Greetings,
To prepare an embedded Linux demo (on RiscV), I'm trying to boot Linux from U-Boot in qemu-system-riscv64, using the "virt" emulated machine... Note that I'm using QEMU 5.0.
The well documented way to boot Linux works:
In Linux master: CROSS_COMPILE=riscv64-linux-gnu- (toolchain built by Buildroot) ARCH=riscv make defconfig make
In opensbi: make PLATFORM=generic FW_PAYLOAD_PATH=../linux/arch/riscv/boot/Image
Running QEMU: qemu-system-riscv64 -nographic -machine virt -kernel opensbi/build/platform/generic/firmware/fw_payload.elf -append "console=ttyS0"
I can also boot U-Boot, but cannot manage to boot the Linux kernel with it:
In U-Boot mainline:
CROSS_COMPILE=riscv64-linux-gnu- make qemu-riscv64_smode_defconfig Modify the environment: - Unset CONFIG_ENV_IS_NOWHERE - CONFIG_ENV_IS_IN_FAT=y - CONFIG_ENV_FAT_INTERFACE="virtio" - CONFIG_ENV_FAT_DEVICE_AND_PART="0:1" - CONFIG_ENV_FAT_FILE="uboot.env" make
Note that having U-Boot in "S" mode seems to be required to boot Linux. If U-Boot is in "M" mode, it works, but there are faults (as expected) when trying to execute Linux.
In opensbi: make PLATFORM=generic FW_PAYLOAD_PATH=../u-boot/u-boot.bin
I then prepared a disk.img image with a first FAT partition containing: - A "dtb" file captured from the first Linux boot (from /sys/firmware/fdt) - A "uImage" file made from the command: mkimage -A riscv -O linux -C none -T kernel -a 80200000 -e 80200000 -n "Linux" -d arch/riscv/boot/Image uImage
Then I'm starting QEMU as follows:
qemu-system-riscv64 -m 1G -nographic -machine virt -bios opensbi/build/platform/generic/firmware/fw_payload.bin -device virtio-blk-device,drive=hd0 -drive file=disk.img,format=raw,id=hd0
OpenSBI v0.8-58-g781cafd ____ _____ ____ _____ / __ \ / ____| _ _ _| | | | |_ __ ___ _ __ | (___ | |_) || | | | | | '_ \ / _ \ '_ \ ___ | _ < | | | |__| | |_) | __/ | | |____) | |_) || |_ ____/| .__/ ___|_| |_|_____/|____/_____| | | |_|
Platform Name : riscv-virtio,qemu Platform Features : timer,mfdeleg Platform HART Count : 1 Firmware Base : 0x80000000 Firmware Size : 104 KB Runtime SBI Version : 0.2
Domain0 Name : root Domain0 Boot HART : 0 Domain0 HARTs : 0* Domain0 Region00 : 0x0000000080000000-0x000000008001ffff () Domain0 Region01 : 0x0000000000000000-0xffffffffffffffff (R,W,X) Domain0 Next Address : 0x0000000080200000 Domain0 Next Arg1 : 0x0000000082200000 Domain0 Next Mode : S-mode Domain0 SysReset : yes
Boot HART ID : 0 Boot HART Domain : root Boot HART ISA : rv64imafdcsu Boot HART Features : scounteren,mcounteren,time Boot HART PMP Count : 16 Boot HART PMP Granularity : 4 Boot HART PMP Address Bits: 54 Boot HART MHPM Count : 0 Boot HART MHPM Count : 0 Boot HART MIDELEG : 0x0000000000000222 Boot HART MEDELEG : 0x000000000000b109
U-Boot 2021.01-rc2-00161-gf6cf78dc6a (Dec 02 2020 - 07:05:39 +0100)
CPU: rv64imafdcsu Model: riscv-virtio,qemu DRAM: 1 GiB Loading Environment from FAT... OK In: uart@10000000 Out: uart@10000000 Err: uart@10000000 Net: No ethernet found. Hit any key to stop autoboot: 0 bootcmd=printenv bootcmd; fatload virtio 0:1 0x84000000 uImage; fatload virtio 0:1 0x88000000 dtb; bootm 0x84000000 - 0x88000000 17704512 bytes read in 39 ms (432.9 MiB/s) 3618 bytes read in 1 ms (3.5 MiB/s) ## Booting kernel from Legacy Image at 84000000 ... Image Name: Linux Image Type: RISC-V Linux Kernel Image (uncompressed) Data Size: 17704448 Bytes = 16.9 MiB Load Address: 80200000 Entry Point: 80200000 Verifying Checksum ... OK ## Flattened Device Tree blob at 88000000 Booting using the fdt blob at 0x88000000 Loading Kernel Image Using Device Tree in place at 0000000088000000, end 0000000088003e21
Starting kernel ...
... and that's all I get, no further output. I'm not sure my dtb file is suitable though. I'm surprised there is no DTS file for the riscv64 "virt" board emulated by QEMU in the Linux kernel sources, as U-Boot will refuse to boot Linux without one.
Note that in U-Boot, the bootargs environment is set to: bootargs=console=ttyS0
I'll be interested in your advise, if you already managed to do something like this.
Cheers,
Michael.