Re: [PATCH net v1] mlxbf_gige: stop interface during shutdown

[Paolo Abeni <pabeni@redhat.com>]

On Mon, 2024-03-25 at 17:09 -0400, David Thompson wrote:
> The mlxbf_gige driver intermittantly encounters a NULL pointer
> exception while the system is shutting down via "reboot" command.
> The mlxbf_driver will experience an exception right after executing
> its shutdown() method.  One example of this exception is:
> 
> Unable to handle kernel NULL pointer dereference at virtual address 0000000000000070
> Mem abort info:
>   ESR = 0x0000000096000004
>   EC = 0x25: DABT (current EL), IL = 32 bits
>   SET = 0, FnV = 0
>   EA = 0, S1PTW = 0
>   FSC = 0x04: level 0 translation fault
> Data abort info:
>   ISV = 0, ISS = 0x00000004
>   CM = 0, WnR = 0
> user pgtable: 4k pages, 48-bit VAs, pgdp=000000011d373000
> [0000000000000070] pgd=0000000000000000, p4d=0000000000000000
> Internal error: Oops: 96000004 [#1] SMP
> CPU: 0 PID: 13 Comm: ksoftirqd/0 Tainted: G S         OE     5.15.0-bf.6.gef6992a #1
> Hardware name: https://www.mellanox.com BlueField SoC/BlueField SoC, BIOS 4.0.2.12669 Apr 21 2023
> pstate: 20400009 (nzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : mlxbf_gige_handle_tx_complete+0xc8/0x170 [mlxbf_gige]
> lr : mlxbf_gige_poll+0x54/0x160 [mlxbf_gige]
> sp : ffff8000080d3c10
> x29: ffff8000080d3c10 x28: ffffcce72cbb7000 x27: ffff8000080d3d58
> x26: ffff0000814e7340 x25: ffff331cd1a05000 x24: ffffcce72c4ea008
> x23: ffff0000814e4b40 x22: ffff0000814e4d10 x21: ffff0000814e4128
> x20: 0000000000000000 x19: ffff0000814e4a80 x18: ffffffffffffffff
> x17: 000000000000001c x16: ffffcce72b4553f4 x15: ffff80008805b8a7
> x14: 0000000000000000 x13: 0000000000000030 x12: 0101010101010101
> x11: 7f7f7f7f7f7f7f7f x10: c2ac898b17576267 x9 : ffffcce720fa5404
> x8 : ffff000080812138 x7 : 0000000000002e9a x6 : 0000000000000080
> x5 : ffff00008de3b000 x4 : 0000000000000000 x3 : 0000000000000001
> x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000000
> Call trace:
>  mlxbf_gige_handle_tx_complete+0xc8/0x170 [mlxbf_gige]
>  mlxbf_gige_poll+0x54/0x160 [mlxbf_gige]
>  __napi_poll+0x40/0x1c8
>  net_rx_action+0x314/0x3a0
>  __do_softirq+0x128/0x334
>  run_ksoftirqd+0x54/0x6c
>  smpboot_thread_fn+0x14c/0x190
>  kthread+0x10c/0x110
>  ret_from_fork+0x10/0x20
> Code: 8b070000 f9000ea0 f95056c0 f86178a1 (b9407002)
> ---[ end trace 7cc3941aa0d8e6a4 ]---
> Kernel panic - not syncing: Oops: Fatal exception in interrupt
> Kernel Offset: 0x4ce722520000 from 0xffff800008000000
> PHYS_OFFSET: 0x80000000
> CPU features: 0x000005c1,a3330e5a
> Memory Limit: none
> ---[ end Kernel panic - not syncing: Oops: Fatal exception in interrupt ]---
> 
> During system shutdown, the mlxbf_gige driver's shutdown() is always executed.
> However, the driver's stop() method will only execute if networking interface
> configuration logic within the Linux distribution has been setup to do so.
> 
> If shutdown() executes but stop() does not execute, NAPI remains enabled
> and this can lead to an exception if NAPI is scheduled while the hardware
> interface has only been partially deinitialized.
> 
> The networking interface managed by the mlxbf_gige driver must be properly
> stopped during system shutdown so that IFF_UP is cleared, the hardware
> interface is put into a clean state, and NAPI is fully deinitialized.
> 
> Fixes: f92e1869d74e ("Add Mellanox BlueField Gigabit Ethernet driver")
> Signed-off-by: David Thompson <davthompson@nvidia.com>

LGTM, but it would be nice if someone else at nvidia could have a look.

Thanks!

Paolo