ARM64 system error

My OverDrive 1000 (Cortex A57) running CURRENT just crashed with the unhelpful message "panic: Unhandled System Error".  Is there any way to get better information?  The ESR value bf000000 translates to "system error with implementation-defined code 0" so that's not much use.  The instruction associated with the interrupt can't fault ("subs w22, w22, #0x1") so it must be an asynchronous error.  On other systems I've seen bits you can test or registers you can read to get details.

  x0:                0
  x1: ffff0000b55bd000 (crypto_dev + b3f34ec0)
  x2:             2880
  x3:               20
  x4:               d3
  x5:                0
  x6:              100
  x7: ffff00011063daa0
  x8: ffff00000077218c (generic_bs_r_2 + 0)
  x9:             2880
 x10: ffff0000001ff9f4 (msk_phy_readreg + 84)
 x11:         a0000045
 x12:         56000000
 x13:         5e4a6f28
 x14: ffff000000c4d038 (vnet_entry_ipport_stoprandom + 0)
 x15: ffffa000016b3000
 x16:         40ef9400
 x17:                a
 x18: ffff0000b550e560 (crypto_dev + b3e86420)
 x19: ffff0000b57dc000 (crypto_dev + b4153ec0)
 x20: ffffa000029dc800
 x21:             2880
 x22:              3c4
 x23:             796d
 x24: ffffa000017f4100
 x25: ffff000000ad3da0 (miibus_readreg_desc + 0)
 x26: ffff000000bb6000 (vop_deallocate_desc + 28)
 x27: ffff000000e36980 (cc_cpu + 80)
 x28: ffff000000b1b828 (lock_class_mtx_sleep + 0)
 x29: ffff0000b550e670 (crypto_dev + b3e86530)
  sp: ffff0000b550e560
  lr: ffff0000001ff9f0 (msk_phy_readreg + 80)
 elr: ffff00000077806c (handle_el1h_irq + 8)
spsr:         a00002c5
 far:                0
 esr:         bf000000
panic: Unhandled System Error
cpuid = 2
time = 1659270153
KDB: stack backtrace:
db_trace_self() at db_trace_self
db_trace_self_wrapper() at db_trace_self_wrapper+0x30
vpanic() at vpanic+0x13c
panic() at panic+0x44
do_serror() at do_serror+0x40
handle_serror() at handle_serror+0x38
--- system error, esr 0xbf000000
handle_el1h_irq() at handle_el1h_irq+0x8
--- interrupt
msk_phy_readreg() at msk_phy_readreg+0x84
e1000phy_status() at e1000phy_status+0x114
e1000phy_service() at e1000phy_service+0x420
mii_tick() at mii_tick+0x50
msk_tick() at msk_tick+0x44
softclock_call_cc() at softclock_call_cc+0x128
softclock_thread() at softclock_thread+0xc4
fork_exit() at fork_exit+0x74
fork_trampoline() at fork_trampoline+0x14
KDB: enter: panic
[ thread pid 2 tid 100026 ]
Stopped at      kdb_enter+0x44: undefined       f907c27f