Risc64 Virt Usage

Basic Usage

Works perfectly:

$ make boot V=1

$ make boot SHARE=1

$ make boot ROOTDEV=/dev/nfs

Buildroot provides rootfs config and toolchain, mainline linux provides the official kernel config, everything goes well. Qemu v4.0.0 has the riscv64 board support.

BIOS

The only difference is riscv64 requires a proxy kernel to do some prepare before running the real linux kernel. and the proxy kernel currently is replaced by the opensbi project.

Newer qemu and kernel support works with the standard -bios option with opensbi.

We can build one in Linux Lab with these commands:

$ cd src/examples/
$ git clone https://github.com/riscv/opensbi
$ cd opensbi
// for riscv32
$ make all PLATFORM=generic LLVM=1 PLATFORM_RISCV_XLEN=32
// for riscv64
$ make all PLATFORM=generic LLVM=1 PLATFORM_RISCV_XLEN=64
$ ls build/platform/generic/firmware/fw_jump.elf

DTS

The cpu, memory and external devices configuration in dts must match the setting from the QEMU options, otherwise, it may not boot.

If want to change the QEMU options, please make sure update the dts configurations too, or, simply reset DTB variable like this to use the default dtb transferred by QEMU:

$ make boot DTB=

The default dtb is dumped out of QEMU:

$ make boot DUMPDTB=1

References

• Qemu RISCV Documentation
• RISCV Software Status
• RV8: RISC-V simulator for x86-64 (Another simulator)
• RISC-V Debian
• Running 64- and 32-bit RISC-V Linux on QEMU
• RISC-V GNU Compiler Toolchain
• Prebuilt GNU Toolchain
• RISC-V Proxy Kernel and Boot Loader
• RISC-V Open Source Supervisor Binary Interface
• buildroot/configs/qemu_riscv64_virt_defconfig
• buildroot/board/qemu/riscv64-virt/