It has a quite complicated syntax and it's not used directly in general. Virsh is a powerful tool that can be used to create and manage VMs. To connect to the console of the VM, the user has to configure a vncserver to start on the guest. If you already have an existing KVM image(the disk image and optionally the kernel image), you can run it from the CLI using the various qemu-system-* commands depending on the desired guest architecture.

To obtain an KVM controller you have to build the kvm-image-minimal target. This layer contains a README that presents all the layer dependencies and the necessary steps to build the target image. The meta-virtualization layer can be found on the official yocto source repositories page at meta-virtualization. An example of how to remotely connect using Virt-manager to control the VMs can be found in the next section. To configure libvirt for other hypervisors you just have to make some minor modifications to the recipe provided by the meta-xen layer. Our layer builds libvirt only for qemu support to keep the image as minimal as possible. The library is also used by a number of modern VM management systems to handle typical tasks when dealing with VMs. The functionality is exposed through the virsh command. The set of tools include an C API library that comes with bindings for common languages, a daemon (libvirtd), and a command line utility (virsh). Libvirt is a toolkit for interacting with virtual machine hypervisors( Xen, KVM, VMWare ESX etc.). If the underlying hardware does not provide support for KVM or if it has been disabled, qemu can be used to run the VMs using software emulation, but with a performance loss. The recipe for the qemu package is included in the standard poky distribution and it comes with built-in support for KVM and for all the new advanced features like virtio, which is the main platform for IO virtualization. QEMU is a popular process emulator that uses dynamic binary translation to achieve a reasonable speed while being easy to port to new architectures.

Since yocto uses 3.4.20 or a newer version of the Linux kernel, no extra packages are required only a proper kernel configuration. The kvm component is included in the mainline Linux kernel starting from version 2.6.20. KVM can be used to run multiple virtual machines that contain unmodified Windows or Linux images. There are a number of other dependencies that come from the meta-oe layer of oe-core.

It also features recipes for the libvirt package and other tools that can be used for the virtual machine management. This layer contains all the necessary recipes for creating VM controllers using the Xen, LXC and KVM hypervisors. The project is part of the meta-virtualization layer. Multiple guest running in the Yocto Project KVM host layer Packages

Qemu libvirt tutorial