Hypervisor

This project was developed as part of the coursework for the university subject AOR2 (Computer Architecture and Organization 2).

It implements a simple mini-hypervisor using the KVM API with three levels of functionality:

• Version A: Basic hypervisor features
• Version B: Support for multiple virtual machines (VMs)
• Version C: File I/O support for guest VMs

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Contents of each version

• mini_hypervisor – the hypervisor executable
• guest*.img – guest machine code files

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Version A – Basic Hypervisor Features

The hypervisor supports:

• Fixed physical memory sizes for the VM: 2 MB, 4 MB or 8 MB
  Command line option: -m, --memory <size_MB>
• VMs run in 64-bit long mode
• Page size: 4 KB or 2 MB
  Command line option: -p, --page <page_size>
• Single virtual CPU per VM
• Serial I/O through port 0xE9 (1 byte per operation)
• Only VMs that terminate with the hlt instruction are supported
• Launching a guest VM:
  -g, --guest <file.img>

Example command: ./mini_hypervisor --memory 4 --page 2 --guest guest.img

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Version B – Multiple VM Support

This version adds support for running multiple VMs:

• Number of VMs is specified via the -g option with a list of guest files
• Each VM runs in its own POSIX thread

Example command: ./mini_hypervisor --memory 4 --page 2 --guest guest1.img guest2.img

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Version C – File I/O Support

This version adds file operations for guest VMs:

• Supports opening, closing, reading and writing files via I/O port 0x0278
• Opening a non-existing file for writing creates that file
• File paths are specified via command line: -f, --file ...
• Copy-on-write: Shared files between VMs are copied locally when a VM writes to prevent conflicts
• Hypervisor ensures that each guest accesses only its own files or allowed shared files

Example command: ./mini_hypervisor -m 4 -p 2 -g guest1.img guest2.img -f ./flowers.png

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Notes

• The hypervisor runs as a 64-bit process
• Guest programs must terminate using the hlt instruction.
• Each VM is isolated in its own thread with separate virtual memory and I/O
• File handling is managed to prevent conflicts between VMs

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Build & Run

Requirements

• Linux environment
• gcc
• make
• POSIX threads support

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Building the Hypervisor

The hypervisor is built using a provided Makefile. Navigate to the wanted version directory.

• To compile the hypervisor, run: make
• To clean the build artifacts, run: make clean

Building Guest Programs

To build a guest program, navigate to the wanted directory and run: make.

This will:

• Compile guest.c into guest.o
• Link the object file using guest.ld
• Generate the final guest image guest.img

To clean guest build files: make clean.

Running the Hypervisor

After building the hypervisor and guest images, run wanted commands and ensure correct file paths to the guest images.