Hedron Microhypervisor

This is the source code for the Hedron microhypervisor.

The Hedron microhypervisor combines microkernel and hypervisor functionality and provides an extremely small trusted computing base for user applications and virtual machines running on top of it. The microhypervisor implements a capability-based authorization model and provides basic mechanisms for virtualization, spatial and temporal separation, scheduling, communication, and management of platform resources.

Hedron can be used with a multi-server environment that implements additional operating-system services in user mode, such as device drivers, protocol stacks, and policies. On machines with hardware virtualization features, multiple unmodified guest operating systems can run concurrently on top of the microhypervisor.

Please talk to us before using it in any production system, because there are important caveats for some use cases.

History

Hedron is derived from the NOVA microhypervisor developed by Udo Steinberg. While NOVA and Hedron are still close in spirit, the last common commit dates from 2015. Since then Hedron has been steadily modernized with a focus on simplicity, testability, and support for modern virtualization features. Over the years, Hedron also adopted patches by Genode Labs developed as part of their NOVA fork.

Supported platforms

The Hedron microhypervisor runs on single- and multi-processor x86 machines that support ACPI, XSAVE and FSGSBASE.

Recommended Intel CPUs are Intel Core processors starting with the Ivy Bridge microarchitecture. AMD support is experimental and currently not actively used.

The virtualization features are available on:

Intel CPUs with VMX and nested paging (EPT),
AMD CPUs with SVM and nested paging (NPT).

Building from source code

You need the following tools to compile the hypervisor:

cmake 3.13 or higher, available from https://cmake.org/
binutils 2.30 or higher, available from http://www.kernel.org/pub/linux/devel/binutils/
gcc 7.4.0 or higher, available from http://gcc.gnu.org/
or alternatively, clang 9.0 or higher, available from http://clang.llvm.org/

To build and run the unit tests (optional), you need:

pkg-config, available from https://github.com/pkgconf/pkgconf
Catch2, available from https://github.com/catchorg/Catch2

You can build a microhypervisor binary as follows:

# Only needs to be done once
mkdir -p build
cd build ; cmake ..

# Build the hypervisor and execute unit tests
make
make test

Building unit tests can be avoided by passing -DBUILD_TESTING=OFF to cmake.

Building from source code with Nix

As an alternative to manually installing depenencies, Hedron can also be built using Nix. After installing Nix, build Hedron using:

nix-build

The hypervisor is then found in result/. With Nix available, other build options for developers become available. See the documentation in nix/release.nix for details.

Booting

The Hedron microhypervisor can be started from a multiboot-compliant bootloader, such as GRUB or PXEGRUB. Here are some examples:

Boot from harddisk 0, partition 0

title         Hedron
kernel        (hd0,0)/boot/hedron/hypervisor
module        (hd0,0)/...
...

Boot from TFTP server aa.bb.cc.dd

title         Hedron
tftpserver    aa.bb.cc.dd
kernel        (nd)/boot/hedron/hypervisor
module        (nd)/...
...

Command-Line Parameters

The following command-line parameters are supported for the microhypervisor. They must be separated by spaces.

iommu - Enables DMA and interrupt remapping.
serial - Enables the microhypervisor to drive the serial console.
nopcid - Disables TLB tags for address spaces.
novga - Disables VGA console.
novpid - Disables TLB tags for virtual machines.

Contact

Feedback and comments should be sent to hypervisor@cyberus-technology.de.

amphi / hedron