Fatal trap 12: page fault on Acer Chromebook 720 (peppy)

Hi,

After upgrading CURRENT to r333992 (from something at least a year
old, quite some changes in mp_machdep.c since), this machine crashes
on boot:

Copyright (c) 1992-2018 The FreeBSD Project.
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	The Regents of the University of California. All rights reserved.
FreeBSD is a registered trademark of The FreeBSD Foundation.
FreeBSD 12.0-CURRENT #1 r333992: Tue May 22 00:31:04 CEST 2018
    root_at_flimsy:/usr/obj/usr/src/amd64.amd64/sys/flimsy amd64
FreeBSD clang version 6.0.0 (tags/RELEASE_600/final 326565) (based on LLVM 6.0.0)
WARNING: WITNESS option enabled, expect reduced performance.
VT(vga): resolution 640x480
CPU: Intel(R) Celeron(R) 2955U _at_ 1.40GHz (1396.80-MHz K8-class CPU)
  Origin="GenuineIntel"  Id=0x40651  Family=0x6  Model=0x45  Stepping=1
  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=0x4ddaebbf<SSE3,PCLMULQDQ,DTES64,MON,DS_CPL,VMX,EST,TM2,SSSE3,SDBG,CX16,
xTPR,PDCM,PCID,SSE4.1,SSE4.2,MOVBE,POPCNT,TSCDLT,XSAVE,OSXSAVE,RDRAND>
  AMD Features=0x2c100800<SYSCALL,NX,Page1GB,RDTSCP,LM>
  AMD Features2=0x21<LAHF,ABM>
  Structured Extended Features=0x2603<FSGSBASE,TSCADJ,ERMS,INVPCID,NFPUSG>
  XSAVE Features=0x1<XSAVEOPT>
  VT-x: (disabled in BIOS) PAT,HLT,MTF,PAUSE,EPT,UG,VPID
  TSC: P-state invariant, performance statistics
real memory  = 4301258752 (4102 MB)
avail memory = 1907572736 (1819 MB)
Event timer "LAPIC" quality 600
ACPI APIC Table: <CORE   COREBOOT>
kernel trap 12 with interrupts disabled

Fatal trap 12: page fault while in kernel mode 
cpuid = 0; apic id = 00
fault virtual address    = 0xfffff80001000000
fault code               = supervisor write data, protection violation
instruction pointer      = 0x20:Oxffffffff8102955f
stack pointer            = 0x28:0xffffffff82a79be0
frame pointer            = 0x28:0xffffffff82a79c10
code segment             = base Ox0, limit Oxfffff, type Ox1b
                         = DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags         = resume, IOPL = 0
current process          = 0 ()
[ thread pid 0 tid 0 ]
Stopped at      native_start_all_aps+0x08f:      movq     %rax,(%rsi)
db>

Any key press in the debugger will reboot the machine.

Booting with kern.smp.disabled=1 works.

Any ideas?

-m

-- 
Michael Gmelin