Facing kernel panic during early boot from 12.0 ALPHA9

Hi,

I have a amd64 based board, where I could able to install upto FreeBSD 12.0
ALPHA8 without issues. But starting ALPHA9, I start to see the below panic
during early boot.  Looks like some sleep at unwanted place.  I am using
the memstick image from dowload page.

Please let me know if you need any details.

*Panic logs :*

GDB: no debug ports present
KDB: debugger backends: ddb
KDB: current backend: ddb
---<<BOOT>>---
Copyright (c) 1992-2018 The FreeBSD Project.
Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
The Regents of the University of California. All rights reserved.
FreeBSD is a registered trademark of the The FreeBSD Foundation.
FreeBSD 12.0-ALPHA9 r339271 GENERIC amd64
FreeBSD clang version 6.0.1 (tags/RELEASE_601/final 335540) (based on LLVM
6.0.1)
WARNING: WITNESS option enabled, expect reduced performance.
panic: vm_wait in early boot
cpuid = 0
time = 1
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame
0xffffffff827098d0
vpanic() at vpanic+0x1a3/frame 0xffffffff82709930
panic() at panic+0x43/frame 0xffffffff82709990
vm_wait_domain() at vm_wait_domain+0xf9/frame 0xffffffff827099c0
vm_domain_alloc_fail() at vm_domain_alloc_fail+0x94/frame 0xffffffff827099f0
vm_page_alloc_domain_after() at vm_page_alloc_domain_after+0x274/frame
0xffffffff82709a60
uma_small_alloc() at uma_small_alloc+0x6e/frame 0xffffffff82709a90
keg_alloc_slab() at keg_alloc_slab+0xf0/frame 0xffffffff82709af0
uma_prealloc() at uma_prealloc+0x92/frame 0xffffffff82709b30
vm_map_startup() at vm_map_startup+0x5f/frame 0xffffffff82709b40
vm_mem_init() at vm_mem_init+0x32/frame 0xffffffff82709b50
mi_startup() at mi_startup+0x118/frame 0xffffffff82709b70
btext() at btext+0x2c
KDB: enter: panic
[ thread pid 0 tid 0 ]
Stopped at kdb_enter+0x3b: movq $0,kdb_why
db>