Paravirtualized block device
From KVM
Paravirtualized Block Device
Host side
run kvm with command-line: -drive file=<path_to_your_raw_qemu_img>,if=virtio
you can also specify boot=on in the command-line: -drive file=<path_to_your_raw_qemu_img>,if=virtio,boot=on
Guest side - Linux
sudo modprobe virtio_blk
to have virtio_blk driver, you need to upgrade the kernel to higher than 2.6.25.
refer to Virtio
Guest side - Windows
You can find Windows drivers at Downloads page.