panic: pmap_demote_pde: firstpte and newpte map different physical addresses
cpuid = 0
time = 1559177717
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x47/frame 0xfffffe0020f9e1f0
vpanic() at vpanic+0x1e0/frame 0xfffffe0020f9e250
panic() at panic+0x43/frame 0xfffffe0020f9e2b0
pmap_demote_pde_locked() at pmap_demote_pde_locked+0x127e/frame 0xfffffe0020f9e380
pmap_remove_all() at pmap_remove_all+0x38e/frame 0xfffffe0020f9e420
vm_object_page_remove() at vm_object_page_remove+0x187/frame 0xfffffe0020f9e480
vnode_pager_setsize() at vnode_pager_setsize+0x107/frame 0xfffffe0020f9e4d0
vtruncbuf() at vtruncbuf+0x50a/frame 0xfffffe0020f9e530
ffs_truncate() at ffs_truncate+0x16bd/frame 0xfffffe0020f9e720
ufs_setattr() at ufs_setattr+0x918/frame 0xfffffe0020f9e7c0
VOP_SETATTR_APV() at VOP_SETATTR_APV+0xc2/frame 0xfffffe0020f9e7f0
vn_truncate() at vn_truncate+0x246/frame 0xfffffe0020f9e930
kern_ftruncate() at kern_ftruncate+0x13b/frame 0xfffffe0020f9e980
amd64_syscall() at amd64_syscall+0x436/frame 0xfffffe0020f9eab0
fast_syscall_common() at fast_syscall_common+0x101/frame 0xfffffe0020f9eab0
--- syscall (198, FreeBSD ELF64, nosys), rip = 0x41311a, rsp = 0x7fffdfffdf38, rbp = 0x2 ---
KDB: enter: panic
[ thread pid 3827 tid 100778 ]
Stopped at      kdb_enter+0x6a: movq    $0,kdb_why