get the device tree in qemu

os/run-fdt.sh

+qemu-system-riscv64 -M 128m -machine virt,dumpdtb=virt.out  \
+-bios ../bootloader/rustsbi-qemu.bin  \
+-device loader,file=target/riscv64gc-unknown-none-elf/release/os.bin,addr=0x80200000  \
+-drive file=../user/target/riscv64gc-unknown-none-elf/release/fs.img,if=none,format=raw,id=x0  \
+-device virtio-blk-device,drive=x0  \
+-device virtio-gpu-device  \
+-device virtio-keyboard-device  \
+-device virtio-mouse-device \
+-serial stdio
+
+fdtdump virt.out    
\ No newline at end of file