9.0 + vimage + nfs root = panic

[Kris Kennaway]

hwpmc: TSC/1/64/0x20<REA> 
IAP/2/40/0x3ff<INT,USR,SYS,EDG,THR,REA,WRI,INV,QUA,PRC> 
IAF/0/0/0x61<INT,REA,WRI>
Trying to mount root from nfs:


Fatal trap 12: page fault while in kernel mode
cpuid = 1; apic id = 01
fault virtual address   = 0x28
fault code              = supervisor read data, page not present
instruction pointer     = 0x20:0xffffffff804a1ff2
stack pointer           = 0x28:0xffffff8000053130
frame pointer           = 0x28:0xffffff8000053150
code segment            = base 0x0, limit 0xfffff, type 0x1b
                         = DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 1 (kernel)
[thread pid 1 tid 100001 ]
Stopped at      ifunit_ref+0x32:        movq    0x28(%rdx),%rax
db> wh
Tracing pid 1 tid 100001 td 0xffffff000185f000
ifunit_ref() at ifunit_ref+0x32
ifioctl() at ifioctl+0xb7
nfs_mountroot() at nfs_mountroot+0x94
nfs_mount() at nfs_mount+0x4d8
vfs_donmount() at vfs_donmount+0xc80
kernel_mount() at kernel_mount+0x88
vfs_mountroot_try() at vfs_mountroot_try+0x17d
vfs_mountroot() at vfs_mountroot+0x37a
start_init() at start_init+0x45
fork_exit() at fork_exit+0x112
fork_trampoline() at fork_trampoline+0xe
--- trap 0, rip = 0, rsp = 0xffffff8000053d30, rbp = 0 ---