Added * Seccomp filtering is configured via the --seccomp-level jailer parameter. * Firecracker logs the starting addresses of host memory areas provided as guest memory slots to KVM. * The metric `panic_count` gets incremented to signal that a panic has occurred. * Firecracker logs a backtrace when it crashes following a panic. * Added basic instrumentation support for measuring boot time. Changed * `StartInstance` is a synchronous API request (it used to be an asynchronous request). Fixed * Ensure that fault messages sent by the API have valid JSON bodies. * Use HTTP response code 500 for internal Firecracker errors, and 400 for user errors on InstanceStart. * Serialize the machine configuration fields to the correct data types (as specified in the Swagger definition). * NUMA node assignment is properly enforced by the jailer. * The `is_root_device` and `is_read_only` properties are now marked as required in the Swagger definition of `Drive` object properties. Removed * `GET` requests on the `/actions` API resource are no longer supported. * The metrics associated with asynchronous actions have been removed. * Remove the `action_id` parameter for `InstanceStart`, both from the URI and the JSON request body.