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Changelog

All notable changes to this project will be documented in this file.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.

[Unreleased]

Added

Changed

Deprecated

Removed

Fixed

  • #5594: Fixed rate limiter bucket updates to preserve budget and one-time burst state (capped at new bucket limits if smaller) instead of resetting to full capacity.

[v1.14.0]

Added

  • #5463: Added support for virtio-pmem devices. See documentation for more information.
  • #5534: Added support for memory hot-plugging through the virtio-mem device. See documentation for more information.
  • #5491: Added support for virtio-balloon free page reporting and hinting. Free page reporting is a developer preview not for production feature. See documentation for more information.

Changed

  • #4028: Firecracker now creates the log and metrics files if they do not exist, simplifying the launch of Firecracker by removing a manual step.
  • #5516: Balloon stats now supports guest kernel >= 6.12, adding metrics on guest OOM kills, memory allocation stalls, and memory scan/reclaim info.
  • #5526: Specify IA32_MTRRdefType MSR on VM boot to allow it to set page attributes for memory regions.

Deprecated

Removed

  • #5439: Removed the rx_partial_writes, tx_partial_reads, sync_response_fails, sync_vmm_send_timeout_count, deprecated_cmd_line_api_calls, log_fails and device_events metrics, as they were never incremented.

Fixed

  • #5418: Fixed typo in Swagger definition of MmdsConfig, where the property imds_compat was spelled as imds_comat. This caused auto-generated clients to create bad requests.
  • #5447: Fixed Intel AMX enabling for kernels that support dynamic XSTATE features for userspace applications but not for KVM guests (e.g. kernel versions >= 5.16 and < 5.17).
  • #5485: Fixed a bug causing a read/write from an iovec to be duplicated when receiving an error on an iovec other than the first. This caused a data corruption issue in the vsock device starting from guest kernel 6.17.
  • #5494: Fixed a watchdog soft lockup bug on microVMs restored from snapshots by calling KVM_KVMCLOCK_CTRL ioctl before resuming.
  • #5538: Fixed a cache coherency issue on non-FWB aarch64 platforms by adding dma-coherent property to virtio-mmio nodes in the FDT.

[1.13.0]

Added

  • #5139: Added support for PVTime. This is used to support steal time on ARM machines.
  • #5175: Allow including a custom cpu template directly in the json configuration file passed to --config-file under the cpu_config key.
  • #5274: Allow taking diff snapshots even if dirty page tracking is disabled, by using mincore(2) to overapproximate the set of dirty pages. Only works if swap is disabled.
  • #5290: Extended MMDS to support the EC2 IMDS-compatible session token headers (i.e. "X-aws-ec2-metadata-token" and "X-aws-ec2-metadata-token-ttl-seconds") alongside the MMDS-specific ones.
  • #5290: Added mmds.rx_invalid_token and mmds.rx_no_token metrics to track the number of GET requests that were rejected due to token validation failures in MMDS version 2. These metrics also count requests that would be rejected in MMDS version 2 when MMDS version 1 is configured. They helps users assess readiness for migrating to MMDS version 2.
  • #5310: Added an optional imds_compat field (default to false if not provided) to PUT requests to /mmds/config to enforce MMDS to always respond plain text contents in the IMDS format regardless of the Accept header in requests. Users need to regenerate snapshots.
  • #5350: Added a /serial endpoint, which allows setting serial_out_path to the path of a pre-created file into which Firecracker should redirect output from the guest's serial console. Not configuring it means Firecracker will continue to print serial output to stdout. Similarly to the logger, this configuration is not persisted across snapshots.
  • #5364: Added PCI support in Firecracker. PCI support is optional. Users can enable it passing the --enable-pci flag when launching the Firecracker process. When Firecracker process is launched with PCI support, it will create all VirtIO devices using a PCI VirtIO transport. If not enabled, Firecracker will use the MMIO transport instead.

Changed

  • #5165: Changed Firecracker snapshot feature from developer preview to generally available. Incremental snapshots remain in developer preview.
  • #5282: Updated jailer to no longer require the executable file name to contain firecracker.
  • #5290: Changed MMDS to validate the value of "X-metadata-token-ttl-seconds" header only if it is a PUT request to /latest/api/token, as in EC2 IMDS.
  • #5290: Changed MMDS version 1 to support the session oriented method as in version 2, allowing easier migration to version 2. Note that MMDS version 1 accepts a GET request even with no token or an invalid token so that existing workloads continue to work.

Deprecated

  • #5274: Deprecated the enable_diff_snapshots parameter of the /snapshot/load API. Use track_dirty_pages instead.

Removed

  • #5411: Removed official support for Intel Skylake instances. Firecracker will continue to work on those instances, but we will no longer perform automated testing on them.

Fixed

  • #5222: Fixed network and rng devices locking up on hosts with non 4K pages.
  • #5226: Fixed MMDS to set Content-Type header correctly (i.e. Content-Type: text/plain for IMDS-formatted or error responses and Content-Type: application/json for JSON-formatted responses).
  • #5260: Fixed a bug allowing the block device to starve all other devices when backed by a sufficiently slow drive.
  • #4207: Fixed GSI numbering on aarch64 to correctly allow up to 96 devices being attached simultaneously.
  • #5290: Fixed MMDS to reject PUT requests containing X-Forwarded-For header regardless of its casing (e.g. x-forwarded-for).
  • #5328: Fixed MMDS to set the token TTL header (i.e. "X-metadata-token-ttl-seconds" or "X-aws-ec2-metadata-token-ttl-seconds") in the response to "PUT /latest/api/token", as EC2 IMDS does.

[1.12.0]

Added

  • #5048: Added support for PVH boot mode. This is used when an x86 kernel provides the appropriate ELF Note to indicate that PVH boot mode is supported. Linux kernels newer than 5.0 compiled with CONFIG_PVH=y set this ELF Note, as do FreeBSD kernels.
  • #5065 Added support for Intel AMX (Advanced Matrix Extensions). To be able to take and restore a snapshot of Intel AMX state, Xsave is used instead of kvm_xsave, so users need to regenerate snapshots.
  • #4731: Added support for modifying the host TAP device name during snapshot restore.
  • #5146: Added Intel Sapphire Rapids as a supported and tested platform for Firecracker.
  • #5148: Added ARM Graviton4 as a supported and tested platform for Firecracker.

Changed

  • #5118: Cleared WAITPKG CPUID bit in CPUID normalization. The feature enables a guest to put a physical processor into an idle state, which is undesirable in a FaaS environment since that is what the host wants to decide.
  • #5142: Clarified what CPU models are supported by each existing CPU template. Firecracker exits with an error if a CPU template is used on an unsupported CPU model.

Deprecated

  • #4948: Deprecated the page_size_kib field in the UFFD handshake, and replaced it with a page_size field. The page_size_kib field is misnamed, as the value Firecracker sets it to is actually the page size in bytes, not KiB. It will be removed in Firecracker 2.0.

Fixed

  • #5074 Fix the SendCtrlAltDel command not working for ACPI-enabled guest kernels, by dropping the i8042.nopnp argument from the default kernel command line Firecracker constructs.
  • #5122: Keep the UFFD Unix domain socket open to prevent the race condition between the guest memory mappings message and the shutdown event that was sometimes causing arrival of an empty message on the UFFD handler side.
  • #5143: Fixed to report process_startup_time_us and process_startup_time_cpu_us metrics for api_server right after the API server starts, while previously reported before applying seccomp filter and starting the API server. Users may observe a bit longer startup time metrics.

[1.11.0]

Added

  • #4987: Reset physical counter register (CNTPCT_EL0) on VM startup. This avoids VM reading the host physical counter value. This is only possible on 6.4 and newer kernels. For older kernels physical counter will still be passed to the guest unmodified. See more info here
  • #5088: Added AMD Genoa as a supported and tested platform for Firecracker.

Changed

  • #4913: Removed unnecessary fields (max_connections and max_pending_resets) from the snapshot format, bumping the snapshot version to 5.0.0. Users need to regenerate snapshots.
  • #4926: Replace underlying implementation for seccompiler from in house one in favor of libseccomp which produces smaller and more optimized BPF code.

Deprecated

Removed

Fixed

  • #4921: Fixed swagger CpuConfig definition to include missing aarch64-specific fields.
  • #4916: Fixed IovDeque implementation to work with any host page size. This fixes virtio-net device on non 4K host kernels.
  • #4991: Fixed mem_size_mib and track_dirty_pages being mandatory for all PATCH /machine-config requests. Now, they can be omitted which leaves these parts of the machine configuration unchanged.
  • #5007: Fixed watchdog softlockup warning on x86_64 guests when a vCPU is paused during GDB debugging.
  • #5021 If a balloon device is inflated post UFFD-backed snapshot restore, Firecracker now causes remove UFFD messages to be sent to the UFFD handler. Previously, no such message would be sent.
  • #5034: Fix an integer underflow in the jailer when computing the value it passes to Firecracker's --parent-cpu-time-us values, which caused development builds of Firecracker to crash (but production builds were unaffected as underflows do not panic in release mode).
  • #5045: Fixed an issue where firecracker intermittently receives SIGHUP when using jailer with --new-pid-ns but without --daemonize.
  • #4995: Firecracker no longer overwrites CPUID leaf 0x80000000 when running AMD hardware, meaning the guest can now discover a greater range of CPUID leaves in the extended function range (this range is host kernel dependent).
  • #5046: Retry KVM_CREATE_VM on EINTR that occasionally happen on heavily loaded hosts to improve reliability of microVM creation.
  • #5052: Build the empty seccomp policy as default for debug builds to avoid crashes on syscalls introduced by debug assertions from Rust 1.80.0.

[1.10.0]

Added

  • #4834: Add VIRTIO_NET_F_RX_MRGBUF support to the virtio-net device. When this feature is negotiated, guest virtio-net driver can perform more efficient memory management which in turn improves RX and TX performance.
  • #4460: Add a call to KVM_KVMCLOCK_CTRL after pausing vCPUs on x86_64 architectures. This ioctl sets a flag in the KVM state of the vCPU indicating that it has been paused by the host userspace. In guests that use kvmclock, the soft lockup watchdog checks this flag. If it is set, it won't trigger the lockup condition. Calling the ioctl for guests that don't use kvmclock will fail. These failures are not fatal. We log the failure and increase the vcpu.kvmclock_ctrl_fails metric.
  • #4869: Added support for Aarch64 systems which feature CPU caches with a number of sets higher than u16::MAX.
  • #4797, #4854: Added GDB debugging support for a microVM guest kernel. Please see our GDB debugging documentation for more information.

Changed

  • #4844: Upgrade virtio-net device to use readv syscall to avoid unnecessary memory copies on RX path, increasing the RX performance.

Deprecated

Removed

  • #4804: Drop Support for guest kernel 4.14. Linux 4.14 reached end-of-life in January 2024 The minimum supported guest kernel now is 5.10.

Fixed

  • #4796: Fixed Vsock not notifying guest about TRANSPORT_RESET_EVENT event after snapshot restore. This resulted in guest waiting indefinitely on a connection which was reset during snapshot creation.
  • #4790: v1.9.0 was missing most of the debugging information in the debuginfo file, due to a change in the Cargo defaults. This has been corrected.
  • #4826: Add missing configuration of tap offload features when restoring from a snapshot. Setting the features was previously moved from net device creation to device activation time, but it was not reflected in the restore path. This was leading to inability to connect to the restored VM if the offload features were used.

[1.9.0]

Added

  • #4687: Added VMGenID support for microVMs running on ARM hosts with 6.1 guest kernels. Support for VMGenID via DeviceTree bindings exists only on mainline 6.10 Linux onwards. Users of Firecracker will need to backport the relevant patches on top of their 6.1 kernels to make use of the feature. As a result, Firecracker snapshot version is now 3.0.0
  • #4732, #4733, #4741, #4746: Added official support for 6.1 microVM guest kernels.
  • #4743: Added support for -h help flag to the Jailer. The Jailer will now print the help message with either --help or -h.

Changed

Deprecated

  • Support for guest kernel 4.14 is now deprecated. We will completely remove 4.14 support with Firecracker version v1.10

Removed

  • #4689: Drop support for host kernel 4.14. Linux 4.14 reached end-of-life in January 2024. The minimum supported kernel now is 5.10. Guest kernel 4.14 is still supported.

Fixed

  • 4680: Fixed an issue (#4659) where the virtio-net device implementation would always assume the guest accepts all VirtIO features the device offers. This is always true with the Linux guest kernels we are testing but other kernels, like FreeBSD make different assumptions. This PR fixes the emulation code to set the TAP features based on the features accepted by the guest.

[1.8.0]

Added

  • #4428: Added ACPI support to Firecracker for x86_64 microVMs. Currently, we pass ACPI tables with information about the available vCPUs, interrupt controllers, VirtIO and legacy x86 devices to the guest. This allows booting kernels without MPTable support. Please see our kernel policy documentation for more information regarding relevant kernel configurations.
  • #4487: Added support for the Virtual Machine Generation Identifier (VMGenID) device on x86_64 platforms. VMGenID is a virtual device that allows VMMs to notify guests when they are resumed from a snapshot. Linux includes VMGenID support since version 5.18. It uses notifications from the device to reseed its internal CSPRNG. Please refer to snapshot support and random for clones documention for more info on VMGenID. VMGenID state is part of the snapshot format of Firecracker. As a result, Firecracker snapshot version is now 2.0.0.

Changed

  • #4492: Changed --config parameter of cpu-template-helper optional. Users no longer need to prepare kernel, rootfs and Firecracker configuration files to use cpu-template-helper.
  • #4537 Changed T2CL template to pass through bit 27 and 28 of MSR_IA32_ARCH_CAPABILITIES (RFDS_NO and RFDS_CLEAR) since KVM consider they are able to be passed through and T2CL isn't designed for secure snapshot migration between different processors.
  • #4537 Changed T2S template to set bit 27 of MSR_IA32_ARCH_CAPABILITIES (RFDS_NO) to 1 since it assumes that the fleet only consists of processors that are not affected by RFDS.
  • #4388: Avoid setting kvm_immediate_exit to 1 if are already handling an exit, or if the vCPU is stopped. This avoids a spurious KVM exit upon restoring snapshots.
  • #4567: Do not initialize vCPUs in powered-off state upon snapshot restore. No functional change, as vCPU initialization is only relevant for the booted case (where the guest expects CPUs to be powered off).

Deprecated

  • Firecracker's --start-time-cpu-us and --start-time-us parameters are deprecated and will be removed in v2.0 or later. They are used by the jailer to pass the value that should be subtracted from the (CPU) time, when emitting the start_time_us and start_time_cpu_us metrics. These parameters were never meant to be used by end customers, and we recommend doing any such time adjustments outside Firecracker.
  • Booting with microVM kernels that rely on MPTable on x86_64 is deprecated and support will be removed in v2.0 or later. We suggest to users of Firecracker to use guest kernels with ACPI support. For x86_64 microVMs, ACPI will be the only way Firecracker passes hardware information to the guest once MPTable support is removed.

Fixed

  • #4526: Added a check in the network TX path that the size of the network frames the guest passes to us is not bigger than the maximum frame the device expects to handle. On the TX path, we copy frames destined to MMDS from guest memory to Firecracker memory. Without the check, a mis-behaving virtio-net driver could cause an increase in the memory footprint of the Firecracker process. Now, if we receive such a frame, we ignore it and increase Net::tx_malformed_frames metric.
  • #4536: Make the first differential snapshot taken after a full snapshot contain only the set of memory pages changed since the full snapshot. Previously, these differential snapshots would contain all memory pages. This will result in potentially much smaller differential snapshots after a full snapshot.
  • #4578: Fix UFFD support not being forward-compatible with new ioctl options introduced in Linux 6.6. See also bytecodealliance/userfaultfd-rs#61.
  • #4618: On x86_64, when taking a snapshot, if a vCPU has MSR_IA32_TSC_DEADLINE set to 0, Firecracker will replace it with the MSR_IA32_TSC value from the same vCPU. This is to guarantee that the vCPU will continue receiving TSC interrupts after restoring from the snapshot even if an interrupt is lost when taking a snapshot.
  • #4666: Fixed Firecracker sometimes restoring MSR_IA32_TSC_DEADLINE before MSR_IA32_TSC. Now it always restores MSR_IA32_TSC_DEADLINE MSR after MSR_IA32_TSC, as KVM relies on the guest TSC for correct restoration of MSR_IA32_TSC_DEADLINE. This fixed guests using the TSC_DEADLINE hardware feature receiving incorrect timer interrupts after snapshot restoration, which could lead to them seemingly getting stuck in sleep-related syscalls (see also #4099).

[1.7.0]

Added

  • #4346: Added support to emit aggregate (minimum/maximum/sum) latency for VcpuExit::MmioRead, VcpuExit::MmioWrite, VcpuExit::IoIn and VcpuExit::IoOut. The average for these VM exits is not emitted since it can be deduced from the available emitted metrics.
  • #4360: Added dev-preview support for backing a VM's guest memory by 2M hugetlbfs pages. Please see the documentation for more information
  • #4486: Added block and net device metrics for file/tap access latencies and queue backlog lengths, which can be used to analyse saturation of the Firecracker VMM thread and underlying layers. Queue backlog length metrics are flushed periodically. They can be used to esimtate an average queue length by request by dividing its value by the number of requests served.

Changed

  • #4230: Changed microVM snapshot format version strategy. Firecracker snapshot format now has a version that is independent of Firecracker version. The current version of the snapshot format is v1.0.0. From now on, the Firecracker binary will define the snapshot format version it supports and it will only be able to load snapshots with format that is backwards compatible with that version. Users can pass the --snapshot-version flag to the Firecracker binary to see its supported snapshot version format. This change renders all previous Firecracker snapshots (up to Firecracker version v1.6.0) incompatible with the current Firecracker version.

  • #4449: Added information about page size to the payload Firecracker sends to the UFFD handler. Each memory region object now contains a page_size_kib field. See also the hugepages documentation.

  • #4498: Only use memfd to back guest memory if a vhost-user-blk device is configured, otherwise use anonymous private memory. This is because serving page faults of shared memory used by memfd is slower and may impact workloads.

Fixed

  • #4409: Fixed a bug in the cpu-template-helper that made it panic during conversion of cpu configuration with SVE registers to the cpu template on aarch64 platform. Now cpu-template-helper will print warnings if it encounters SVE registers during the conversion process. This is because cpu templates are limited to only modify registers less than 128 bits.
  • #4413: Fixed a bug in the Firecracker that prevented it to restore snapshots of VMs that had SVE enabled.
  • #4414: Made PATCH requests to the /machine-config endpoint transactional, meaning Firecracker's configuration will be unchanged if the request returns an error. This fixes a bug where a microVM with incompatible balloon and guest memory size could be booted, due to the check for this condition happening after Firecracker's configuration was updated.
  • #4259: Added a double fork mechanism in the Jailer to avoid setsid() failures occurred while running Jailer as the process group leader. However, this changed the behaviour of Jailer and now the Firecracker process will always have a different PID than the Jailer process. #4436: Added a "Known Limitations" section in the Jailer docs to highlight the above change in behaviour introduced in PR#4259. #4442: As a solution to the change in behaviour introduced in PR#4259, provided a mechanism to reliably fetch Firecracker PID. With this change, Firecracker process's PID will always be available in the Jailer's root directory regardless of whether new_pid_ns was set.
  • #4468: Fixed a bug where a client would hang or timeout when querying for an MMDS path whose content is empty, because the 'Content-Length' header field was missing in a response.

[1.6.0]

Added

  • #4145: Added support for per net device metrics. In addition to aggregate metrics net, each individual net device will emit metrics under the label "net_{iface_id}". E.g. the associated metrics for the endpoint "/network-interfaces/eth0" will be available under "net_eth0" in the metrics json object.
  • #4202: Added support for per block device metrics. In addition to aggregate metrics block, each individual block device will emit metrics under the label "block_{drive_id}". E.g. the associated metrics for the endpoint "/drives/{drive_id}" will be available under "block_drive_id" in the metrics json object.
  • #4205: Added a new vm-state subcommand to info-vmstate command in the snapshot-editor tool to print MicrovmState of vmstate snapshot file in a readable format. Also made the vcpu-states subcommand available on x86_64.
  • #4063: Added source-level instrumentation based tracing. See tracing for more details.
  • #4138, #4170, #4223, #4247, #4226: Added developer preview only (NOT for production use) support for vhost-user block devices. Firecracker implements a vhost-user frontend. Users are free to choose from existing open source backend solutions or their own implementation. Known limitation: snapshotting is not currently supported for microVMs containing vhost-user block devices. See the related doc page for details. The device emits metrics under the label "vhost_user_{device}_{drive_id}".

Changed

  • #4309: The jailer's option --parent-cgroup will move the process to that cgroup if no cgroup options are provided.
  • Simplified and clarified the removal policy of deprecated API elements to follow semantic versioning 2.0.0. For more information, please refer to this GitHub discussion.
  • #4180: Refactored error propagation to avoid logging and printing an error on exits with a zero exit code. Now, on successful exit "Firecracker exited successfully" is logged.
  • #4194: Removed support for creating Firecracker snapshots targeting older versions of Firecracker. With this change, running 'firecracker --version' will not print the supported snapshot versions.
  • #4301: Allow merging of diff snapshots into base snapshots by directly writing the diff snapshot on top of the base snapshot's memory file. This can be done by setting the mem_file_path to the path of the pre-existing full snapshot.

Deprecated

  • #4209: rebase-snap tool is now deprecated. Users should use snapshot-editor for rebasing diff snapshots.

Fixed

  • #4171: Fixed a bug that ignored the --show-log-origin option, preventing it from printing the source code file of the log messages.
  • #4178: Fixed a bug reporting a non-zero exit code on successful shutdown when starting Firecracker with --no-api.
  • #4261: Fixed a bug where Firecracker would log "RunWithApiError error: MicroVMStopped without an error: GenericError" when exiting after encountering an emulation error. It now correctly prints "RunWithApiError error: MicroVMStopped with an error: GenericError".
  • #4242: Fixed a bug introduced in #4047 that limited the --level option of logger to Pascal-cased values (e.g. accepting "Info", but not "info"). It now ignores case again.
  • #4286: Fixed a bug in the asynchronous virtio-block engine that rendered the device non-functional after a PATCH request was issued to Firecracker for updating the path to the host-side backing file of the device.
  • #4301: Fixed a bug where if Firecracker was instructed to take a snapshot of a microvm which itself was restored from a snapshot, specifying mem_file_path to be the path of the memory file from which the microvm was restored would result in both the microvm and the snapshot being corrupted. It now instead performs a "write-back" of all memory that was updated since the snapshot was originally loaded.

[1.5.0]

Added

  • #3837: Added official support for Linux 6.1. See prod-host-setup for some security and performance considerations.
  • #4045 and #4075: Added snapshot-editor tool for modifications of snapshot files. It allows for rebasing of memory snapshot files, printing and removing aarch64 registers from the vmstate and obtaining snapshot version.
  • #3967: Added new fields to the custom CPU templates. (aarch64 only) vcpu_features field allows modifications of vCPU features enabled during vCPU initialization. kvm_capabilities field allows modifications of KVM capability checks that Firecracker performs during boot. If any of these fields are in use, minimal target snapshot version is restricted to 1.5.

Changed

  • Updated deserialization of bitmap for custom CPU templates to allow usage of '_' as a separator.
  • Changed the strip feature of cpu-template-helper tool to operate bitwise.
  • Better logs during validation of CPU ID in snapshot restoration path. Also Firecracker now does not fail if it can't get CPU ID from the host or can't find CPU ID in the snapshot.
  • Changed the serial device to only try to initialize itself if stdin is a terminal or a FIFO pipe. This fixes logged warnings about the serial device failing to initialize if the process is daemonized (in which case stdin is /dev/null instead of a terminal).
  • Changed to show a warning message when launching a microVM with C3 template on a processor prior to Intel Cascade Lake, because the guest kernel does not apply the mitigation against MMIO stale data vulnerability when it is running on a processor that does not enumerate FBSDP_NO, PSDP_NO and SBDR_SSDP_NO on IA32_ARCH_CAPABILITIES MSR.
  • Made Firecracker resize its file descriptor table on process start. It now preallocates the in-kernel fdtable to hold RLIMIT_NOFILE many fds (or 2048 if no limit is set). This avoids the kernel reallocating the fdtable during Firecracker operations, resulting in a 30ms to 70ms reduction of snapshot restore times for medium to large microVMs with many devices attached.
  • Changed the dump feature of cpu-template-helper tool not to enumerate program counter (PC) on ARM because it is determined by the given kernel image and it is useless in the custom CPU template context.
  • The ability to create snapshots for an older version of Firecracker is now deprecated. As a result, the version body field in PUT on /snapshot/create request in deprecated.
  • Added support for the /dev/userfaultfd device available on linux kernels >= 6.1. This is the default for creating UFFD handlers on these kernel versions. If it is unavailable, Firecracker falls back to the userfaultfd syscall.
  • Deprecated cpu_template field in PUT and PATCH requests on /machine-config API, which is used to set a static CPU template. Custom CPU templates added in v1.4.0 are available as an improved iteration of the static CPU templates. For more information about the transition from static CPU templates to custom CPU templates, please refer to this GitHub discussion.
  • Changed default log level from Warn to Info. This results in more logs being output by default.

Fixed

  • Fixed a change in behavior of normalize host brand string that breaks Firecracker on external instances.
  • Fixed the T2A CPU template not to unset the MMX bit (CPUID.80000001h:EDX[23]) and the FXSR bit (CPUID.80000001h:EDX[24]).
  • Fixed the T2A CPU template to set the RstrFpErrPtrs bit (CPUID.80000008h:EBX[2]).
  • Fixed a bug where Firecracker would crash during boot if a guest set up a virtio queue that partially overlapped with the MMIO gap. Now Firecracker instead correctly refuses to activate the corresponding virtio device.
  • Fixed the T2CL CPU template to pass through security mitigation bits that are listed by KVM as bits able to be passed through. By making the most use of the available hardware security mitigations on a processor that a guest is running on, the guest might be able to benefit from performance improvements.
  • Fixed the T2S CPU template to set the GDS_NO bit of the IA32_ARCH_CAPABILITIES MSR to 1 in accordance with an Intel microcode update. To use the template securely, users should apply the latest microcode update on the host.
  • Fixed the spelling of the nomodule param passed in the default kernel command line parameters. This is a breaking change for setups that use the default kernel command line which also depend on being able to load kernel modules at runtime. This may also break setups which use the default kernel command line and which use an init binary that inadvertently depends on the misspelled param ("nomodules") being present at the command line, since this param will no longer be passed.

[1.4.0]

Added

  • Added support for custom CPU templates allowing users to adjust vCPU features exposed to the guest via CPUID, MSRs and ARM registers.
  • Introduced V1N1 static CPU template for ARM to represent Neoverse V1 CPU as Neoverse N1.
  • Added support for the virtio-rng entropy device. The device is optional. A single device can be enabled per VM using the /entropy endpoint.
  • Added a cpu-template-helper tool for assisting with creating and managing custom CPU templates.

Changed

  • Set FDP_EXCPTN_ONLY bit (CPUID.7h.0:EBX[6]) and ZERO_FCS_FDS bit (CPUID.7h.0:EBX[13]) in Intel's CPUID normalization process.

Fixed

  • Fixed feature flags in T2S CPU template on Intel Ice Lake.
  • Fixed CPUID leaf 0xb to be exposed to guests running on AMD host.
  • Fixed a performance regression in the jailer logic for closing open file descriptors. Related to: #3542.
  • A race condition that has been identified between the API thread and the VMM thread due to a misconfiguration of the api_event_fd.
  • Fixed CPUID leaf 0x1 to disable perfmon and debug feature on x86 host.
  • Fixed passing through cache information from host in CPUID leaf 0x80000006.
  • Fixed the T2S CPU template to set the RRSBA bit of the IA32_ARCH_CAPABILITIES MSR to 1 in accordance with an Intel microcode update.
  • Fixed the T2CL CPU template to pass through the RSBA and RRSBA bits of the IA32_ARCH_CAPABILITIES MSR from the host in accordance with an Intel microcode update.
  • Fixed passing through cache information from host in CPUID leaf 0x80000005.
  • Fixed the T2A CPU template to disable SVM (nested virtualization).
  • Fixed the T2A CPU template to set EferLmsleUnsupported bit (CPUID.80000008h:EBX[20]), which indicates that EFER[LMSLE] is not supported.

[1.3.0]

Added

  • Introduced T2CL (Intel) and T2A (AMD) CPU templates to provide instruction set feature parity between Intel and AMD CPUs when using these templates.
  • Added Graviton3 support (c7g instance type).

Changed

  • Improved error message when invalid network backend provided.
  • Improved TCP throughput by between 5% and 15% (depending on CPU) by using scatter-gather I/O in the net device's TX path.
  • Upgraded Rust toolchain from 1.64.0 to 1.66.0.
  • Made seccompiler output bit-reproducible.

Fixed

  • Fixed feature flags in T2 CPU template on Intel Ice Lake.

[1.2.0]

Added

  • Added a new CPU template called T2S. This exposes the same CPUID as T2 to the Guest and also overwrites the ARCH_CAPABILITIES MSR to expose a reduced set of capabilities. With regards to hardware vulnerabilities and mitigations, the Guest vCPU will apear to look like a Skylake CPU, making it safe to snapshot uVMs running on a newer host CPU (Cascade Lake) and restore on a host that has a Skylake CPU.
  • Added a new CLI option --metrics-path PATH. It accepts a file parameter where metrics will be sent to.
  • Added baselines for m6i.metal and m6a.metal for all long running performance tests.
  • Releases now include debuginfo files.

Changed

  • Changed the jailer option --exec-file to fail if the filename does not contain the string firecracker to prevent from running non-firecracker binaries.
  • Upgraded Rust toolchain from 1.52.1 to 1.64.0.
  • Switched to specifying our dependencies using caret requirements instead of comparison requirements.
  • Updated all dependencies to their respective newest versions.

Fixed

  • Made the T2 template more robust by explicitly disabling additional CPUID flags that should be off but were missed initially or that were not available in the spec when the template was created.
  • Now MAC address is correctly displayed when queried with GET /vm/config if left unspecified in both pre and post snapshot states.
  • Fixed a self-DoS scenario in the virtio-queue code by reporting and terminating execution when the number of available descriptors reported by the driver is higher than the queue size.
  • Fixed the bad handling of kernel cmdline parameters when init arguments were provided in the boot_args field of the JSON body of the PUT /boot-source request.
  • Fixed a bug on ARM64 hosts where the upper 64bits of the V0-V31 FL/SIMD registers were not saved correctly when taking a snapshot, potentially leading to data loss. This change invalidates all ARM64 snapshots taken with versions of Firecracker <= 1.1.3.
  • Improved stability and security when saving CPU MSRs in snapshots.

[1.1.0]

Added

  • The API PATCH methods for machine-config can now be used to reset the cpu_template to "None". Until this change there was no way to reset the cpu_template once it was set.
  • Added a rebase-snap tool for rebasing a diff snapshot over a base snapshot.
  • Mmds version is persisted across snapshot-restore. Snapshot compatibility is preserved bidirectionally, to and from a Firecracker version that does not support persisting the Mmds version. In such cases, the default V1 option is used.
  • Added --mmds-size-limit for limiting the mmds data store size instead of piggy-backing on --http-api-max-payload-size. If left unconfigured it defaults to the value of --http-api-max-payload-size, to provide backwards compatibility.
  • Added optional mem_backend body field in PUT requests on /snapshot/load. This new parameter is an object that defines the configuration of the backend responsible for handling memory loading during snapshot restore. The mem_backend parameter contains backend_type and backend_path required fields. backend_type is an enum that can take either File or Uffd as value. Interpretation of backend_path field depends on the value of backend_type. If File, then the user must provide the path to file that contains the guest memory to be loaded. Otherwise, if backend_type is Uffd, then backend_path is the path to a unix domain socket where a custom page fault handler process is listening and expecting a UFFD to be sent by Firecracker. The UFFD is used to handle the guest memory page faults in the separate process.
  • Added logging for the snapshot/restore and async block device IO engine features to indicate they are in development preview.

Changed

  • The API PATCH method for /machine-config can be now used to change track_dirty_pages on aarch64.
  • MmdsV2 is now Generally Available.
  • MmdsV1 is now deprecated and will be removed in Firecracker v2.0.0. Use MmdsV2 instead.
  • Deprecated mem_file_path body field in PUT on /snapshot/load request.

Fixed

  • Fixed inconsistency that allowed the start of a microVM from a JSON file without specifying the vcpu_count and mem_size_mib parameters for machine-config although they are mandatory when configuring via the API. Now these fields are mandatory when specifying machine-config in the JSON file and when using the PUT request on /machine-config.
  • Fixed inconsistency that allowed a user to specify the cpu_template parameter and set smt to True in machine-config when starting from a JSON file on aarch64 even though they are not permitted when using PUT or PATCH in the API. Now Firecracker will return an error on aarch64 if smt is set to True or if cpu_template is specified.
  • Fixed inconsistent behaviour of the PUT method for /machine-config that would reset the track_dirty_pages parameter to false if it was not specified in the JSON body of the request, but left the cpu_template parameter intact if it was not present in the request. Now a PUT request for /machine-config will reset all optional parameters (smt, cpu_template, track_dirty_pages) to their default values if they are not specified in the PUT request.
  • Fixed incosistency in the swagger definition with the current state of the /vm/config endpoint.

[1.0.0]

Added

  • Added jailer option --parent-cgroup <relative_path> to allow the placement of microvm cgroups in custom cgroup nested hierarchies. The default value is <exec-file> which is backwards compatible to the behavior before this change.
  • Added jailer option --cgroup-version <1|2> to support running the jailer on systems that have cgroup-v2. Default value is 1 which means that if --cgroup-version is not specified, the jailer will try to create cgroups on cgroup-v1 hierarchies only.
  • Added --http-api-max-payload-size parameter to configure the maximum payload size for PUT and PATCH requests.
  • Limit MMDS data store size to --http-api-max-payload-size.
  • Cleanup all environment variables in Jailer.
  • Added metrics for accesses to deprecated HTTP and command line API endpoints.
  • Added permanent HTTP endpoint for GET on /version for getting the Firecracker version.
  • Added --metadata parameter to enable MMDS content to be supplied from a file allowing the MMDS to be used when using --no-api to disable the API server.
  • Checksum file for the release assets.
  • Added support for custom headers to MMDS requests. Accepted headers are: X-metadata-token, which accepts a string value that provides a session token for MMDS requests; and X-metadata-token-ttl-seconds, which specifies the lifetime of the session token in seconds.
  • Support and validation for host and guest kernel 5.10.
  • A kernel support policy.
  • Added io_engine to the pre-boot block device configuration. Possible values: Sync (the default option) or Async (only available for kernels newer than 5.10.51). The Async variant introduces a block device engine that uses io_uring for executing requests asynchronously, which is in developer preview (NOT for production use). See docs/api_requests/block-io-engine.md.
  • Added block.io_engine_throttled_events metric for measuring the number of virtio events throttled because of the IO engine.
  • New optional version field to PUT requests towards /mmds/config to configure MMDS version. Accepted values are V1 and V2 and default is V1. MMDS V2 is developer preview only (NOT for production use) and it does not currently work after snapshot load.
  • Mandatory network_interfaces field to PUT requests towards /mmds/config which contains a list of network interface IDs capable of forwarding packets to MMDS.

Changed

  • Removed the --node jailer parameter.
  • Deprecated vsock_id body field in PUTs on /vsock.
  • Removed the deprecated the --seccomp-level parameter.
  • GET requests to MMDS require a session token to be provided through X-metadata-token header when using V2.
  • Allow PUT requests to MMDS in order to generate a session token to be used for future GET requests when version 2 is used.
  • Remove allow_mmds_requests field from the request body that attaches network interfaces. Specifying interfaces that allow forwarding requests to MMDS is done by adding the network interface's ID to the network_interfaces field of PUT /mmds/config request's body.
  • Renamed /machine-config ht_enabled to smt.
  • smt field is now optional on PUT /machine-config, defaulting to false.
  • Configuring smt: true on aarch64 via the API is forbidden.

Fixed

  • GET /vm/config was returning a default config object after restoring from a snapshot. It now correctly returns the config of the original microVM, except for boot_config and the cpu_template and smt fields of the machine config, which are currently lost.
  • Fixed incorrect propagation of init parameters in kernel commandline. Related to: #2709.
  • Adapt T2 and C3 CPU templates for kernel 5.10. Firecracker was not previously masking some CPU features of the host or emulated by KVM, introduced in more recent kernels: umip, vmx, avx512_vnni.
  • Fix jailer's cgroup implementation to accept properties that contain multiple dots.

[0.25.0]

Added

  • Added devtool build --ssh-keys flag to support fetching from private git repositories.
  • Added option to configure block device flush.
  • Added --new-pid-ns flag to the Jailer in order to spawn the Firecracker process in a new PID namespace.
  • Added API metrics for GET, PUT and PATCH requests on /mmds endpoint.
  • Added --describe-snapshot flag to Firecracker to fetch the data format version of a snapshot state file provided as argument.
  • Added --no-seccomp parameter for disabling the default seccomp filters.
  • Added --seccomp-filter parameter for supplying user-provided, custom filters.
  • Added the seccompiler-bin binary that is used to compile JSON seccomp filters into serialized BPF for Firecracker consumption.
  • Snapshotting support for GICv2 enabled guests.
  • Added devtool install to deploy built binaries in /usr/local/bin or a given path.
  • Added code logic to send VIRTIO_VSOCK_EVENT_TRANSPORT_RESET on snapshot creation, when the Vsock device is active. The event will close active connections on the guest.
  • Added GET request on /vm/config that provides full microVM configuration as a JSON HTTP response.
  • Added --resource-limit flag to jailer to limit resources such as: number of file descriptors allowed at a time (with a default value of 2048) and maximum size of files created by the process.

Changed

  • Changed Docker images repository from DockerHub to Amazon ECR.
  • Fixed off-by-one error in virtio-block descriptor address validation.
  • Changed the PATCH request on /balloon/statistics to schedule the first statistics update immediately after processing the request.
  • Deprecated the --seccomp-level parameter. It will be removed in a future release. Using it logs a runtime warning.
  • Experimental gnu libc builds use empty default seccomp filters, allowing all system calls.

Fixed

  • Fixed non-compliant check for the RTC device ensuring a fixed 4-sized data buffer.
  • Unnecessary interrupt assertion was removed from the RTC. However, a dummy interrupt is still allocated for snapshot compatibility reasons.
  • Fixed the SIGPIPE signal handler so Firecracker no longer exits. The signal is still recorded in metrics and logs.
  • Fixed ballooning API definitions by renaming all fields which mentioned "MB" to use "MiB" instead.
  • Snapshot related host files (vm-state, memory, block backing files) are now flushed to their backing mediums as part of the CreateSnapshot operation.
  • Fixed the SSBD mitigation not being enabled on aarch64 with the provided prod-host-setup.md.
  • Fixed the balloon statistics not working after a snapshot restore event.
  • The utc_timestamp_ms now reports the timestamp in ms from the UTC UNIX Epoch, as the name suggests. It was previously using a monotonic clock with an undefined starting point.

[0.24.0]

Added

  • Added optional resume_vm field to /snapshot/load API call.
  • Added support for block rate limiter PATCH.
  • Added devtool test -c|--cpuset-cpus flag for cpus confinement when tests run.
  • Added devtool test -m|--cpuset-mems flag for memory confinement when tests run.
  • Added the virtio traditional memory ballooning device.
  • Added a mechanism to handle vCPU/VMM errors that result in process termination.
  • Added incremental guest memory snapshot support.
  • Added aarch64 snapshot support.

Changed

  • Change the information provided in DescribeInstance command to provide microVM state information (Not started/Running/Paused) instead of whether it's started or not.
  • Removed the jailer --extra-args parameter. It was a noop, having been replaced by the -- separator for extra arguments.
  • Changed the output of the --version command line parameter to include a list of supported snapshot data format versions for the firecracker binary.
  • Increased the maximum number of virtio devices from 11 to 19.
  • Added a new check that prevents creating v0.23 snapshots when more than 11 devices are attached.
  • If the stdout buffer is full and non-blocking, the serial writes no longer block. Any new bytes will be lost, until the buffer is freed. The device also logs these errors and increments the uart.error_count metric for each lost byte.

Fixed

  • Fixed inconsistency in YAML file InstanceInfo definition

[0.23.0]

Added

  • Added metric for throttled block device events.
  • Added metrics for counting rate limiter throttling events.
  • Added metric for counting MAC address updates.
  • Added metrics for counting TAP read and write errors.
  • Added metrics for counting RX and TX partial writes.
  • Added metrics that measure the duration of pausing and resuming the microVM, from the VMM perspective.
  • Added metric for measuring the duration of the last full/diff snapshot created, from the VMM perspective.
  • Added metric for measuring the duration of loading a snapshot, from the VMM perspective.
  • Added metrics that measure the duration of pausing and resuming the microVM, from the API (user) perspective.
  • Added metric for measuring the duration of the last full/diff snapshot created, from the API (user) perspective.
  • Added metric for measuring the duration of loading a snapshot, from the API (user) perspective.
  • Added track_dirty_pages field to machine-config. If enabled, Firecracker can create incremental guest memory snapshots by saving the dirty guest pages in a sparse file.
  • Added a new API call, PATCH /vm, for changing the microVM state (to Paused or Resumed).
  • Added a new API call, PUT /snapshot/create, for creating a full or diff snapshot.
  • Added a new API call, PUT /snapshot/load, for loading a snapshot.
  • Added new jailer command line argument --cgroup which allow the user to specify the cgroups that are going to be set by the Jailer.
  • Added full support for AMD CPUs (General Availability). More details here.

Fixed

  • Boot time on AMD achieves the desired performance (i.e under 150ms).

Changed

  • The logger level field is now case-insensitive.
  • Disabled boot timer device after restoring a snapshot.
  • Enabled boot timer device only when specifically requested, by using the --boot-timer dedicated cmdline parameter.
  • firecracker and jailer --version now gets updated on each devtool build to the output of git describe --dirty, if the git repo is available.
  • MicroVM process is only attached to the cgroups defined by using --cgroups or the ones defined indirectly by using --node.
  • Changed devtool build to build jailer binary for musl only targets. Building jailer binary for non-musl targets have been removed.

[0.22.0]

Added

  • Added a new API call, PUT /metrics, for configuring the metrics system.
  • Added app_name field in InstanceInfo struct for storing the application name.
  • New command-line parameters for firecracker, named --log-path, --level, --show-level and --show-log-origin that can be used for configuring the Logger when starting the process. When using this method for configuration, only --log-path is mandatory.
  • Added a guide for updating the dev container image.
  • Added a new API call, PUT /mmds/config, for configuring the MMDS with a custom valid link-local IPv4 address.
  • Added experimental JSON response format support for MMDS guest applications requests.
  • Added metrics for the vsock device.
  • Added devtool strip command which removes debug symbols from the release binaries.
  • Added the tx_malformed_frames metric for the virtio net device, emitted when a TX frame missing the VNET header is encountered.

Fixed

  • Added --version flag to both Firecracker and Jailer.
  • Return 405 Method Not Allowed MMDS response for non HTTP GET MMDS requests originating from guest.
  • Fixed folder permissions in the jail (#1802).
  • Any number of whitespace characters are accepted after ":" when parsing HTTP headers.
  • Potential panic condition caused by the net device expecting to find a VNET header in every frame.
  • Potential crash scenario caused by "Content-Length" HTTP header field accepting negative values.
  • Fixed #1754 - net: traffic blocks when running ingress UDP performance tests with very large buffers.

Changed

  • Updated CVE-2019-3016 mitigation information in Production Host Setup
  • In case of using an invalid JSON as a 'config-file' for Firecracker, the process will exit with return code 152.
  • Removed the testrun.sh wrapper.
  • Removed metrics_fifo field from the logger configuration.
  • Renamed log_fifo field from LoggerConfig to log_path and metrics_fifo field from MetricsConfig to metrics_path.
  • PATCH /drives/{id} only allowed post-boot. Use PUT for pre-boot updates to existing configurations.
  • PATCH /network-interfaces/{id} only allowed post-boot. Use PUT for pre-boot updates to existing configurations.
  • Changed returned status code from 500 Internal Server Error to 501 Not Implemented, for queries on the MMDS endpoint in IMDS format, when the requested resource value type is unsupported.
  • Allowed the MMDS data store to be initialized with all supported JSON types. Retrieval of these values within the guest, besides String, Array, and Dictionary, is only possible in JSON mode.
  • PATCH request on /mmds before the data store is initialized returns 403 BadRequest.
  • Segregated MMDS documentation in MMDS design documentation and MMDS user guide documentation.

[0.21.0]

Added

  • Support for booting with an initial RAM disk image. This image can be specified through the new initrd_path field of the /boot-source API request.

Fixed

  • Fixed #1469 - Broken GitHub location for Firecracker release binary.
  • The jailer allows changing the default api socket path by using the extra arguments passed to firecracker.
  • Fixed #1456 - Occasional KVM_EXIT_SHUTDOWN and bad syscall (14) during VM shutdown.
  • Updated the production host setup guide with steps for addressing CVE-2019-18960.
  • The HTTP header parsing is now case insensitive.
  • The put_api_requests and patch_api_requests metrics for net devices were un-swapped.

Changed

  • Removed redundant --seccomp-level jailer parameter since it can be simply forwarded to the Firecracker executable using "end of command options" convention.
  • Removed memory.dirty_pages metric.
  • Removed options field from the logger configuration.
  • Decreased release binary size by ~15%.
  • Changed default API socket path to /run/firecracker.socket. This path also applies when running with the jailer.
  • Disabled KVM dirty page tracking by default.
  • Removed redundant RescanBlockDevice action from the /actions API. The functionality is available through the PATCH /drives API. See docs/api_requests/patch-block.md.

[0.20.0]

Added

  • Added support for GICv2.

Fixed

  • Fixed CVE-2019-18960 - Fixed a logical error in bounds checking performed on vsock virtio descriptors.
  • Fixed #1283 - Can't start a VM in AARCH64 with vcpus number more than 16.
  • Fixed #1088 - The backtrace are printed on panic, no longer causing a seccomp fault.
  • Fixed #1375 - Change logger options type from Value to Vec<LogOption> to prevent potential unwrap on None panics.
  • Fixed #1436 - Raise interrupt for TX queue used descriptors
  • Fixed #1439 - Prevent achieving 100% cpu load when the net device rx is throttled by the ratelimiter
  • Fixed #1437 - Invalid fields in rate limiter related API requests are now failing with a proper error message.
  • Fixed #1316 - correctly determine the size of a virtio device backed by a block device.
  • Fixed #1383 - Log failed api requests.

Changed

  • Decreased release binary size by 10%.

[0.19.0]

Added

  • New command-line parameter for firecracker, named --no-api, which will disable the API server thread. If set, the user won't be able to send any API requests, neither before, nor after the vm has booted. It must be paired with --config-file parameter. Also, when API server is disabled, MMDS is no longer available now.
  • New command-line parameter for firecracker, named --config-file, which represents the path to a file that contains a JSON which can be used for configuring and starting a microVM without sending any API requests.
  • The jailer adheres to the "end of command options" convention, meaning all parameters specified after -- are forwarded verbatim to Firecracker.
  • Added KVM_PTP support to the recommended guest kernel config.
  • Added entry in FAQ.md for Firecracker Guest timekeeping.

Changed

  • Vsock API call: PUT /vsocks/{id} changed to PUT /vsock and no longer appear to support multiple vsock devices. Any subsequent calls to this API endpoint will override the previous vsock device configuration.
  • Removed unused 'Halting' and 'Halted' instance states.
  • Vsock host-initiated connections now implement a trivial handshake protocol. See the vsock doc for details. Related to: #1253, #1432, #1443

Fixed

  • Fixed serial console on aarch64 (GitHub issue #1147).
  • Upon panic, the terminal is now reset to canonical mode.
  • Explicit error upon failure of vsock device creation.
  • The failure message returned by an API call is flushed in the log FIFOs.
  • Insert virtio devices in the FDT in order of their addresses sorted from low to high.
  • Enforce the maximum length of the network interface name to be 16 chars as specified in the Linux Kernel.
  • Changed the vsock property id to vsock_id so that the API client can be successfully generated from the swagger definition.

[0.18.0]

Added

  • New device: virtio-vsock, backed by Unix domain sockets (GitHub issue #650). See docs/vsock.md.

Changed

  • No error is thrown upon a flush metrics intent if logger has not been configured.

Fixed

  • Updated the documentation for integration tests.
  • Fixed high CPU usage before guest network interface is brought up (GitHub issue #1049).
  • Fixed an issue that caused the wrong date (month) to appear in the log.
  • Fixed a bug that caused the seccomp filter to reject legit syscalls in some rare cases (GitHub issue #1206).
  • Docs: updated the production host setup guide.
  • Docs: updated the rootfs and kernel creation guide.

Removed

  • Removed experimental support for vhost-based vsock devices.

[0.17.0]

Added

  • New API call: PATCH /machine-config/, used to update VM configuration, before the microVM boots.
  • Added an experimental swagger definition that includes the specification for the vsock API call.
  • Added a signal handler for SIGBUS and SIGSEGV that immediately terminates the process upon intercepting the signal.
  • Added documentation for signal handling utilities.
  • Added [alpha] aarch64 support.
  • Added metrics for successful read and write operations of MMDS, Net and Block devices.

Changed

  • vcpu_count, mem_size_mib and ht_enabled have been changed to be mandatory for PUT requests on /machine-config/.
  • Disallow invalid seccomp levels by exiting with error.

Fixed

  • Incorrect handling of bind mounts within the jailed rootfs.
  • Corrected the guide for Alpine guest setup.

[0.16.0]

Added

  • Added [alpha] AMD support.
  • New devtool command: prepare_release. This updates the Firecracker version, crate dependencies and credits in preparation for a new release.
  • New devtool command: tag. This creates a new git tag for the specified release number, based on the changelog contents.
  • New doc section about building with glibc.

Changed

  • Dropped the JSON-formatted context command-line parameter from Firecracker in favor of individual classic command-line parameters.
  • When running with jailer the location of the API socket has changed to <jail-root-path>/api.socket (API socket was moved inside the jail).
  • PUT and PATCH requests on /mmds with data containing any value type other than String, Array, Object will returns status code 400.
  • Improved multiple error messages.
  • Removed all kernel modules from the recommended kernel config.

Fixed

  • Corrected the seccomp filter when building with glibc.

Removed

  • Removed the seccomp.bad_syscalls metric.

[0.15.2]

Fixed

  • Corrected the conditional compilation of the seccomp rule for madvise.

[0.15.1]

Fixed

  • A madvise call issued by the musl allocator was added to the seccomp allow list to prevent Firecracker from terminating abruptly when allocating memory in certain conditions.

[0.15.0]

Added

  • New API action: SendCtrlAltDel, used to initiate a graceful shutdown, if the guest has driver support for i8042 and AT Keyboard. See the docs for details.
  • New metric counting the number of egress packets with a spoofed MAC: net.tx_spoofed_mac_count.
  • New API call: PATCH /network-interfaces/, used to update the rate limiters on a network interface, after the start of a microVM.

Changed

  • Added missing vmm_version field to the InstanceInfo API swagger definition, and marked several other mandatory fields as such.
  • New default command line for guest kernel: reboot=k panic=1 pci=off nomodules 8250.nr_uarts=0 i8042.noaux i8042.nomux i8042.nopnp i8042.dumbkbd.

Fixed

  • virtio-blk: VIRTIO_BLK_T_FLUSH now working as expected.
  • Vsock devices can be attached when starting Firecracker using the jailer.
  • Vsock devices work properly when seccomp filtering is enabled.

[0.14.0]

Added

  • Documentation for development environment setup on AWS in dev-machine-setup.md.
  • Documentation for microVM networking setup in docs/network-setup.md.
  • Limit the maximum supported vCPUs to 32.

Changed

  • Log the app version when the Logger is initialized.
  • Pretty print panic information.
  • Firecracker terminates with exit code 148 when a syscall which is not present in the allow list is intercepted.

Fixed

  • Fixed build with the vsock feature.

[0.13.0]

Added

  • Documentation for Logger API Requests in docs/api_requests/logger.md.
  • Documentation for Actions API Requests in docs/api_requests/actions.md.
  • Documentation for MMDS in docs/mmds.md.
  • Flush metrics on request via a PUT /actions with the action_type field set to FlushMetrics.

Changed

  • Updated the swagger definition of the Logger to specify the required fields and provide default values for optional fields.
  • Default seccomp-level is 2 (was previously 0).
  • API Resource IDs can only contain alphanumeric characters and underscores.

Fixed

  • Seccomp filters are now applied to all Firecracker threads.
  • Enforce minimum length of 1 character for the jailer ID.
  • Exit with error code when starting the jailer process fails.

Removed

  • Removed InstanceHalt from the list of possible actions.

[0.12.0]

Added

  • The /logger API has a new field called options. This is an array of strings that specify additional logging configurations. The only supported value is LogDirtyPages.
  • When the LogDirtyPages option is configured via PUT /logger, a new metric called memory.dirty_pages is computed as the number of pages dirtied by the guest since the last time the metric was flushed.
  • Log messages on both graceful and forceful termination.
  • Availability of the list of dependencies for each commit inside the code base.
  • Documentation on vsock experimental feature and host setup recommendations.

Changed

  • PUT requests on /mmds always return 204 on success.
  • PUT operations on /network-interfaces API resources no longer accept the previously required state parameter.
  • The jailer starts with --seccomp-level=2 (was previously 0) by default.
  • Log messages use anonymous-instance as instance id if none is specified.

Fixed

  • Fixed crash upon instance start on hosts without 1GB huge page support.
  • Fixed "fault_message" inconsistency between Open API specification and code base.
  • Ensure MMDS compatibility with C5's IMDS implementation.
  • Corrected the swagger specification to ensure OpenAPI 2.0 compatibility.

[0.11.0]

Added

Changed

  • Improved MMDS network stack performance.
  • If the logging system is not yet initialized (via PUT /logger), log events are now sent to stdout/stderr.
  • Moved the instance_info_fails metric under get_api_requests
  • Improved readme and added links to more detailed information, now featured in subject-specific docs.

Fixed

  • Fixed bug in the MMDS network stack, that caused some RST packets to be sent without a destination.
  • Fixed bug in PATCH /drives, whereby the ID in the path was not checked against the ID in the body.

[0.10.1]

Fixed

  • The Swagger definition was corrected.

[0.10.0]

Added

  • Each Firecracker process has an associated microVM Metadata Store (MMDS). Its contents can be configured using the /mmds API resource.

Changed

  • The boot source is specified only with the kernel_image_path and the optional parameter boot_args. All other fields are removed.
  • The path_on_host property in the drive specification is now marked as mandatory.
  • PATCH drive only allows patching/changing the path_on_host property.
  • All PUT and PATCH requests return the status code 204.
  • CPUID brand string (aka model name) now includes the host CPU frequency.
  • API requests which add guest network interfaces have an additional parameter, allow_mmds_requests which defaults to false.
  • Stopping the guest (e.g. using the reboot command) also terminates the Firecracker process. When the Firecracker process ends for any reason, (other than kill -9), metrics are flushed at the very end.
  • On startup jailer closes all inherited file descriptors based on sysconf(_SC_OPEN_MAX) except input, output and error.
  • The microVM ID prefixes each Firecracker log line. This ID also appears in the process cmdline so it's now possible to ps | grep <ID> for it.

[0.9.0]

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.

[0.8.0]

Added

  • The jailer can now be configured to enter a preexisting network namespace, and to run as a daemon.
  • Enabled PATCH operations on /drives resources.

Changed

  • The microVM id supplied to the jailer may now contain alphanumeric characters and hyphens, up to a maximum length of 64 characters.
  • Replaced the permissions property of /drives resources with a boolean.
  • Removed the state property of /drives resources.

[0.7.0]

Added

  • Rate limiting functionality allows specifying an initial one time burst size.
  • Firecracker can now boot from an arbitrary boot partition by specifying its unique id in the driver's API call.
  • Block device rescan is triggered via a PUT /actions with the drive ID in the action body's payload field and the action_type field set to BlockDeviceRescan.

Changed

  • Removed noapic from the default guest kernel command line.
  • The action_id parameter is no longer required for synchronous PUT requests to /actions.
  • PUT requests are no longer allowed on /drives resources after the guest has booted.

Fixed

  • Fixed guest instance kernel loader to accelerate vCPUs launch and consequently guest kernel boot.
  • Fixed network emulation to improve IO performance.

[0.6.0]

Added

  • Firecracker uses two different named pipes to record human readable logs and metrics, respectively.

Changed

  • Seccomp filtering can be enabled via setting the USE_SECCOMP environment variable.
  • It is possible to supply only a partial specification when attaching a rate limiter (i.e. just the bandwidth or ops parameter).
  • Errors related to guest network interfaces are now more detailed.

Fixed

  • Fixed a bug that was causing Firecracker to panic whenever a PUT request was sent on an existing network interface.
  • The id parameter of the jailer is required to be an RFC 4122-compliant UUID.
  • Fixed an issue which caused the network RX rate limiter to be more restrictive than intended.
  • API requests which contain unknown fields will generate an error.
  • Fixed an issue related to high CPU utilization caused by improper KVM PIT configuration.
  • It is now possible to create more than one network tun/tap interface inside a jailed Firecracker.

[0.5.0]

Added

  • Added metrics for API requests, VCPU and device actions for the serial console (UART), keyboard (i8042), block and network devices. Metrics are logged every 60 seconds.
  • A CPU features template for C3 is available, in addition to the one for T2.
  • Seccomp filters restrict Firecracker from calling any other system calls than the minimum set it needs to function properly. The filters are enabled by setting the USE_SECCOMP environment variable to 1 before running Firecracker.
  • Firecracker can be started by a new binary called jailer. The jailer takes as command line arguments a unique ID, the path to the Firecracker binary, the NUMA node that Firecracker will be assigned to and a uid and gid for Firecracker to run under. It sets up a chroot environment and a cgroup, and calls exec to morph into Firecracker.

Changed

  • In case of failure, the metrics and the panic location are logged before aborting.
  • Metric values are reset with every flush.
  • CPUTemplate is now called CpuTemplate in order to work seamlessly with the swagger code generator for Go.
  • firecracker-beta.yaml is now called firecracker.yaml.

Fixed

  • Handling was added for several untreated KVM exit scenarios, which could have led to panic.
  • Fixed a bug that caused Firecracker to crash when attempting to disable the IA32_DEBUG_INTERFACE MSR flag in the T2 CPU features.

Removed

  • Removed a leftover file generated by the logger unit tests.
  • Removed firecracker-v1.0.yaml.

[0.4.0]

Added

  • The CPU Template can be set with an API call on PUT /machine-config. The only available template is T2.
  • Hyperthreading can be enabled/disabled with an API call on PUT /machine-config. By default, hyperthreading is disabled.
  • Added boot time performance test (tests/performance/test_boottime.py).
  • Added Rate Limiter for VirtIO/net and VirtIO/net devices. The Rate Limiter uses two token buckets to limit rate on bytes/s and ops/s. The rate limiter can be (optionally) configured per drive with a PUT on /drives/{drive_id} and per network interface with a PUT on /network-interface/{iface_id}.
  • Implemented pre-boot PUT updates for /boot-source, /drives, /network-interfaces and /vsock.
  • Added integration tests for PUT updates.

Changed

  • Moved the API definition (swagger/firecracker-beta.yaml) to the api_server crate.
  • Removed "console=ttyS0" and added "8250.nr_uarts=0" to the default kernel command line to decrease the boot time.
  • Changed the CPU topology to have all logical CPUs on a single socket.
  • Removed the upper bound on CPU count as with musl there is no good way to get the total number of logical processors on a host.
  • Build time tests now print the full output of commands.
  • Disabled the Performance Monitor Unit and the Turbo Boost.
  • Check the expected KVM capabilities before starting the VM.
  • Logs now have timestamps.

Fixed

  • testrun.sh can run on platforms with more than one package manager by setting the package manager via a command line parameter (-p).
  • Allow correct set up of multiple network-interfaces with auto-generated MAC.
  • Fixed sporadic bug in VirtIO which was causing lost packages.
  • Don't allow PUT requests with empty body on /machine-config.
  • Deny PUT operations after the microvm boots (exception: the temporarily fix for live resize of block devices).

Removed

  • Removed examples crate. This used to have a Python example of starting Firecracker. This is replaced by test_api.py integration tests.
  • Removed helper scripts for getting coverage and coding style errors. These were replaced by test_coverage.py and test_style.py test integration tests.
  • Removed --vmm-no-api command line option. Firecracker can only be started via the API.

[0.3.0]

Added

  • Users can interrogate the Machine Configuration (i.e. vcpu count and memory size) using a GET request on /machine-config.
  • The logging system can be configured through the API using a PUT on /logger.
  • Block devices support live resize by calling PUT with the same parameters as when the block was created.
  • Release builds have Link Time Optimization (LTO) enabled.
  • Firecracker is built with musl, resulting in a statically linked binary.
  • More in-tree integration tests were added as part of the continuous integration system.

Changed

  • The vcpu count is enforced to 1 or an even number.
  • The Swagger definition of rate limiters was updated.
  • Syslog-enabled logs were replaced with a host-file backed mechanism.

Fixed

  • The host topology of the CPU and the caches is not leaked into the microvm anymore.
  • Boot time was improved by advertising the availability of the TSC deadline timer.
  • Fixed an issue which prevented Firecracker from working on 4.14 (or newer) host kernels.
  • Specifying the MAC address for an interface through the API is optional.

Removed

  • Removed support for attaching vsock devices.
  • Removed support for building Firecracker with glibc.

[0.2.0]

Added

  • Users can now interrogate Instance Information (currently just instance state) through the API.

Changed

  • Renamed api/swagger/all.yaml to api/swagger/firecracker-v1.0.yaml which specifies targeted API support for Firecracker v1.0.
  • Renamed api/swagger/firecracker-v0.1.yaml to api/swagger/firecracker-beta.yaml which specifies the currently supported API.
  • Users can now enforce that an emulated block device is read-only via the API. To specify whether a block device is read-only or read-write, an extra "permissions" field was added to the Drive definition in the API. The root filesystem is automatically mounted in the guest OS as ro/rw according to the specified "permissions". It's the responsibility of the user to mount any other read-only block device as such within the guest OS.
  • Users can now stop the guest VM using the API. Actions of type InstanceHalt are now supported via the API.

Fixed

  • Added support for getDeviceID() in virtIO-block. Without this, the guest Linux kernel would complain at boot time that the operation is unsupported.
  • stdin control is returned to the Firecracker process when guest VM is inactive. Raw mode stdin is forwarded to the guest OS when guest VM is running.

Removed

  • Removed api/swagger/actions.yaml.
  • Removed api/swagger/devices.yaml.
  • Removed api/swagger/firecracker-mvp.yaml.
  • Removed api/swagger/limiters.yaml.

[0.1.1]

Changed

  • Users can now specify the MAC address of a guest network interface via the PUT network interface API request. Previously, the guest MAC address parameter was ignored.

Fixed

  • Fixed a guest memory allocation issue, which previously led to a potentially significant memory chunk being wasted.
  • Fixed an issue which caused compilation problems, due to a compatibility breaking transitive dependency in the tokio suite of crates.

[0.1.0]

Added

  • One-process virtual machine manager (one Firecracker per microVM).
  • RESTful API running on a unix socket. The API supported by v0.1 can be found at api/swagger/firecracker-v0.1.yaml.
  • Emulated keyboard (i8042) and serial console (UART). The microVM serial console input and output are connected to those of the Firecracker process (this allows direct console access to the guest OS).
  • The capability of mapping an existing host tun-tap device as a VirtIO/net device into the microVM.
  • The capability of mapping an existing host file as a GirtIO/block device into the microVM.
  • The capability of creating a VirtIO/vsock between the host and the microVM.
  • Default demand fault paging & CPU oversubscription.