cloud-hypervisor/release-notes.md

# v0.2.0

This release has been tracked through the [0.2.0 project](https://github.com/intel/cloud-hypervisor/projects/2).

Highlights for `cloud-hypervisor` version 0.2.0 include:

### Network device offloading

As part of our general effort to offload paravirtualized I/O to external
processes, we added support for
[vhost-user-net](https://access.redhat.com/solutions/3394851) backends. This
enables `cloud-hypervisor` users to plug a `vhost-user` based networking device
(e.g. [DPDK](https://dpdk.org)) into the VMM as their virtio network backend.

### Minimal hardware-reduced ACPI

In order to properly implement and guest reset and shutdown, we implemented
a minimal version of the hardware-reduced ACPI specification. Together with
a tiny I/O port based ACPI device, this allows `cloud-hypervisor` guests to
cleanly reboot and shutdown.

The ACPI implementation is a `cloud-hypervisor` build time option that is
enabled by default.

### Debug I/O port

Based on the Firecracker idea of using a dedicated I/O port to measure guest
boot times, we added support for logging guest events through the
[0x80](https://www.intel.com/content/www/us/en/support/articles/000005500/boards-and-kits.html)
PC debug port. This allows, among other things, for granular guest boot time
measurements. See our [debug port documentation](https://github.com/intel/cloud-hypervisor/blob/master/docs/debug-port.md)
for more details.

### Improved direct device assignment

We fixed a major performance issue with our initial VFIO implementation: When
enabling VT-d through the KVM and VFIO APIs, our guest memory writes and reads
were (in many cases) not cached. After correctly tagging the guest memory from
`cloud-hypervisor` we're now able to reach the expected performance from
directly assigned devices.

### Improved shared filesystem

We added shared memory region with [DAX](https://www.kernel.org/doc/Documentation/filesystems/dax.txt)
support to our [virtio-fs](https://virtio-fs.gitlab.io/) shared file system.
This provides better shared filesystem IO performance with a smaller guest
memory footprint.

### Ubuntu bionic based CI

Thanks to our [simple KVM firmware](https://github.com/intel/rust-hypervisor-firmware)
improvements, we are now able to boot Ubuntu bionic images. We added those to
our CI pipeline.

# v0.1.0

This release has been tracked through the [0.1.0 project](https://github.com/intel/cloud-hypervisor/projects/1).

Highlights for `cloud-hypervisor` version 0.1.0 include:

### Shared filesystem

We added support for the [virtio-fs](https://virtio-fs.gitlab.io/) shared file
system, allowing for an efficient and reliable way of sharing a filesystem
between the host and the `cloud-hypervisor` guest.

See our [filesystem sharing](https://github.com/intel/cloud-hypervisor/blob/master/docs/fs.md)
documentation for more details on how to use virtio-fs with `cloud-hypervisor`.

### Initial direct device assignment support

VFIO (Virtual Function I/O) is a kernel framework that exposes direct device
access to userspace. `cloud-hypervisor` uses VFIO to directly assign host
physical devices into its guest.

See our [VFIO](https://github.com/intel/cloud-hypervisor/blob/master/docs/vfio.md)
documentation for more detail on how to directly assign host devices to
`cloud-hypervisor` guests.

### Userspace IOAPIC

`cloud-hypervisor` supports a so-called split IRQ chip implementation by
implementing support for the [IOAPIC](https://wiki.osdev.org/IOAPIC).
By moving part of the IRQ chip implementation from kernel space to user space,
the IRQ chip emulation does not always run in a fully privileged mode.

### Virtual persistent memory

The `virtio-pmem` implementation emulates a virtual persistent memory device
that `cloud-hypervisor` can e.g. boot from. Booting from a `virtio-pmem` device
allows to bypass the guest page cache and improve the guest memory footprint.

### Linux kernel bzImage

The `cloud-hypervisor` linux kernel loader now supports direct kernel boot from
`bzImage` kernel images, which is usually the format that Linux distributions
use to ship their kernels. For example, this allows for booting from the host
distribution kernel image.

### Console over virtio

`cloud-hypervisor` now exposes a `virtio-console` device to the guest. Although
using this device as a guest console can potentially cut some early boot
messages, it can reduce the guest boot time and provides a complete console
implementation.

The `virtio-console` device is enabled by default for the guest console.
Switching back to the legacy serial port is done by selecting
`--serial tty --console off` from the command line.

### Unit testing

We now run all unit tests from all our crates directly from our CI.

### Integration tests parallelization

The CI cycle run time has been significantly reduced by refactoring our
integration tests; allowing them to all be run in parallel.