Hi Andrew,

I just retest this manually on node entei with the steps in comment #3, and this issue can be reproduced (system gets reboot) with a different message from the ipmi console.

[  417.696448] BUG: Unable to handle kernel instruction fetch (NULL pointer?)
[  417.696522] Faulting instruction address: 0x00000000
[  417.696677] Oops: Kernel access of bad area, sig: 11 [#1]
[  417.696693] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA PowerNV
[  417.696715] Modules linked in: binfmt_misc dm_multipath scsi_dh_rdac scsi_dh_emc scsi_dh_alua joydev input_leds mac_hid ofpart plx_dma cmdlinepart ipmi_powernv pow
ernv_flash ipmi_devintf ibmpowernv at24 vmx_crypto opal_prd ipmi_msghandler powernv_rng mtd uio_pdrv_genirq uio sch_fq_codel ip_tables x_tables autofs4 btrfs blake2b_
generic uas raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor hid_generic usbhid hid usb_storage async_tx xor raid6_pq libcrc32c raid1 raid0 multipath 
linear ast drm_vram_helper i2c_algo_bit drm_ttm_helper ttm drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops crct10dif_vpmsum cec crc32c_vpmsum rc_core drm
 ahci tg3 xhci_pci libahci drm_panel_orientation_quirks xhci_pci_renesas
[  417.697008] CPU: 0 PID: 3117 Comm: reuseport_bpf_c Not tainted 5.11.0-27-generic #29~20.04.1-Ubuntu
[  417.697034] NIP:  0000000000000000 LR: c000000000e77ba8 CTR: 0000000000000000
[  417.697055] REGS: c0000007ff6e74d0 TRAP: 0400   Not tainted  (5.11.0-27-generic)
[  417.697077] MSR:  9000000040009033 <SF,HV,EE,ME,IR,DR,RI,LE>  CR: 28022444  XER: 20000000
[  417.697309] CFAR: c000000000010300 IRQMASK: 0 
[  417.697309] GPR00: c000000000e77b80 c0000007ff6e7770 c000000001e99600 c000000014cecd00 
[  417.697309] GPR04: c008000004230038 c000000014cecd00 0000000000000008 0000000000000001 
[  417.697309] GPR08: 0000000000000001 0000000000000000 c0000000501e9580 0000000000000000 
[  417.697309] GPR12: 0000000000000000 c000000002150000 0000000000000000 0000000000000000 
[  417.697309] GPR16: 0000000000000040 c00000078e09a480 0000000000000001 0000000000000001 
[  417.697309] GPR20: 00000000000022b8 0000000000000000 000000000000cfb3 000000000100007f 
[  417.697309] GPR24: 0000000000000000 0000000000000008 c000000001dba880 c008000004230000 
[  417.697309] GPR28: 0000000000000080 c000000003292000 0000000090dd40dc c000000014cecd00 
[  417.697503] NIP [0000000000000000] 0x0
[  417.697517] LR [c000000000e77ba8] reuseport_select_sock+0x108/0x3f0
[  417.697541] Call Trace:
[  417.697550] [c0000007ff6e7810] [c000000000f64314] udp4_lib_lookup2+0x1a4/0x2b0
[  417.697576] [c0000007ff6e7890] [c000000000f65928] __udp4_lib_lookup+0x358/0x540
[  417.697602] [c0000007ff6e79d0] [c000000000f66978] __udp4_lib_rcv+0x608/0xe10
[  417.697626] [c0000007ff6e7af0] [c000000000f0fa20] ip_protocol_deliver_rcu+0x60/0x2c0
[  417.697813] [c0000007ff6e7b40] [c000000000f0fcf0] ip_local_deliver_finish+0x70/0x90
[  417.697838] [c0000007ff6e7b60] [c000000000f0fda0] ip_local_deliver+0x90/0x180
[  417.697861] [c0000007ff6e7be0] [c000000000f0f140] ip_rcv_finish+0xc0/0xf0
[  417.697883] [c0000007ff6e7c20] [c000000000f0ffa8] ip_rcv+0x118/0x130
[  417.697904] [c0000007ff6e7ca0] [c000000000e3a3b4] __netif_receive_skb_one_core+0x74/0xb0
[  417.698083] [c0000007ff6e7cf0] [c000000000e3a770] process_backlog+0xd0/0x230
[  417.698108] [c0000007ff6e7d60] [c000000000e3cf88] net_rx_action+0x1e8/0x580
[  417.698130] [c0000007ff6e7e70] [c0000000010a94c0] __do_softirq+0x160/0x404
[  417.698152] [c0000007ff6e7f90] [c00000000002bad8] call_do_softirq+0x14/0x24
[  417.698174] [c00000005021b760] [c000000000017158] do_softirq_own_stack+0x38/0x50
[  417.698199] [c00000005021b780] [c0000000001576e0] do_softirq+0xa0/0xb0
[  417.698391] [c00000005021b7b0] [c0000000001577e8] __local_bh_enable_ip+0xf8/0x120
[  417.698415] [c00000005021b7d0] [c000000000f1418c] ip_finish_output2+0x1fc/0x730
[  417.698439] [c00000005021b870] [c000000000f178fc] ip_output+0xdc/0x1c0
[  417.698460] [c00000005021b920] [c000000000f16cb4] ip_local_out+0x64/0x90
[  417.698482] [c00000005021b960] [c000000000f18634] ip_send_skb+0x34/0xc0
[  417.698667] [c00000005021b990] [c000000000f6074c] udp_send_skb.isra.0+0x16c/0x4a0
[  417.698691] [c00000005021b9e0] [c000000000f61490] udp_sendmsg+0x960/0xcf0
[  417.698714] [c00000005021bbd0] [c000000000f77cd4] inet_sendmsg+0x64/0xb0
[  417.698735] [c00000005021bc10] [c000000000dfb3a0] sock_sendmsg+0x80/0xb0
[  417.698758] [c00000005021bc40] [c000000000dfffd8] __sys_sendto+0xf8/0x1b0
[  417.698910] [c00000005021bd90] [c000000000e00100] sys_send+0x30/0x40
[  417.698932] [c00000005021bdb0] [c000000000036204] system_call_exception+0xf4/0x200
[  417.698999] [c00000005021be10] [c00000000000d860] system_call_common+0xf0/0x27c
[  417.699023] --- interrupt: c00 at 0x7aef2b250724
[  417.699040] NIP:  00007aef2b250724 LR: 000005f77e131568 CTR: 0000000000000000
[  417.716065] REGS: c00000005021be80 TRAP: 0c00   Not tainted  (5.11.0-27-generic)
[  417.716693] MSR:  900000000280f033 <SF,HV,VEC,VSX,EE,PR,FP,ME,IR,DR,RI,LE>  CR: 28004440  XER: 00000000
[  417.717786] IRQMASK: 0 
[  417.717786] GPR00: 000000000000014e 00007fffed1b68e0 00007aef2b337100 0000000000000084 
[  417.717786] GPR04: 000005f77e131f08 0000000000000001 0000000000000000 0000000000000000 
[  417.717786] GPR08: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 
[  417.717786] GPR12: 0000000000000000 00007aef2b3ca330 0000000000000000 0000000000000000 
[  417.717786] GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 
[  417.717786] GPR20: 0000000000000001 000005f7b987049c 000000000000007f 00007fffed1b6b88 
[  417.717786] GPR24: 000005f7b987029c 0000000000000083 000005f7b98702a0 0000000000000002 
[  417.717786] GPR28: 0000000000000000 0000000000000080 0000000000000002 0000000000000084 
[  417.735682] NIP [00007aef2b250724] 0x7aef2b250724
[  417.736172] LR [000005f77e131568] 0x5f77e131568
[  417.736699] --- interrupt: c00
[  417.736710] Instruction dump:
[  417.737229] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX 
[  417.737755] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX 
[  417.738770] ---[ end trace 9fc532dd6c3c783a ]---
[  417.900679] 
[  418.900837] Kernel panic - not syncing: Aiee, killing interrupt handler!
[  419.063147] Rebooting in 10 seconds..
[  481.430090023,5] OPAL: Reboot request...