alpine linux for riscv64 based apps(using musl-libc) in ext4fs image
/* prepare qemu, YOUR-KERNEL.elf (elf format) for riscv64*/
$ xz -d alpine-linux-riscv64-ext4fs.img.xz
$ qemu-system-riscv64 -kernel YOUR-KERNEL.elf -m 1G -nographic -smp 1 -drive if=none,format=raw,id=disk0,file=alpine-linux-riscv64-ext4fs.img -device virtio-blk-pci,drive=disk0 -device virtio-net-pci,netdev=net0 -netdev user,id=net0