Help saving 4.7 kernel dump to disk

Hi, I tied to save the kernel core dump following Michael Lucas instructions, but it only works when the kernel is already loaded. I am experiencing kernel trap during kernel boot, and the show disk/device and ddb> call setdumpdev (0xf000b444) does not work for me. What else can I try to save

Re: Help saving 4.7 kernel dump to disk

The patch works for me. dmesg: ... ugen0: Sony USB Memory Stick Slot, rev 1.10/1.80, addr 2 pcm0: port 0x1880-0x18bf,0x1c00-0x1cff irq 9 at device 31.5 on pci0 pci0: (vendor=0x8086, dev=0x2446) at 31.6 irq 9 eisa0: on motherboard eisa0: unknown card @H@ (0x0100) at slot 1 orm0: at io