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Goal

I'd like to emulate the boot process (any boot process) in AArch64 (ARM64) on the actual, real, AArch64 hardware as I'm working on a bootloader and an emulation workflow is much faster.

Problem

Every attempt to use QEMU results in a blank screen. I have tried running bootloaders, and tried to boot Linux directly. There are no error messages.

Various Attempts

First attempt:

# sudo apt-get install qemu qemu-system-arm qemu-efi-aarch64 qemu-utils qemu-system-aarch64 -nographic -machine virt,gic-version=3 -m 512M -smp 4 some-aarch64-linux.iso # Blank screen. Press ctrl+a c to exit.

Second attempt:

# Create an EFI bootloader dd if=/dev/zero of=flash0.img bs=1M count=64 dd if=/usr/share/qemu-efi-aarch64/QEMU_EFI.fd of=flash0.img conv=notrunc qemu-system-aarch64 -nographic -machine virt,gic-version=3 -m 512M -smp 4 \ -drive file=flash0.img,format=raw,if=pflash # Blank screen. Press ctrl+a c to exit.

Third attempt:

qemu-img create -f qcow2 alpine.img 8G wget -O alpine-virt.iso http://dl-cdn.alpinelinux.org/alpine/v3.12/releases/aarch64/alpine-virt-3.12.1-aarch64.iso sudo kvm -machine virt -hda alpine.img -cdrom alpine-virt.iso -m 512 > KVM is not supported for this guest CPU type > kvm_init_vcpu failed: Invalid argument

Fourth attempt:

qemu-img create -f qcow2 alpine.img 8G wget -O alpine-virt.iso http://dl-cdn.alpinelinux.org/alpine/v3.12/releases/aarch64/alpine-virt-3.12.1-aarch64.iso qemu-system-aarch64 -nographic -machine virt -hda alpine.img -cdrom alpine-virt.iso -m 512 # Blank screen. Press ctrl+a c to exit.

Fifth attempt with Docker on an x86-64 machine:

docker run -it --rm --name qemu-container \ -e QEMU_ARCH=aarch64 \ -e QEMU_HDA=/tmp/hda.qcow2 \ -e QEMU_HDA_SIZE=1G \ -e QEMU_CPU=4 \ -e QEMU_RAM=512 \ -v ${PWD}/alpine-virt-3.12.1-aarch64.iso:/tmp/os.iso:ro \ -e QEMU_CDROM=/tmp/os.iso \ -e QEMU_BOOT='order=d' \ -e QEMU_PORTS='2375 2376' \ tianon/qemu start-qemu -machine virt # Results: # + qemu-img create -f qcow2 -o preallocation=off /tmp/hda.qcow2 1G # Formatting '/tmp/hda.qcow2', fmt=qcow2 cluster_size=65536 preallocation=off compression_type=zlib size=1073741824 lazy_refcounts=off refcount_bits=16 # + exec qemu-system-aarch64 -smp 4 -m 512 -drive file=/tmp/hda.qcow2,index=0,media=disk,discard=unmap,detect-zeroes=unmap,if=none,id=hda -device virtio-scsi-pci -device scsi-hd,drive=hda -cdrom /tmp/os.iso -boot order=d -netdev user,hostname=30047d3b64c0,hostfwd=tcp::22-:22,hostfwd=udp::22-:22,hostfwd=tcp::2375-:2375,hostfwd=udp::2375-:2375,hostfwd=tcp::2376-:2376,hostfwd=udp::2376-:2376,id=net -device virtio-net-pci,netdev=net -serial stdio -vnc :0 # Frozen. Press ctrl+c to send a signal

Prior Research:

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  • 1
    You say you want to work on a bootloader, but then you try to boot Linux. So I don't understand what you're trying to do. Which stage bootloader are you working on? You seem to be keen on EFI: does your real hardware have EFI? Arm bootloaders aren't standardized across manufacturers so a Linux image for a particular kind of hardware might not work on Qemu: you need an image for Qemu — but that would come with a bootloader as a black box. Commented Nov 7, 2020 at 21:53
  • Honestly, at this point, I'm just trying to get anything but a blank screen. But yes, I need to compile U-Boot from source, so if my bootloader functions, then I can boot linux. From my attempts with QEMU I'm just trying to get anything but a blank screen. Commented Nov 7, 2020 at 22:04
  • @Gilles'SO-stopbeingevil' "I'd like to emulate the boot process (any boot process)" if that clarifies your comment. Commented Nov 8, 2020 at 2:00

1 Answer 1

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Failure (Results in a blank screen):

qemu-system-aarch64 \ -machine virt \ -serial stdio \ -bios u-boot.bin

Success (The bootloader runs):

qemu-system-aarch64 \ -machine virt \ -serial stdio \ -cpu cortex-a53 \ -bios u-boot.bin

Solution:

On dissimilar architectures between the host and the guest, add a CPU flag so QEMU doesn't default to the host CPU virtualization:

-cpu cortex-a53

On identical host hardware to emulation, this flag shouldn't be needed (not needed on x86-64 emulation/hardware?), but in my case it is. Adding this parameter to QEMU emulating AArch64 on real AArch64 hardware allowed the bootloader to run and show output to the console:

~$ qemu-system-aarch64 -machine virt -serial stdio -cpu cortex-a53 -bios u-boot.bin U-Boot 2021.01-rc1-g896cc5aa (Nov 06 2020 - 23:33:35 -0800) DRAM: 128 MiB Flash: 128 MiB *** Warning - bad CRC, using default environment In: pl011@9000000 Out: pl011@9000000 Err: pl011@9000000 Net: No ethernet found. Hit any key to stop autoboot: 0 starting USB... No working controllers found USB is stopped. Please issue 'usb start' first. scanning bus for devices... ...

Running qemu-system-aarch64 -cpu help:

Available CPUs: arm1026 arm1136 arm1136-r2 arm1176 arm11mpcore arm926 arm946 cortex-a15 cortex-a53 cortex-a57 cortex-a7 cortex-a8 cortex-a9 cortex-m3 cortex-m4 cortex-r5 pxa250 pxa255 pxa260 pxa261 pxa262 pxa270-a0 pxa270-a1 pxa270 pxa270-b0 pxa270-b1 pxa270-c0 pxa270-c5 sa1100 sa1110 ti925t host (only available in KVM mode)
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