Add ACPI support for x86_64

CHANGELOG.md

@@ -10,6 +10,14 @@ and this project adheres to
 
 ### Added
 
+- [#4428](https://github.com/firecracker-microvm/firecracker/pull/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](docs/kernel-policy.md) for more information
+  regarding relevant kernel configurations.
+
 ### Changed
 
 - [#4492](https://github.com/firecracker-microvm/firecracker/pull/4492): Changed
@@ -25,6 +33,11 @@ and this project adheres to
   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
 

Cargo.toml

@@ -1,6 +1,6 @@
 [workspace]
-members = ["src/clippy-tracing", "src/cpu-template-helper", "src/firecracker", "src/jailer", "src/log-instrument", "src/log-instrument-macros", "src/rebase-snap", "src/seccompiler", "src/snapshot-editor"]
-default-members = ["src/clippy-tracing", "src/cpu-template-helper", "src/firecracker", "src/rebase-snap", "src/seccompiler", "src/snapshot-editor"]
+members = ["src/acpi-tables", "src/clippy-tracing", "src/cpu-template-helper", "src/firecracker", "src/jailer", "src/log-instrument", "src/log-instrument-macros", "src/rebase-snap", "src/seccompiler", "src/snapshot-editor"]
+default-members = ["src/clippy-tracing", "src/cpu-template-helper", "src/firecracker", "src/rebase-snap", "src/seccompiler", "src/snapshot-editor", "src/acpi-tables"]
 resolver = "2"
 
 [workspace.lints.rust]

DEPRECATED.md

@@ -16,3 +16,6 @@ a future major Firecracker release, in accordance with our
   `rebase-snap` tool
 - \[[#4500](https://github.com/firecracker-microvm/firecracker/pull/4500)\] The
   `--start-time-cpu-us` and `--start-time-us` CLI arguments
+- \[[#4428](https://github.com/firecracker-microvm/firecracker/pull/4428)\]
+  Booting microVMs using MPTable and command line parameters for VirtIO devices.
+  The functionality is substituted with ACPI.

docs/kernel-policy.md

@@ -47,6 +47,7 @@ The configuration items that may be relevant for Firecracker are:
 - guest RNG - `CONFIG_RANDOM_TRUST_CPU`
   - use CPU RNG instructions (if present) to initialize RNG. Available for >=
     5.10
+- ACPI support - `CONFIG_ACPI` and `CONFIG_PCI`
 
 There are also guest config options which are dependant on the platform on which
 Firecracker is run:
@@ -81,16 +82,53 @@ the minimal configuration for a guest kernel for a successful microVM boot is:
     - `CONFIG_VIRTIO_BLK=y`
   - x86_64
     - `CONFIG_VIRTIO_BLK=y`
-    - `CONFIG_VIRTIO_MMIO_CMDLINE_DEVICES=y`
+    - `CONFIG_ACPI=y`
+    - `CONFIG_PCI=y`
     - `CONFIG_KVM_GUEST=y`.
 
 *Optional*: To enable boot logs set `CONFIG_SERIAL_8250_CONSOLE=y` and
 `CONFIG_PRINTK=y` in the guest kernel config.
 
+##### Booting with ACPI (x86_64 only):
+
+Firecracker supports booting kernels with ACPI support. The relevant
+configurations for the guest kernel are:
+
+- `CONFIG_ACPI=y`
+- `CONFIG_PCI=y`
+
+Please note that Firecracker does not support PCI devices. The `CONFIG_PCI`
+option is needed for ACPI initialization inside the guest.
+
+ACPI supersedes the legacy way of booting a microVM, i.e. via MPTable and
+command line parameters for VirtIO devices.
+
+We suggest that users disable MPTable and passing VirtIO devices via kernel
+command line parameters. These boot mechanisms are now deprecated. Users can
+disable these features by disabling the corresponding guest kernel configuration
+parameters:
+
+- `CONFIG_X86_MPPARSE=n`
+- `CONFIG_VIRTIO_MMIO_CMDLINE_DEVICES=n`
+
+During the deprecation period Firecracker will continue to support the legacy
+way of booting a microVM. Firecracker will be able to boot kernels with the
+following configurations:
+
+- Only ACPI
+- Only legacy mechanisms
+- Both ACPI and legacy mechanisms
+
 ## Caveats
 
 - When using a 4.14 host and a 5.10 guest, we disable the SVE extension in the
   guest. This is due to the introduction of the SVE extension in Graviton3,
   which causes the default 5.10 guest (with SVE support enabled), to crash if
   run with a 4.14 host which does not support SVE.
 - [Snapshot compatibility across kernel versions](snapshotting/snapshot-support.md#snapshot-compatibility-across-kernel-versions)
+- When booting with kernels that support both ACPI and legacy boot mechanisms
+  Firecracker passes VirtIO devices to the guest twice, once through ACPI and a
+  second time via kernel command line parameters. In these cases, the guest
+  tries to initialize devices twice. The second time, initialization fails and
+  the guest will emit warning messages in `dmesg`, however the devices will work
+  correctly.