Today I updated my host system from 12 to 12.1 . I ran updates on my first jail. stopped the jail and got a system freez. I tried it a second time and after stopping the jail , system freezed again. 

I could get this from my console server.

Fatal trap 12: page fault while in kernel mode
cpuid = 2; apic id = 02
fault virtual address   = 0x40
fault code              = supervisor read data, page not present
instruction pointer     = 0x20:0xffffffff83253f5f
stack pointer           = 0x28:0xfffffe0000466800
frame pointer           = 0x28:0xfffffe0000466840
code segment            = base rx0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 0 (thread taskq)
trap number             = 12
panic: page fault
cpuid = 2
time = 1586637015
KDB: stack backtrace:
#0 0xffffffff80c1d2f7 at kdb_backtrace+0x67
#1 0xffffffff80bd062d at vpanic+0x19d
#2 0xffffffff80bd0483 at panic+0x43
#3 0xffffffff810a7dcc at trap_fatal+0x39c
#4 0xffffffff810a7e19 at trap_pfault+0x49
#5 0xffffffff810a740f at trap+0x29f
#6 0xffffffff81081bdc at calltrap+0x8
#7 0xffffffff80cd041d at if_down+0x14d
#8 0xffffffff80ccdc5a at if_detach_internal+0x87a
#9 0xffffffff80cd496c at if_vmove+0x3c
#10 0xffffffff80cd4918 at vnet_if_return+0x48
#11 0xffffffff80cfe324 at vnet_destroy+0x124
#12 0xffffffff80b988d0 at prison_deref+0x2a0
#13 0xffffffff80c2fad4 at taskqueue_run_locked+0x154
#14 0xffffffff80c30e08 at taskqueue_thread_loop+0x98
#15 0xffffffff80b90c43 at fork_exit+0x83
#16 0xffffffff81082c1e at fork_trampoline+0xe
Uptime: 9m57s
Dumping 1495 out of 16232 MB:..2%..11%..21%..32%..41%..51%..61%..71%..81%..91%
Dump complete



╰─ cat core.txt.0
/dev/stdin:1: Error in sourced command file:
Cannot access memory at address 0x65657246
/dev/stdin:1: Error in sourced command file:
Cannot access memory at address 0x65657246
/dev/stdin:1: Error in sourced command file:
Cannot access memory at address 0x65657246
/dev/stdin:1: Error in sourced command file:
Cannot access memory at address 0x65657246
/dev/stdin:1: Error in sourced command file:
Cannot access memory at address 0x65657246
Unable to find matching kernel for /var/crash/vmcore.0

╰─ sudo cat info.0
Dump header from device: /dev/ada0p4
  Architecture: amd64
  Architecture Version: 2
  Dump Length: 1568067584
  Blocksize: 512
  Compression: none
  Dumptime: Sat Apr 11 22:30:15 2020
  Hostname: freebsd.home.lan
  Magic: FreeBSD Kernel Dump
  Version String: FreeBSD 12.1-RELEASE-p3 GENERIC
  Panic String: page fault
  Dump Parity: 3395401551
  Bounds: 0
  Dump Status: good

╰─ sudo cat info.last
Dump header from device: /dev/ada0p4
  Architecture: amd64
  Architecture Version: 2
  Dump Length: 1568067584
  Blocksize: 512
  Compression: none
  Dumptime: Sat Apr 11 22:30:15 2020
  Hostname: freebsd.home.lan
  Magic: FreeBSD Kernel Dump
  Version String: FreeBSD 12.1-RELEASE-p3 GENERIC
  Panic String: page fault
  Dump Parity: 3395401551
  Bounds: 0
  Dump Status: good


Anything I can do ?

I can upload the core dump if you're interested. 

thank you !