panic: lapic_enable_cmc: missing APIC 0

[Ronald van der Pol]

I am trying to move to current from 8.1-PRERELEASE. After
buildworld, buildkernel, installkernel and rebooting I get:

panic: lapic_enable_cmc: missing APIC 0
cpuid = 0
KDB: enter : panic

while the kernel is booting. This is some boot info from 8.1-PRERELEASE:

CPU: Intel(R) Xeon(R) CPU           X5550  @ 2.67GHz (2660.02-MHz K8-class CPU)
  Origin = "GenuineIntel"  Id = 0x106a5  Family = 6  Model = 1a  Stepping = 5
  Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
  Features2=0x9ce3bd<SSE3,DTES64,MON,DS_CPL,VMX,EST,TM2,SSSE3,CX16,xTPR,PDCM,DCA,SSE4.1,SSE4.2,POPCNT>
  AMD Features=0x28100800<SYSCALL,NX,RDTSCP,LM>
  AMD Features2=0x1<LAHF>
  TSC: P-state invariant
real memory  = 6442450944 (6144 MB)
avail memory = 6172110848 (5886 MB)
ACPI APIC Table: <DELL   PE_SC3  >
FreeBSD/SMP: Multiprocessor System Detected: 8 CPUs
FreeBSD/SMP: 1 package(s) x 4 core(s) x 2 SMT threads
 cpu0 (BSP): APIC ID: 16
 cpu1 (AP): APIC ID: 17
 cpu2 (AP): APIC ID: 18
 cpu3 (AP): APIC ID: 19
 cpu4 (AP): APIC ID: 20
 cpu5 (AP): APIC ID: 21
 cpu6 (AP): APIC ID: 22
 cpu7 (AP): APIC ID: 23
ioapic1: Changing APIC ID to 1
ioapic0 <Version 2.0> irqs 0-23 on motherboard
ioapic1 <Version 2.0> irqs 32-55 on motherboard
kbd1 at kbdmux0
acpi0: <DELL PE_SC3> on motherboard
acpi0: [ITHREAD]
acpi0: Power Button (fixed)
Timecounter "ACPI-fast" frequency 3579545 Hz quality 1000
acpi_timer0: <24-bit timer at 3.579545MHz> port 0x808-0x80b on acpi0
cpu0: <ACPI CPU> on acpi0
cpu1: <ACPI CPU> on acpi0
cpu2: <ACPI CPU> on acpi0
cpu3: <ACPI CPU> on acpi0
cpu4: <ACPI CPU> on acpi0
cpu5: <ACPI CPU> on acpi0
cpu6: <ACPI CPU> on acpi0
cpu7: <ACPI CPU> on acpi0
acpi_hpet0: <High Precision Event Timer> iomem 0xfed00000-0xfed003ff on acpi0
Timecounter "HPET" frequency 14318180 Hz quality 900

	rvdp