 complete_sw=0 valid=0 level=0)
[   34.396044] hash(0x0 sw=0 l4=0) proto=0x0800 pkttype=0 iif=0
[   34.425196] dev name=eth0 feat=0x0x0000010000004000
[   34.430231] skb headroom: 00000000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[   34.438064] skb headroom: 00000010: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[   34.445863] skb headroom: 00000020: ff ff ff ff ff ff ff ff ff ff ff fe ff ff ff ff
[   34.453660] skb headroom: 00000030: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[   34.461453] skb headroom: 00000040: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[   34.469246] skb headroom: 00000050: ff ff ff ff ff fe ff ff ff ff ef ff ff ff ff ff
[   34.477038] skb headroom: 00000060: ff ff ff ff ff ff ff ff fd fe ff ff ff ff ff ff
[   34.484831] skb headroom: 00000070: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff f7
[   34.492629] skb headroom: 00000080: 00 11 22 33 44 55 08 00 27 a0 90 eb 08 00
[   34.499895] skb linear:   00000000: 45 00 00 a8 54 06 40 00 40 06 50 f6 c0 a8 0a 01
[   34.507692] skb linear:   00000010: c0 a8 0a 02 08 01 03 0c 1d aa 76 e1 a3 4b 1c d8
[   34.515488] skb linear:   00000020: 80 18 21 55 72 75 00 00 01 01 08 0a da da 94 96
[   34.523283] skb linear:   00000030: b5 fb f1 40 80 00 00 70 d9 4a 86 c0 00 00 00 01
[   34.531078] skb linear:   00000040: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[   34.538873] skb linear:   00000050: 00 00 00 00 00 00 00 05 00 00 01 ff 00 00 00 01
[   34.546668] skb linear:   00000060: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 11
[   34.554462] skb linear:   00000070: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[   34.562260] skb linear:   00000080: 58 9d 6c 79 80 e3 86 f2 00 00 00 00 00 9a 8d 38
[   34.570055] skb linear:   00000090: 61 65 87 ee 22 8c 2f b9 61 4a 17 fb 35 09 00 98
[   34.577850] skb linear:   000000a0: 61 4a 17 fb 35 09 00 98
[   34.583534] skb tailroom: 00000000: 00 00 00 00 21 07 00 b0 63 70 47 f9 42 5f 47 f9
[   34.591329] skb tailroom: 00000010: 21 f8 47 f9 80 74 47 f9 de 60 fc 97 a0 06 00 f9

[   42.262329] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.15.0-rc4-arm64-renesas-01223-g75a50e114cb6-dirty #416
[   42.272370] Hardware name: Renesas SMARC EVK based on r9a07g044l2 (DT)
[   42.278979] Call trace:
[   42.281460]  dump_backtrace+0x0/0x188
[   42.285186]  show_stack+0x14/0x20
[   42.288550]  dump_stack_lvl+0x88/0xb0
[   42.292267]  dump_stack+0x14/0x2c
[   42.295629]  do_netdev_rx_csum_fault+0x44/0x50
[   42.300134]  __skb_gro_checksum_complete+0xb0/0xb8
[   42.304994]  tcp4_gro_receive+0xbc/0x198
[   42.308974]  inet_gro_receive+0x300/0x410
[   42.313039]  dev_gro_receive+0x308/0x898
[   42.317018]  napi_gro_receive+0x88/0x370
[   42.320996]  ravb_rx_gbeth+0x36c/0x568
[   42.324801]  ravb_poll+0xd0/0x278
[   42.328163]  __napi_poll+0x38/0x2e0
[   42.331702]  net_rx_action+0xf4/0x248
[   42.335416]  _stext+0x150/0x5d8
[   42.338604]  irq_exit+0x198/0x1b8
[   42.341970]  handle_domain_irq+0x60/0x88
[   42.345950]  gic_handle_irq+0x50/0x110
[   42.349755]  call_on_irq_stack+0x28/0x3c
[   42.353733]  do_interrupt_handler+0x4c/0x58
[   42.357974]  el1_interrupt+0x2c/0x108
[   42.361688]  el1h_64_irq_handler+0x14/0x20
[   42.365841]  el1h_64_irq+0x74/0x78
[   42.369291]  arch_cpu_idle+0x14/0x20
[   42.372918]  default_idle_call+0x78/0x330
[   42.376984]  do_idle+0x22c/0x278
[   42.380261]  cpu_startup_entry+0x20/0x68
[   42.384239]  rest_init+0x180/0x280
[   42.387689]  arch_call_rest_init+0xc/0x14
[   42.391759]  start_kernel+0x62c/0x664
[   42.395472]  __primary_switched+0xa0/0xa8


Regards,
Biju

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