Re: [PATCH] net: stmmac: fix oops when split header is enabled

[Jacob Keller <jacob.e.keller@intel.com>]

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On 12/1/2025 6:54 PM, Jie Zhang wrote:
> For GMAC4, when split header is enabled, in some rare cases, the
> hardware does not fill buf2 of the first descriptor with payload.
> Thus we cannot assume buf2 is always fully filled if it is not
> the last descriptor. Otherwise, the length of buf2 of the second
> descriptor will be calculated wrong and cause an oops:
> 
> Unable to handle kernel paging request at virtual address ffff00019246bfc0
> Mem abort info:
>   ESR = 0x0000000096000145
>   EC = 0x25: DABT (current EL), IL = 32 bits
>   SET = 0, FnV = 0
>   EA = 0, S1PTW = 0
>   FSC = 0x05: level 1 translation fault
> Data abort info:
>   ISV = 0, ISS = 0x00000145, ISS2 = 0x00000000
>   CM = 1, WnR = 1, TnD = 0, TagAccess = 0
>   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
> swapper pgtable: 4k pages, 48-bit VAs, pgdp=0000000090d8b000
> [ffff00019246bfc0] pgd=180000009dfff403, p4d=180000009dfff403, pud=0000000000000000
> Internal error: Oops: 0000000096000145 [#1]  SMP
> Modules linked in:
> CPU: 0 UID: 0 PID: 157 Comm: iperf3 Not tainted 6.18.0-rc6 #1 PREEMPT
> Hardware name: ADI 64-bit SC598 SOM EZ Kit (DT)
> pstate: 00400009 (nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : dcache_inval_poc+0x28/0x58
> lr : arch_sync_dma_for_cpu+0x28/0x34
> sp : ffff800080dcbc40
> x29: ffff800080dcbc40 x28: 0000000000000008 x27: ffff000091c50980
> x26: ffff000091c50980 x25: 0000000000000000 x24: ffff000092a5fb00
> x23: ffff000092768f28 x22: 000000009246c000 x21: 0000000000000002
> x20: 00000000ffffffdc x19: ffff000091844c10 x18: 0000000000000000
> x17: ffff80001d308000 x16: ffff800080dc8000 x15: ffff0000929fb034
> x14: 70f709157374dd21 x13: ffff000092812ec0 x12: 0000000000000000
> x11: 000000000000dd86 x10: 0000000000000040 x9 : 0000000000000600
> x8 : ffff000092a5fbac x7 : 0000000000000001 x6 : 0000000000004240
> x5 : 000000009246c000 x4 : ffff000091844c10 x3 : 000000000000003f
> x2 : 0000000000000040 x1 : ffff00019246bfc0 x0 : ffff00009246c000
> Call trace:
>  dcache_inval_poc+0x28/0x58 (P)
>  dma_direct_sync_single_for_cpu+0x38/0x6c
>  __dma_sync_single_for_cpu+0x34/0x6c
>  stmmac_napi_poll_rx+0x8f0/0xb60
>  __napi_poll.constprop.0+0x30/0x144
>  net_rx_action+0x160/0x274
>  handle_softirqs+0x1b8/0x1fc
>  __do_softirq+0x10/0x18
>  ____do_softirq+0xc/0x14
>  call_on_irq_stack+0x30/0x48
>  do_softirq_own_stack+0x18/0x20
>  __irq_exit_rcu+0x64/0xe8
>  irq_exit_rcu+0xc/0x14
>  el1_interrupt+0x3c/0x58
>  el1h_64_irq_handler+0x14/0x1c
>  el1h_64_irq+0x6c/0x70
>  __arch_copy_to_user+0xbc/0x240 (P)
>  simple_copy_to_iter+0x28/0x30
>  __skb_datagram_iter+0x1bc/0x268
>  skb_copy_datagram_iter+0x1c/0x24
>  tcp_recvmsg_locked+0x3ec/0x778
>  tcp_recvmsg+0x10c/0x194
>  inet_recvmsg+0x64/0xa0
>  sock_recvmsg_nosec+0x1c/0x24
>  sock_read_iter+0x8c/0xdc
>  vfs_read+0x144/0x1a0
>  ksys_read+0x74/0xdc
>  __arm64_sys_read+0x14/0x1c
>  invoke_syscall+0x60/0xe4
>  el0_svc_common.constprop.0+0xb0/0xcc
>  do_el0_svc+0x18/0x20
>  el0_svc+0x80/0xc8
>  el0t_64_sync_handler+0x58/0x134
>  el0t_64_sync+0x170/0x174
> Code: d1000443 ea03003f 8a230021 54000040 (d50b7e21)
> ---[ end trace 0000000000000000 ]---
> Kernel panic - not syncing: Oops: Fatal exception in interrupt
> Kernel Offset: disabled
> CPU features: 0x080000,00008000,08006281,0400520b
> Memory Limit: none
> ---[ end Kernel panic - not syncing: Oops: Fatal exception in interrupt ]---
> 

You could probably minify the crash here a bit since much of this
information isn't that helpful in showing the crash. Not too big a deal
overall.

> To fix this, the PL bit-field in RDES3 register is used for all
> descriptors, whether it is the last descriptor or not.
> 
> Signed-off-by: Jie Zhang <jie.zhang@analog.com>


Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>

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