rants, tirades, ruminations

It seems like a recent Debian kernel change may have moved the vfio_iommu_type1 feature in the kernel from being statically compiled to a module. This meant I was getting the following when trying to start up qemu:

qemu-system-x86_64: -device vfio-pci,host=02:00.0,bus=root,addr=00.0,multifunction=on,x-vga=on: vfio: No available IOMMU models
qemu-system-x86_64: -device vfio-pci,host=02:00.0,bus=root,addr=00.0,multifunction=on,x-vga=on: vfio: failed to setup container for group 18
qemu-system-x86_64: -device vfio-pci,host=02:00.0,bus=root,addr=00.0,multifunction=on,x-vga=on: vfio: failed to get group 18
qemu-system-x86_64: -device vfio-pci,host=02:00.0,bus=root,addr=00.0,multifunction=on,x-vga=on: Device initialization failed
qemu-system-x86_64: -device vfio-pci,host=02:00.0,bus=root,addr=00.0,multifunction=on,x-vga=on: Device 'vfio-pci' could not be initialized

The esteemed Alex Williamson was quick to reply that this was due to a missing kernel module, vfio_iommu_type1 to be exact. So, add that into /etc/modules and go ahead and modprobe it to avoid a reboot, and you should be good to go.