Subject: Re: stmmac and XDP/ZC issue

From: Maciej Fijalkowski <[email-masked]>
Date: Tue, 20 Feb 2024 15:43:03 +0100

On Tue, Feb 20, 2024 at 04:18:54PM +0300, Serge Semin wrote:
> Hi Kurt
> 
> On Tue, Feb 20, 2024 at 12:02:25PM +0100, Kurt Kanzenbach wrote:
> > Hello netdev community,
> > 
> > after updating to v6.8 kernel I've encountered an issue in the stmmac
> > driver.
> > 
> > I have an application which makes use of XDP zero-copy sockets. It works
> > on v6.7. On v6.8 it results in the stack trace shown below. The program
> > counter points to:
> > 
> >  - ./include/net/xdp_sock.h:192 and
> >  - ./drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:2681
> > 
> > It seems to be caused by the XDP meta data patches. This one in
> > particular 1347b419318d ("net: stmmac: Add Tx HWTS support to XDP ZC").
> > 
> > To reproduce:
> > 
> >  - Hardware: imx93
> >  - Run ptp4l/phc2sys
> >  - Configure Qbv, Rx steering, NAPI threading
> >  - Run my application using XDP/ZC on queue 1
> > 
> > Any idea what might be the issue here?
> > 
> > Thanks,
> > Kurt
> > 
> > Stack trace:
> > 
> > |[  169.248150] imx-dwmac 428a0000.ethernet eth1: configured EST
> > |[  191.820913] imx-dwmac 428a0000.ethernet eth1: EST: SWOL has been switched
> > |[  226.039166] imx-dwmac 428a0000.ethernet eth1: entered promiscuous mode
> > |[  226.203262] imx-dwmac 428a0000.ethernet eth1: Register MEM_TYPE_PAGE_POOL RxQ-0
> > |[  226.203753] imx-dwmac 428a0000.ethernet eth1: Register MEM_TYPE_PAGE_POOL RxQ-1
> > |[  226.303337] imx-dwmac 428a0000.ethernet eth1: Register MEM_TYPE_XSK_BUFF_POOL RxQ-1
> > |[  255.822584] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
> > |[  255.822602] Mem abort info:
> > |[  255.822604]   ESR = 0x0000000096000044
> > |[  255.822608]   EC = 0x25: DABT (current EL), IL = 32 bits
> > |[  255.822613]   SET = 0, FnV = 0
> > |[  255.822616]   EA = 0, S1PTW = 0
> > |[  255.822618]   FSC = 0x04: level 0 translation fault
> > |[  255.822622] Data abort info:
> > |[  255.822624]   ISV = 0, ISS = 0x00000044, ISS2 = 0x00000000
> > |[  255.822627]   CM = 0, WnR = 1, TnD = 0, TagAccess = 0
> > |[  255.822630]   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
> > |[  255.822634] user pgtable: 4k pages, 48-bit VAs, pgdp=0000000085fe1000
> > |[  255.822638] [0000000000000000] pgd=0000000000000000, p4d=0000000000000000
> > |[  255.822650] Internal error: Oops: 0000000096000044 [#1] PREEMPT_RT SMP
> > |[  255.822655] Modules linked in:
> > |[  255.822660] CPU: 0 PID: 751 Comm: napi/eth1-261 Not tainted 6.8.0-rc4-rt4-00100-g9c63d995ca19 #8
> > |[  255.822666] Hardware name: NXP i.MX93 11X11 EVK board (DT)
> > |[  255.822669] pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> > |[  255.822674] pc : stmmac_tx_clean.constprop.0+0x848/0xc38
> > |[  255.822690] lr : stmmac_tx_clean.constprop.0+0x844/0xc38
> > |[  255.822696] sp : ffff800085ec3bc0
> > |[  255.822698] x29: ffff800085ec3bc0 x28: ffff000005b609e0 x27: 0000000000000001
> > |[  255.822706] x26: 0000000000000000 x25: ffff000005b60ae0 x24: 0000000000000001
> > |[  255.822712] x23: 0000000000000001 x22: ffff000005b649e0 x21: 0000000000000000
> > |[  255.822719] x20: 0000000000000020 x19: ffff800085291030 x18: 0000000000000000
> > |[  255.822725] x17: ffff7ffffc51c000 x16: ffff800080000000 x15: 0000000000000008
> > |[  255.822732] x14: ffff80008369b880 x13: 0000000000000000 x12: 0000000000008507
> > |[  255.822738] x11: 0000000000000040 x10: 0000000000000a70 x9 : ffff800080e32f84
> > |[  255.822745] x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000003ff0
> > |[  255.822751] x5 : 0000000000003c40 x4 : ffff000005b60000 x3 : 0000000000000000
> > |[  255.822757] x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000000
> > |[  255.822764] Call trace:
> > |[  255.822766]  stmmac_tx_clean.constprop.0+0x848/0xc38

Shouldn't xsk_tx_metadata_complete() be called only when corresponding
buf_type is STMMAC_TXBUF_T_XSK_TX?

> > |[  255.822772]  stmmac_napi_poll_rxtx+0xc4/0xec0
> > |[  255.822778]  __napi_poll.constprop.0+0x40/0x220
> > |[  255.822785]  napi_threaded_poll+0xd8/0x228
> > |[  255.822790]  kthread+0x108/0x120
> > |[  255.822798]  ret_from_fork+0x10/0x20
> > |[  255.822808] Code: 910303e0 f9003be1 97ffdec0 f9403be1 (f9000020) 
> > |[  255.822812] ---[ end trace 0000000000000000 ]---
> > |[  255.822817] Kernel panic - not syncing: Oops: Fatal exception in interrupt
> > |[  255.822819] SMP: stopping secondary CPUs
> > |[  255.822827] Kernel Offset: disabled
> > |[  255.822829] CPU features: 0x0,c0000000,4002814a,2100720b
> > |[  255.822834] Memory Limit: none
> > |[  256.062429] ---[ end Kernel panic - not syncing: Oops: Fatal exception in interrupt ]---
> 
> Just confirmed the same problem on my MIPS-based SoC:
> 
> Device #1:
> $ ifconfig eth2 192.168.2.2 up
> $ pktgen.sh -v -i eth2 -d 192.168.2.3 -m 4C:A5:15:59:A6:86 -n 0 -s 1496
> 
> Device #2:
> $ mount -t bpf none /sys/fs/bpf/
> $ sysctl -w net.core.bpf_jit_enable=1
> $ ifconfig eth0 192.168.2.3 up
> $ xdp-bench tx eth0
> ...
> [  559.663885] CPU 0 Unable to handle kernel paging request at virtual address 00000000, epc == 809a81e0, ra == 809a81dc
> [  559.675786] Oops[#1]:
> [  559.678324] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.8.0-rc3-bt1-00322-gb2c1210b8fe6-dirty #2176
> [  559.695824] $ 0   : 00000000 00000001 00000000 00000000
> [  559.701676] $ 4   : eb019c48 00000000 bf054000 81ddfe53
> [  559.707524] $ 8   : 00000000 84ea05c0 00000000 00000000
> [  559.713372] $12   : 00000000 0000002e 816e9d00 81080000
> [  559.719221] $16   : 00000002 a254c020 00000000 00000000
> [  559.725069] $20   : 84ea05c0 00000000 852b8000 00000040
> [  559.730917] $24   : 00000000 00000000
> [  559.736766] $28   : 815d8000 81ddfd88 84ea05c0 809a81dc
> [  559.742615] Hi    : 00000007
> [  559.745826] Lo    : 00000000
> [  559.749029] epc   : 809a81e0 stmmac_tx_clean+0x9f8/0xd64
> [  559.754974] ra    : 809a81dc stmmac_tx_clean+0x9f4/0xd64
> [  559.760909] Status: 10000003 KERNEL EXL IE
> [  559.765588] Cause : 0080040c (ExcCode 03)
> [  559.770063] BadVA : 00000000
> [  559.773266] PrId  : 0001a830
> [  559.777740] Modules linked in:
> [  559.781150] Process swapper/0 (pid: 0, threadinfo=9e75df13, task=e559c9e5, tls=00000000)
> [  559.790194] Stack : 00000001 00000001 00003138 00000001 001a07f2 4696b1a6 00000000 00000000
> [  559.799552]         00000000 00000001 00000000 81080000 00000001 00000000 84ea0b40 84ea2880
> [  559.808909]         84ea0e20 00000000 00000000 00000001 81600000 81ddfe53 810d6bcc 817b0000
> [  559.818265]         815d8000 81ddfe10 0000012c 80e83fd4 84ea05c0 a254c020 00000000 80142518
> [  559.827622]         00800400 eb019c48 81600000 00000040 81ddfebc 84ea05c0 00000000 84ea1320
> [  559.836979]         ...
> [  559.839710] Call Trace:
> [  559.842435] [<809a81e0>] stmmac_tx_clean+0x9f8/0xd64
> [  559.847985] [<809a8610>] stmmac_napi_poll_tx+0xc4/0x18c
> [  559.858885] [<80b2db94>] net_rx_action+0x128/0x288
> [  559.864232] [<80e84d48>] __do_softirq+0x134/0x4e0
> [  559.869489] [<80142484>] irq_exit+0xd4/0x138
> [  559.874261] [<807cc768>] __gic_irq_dispatch+0x154/0x1f0
> [  559.880101] [<80102d50>] except_vec_vi_end+0xc4/0xd0
> [  559.885641] [<80e78884>] default_idle_call+0x64/0x168
> [  559.891288] [<801975c4>] do_idle+0xf4/0x198
> [  559.895965] [<80197990>] cpu_startup_entry+0x30/0x40
> [  559.901513] [<80e78c1c>] kernel_init+0x0/0x120
> [  559.906477] 
> [  559.908126] Code: 0c2682db  afa50048  8fa50048 <aca20000> aca30004  1000fded  8fc208b0  8fc308ac  0000a825 
> [  559.919047] 
> [  559.920734] ---[ end trace 0000000000000000 ]---
> [  559.925908] Kernel panic - not syncing: Fatal exception in interrupt
> 
> No problem has been spotted for the XDP drop and pass benches.
> 
> As you pointed out reverting the commit 1347b419318d ("net: stmmac:
> Add Tx HWTS support to XDP ZC") fixes the bug.
> 
> -Serge(y)
> 
>