Running Unikraft on Xen

Xen is an open-source hypervisor of type 1 that have two types of virtualizations available. Unikraft supports this platform and has some ported applications to run on Xen. All applications will run in a separate domain and can be controlled by the xl tool.

Build and run Unikraft on Xen using kraft

In order to configure a Unikraft image to target the Xen platform, we simply select one of the Xen images at the configuration step, according to the target architecture (ARM64 or x86_64):

$ kraft configure

[?] Which target would you like to configure?: helloworld_xen-x86_64
   helloworld_linuxu-x86_64
   helloworld_kvm-x86_64
 > helloworld_xen-x86_64
   helloworld_linuxu-arm64
   helloworld_kvm-arm64
   helloworld_linuxu-arm

After this step, kraft build and kraft run should work the same.

By default, what kraft run does behind the scenes is to check if the host machine architecture is the same as the target one. If they are the same, hardware acceleration is used. If not, it is automatically disabled.

Build and run Unikraft on Xen using make and xl

You can also build and run Unikraft on Xen by using the Makefile method (basically, reproducing the internals of kraft). This could be useful in the development stage.

In this section, we suppose you already have an application directory with a Makefile and Makefile.uk, as described in the Advanced section.

For the configuration step, run make menuconfig, go to Architecture selection -> Architecture and select one of the 3 alternatives. Then, go to Platform Configuration and select Xen guest.

After creating the configuration, exit the configuration menu and build the image using make.

In order to run, you need to create a configuration file helloworld.cfg, that should look something like:

name          = "helloworld"
vcpus         = "1"
memory        = "4"
kernel        = "./build/helloworld_xen-x86_64"

After this you can run the application using xl:

xl create -c helloworld.cfg

Of course, more configurations can be made, for more details about these options you can see what are all the possible parameters in a domain configuration file documentation.

Using xen-guest to run Unikraft on Xen

xen-guest is a useful script used by kraft to run its Xen images. What xen-guest does it taking a simple list of arguments from the user and gemerate a more complex xl command. Here is the xen-guest command for running app-helloworld on x86_64:

$ xen-guest -k build/app-helloworld_xen-x86_64

If we add the -D option, we can see the generated xl command and the configuration file.

xen-guest offers all kind of options, just like xl does. You can run xen-guest -help to find the option you need for a specific use case.