also a panic with a non-parallel build (make build without -j4):
ddb{0}> show panic
*cpu0: uvm_fault(0xffffffff82a92620, 0xfffffd03cf254600, 0, 2) -> e
ddb{0}> trace
pool_cache_get(ffffffff82a35f48) at pool_cache_get+0xeb
pool_get(ffffffff82a35f48,2) at pool_get+0x62
pmap_enter(fffffd84285da2a8,4177000,42a210000,4,20) at pmap_enter+0xc0
uvm_fault_lower_lookup(ffff800048bcf458,ffff800048bcf490,ffff800048bcf3d0)
at uvm_fault_lower_lookup+0x11a
uvm_fault_lower(ffff800048bcf458,ffff800048bcf490,ffff800048bcf3d0) at
uvm_fault_lower+0x5c
uvm_fault(fffffd838c9f65b8,4176000,0,4) at uvm_fault+0x1c5
upageflttrap(ffff800048bcf5c0,41763b0) at upageflttrap+0x6c
usertrap(ffff800048bcf5c0) at usertrap+0x217
recall_trap() at recall_trap+0x8
end of kernel
end trace frame: 0x72a527e5c430, count: -9
ddb{0}> show registers
rdi 0xa
rsi 0xfffffd03cf2545f8
rbp 0xffff800048bcf0b0
rbx 0xfffffd847f167000
rdx 0xffffffff82a36038 pmap_pv_pool+0xf0
rcx 0xffffffff82a36038 pmap_pv_pool+0xf0
rax 0xfffffd03cf2545e8
r8 0x20
r9 0xfffffd811a151100
r10 0
r11 0xab6ea9e167751a18
r12 0xffffffff82a35f48 pmap_pv_pool
r13 0xffffffff82a36020 pmap_pv_pool+0xd8
r14 0xfffffd83ef33e3b0
r15 0
rip 0xffffffff824500bb pool_cache_get+0xeb
cs 0x8
rflags 0x10286 __ALIGN_SIZE+0xf286
rsp 0xffff800048bcf050
ss 0
pool_cache_get+0xeb: movq %rcx,0x8(%rsi)
