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Xen as Static Partitioning Hypervisor for Embedded and Automotive

You might already know that Xen powers some of the largest clouds in production today, but did you know that Xen is also an excellent static partitioning hypervisor for embedded applications?

Xen can be configured for embedded static partitioning using Dom0less and the null scheduler.

Dom0less enables Xen to create multiple VMs in parallel at boot without any Dom0 interactions.

Boot times become much shorter, making it easy to achieve sub-second boot times for an RTOS on top of Xen. Dom0 becomes just optional: it could be removed entirely, or a small RTOS could be used as Dom0 just for monitoring the system. For a quick way to setup Dom0less, refer to ImageBuilder.

The null scheduler is hard real-time scheduler that statically assign physical CPUs to virtual CPUs. With the null scheduler, there are no context switches and you get the best possible interrupt latency. Enabling the null scheduler is as easy as adding sched=null to the Xen command line, which ImageBuilder does automatically for you.

Use Dom0less and the null scheduler together to achieve a true static partitioning configuration.

Cache Coloring and Deterministic Interrupt Latency

If you need fully deterministic interrupt latency and hard real-time, a shared L2 cache across CPU cores can be a vehicle for interference. Xen solves the problem by splitting the L2 cache in software using a technology called "Cache Coloring". Xen with Cache Coloring has a deterministic interrupt latency of 4 microseconds on Xilinx Ultrascale+, even under heavy interference from multiple sources.

Checkout the original Cache Coloring presentation for more details.

Xen Safety-Certifications

Multiple safety assessors from well-known companies in the safety industry have evaluated Xen and deemed it safety-certifiable.

If you are interested in safety certifications, join the Xen FuSa Special Interest Group or watch one of the latest presentations.

The Xen FuSa SIG has the specific goal of making upstream Xen releases easier to safety certify. The working group is active in a number of areas, from documentation to testing and traceability. Specific examples of Xen FuSa SIG activities are MISRA C compatibility improvements and the introduction of more tests to validate Xen external interfaces.