panic shortly after boot when amdgpu.ko is loaded (fpu?)

I have a Threadripper 2990WX system that I recently installed an AMD 
Radeon Pro W5700 into. It runs fine unless I load the amdgpu driver, at 
which point it panics several seconds after boot: I have enough time to 
login and run a few commands, but even if I just leave it it'll panic.  
I'm running:


FreeBSD photon.int.bluestop.org 13.0-CURRENT FreeBSD 13.0-CURRENT #0 
6db1a3e8098-c273171(master): Thu Nov 26 01:26:17 MST 2020 
bcran_at_photon.int.bluestop.org:/usr/obj/usr/src/amd64.amd64/sys/GENERIC-NODEBUG 
amd64


I rebuilt the drm-current-kmod-5.4.62.g20201109_1 port today.


The panic is:

Fatal trap 9: general protection fault while in kernel mode
cpuid = 24; apic id = 18
instruction pointer	= 0x20:0xffffffff81002dcf
stack pointer	        = 0x0:0xfffffe016e6ffaa0
frame pointer	        = 0x0:0xfffffe016e6ffaa0
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		= 4372 (hald)
trap number		= 9
panic: general protection fault
cpuid = 24
time = 1606450595
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe016e6ff7b0
vpanic() at vpanic+0x181/frame 0xfffffe016e6ff800
panic() at panic+0x43/frame 0xfffffe016e6ff860
trap_fatal() at trap_fatal+0x387/frame 0xfffffe016e6ff8c0
trap() at trap+0x8e/frame 0xfffffe016e6ff9d0
calltrap() at calltrap+0x8/frame 0xfffffe016e6ff9d0
--- trap 0x9, rip = 0xffffffff81002dcf, rsp = 0xfffffe016e6ffaa0, rbp = 0xfffffe016e6ffaa0 ---
fpurestore_xrstor3264() at fpurestore_xrstor3264+0x2f/frame 0xfffffe016e6ffaa0
restore_fpu_curthread() at restore_fpu_curthread+0x85/frame 0xfffffe016e6ffac0
fpudna() at fpudna+0x3a/frame 0xfffffe016e6ffae0
trap() at trap+0x246/frame 0xfffffe016e6ffbf0
calltrap() at calltrap+0x8/frame 0xfffffe016e6ffbf0
--- trap 0x16, rip = 0x80067137f, rsp = 0x7fffffffd8b0, rbp = 0x7fffffffd8f0 ---
Uptime: 1m4s
Dumping 4193 out of 130894 MB:..1%..11%..21%..31%..41%..51%..61%..71%..81%..91%


I've uploaded details (core.txt, dmesg.txt etc.) to 
https://bsdio.com/freebsd/crashes/2020-11-26-amdgpu/ and the vmcore file 
is available on request.


-- 
Rebecca Cran