kern/54839: Update from 9.99.18 to 9.99.34/amd64 freezes at "cpu1 at mainbus0 apid 2"

[prlw1%cam.ac.uk@localhost]

>Number:         54839
>Category:       kern
>Synopsis:       Update from 9.99.18 to 9.99.34/amd64 freezes at "cpu1 at mainbus0 apid 2"
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Jan 06 16:40:00 +0000 2020
>Originator:     Patrick Welche
>Release:        9.99.34/amd64
>Organization:
>Environment:
>Description:
When booting a 9.99.34 GENERIC kernel, booting stops at the point labeled XXX below:

NetBSD 9.99.18 (GENERIC) #3: Thu Nov 21 14:46:51 GMT 2019
        prlw1@waxwing:/usr/src/sys/arch/amd64/compile/obj.amd64/GENERIC
total memory = 16180 MB
avail memory = 15683 MB
pool redzone disabled for 'buf4k'
pool redzone disabled for 'buf64k'
cpu_rng: RDSEED
timecounter: Timecounters tick every 10.000 msec
Kernelized RAIDframe activated
running cgd selftest aes-xts-256 aes-xts-512 done
timecounter: Timecounter "i8254" frequency 1193182 Hz quality 100
efi: systbl at pa 2ff66018
ZOTAC ZBOX-MI553 (02)
mainbus0 (root)
ACPI: RSDP 0x000000002F565000 000024 (v02 ALASKA)
ACPI: XSDT 0x000000002F5650B0 0000DC (v01 ALASKA A M I    01072009 AMI  00010013)
ACPI: FACP 0x000000002F58D1E8 000114 (v06 ALASKA A M I    01072009 AMI  00010013)
ACPI: DSDT 0x000000002F565220 027FC1 (v02 ALASKA A M I    01072009 INTL 20160422)
ACPI: FACS 0x000000002F5D9F00 000040
ACPI: APIC 0x000000002F58D300 000084 (v03 ALASKA A M I    01072009 AMI  00010013)
ACPI: FPDT 0x000000002F58D388 000044 (v01 ALASKA A M I    01072009 AMI  00010013)
ACPI: FIDT 0x000000002F58D3D0 00009C (v01 ALASKA A M I    01072009 AMI  00010013)
ACPI: MCFG 0x000000002F58D470 00003C (v01 ALASKA A M I    01072009 MSFT 00000097)
ACPI: SSDT 0x000000002F58D4B0 000359 (v01 SataRe SataTabl 00001000 INTL 20160422)
ACPI: SSDT 0x000000002F58D810 003164 (v02 SaSsdt SaSsdt   00003000 INTL 20160422)
ACPI: HPET 0x000000002F590978 000038 (v01 INTEL  KBL      00000001 MSFT 0000005F)
ACPI: SSDT 0x000000002F5909B0 000DE5 (v02 INTEL  Ther_Rvp 00001000 INTL 20160422)
ACPI: SSDT 0x000000002F591798 0008FE (v02 INTEL  xh_rvp11 00000000 INTL 20160422)
ACPI: UEFI 0x000000002F592098 000042 (v01 ALASKA A M I    00000002      01000013)
ACPI: SSDT 0x000000002F5920E0 000EDE (v02 CpuRef CpuSsdt  00003000 INTL 20160422)
ACPI: LPIT 0x000000002F592FC0 000094 (v01 INTEL  KBL      00000000 MSFT 0000005F)
ACPI: SSDT 0x000000002F593058 000141 (v02 INTEL  HdaDsp   00000000 INTL 20160422)
ACPI: SSDT 0x000000002F5931A0 00029F (v02 INTEL  sensrhub 00000000 INTL 20160422)
ACPI: SSDT 0x000000002F593440 003002 (v02 INTEL  PtidDevc 00001000 INTL 20160422)
ACPI: SSDT 0x000000002F596448 00050D (v02 INTEL  TbtTypeC 00000000 INTL 20160422)
ACPI: DBGP 0x000000002F596958 000034 (v01 INTEL           00000002 MSFT 0000005F)
ACPI: DBG2 0x000000002F596990 000054 (v00 INTEL           00000002 MSFT 0000005F)
ACPI: SSDT 0x000000002F5969E8 0010B0 (v02 ALASKA UsbCTabl 00001000 INTL 20160422)
ACPI: DMAR 0x000000002F597A98 0000A8 (v01 INTEL  KBL      00000001 INTL 00000001)
ACPI: BGRT 0x000000002F597B40 000038 (v01 ALASKA A M I    01072009 AMI  00010013)
ACPI: WSMT 0x000000002F597B78 000028 (v01 ALASKA A M I    01072009 AMI  00010013)
ACPI: 11 ACPI AML tables successfully acquired and loaded
ioapic0 at mainbus0 apid 2: pa 0xfec00000, version 0x20, 120 pins
cpu0 at mainbus0 apid 0
cpu0: Intel(R) Core(TM) i5-7300HQ CPU @ 2.50GHz, id 0x906e9
cpu0: package 0, core 0, smt 0
cpu1 at mainbus0 apid 2
XXX 9.99.34 prints the line above and everything repeatably freezes XXX
cpu1: Intel(R) Core(TM) i5-7300HQ CPU @ 2.50GHz, id 0x906e9
cpu1: Intel(R) Core(TM) i5-7300HQ CPU @ 2.50GHz, id 0x906e9
cpu1: package 0, core 1, smt 0
cpu2 at mainbus0 apid 4
cpu2: Intel(R) Core(TM) i5-7300HQ CPU @ 2.50GHz, id 0x906e9
cpu2: package 0, core 2, smt 0
cpu3 at mainbus0 apid 6
cpu3: Intel(R) Core(TM) i5-7300HQ CPU @ 2.50GHz, id 0x906e9
cpu3: package 0, core 3, smt 0
acpi0 at mainbus0: Intel ACPICA 20190816
acpi0: X/RSDT: OemId <ALASKA,  A M I ,01072009>, AslId <AMI ,00010013>
acpi0: MCFG: segment 0, bus 0-255, address 0x00000000e0000000

Booting a GENERIC kernel with DEBUG + LOCKDEBUG showed exactly the same behaviour.
>How-To-Repeat:

>Fix: