# vm-memory

## Design

In a typical Virtual Machine Monitor (VMM) there are several components, such
as boot loader, virtual device drivers, virtio backend drivers and vhost
drivers, that need to access the VM physical memory. The `vm-memory` crate
provides a set of traits to decouple VM memory consumers from VM memory
providers. Based on these traits, VM memory consumers can access the physical
memory of the VM without knowing the implementation details of the VM memory
provider. Thus VMM components based on these traits can be shared and reused by
multiple virtualization solutions.

The detailed design of the `vm-memory` crate can be found [here](DESIGN.md).

### Platform Support

- Arch: x86, AMD64, ARM64
- OS: Linux/Unix/Windows

## Usage

Add `vm-memory` as a dependency in `Cargo.toml`

```toml
[dependencies]
vm-memory = "*"
```

Then add `extern crate vm-memory;` to your crate root.

## Examples

- Creating a VM physical memory object in hypervisor specific ways using the
  `GuestMemoryMmap` implementation of the `GuestMemory` trait:

```rust
fn provide_mem_to_virt_dev() {
    let gm = GuestMemoryMmap::from_ranges(&[
        (GuestAddress(0), 0x1000),
        (GuestAddress(0x1000), 0x1000)
    ]).unwrap();
    virt_device_io(&gm);
}
```

- Consumers accessing the VM's physical memory:

```rust
fn virt_device_io<T: GuestMemory>(mem: &T) {
    let sample_buf = &[1, 2, 3, 4, 5];
    assert_eq!(mem.write(sample_buf, GuestAddress(0xffc)).unwrap(), 5);
    let buf = &mut [0u8; 5];
    assert_eq!(mem.read(buf, GuestAddress(0xffc)).unwrap(), 5);
    assert_eq!(buf, sample_buf);
}
```

## License

This project is licensed under either of

- [Apache License](http://www.apache.org/licenses/LICENSE-2.0), Version 2.0
- [BSD-3-Clause License](https://opensource.org/licenses/BSD-3-Clause)
