MilvusVisor

MilvusVisor is a thin hypervisor that runs on aarch64 CPUs.

The features of the MilvusVisor are the following.

• (Theoretically) Smaller footprint and overhead than typical VMM (e.g. QEMU/KVM, Xen)
• Support running only one guest OS simultaneously for keeping it simple and thin
• Written in Rust

MilvusVisor allows providing functions OS-independently without the overhead of device virtualization. We are currently developing MilvusVisor as a research activity to achieve HPC environments that provide root privilege to the users without virtualization overhead.

Functions

Currently, MilvusVisor provides the following function.

You can build with enabling some functions by cargo xtask build -f feature1,feautre2,....(featureN is described like Feature Name: feature_name in each section.)
If you want to build with extra features, you can build by cargo xtask build -f default,feature1,feature2,.... If you want to build without any features, you can build by cargo xtask build -f minimum.

• Protecting non-volatile data in devices from guest OS (e.g. Firmware, MAC address)
  • Intel I210 (Feature Name: i210)
    • Protect EEPROM from writing access
  • Mellanox Technologies MT27800 (Feature Name: mt27800)
    • Protect from firmware update
• Protecting MilvusVisor itself against DMA attack (Feature Name: smmu)
  • Using SMMUv3 Stage 2 Page Translation to protect from DMA attack
  • Stage 1 translation is available from guest OS
• Fast restore: Fast restoring the guest environments without reboot the machine (Feature Name: fast_restore)
  • Taking a snapshot just before the first boot of the guest OS
  • Restoring it on rebooting/shutting down the guest OS
• Protecting ACPI Tables from write accesses (Feature Name: acpi_table_protection)
  • For the Fast Restore
• Linked-List Style Memory Allocator (Feature Name: advanced_memory_manager)
• Contiguous Bit (Feature Name: contiguous_bit)
  • Set contiguous bit enabled if available (TLB will be optimized by the contiguous bit)
  • Some machine may not work fine with the contiguous bit
• A64FX specific registers' initialization (Feature Name: a64fx)
  • Control some A64FX specific registers
• PXE Boot (Feature Name: tftp)
  • Download hypervisor_kernel and payload(usually, bootloader) via TFTP
• Raspberry Pi 4 (Feature Name: raspberrypi)
  • For running MilvusVisor on a Raspberry Pi 4. See the document for details.
  • Note that you do not need to use this option for Raspberry Pi 5. Please see the "Tested machines" section for more detail.
• Virtio Network (Feature Name: virtio_net)
  • Add virtual devices to communicate with OS
  • This is the interface, you must implement a protocol stack
  • For more detail, see virtio_net.rs
  • This is an experimental feature, this may not work on some devices
• Embed the hypervisor kernel into the bootloader (Feature Name: embed_kernel)
  • Embed the hypervisor kernel and use the built-in hypervisor kernel
  • This is for the device which does not support file systems

Tested machines

We have tested MilvusVisor on the following machines.

• FUJITSU FX700
• FUJITSU FX1000
• GIGABYTE E252-P30
• QEMU (>= 7.1.0)
• Bluefield-2
• Rasspberry Pi 4 model B
  • The setup steps for Raspbrry pi are different from the other machines. So please also see the document when you try MilvusVisor on Raspberry pi.
• Raspberry Pi 5
  • With https://github.com/worproject/rpi5-uefi
  • Build without raspberrypi

The following table shows which feature worked on which machines.

Test items (o: works, -: Not works, ?: Not tested) \ Machine	FX700	FX1000	E252-P30	QEMU	Bluefield-2	RPi4B	RPi5
Booting Linux on MilvusVisor (Multi-core)	o	o	o	o	o	o	o
Protecting non-volatile data of Intel I210	o	-	-	?	-	-	?
Protecting firmware update of Mellanox Technologies MT27800	o	-	-	?	-	-	?
Protecting MilvusVisor itself against DMA attack	o	-	-	-	-	-	-
Fast Restore	o	o	-	o	-	-	o
Virtio Network	-	-	?	o	o	-	-

How to build the hypervisor

By Rust toolchains

Requirements

• Rust 1.88 or later
• cargo
• rustc

Steps (commands list)

cd path/to/repo-root/src
cargo xtask build # Debug Build
cargo xtask build -r # Release build

To customize build options, please see cargo xtask help.

Next How to run the hypervisor

By docker

Requirements

• Docker (Tested by Docker version 20.10.8, build 3967b7d28e)
  • I tested by non-root users ( See this to run docker command by non-root user)

Steps (commands list)

cd path/to/repo-root/src
./build_by_docker.sh # You can add arguments to pass the cargo xtask command, like as `-f ...`

For more detail, please see the scripts.

How to run the hypervisor

On QEMU

First, please install QEMU that supports emulating QEMU ARM Virtual Machine, a64fx CPU. Then, you should build the hypervisor by the above method. After that, run the following command to run the built hypervisor.

cd path/to/repo-root/src
cargo xtask run --bios /usr/share/qemu-efi/QEMU_EFI.fd #Please set the path of your QEMU_EFI.fd

For more options, please see cargo xtask help.

On a physical machine from a USB memory stick

Requirement

• Prepare a USB memory that has an EFI (FAT) partition that has /EFI/BOOT/ directory. Please confirm that there is no important file in the partition.
• Prepare a physical machine that has ARMv8.1-A or later, and UEFI firmware.

Steps

1. Build the hypervisor by the above method.
2. Attach your USB memory stick to the development machine which built the hypervisor binary.
3. Identify the EFI partition (in the following description, /dev/sdX1 is the EFI partition).
4. Run cargo xtask write -d /dev/sdX1 to copy the binary. !! Please be careful not to specify a wrong partition as DEVICE because the script mount/unmount the partition and copies the binary file with root privilege.!!
5. Detach the USB memory from the development machine, and attach it to the physical machine to run the hypervisor.
6. Boot the physical machine with UEFI, and specify BOOTAA64.EFI in the EFI partition as the EFI application to boot.

cargo xtask write uses sudo command. If you can access the target device without the root privilege, you can add the -u option. For more options, please see cargo xtask help.

PXE Boot

Requirement

Modify each PATH in src/common/src/lib.rs.

• HYPERVISOR_TFTP_PATH : The absolute path of hypervisor_kernel at the tftp server
• UEFI_PAYLOAD_PATH : The absolute path of payload UEFI Application like OS bootloader at the tftp server

The default settings assume that files are deploy on tftp server likes below.

(tftp root)
`-- uefi
    |-- BOOTAA64.EFI
    |-- grubaa64.efi
    `-- hypervisor_kernel

Steps

1. Build MilvusVisor with tfp feature like cargo xtask build -f default,tftp
2. Deploy BOOTAA64.EFI and hypervisor_kernel on tftp server.(you can rename BOOTAA64.EFI)
3. Modify DHCP setting to change the boot file to BOOTAA64.EFI(if you renamed, adjust the name).

How to generate the documentation

You can generate the document by cargo doc in each cargo project directory.

If you want to see bootloader's document, please run the following command.

cd path/to/repo-root/src/hypervisor_bootloader
cargo doc --open # Browser will open

If you want to see kernel's document, please run the following command.

cd path/to/repo-root/src/hypervisor_kernel
cargo doc --open # Browser will open

Acknowledgment

This work was supported by JSPS KAKENHI Grant Number 21K17727.