iflib panic on 13.0-RELEASE

[Chuck Tuffli]

I have a VM running FreeBSD 13.0-RELEASE that panics with a particular
network configuration. Any suggestions as to where to poke / look?

...
igb0: <Intel(R) PRO/1000 PCI-Express Network Driver> mem
0x1000014000-0x1000017fff,0x1000010000-0x1000013fff at device 3.0 on
pci0
panic: vm_fault_lookup: fault on nofault entry, addr: 0xfffffe013a589000
cpuid = 1
time = 1
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xffffffff827c2f50
vpanic() at vpanic+0x181/frame 0xffffffff827c2fa0
panic() at panic+0x43/frame 0xffffffff827c3000
vm_fault() at vm_fault+0x1465/frame 0xffffffff827c3100
vm_fault_trap() at vm_fault_trap+0xb1/frame 0xffffffff827c3150
trap_pfault() at trap_pfault+0x1f8/frame 0xffffffff827c31b0
trap() at trap+0x27d/frame 0xffffffff827c32c0
calltrap() at calltrap+0x8/frame 0xffffffff827c32c0
--- trap 0xc, rip = 0xffffffff80655618, rsp = 0xffffffff827c3390, rbp
= 0xffffffff827c33c0 ---
e1000_disable_ulp_lpt_lp() at e1000_disable_ulp_lpt_lp+0x68/frame
0xffffffff827c33c0
em_if_attach_pre() at em_if_attach_pre+0xeb6/frame 0xffffffff827c3430
iflib_device_register() at iflib_device_register+0x152/frame 0xffffffff827c37a0
iflib_device_attach() at iflib_device_attach+0xb5/frame 0xffffffff827c37d0
device_attach() at device_attach+0x3dd/frame 0xffffffff827c3820
bus_generic_attach() at bus_generic_attach+0x4b/frame 0xffffffff827c3850
pci_attach() at pci_attach+0xd3/frame 0xffffffff827c3890
acpi_pci_attach() at acpi_pci_attach+0x19/frame 0xffffffff827c38e0
device_attach() at device_attach+0x3dd/frame 0xffffffff827c3930
bus_generic_attach() at bus_generic_attach+0x4b/frame 0xffffffff827c3960
acpi_pcib_acpi_attach() at acpi_pcib_acpi_attach+0x40d/frame 0xffffffff827c39c0
device_attach() at device_attach+0x3dd/frame 0xffffffff827c3a10
bus_generic_attach() at bus_generic_attach+0x4b/frame 0xffffffff827c3a40
acpi_attach() at acpi_attach+0xd2a/frame 0xffffffff827c3b50
device_attach() at device_attach+0x3dd/frame 0xffffffff827c3ba0
bus_generic_attach() at bus_generic_attach+0x4b/frame 0xffffffff827c3bd0
device_attach() at device_attach+0x3dd/frame 0xffffffff827c3c20
bus_generic_new_pass() at bus_generic_new_pass+0x127/frame 0xffffffff827c3c50
root_bus_configure() at root_bus_configure+0x36/frame 0xffffffff827c3c80
configure() at configure+0x9/frame 0xffffffff827c3c90
mi_startup() at mi_startup+0xdf/frame 0xffffffff827c3cb0
btext() at btext+0x2c
KDB: enter: panic
[ thread pid 0 tid 100000 ]
Stopped at      kdb_enter+0x37: movq    $0,0x10745be(%rip)
db>