panic in iic_search()

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

I have an AMD64 server running 8/amd64, which ran happily (other than USB 
issues, which is another story) with 8.1_STABLE from September 2019.
I updated to netbsd-8 from yesterday (so that's 8.2_STABLE) and a newly 
compiled kernel crashes in iic_search(). The last line printed before that is:
	iic0 at piixpm0: I2C bus
With the working kernel, the next line is:
	spdmem0 at iic0 addr 0x50: NT4GC72B4NA1NL-CG

Obviously, I have the spdmem* at iic? addr 0xxx lines uncommented in my config.

The panic is:
uvm_fault(0xffffffff90afec40, 0x0, 4) -> e
fatal page fault in supervisor mode
trap type 6 code 0x10 rip 0 cs 0x8 rflags 0x10246 cr2 0 ilevel 0x8 rsp 0xffffffff80d4f485
curlwp 0xffffffff80a1b600 pid 0.1 lowest kstack 0xffffffff80d4c2c0
kernel: page fault trap, code=0
Stopped in pid 0.1 (system) at  0:uvm_fault(0xffffffff80afec40, 0x7fbfc0000000, 1) -> e
fatal page fault in supervisor mode
trap type 6 code 0 rip 0xffffffff80d4f070 cs 0x8 rflags 0x10216 cr2 0x7fbfc0000000 ilevel 0x8 rsp 0xffffffff80d4f070
curlwp 0xffffffff80a1b600 pid 0.1 lowest kstack 0xffffffff80d4c2c0
	kernel: page fault trap, code=0
Stopped in pid 0.1 (system) at  netbsd:db_disasm+0x65:	testb	$0x1,0(%rdx,%rcx,8)

Backtrace:
db_disasm() at netbsd:db_disasm+0x65
db_trap() at netbsd:db_trap+0xf4
kpd_trap() at netbsd:kpd_trap+0xe2
trap() at netbsd:trap+0x5d6
-- trap (number 6) ---
?() at 0
iic_search() at netbsd:iic_search+0x92
mapply() at netbsd:mapply+0x39
config_search_loc() at netbsd:config_search_loc+0xaf
iic_attach() at netbsd:iic_attach+0x4cd
config_attach_loc() at netbsd:config_attach_loc+0x19c
config_found_sm_loc() at netbsd:config_found_sm_loc+0x48
piixpm_rescan() at netbsd:piixpm_rescan+0xed
piixpm_attach() at netbsd:piixpm_attach+0x1e7
config_attach_loc() at netbsd:config_attach_loc+0x19c
config_found_sm_loc() at netbsd:config_found_sm_loc+0x48
pci_probe_device() at netbsd:pci_probe_device+0x57e
pci_enumerate_bus() at netbsd:pci_enumerate_bus+0x198
pciattach() at netbsd:pciattach+0x198
config_attach_loc() at netbsd:config_attach_loc+0x19c
config_found_sm_loc() at netbsd:config_found_sm_loc+0x48
mp_pci_scan() at netbsd:mp_pci_scan+0x9c
mainbus_attach() at netbsd:mainbus_attach+0x2ce
config_attach_loc() at netbsd:config_attach_loc+0x19c
cpu_configure() at netbsd:cpu_configure+0x2b
main() at netbsd:main+0x2a8

Where to go from here?