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“To EL2, and Beyond!” is a 2017 presentation about using ARM’s Virtualization Host Extensions (VHE) to change how Linux and KVM run on ARM processors. Its central contrast is between a split design, with Linux at EL1 and a small hypervisor component at EL2, and a VHE design that lets an EL1-oriented Linux system run at EL2. The slides also describe changes to KVM’s vCPU run loop and timer handling. Their implementation and performance claims are historical, not evidence of current kernel behavior or present-day performance.
What does EL2 mean on ARM?
ARM processors use exception levels to separate execution contexts and privileges. In the presentation’s framing, EL1 is where an ordinary operating-system kernel runs, while EL2 is the execution level intended for hypervisor functions. A hypervisor manages virtual machines and mediates access to processor resources.
That division creates a design question for KVM/ARM: how should a Linux host kernel and the hypervisor functions needed to run guests be arranged across those levels? The talk treats EL2 as a distinct CPU mode with limitations compared with running a full operating system at EL1, then examines whether VHE can make EL2 a more practical home for the host.
What does VHE change for KVM/ARM?
ARMv8.1 Virtualization Host Extensions are presented as allowing an unmodified, EL1-oriented operating system to run at EL2 with expanded EL2 functionality. The slides discuss support for userspace at EL0, system-register redirection, and backward compatibility when VHE is disabled. In broad terms, VHE gives the host kernel a way to use EL2 without requiring it to be rewritten as a hypervisor-specific operating system.
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| Design in the presentation | Where host Linux runs | Role of EL2 | Processor support |
|---|---|---|---|
| Split-mode KVM/ARM | EL1 | A small hypervisor component runs at EL2 | Does not depend on VHE in the design described |
| VHE design | EL2 | Linux and KVM run at EL2, with VHE providing expanded functionality | Requires a processor with VHE support |
This is the presentation’s historical architectural comparison, not a complete map of current Linux KVM code. For details, see the presentation slides.
What KVM optimizations did the talk describe?
Moving work out of the vCPU run loop
The talk describes moving some work out of the vCPU run loop and into load/put handling. The design goal was to reduce work performed as a virtual CPU enters or leaves guest execution. The presentation’s description is useful for understanding the proposed optimization, but it should not be taken as a description of every current KVM/arm64 implementation.
Changing timer handling
The slides also discuss changing timer handling so timer work can be managed while KVM is running. This is another implementation idea from the talk; its current status and behavior are not established by the presentation record.
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What did the 2017 presentation measure?
The authors described experiments on an AMD Seattle B0 ARM server with a 2.0 GHz AMD A1100 CPU, eight-way SMP, 16 GB of RAM, and 10 GB Ethernet passthrough. These are the test setup stated in the slides, not a current hardware recommendation. The presentation identifies Linux v4.16 as a target, and the KVM project’s file record dates its archived PDF to December 22, 2017.
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The slides characterize their microbenchmark and application benchmark results positively and compare performance characteristics with x86. Those are the presenters’ historical claims; they have not been independently validated here and should not be generalized to today’s processors, kernels, or workloads. A hypercall comparison is labeled “3.181” for non-VHE and “3.045” for VHE, but the indexed text does not establish units or enough methodological context to interpret those figures reliably. They are not suitable as a standalone speedup claim.
The KVM project file record identifies the archived presentation copy and its revision date. An indexed copy is also available on Scribd; the Linux KVM project PDF is the primary source for the talk’s claims.
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- 4K HDMI Output: Supports high-resolution display up to 4K for enhanced visual experience and crystal-clear remote viewing
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- PoE Powered: Simplifies setup with power-over-Ethernet support for NanoKVM Pro, eliminating the need for separate power adapters
- WiFi6 and GbE Connectivity: Ensures fast and stable network performance with dual connectivity options for flexible deployment
How should readers use the presentation today?
Use it as a historical explanation of the VHE design direction and the optimization questions its authors explored—not as a current implementation guide, compatibility list, benchmark, or buying guide. The slides name Linux v4.16 as a target, but the available records do not establish whether the specific patches remain current, upstream, or supported.
To evaluate a modern KVM/arm64 system, check the processor’s VHE support, the kernel version and configuration, and current Arm and Linux documentation. Then assess the exact workload and measurement method rather than relying on the 2017 talk’s benchmark characterizations. The sources for this presentation do not establish a specific current server or development board to recommend.
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