| name | qemu-for-kernel-development |
| description | QEMU kernel development skill for driver and kernel testing. Use when booting custom kernels in QEMU, Buildroot/Yocto rootfs, virtio devices, or NFS root for driver iteration. Activates on queries about QEMU kernel dev, Buildroot QEMU, virtio block, kernel module test QEMU, or -append root= |
QEMU for Kernel Development
Purpose
Guide agents through QEMU-based kernel and driver development workflows: building/booting custom kernels, attaching virtio block/network, using Buildroot or minimal initramfs, and rapid module test cycles — focused on kernel dev vs general skills/virtualization/qemu-kvm.
When to Use
- Test kernel patch without bare metal
- Develop driver against virtio or emulated DT platform
- CI kernel boot smoke test
- NFS or 9p root for fast edit-compile-test
Workflow
1. Minimal direct kernel boot (arm64 virt)
qemu-system-aarch64 \
-machine virt -cpu cortex-a57 -smp 4 -m 2G \
-kernel arch/arm64/boot/Image \
-append "console=ttyAMA0 root=/dev/vda rw" \
-drive if=virtio,file=rootfs.ext4,format=raw \
-netdev user,id=net0 -device virtio-net-device,netdev=net0 \
-nographic
x86_64:
qemu-system-x86_64 -enable-kvm -m 4G -smp 4 \
-kernel arch/x86/boot/bzImage \
-append "console=ttyS0 root=/dev/vda rw" \
-drive file=rootfs.img,format=raw,if=virtio \
-nographic
2. Buildroot rootfs loop
cd buildroot
make qemu_aarch64_virt_defconfig
make
Integrate custom kernel: set BR2_LINUX_KERNEL_CUSTOM_VERSION or external tree.
3. Out-of-tree module test
make -C $KERNEL_SRC M=$PWD modules
insmod mydriver.ko
dmesg | tail
Share tree with 9p:
-fsdev local,id=dev,path=$PWD,security_model=none \
-device virtio-9p-pci,fsdev=dev,mount_tag=hostshare
4. GDB stub for kernel
qemu-system-aarch64 ... -s -S
gdb vmlinux
(gdb) target remote :1234
(gdb) break start_kernel
Use CONFIG_KGDB for live kernel debugging after boot.
5. Device tree overrides
qemu-system-aarch64 -machine virt -dtb myboard.dtb ...
virt machine provides virtio devices; platform drivers can target QEMU -device models.
6. Agent usage
/qemu-for-kernel-development Boot arm64 virt with custom Image and virtio rootfs for driver CI
Common Problems
| Symptom | Cause | Fix |
|---|
| Kernel panic no root | Wrong root= | root=/dev/vda for virtio blk |
| No console output | Missing console= on cmdline | console=ttyAMA0 / ttyS0 |
| Module vermagic error | Built against wrong tree | Same KERNEL_SRC as booted image |
| Slow without KVM | TCG emulation | -enable-kvm on x86 host |
| DTB mismatch | Wrong machine | Use virt DTB from kernel make dtbs |
Related Skills
skills/virtualization/qemu-kvm — KVM, VFIO, libvirtskills/qemu/qemu-embedded-simulation — bare-metal MCU QEMUskills/kernel/kernel-testing — KUnit, kselftestskills/kernel-dev/device-tree — DT for virt/platformskills/debuggers/gdb — remote GDB basics
