Running an x86 Yocto Linux image under QEMU KVM

Host OS preparation (VM manager host OS)

1.Enable KVM on the host machine

2. Enable on host OS vhost-net virtio networking accelerator to mitigate overhead on QEMU virtualization environment.
Load vhost-net module on KVM Host.

[root@dlp ~]#modprobe vhost_net
[root@dlp ~]#lsmod | grep vhost

The result of running the commands should be similar to the following:

vhost_net 24241 0
macvtap 7867 1 vhost_net
tun16825 3 vhost_net

Basically, follow the same guide as for enabling KVM on the host (step 1.), but replace kvm with vhost_net

3. Start the VM using the line below:

ubik@sentry:~/yoctoproject/build$ sudo kvm -kernel /home/ubik/yoctoproject/build/tmp/deploy/images/bzImage-qemux86.bin -net nic,model=virtio -net \
    tap,vlan=0,ifname=tap0,script=no,downscript=no,vhost=on -drive file=/home/ubik/yoctoproject/build/tmp/deploy/images/core-image-core-qemux86.ext3,if=virtio \
   -show-cursor -usb - usbdevice wacom-tablet -vga vmware -no-reboot -enable-kvm -cpu host -m 128 --append "vga=0 root=/dev/vda rw mem=128M \
   ip=192.168.7.2::192.168.7.1:255.255.255.0 oprofile.timer=1 " 

This is an example of running a virtualized Yocto image, with KVM active, cpu host features exported in the Yocto VM, paravirtualization enabled, and using virtio interfaces for disk access and networking. On a machine equipped with a Core i7 2600 (3.4GHz, 4 cores, 8 threads)/8 GB RAM/Intel SSD G3 120GB qemux86 Yocto Linux boots in around 7 seconds for a core-image-x11. The same image boots in 20 seconds without virtualization optimizations and feels slower in usage.

See the following screenshots:

Yocto Linux guest running under QEMU KVM with paravirtualization and virtio tech.

CPU host features exported to Yocto Linux guest.

Guest OS preparation

The following kernel configs needs to be enabled for Yocto Linux guest OS:

[...]
CONFIG_PARAVIRT_GUEST=y
CONFIG_KVM_CLOCK=y
CONFIG_KVM_GUEST=y
CONFIG_PARAVIRT=y
CONFIG_PARAVIRT_CLOCK=y
CONFIG_VIRTIO_MMIO=y
[..]