kernel trap 12 with interrupts disabled
Fatal trap 12: page fault while in kernel mode
cpuid = 0; apic id = 00
fault virtual address = 0x320
fault code = supervisor read data, page not present
instruction pointer = 0x20:0xffffffff8153fae0
stack pointer = 0x28:0xfffffe000059d7b0
frame pointer = 0x28:0xfffffe000059d820
code segment = base 0x0, limit 0xfffff, type 0x1b
= DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags = resume, IOPL = 0
current process = 21 (dom0)
trap number = 12
panic: page fault
cpuid = 0
time = 1623189232
KDB: enter: panic
db:0:kdb.enter.default> bt
Tracing pid 21 tid 100091 td 0xfffff800049a8000
kdb_enter() at kdb_enter+0x37/frame 0xfffffe000059d470
vpanic() at vpanic+0x197/frame 0xfffffe000059d4c0
panic() at panic+0x43/frame 0xfffffe000059d520
trap_fatal() at trap_fatal+0x391/frame 0xfffffe000059d580
trap_pfault() at trap_pfault+0x4f/frame 0xfffffe000059d5d0
trap() at trap+0x286/frame 0xfffffe000059d6e0
calltrap() at calltrap+0x8/frame 0xfffffe000059d6e0
--- trap 0xc, rip = 0xffffffff8153fae0, rsp = 0xfffffe000059d7b0, rbp = 0xfffffe000059d820 ---
smp_targeted_tlb_shootdown() at smp_targeted_tlb_shootdown+0x420/frame 0xfffffe000059d820
pmap_ts_referenced() at pmap_ts_referenced+0x5c6/frame 0xfffffe000059d8f0
vm_pageout_worker() at vm_pageout_worker+0xf88/frame 0xfffffe000059dcb0
vm_pageout() at vm_pageout+0x193/frame 0xfffffe000059dcf0
fork_exit() at fork_exit+0x7e/frame 0xfffffe000059dd30
fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe000059dd30
I don't recognize that backtrace, but it seems to be pretty deep in an area unlikely to have a bug. It see it's running in KVM. It could be an issue in the Hypervisor hardware, or something else in the VM settings, but it's unlikely to be a problem in pfSense itself.
I'd snapshot it and upgrade it to 2.5.2-RC before anything else, though.