snapshot: add state types for previous versions

Add descriptions for MicovmState from previous Firecracker versions.
Moreover, add methods to translate a snapshot file from previous
versions in the current one.

Signed-off-by: Babis Chalios <babis.chalios@e2b.dev>

Author: bchalios

src/vmm/src/arch/x86_64/vm.rs

@@ -224,13 +224,18 @@ pub struct VmState {
     pub memory: GuestMemoryState,
     /// resource allocator
     pub resource_allocator: ResourceAllocator,
-    pitstate: kvm_pit_state2,
-    clock: kvm_clock_data,
+    /// KVM interrupt timer
+    pub pitstate: kvm_pit_state2,
+    /// KVM clock data
+    pub clock: kvm_clock_data,
     // TODO: rename this field to adopt inclusive language once Linux updates it, too.
-    pic_master: kvm_irqchip,
+    /// Master PIC controller
+    pub pic_master: kvm_irqchip,
     // TODO: rename this field to adopt inclusive language once Linux updates it, too.
-    pic_slave: kvm_irqchip,
-    ioapic: kvm_irqchip,
+    /// Slave PIC controller
+    pub pic_slave: kvm_irqchip,
+    /// IOAPIC
+    pub ioapic: kvm_irqchip,
 }
 
 impl fmt::Debug for VmState {

src/vmm/src/device_manager/persist.rs

@@ -168,9 +168,9 @@ impl fmt::Debug for MMIODevManagerConstructorArgs<'_> {
 
 #[derive(Default, Debug, Clone, Serialize, Deserialize)]
 pub struct ACPIDeviceManagerState {
-    vmgenid: VMGenIDState,
+    pub vmgenid: VMGenIDState,
     #[cfg(target_arch = "x86_64")]
-    vmclock: VmClockState,
+    pub vmclock: VmClockState,
 }
 
 impl<'a> Persist<'a> for ACPIDeviceManager {

src/vmm/src/devices/acpi/mod.rs

@@ -1,6 +1,6 @@
 // Copyright 2024 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 // SPDX-License-Identifier: Apache-2.0
 
-mod generated;
+pub mod generated;
 pub mod vmclock;
 pub mod vmgenid;

src/vmm/src/devices/acpi/vmclock.rs

@@ -22,7 +22,7 @@ use crate::vstate::resources::ResourceAllocator;
 unsafe impl ByteValued for vmclock_abi {}
 
 // We are reserving a physical page to expose the [`VmClock`] data
-const VMCLOCK_SIZE: u32 = 0x1000;
+pub const VMCLOCK_SIZE: u32 = 0x1000;
 
 // Write a value in `vmclock_abi` both in the Firecracker-managed state
 // and inside guest memory address that corresponds to it.

src/vmm/src/devices/virtio/balloon/device.rs

@@ -68,7 +68,7 @@ unsafe impl ByteValued for ConfigSpace {}
 
 /// Holds state of the free page hinting run
 #[derive(Copy, Clone, Debug, Default, Serialize, Deserialize)]
-pub(crate) struct HintingState {
+pub struct HintingState {
     /// The command requested by us. Set to STOP by default.
     pub host_cmd: u32,
     /// The last command supplied by guest.

src/vmm/src/devices/virtio/balloon/persist.rs

@@ -31,22 +31,22 @@ pub struct BalloonConfigSpaceState {
 /// at snapshot.
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct BalloonStatsState {
-    swap_in: Option<u64>,
-    swap_out: Option<u64>,
-    major_faults: Option<u64>,
-    minor_faults: Option<u64>,
-    free_memory: Option<u64>,
-    total_memory: Option<u64>,
-    available_memory: Option<u64>,
-    disk_caches: Option<u64>,
-    hugetlb_allocations: Option<u64>,
-    hugetlb_failures: Option<u64>,
-    oom_kill: Option<u64>,
-    alloc_stall: Option<u64>,
-    async_scan: Option<u64>,
-    direct_scan: Option<u64>,
-    async_reclaim: Option<u64>,
-    direct_reclaim: Option<u64>,
+    pub swap_in: Option<u64>,
+    pub swap_out: Option<u64>,
+    pub major_faults: Option<u64>,
+    pub minor_faults: Option<u64>,
+    pub free_memory: Option<u64>,
+    pub total_memory: Option<u64>,
+    pub available_memory: Option<u64>,
+    pub disk_caches: Option<u64>,
+    pub hugetlb_allocations: Option<u64>,
+    pub hugetlb_failures: Option<u64>,
+    pub oom_kill: Option<u64>,
+    pub alloc_stall: Option<u64>,
+    pub async_scan: Option<u64>,
+    pub direct_scan: Option<u64>,
+    pub async_reclaim: Option<u64>,
+    pub direct_reclaim: Option<u64>,
 }
 
 impl BalloonStatsState {
@@ -101,11 +101,11 @@ impl BalloonStatsState {
 /// at snapshot.
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct BalloonState {
-    stats_polling_interval_s: u16,
-    stats_desc_index: Option<u16>,
-    latest_stats: BalloonStatsState,
-    config_space: BalloonConfigSpaceState,
-    hinting_state: HintingState,
+    pub stats_polling_interval_s: u16,
+    pub stats_desc_index: Option<u16>,
+    pub latest_stats: BalloonStatsState,
+    pub config_space: BalloonConfigSpaceState,
+    pub hinting_state: HintingState,
     pub virtio_state: VirtioDeviceState,
 }
 

src/vmm/src/devices/virtio/block/vhost_user/persist.rs

@@ -15,14 +15,14 @@ use crate::snapshot::Persist;
 /// vhost-user block device state.
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct VhostUserBlockState {
-    id: String,
-    partuuid: Option<String>,
-    cache_type: CacheType,
-    root_device: bool,
-    socket_path: String,
-    vu_acked_protocol_features: u64,
-    config_space: Vec<u8>,
-    virtio_state: VirtioDeviceState,
+    pub id: String,
+    pub partuuid: Option<String>,
+    pub cache_type: CacheType,
+    pub root_device: bool,
+    pub socket_path: String,
+    pub vu_acked_protocol_features: u64,
+    pub config_space: Vec<u8>,
+    pub virtio_state: VirtioDeviceState,
 }
 
 impl Persist<'_> for VhostUserBlock {

src/vmm/src/devices/virtio/block/virtio/persist.rs

@@ -53,14 +53,14 @@ impl From<FileEngineTypeState> for FileEngineType {
 /// Holds info about the block device. Gets saved in snapshot.
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct VirtioBlockState {
-    id: String,
-    partuuid: Option<String>,
-    cache_type: CacheType,
-    root_device: bool,
-    disk_path: String,
+    pub id: String,
+    pub partuuid: Option<String>,
+    pub cache_type: CacheType,
+    pub root_device: bool,
+    pub disk_path: String,
     pub virtio_state: VirtioDeviceState,
-    rate_limiter_state: RateLimiterState,
-    file_engine_type: FileEngineTypeState,
+    pub rate_limiter_state: RateLimiterState,
+    pub file_engine_type: FileEngineTypeState,
 }
 
 impl Persist<'_> for VirtioBlock {

src/vmm/src/devices/virtio/net/persist.rs

@@ -46,13 +46,13 @@ pub struct RxBufferState {
 pub struct NetState {
     pub id: String,
     pub tap_if_name: String,
-    rx_rate_limiter_state: RateLimiterState,
-    tx_rate_limiter_state: RateLimiterState,
+    pub rx_rate_limiter_state: RateLimiterState,
+    pub tx_rate_limiter_state: RateLimiterState,
     /// The associated MMDS network stack.
     pub mmds_ns: Option<MmdsNetworkStackState>,
-    config_space: NetConfigSpaceState,
+    pub config_space: NetConfigSpaceState,
     pub virtio_state: VirtioDeviceState,
-    rx_buffers_state: RxBufferState,
+    pub rx_buffers_state: RxBufferState,
 }
 
 /// Auxiliary structure for creating a device when resuming from a snapshot.

src/vmm/src/devices/virtio/persist.rs

@@ -194,13 +194,13 @@ impl VirtioDeviceState {
 #[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
 pub struct MmioTransportState {
     // The register where feature bits are stored.
-    features_select: u32,
+    pub features_select: u32,
     // The register where features page is selected.
-    acked_features_select: u32,
-    queue_select: u32,
-    device_status: u32,
-    config_generation: u32,
-    interrupt_status: u32,
+    pub acked_features_select: u32,
+    pub queue_select: u32,
+    pub device_status: u32,
+    pub config_generation: u32,
+    pub interrupt_status: u32,
 }
 
 /// Auxiliary structure for initializing the transport when resuming from a snapshot.