refactor: Split struct Vm into arch-specific structs

Similarly to what we do in the vcpu module for the Vcpu/KvmVcpu
structs. The difference is that we do not implement any function on
`ArchVm`, so that common fields like `fd` can live in `Vm`, instead of
needing to be duplicated into all the `ArchVm` types.

Signed-off-by: Patrick Roy <[email protected]>

Author: roypat

src/vmm/src/vstate/vm/aarch64.rs

@@ -1,10 +1,20 @@
 // Copyright 2025 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 // SPDX-License-Identifier: Apache-2.0
 
+use kvm_ioctls::VmFd;
 use serde::{Deserialize, Serialize};
 
+use super::VmError;
 use crate::arch::aarch64::gic::GicState;
-use crate::Vm;
+use crate::vstate::kvm::Kvm;
+
+/// Structure representing the current architecture's understand of what a "virtual machine" is.
+#[derive(Debug)]
+pub struct ArchVm {
+    pub(super) fd: VmFd,
+    // On aarch64 we need to keep around the fd obtained by creating the VGIC device.
+    irqchip_handle: Option<crate::arch::aarch64::gic::GICDevice>,
+}
 
 /// Error type for [`Vm::restore_state`]
 #[derive(Debug, PartialEq, Eq, thiserror::Error, displaydoc::Display)]
@@ -17,7 +27,16 @@ pub enum ArchVmError {
     RestoreGic(crate::arch::aarch64::gic::GicError),
 }
 
-impl Vm {
+impl ArchVm {
+    /// Create a new `Vm` struct.
+    pub fn new(kvm: &Kvm) -> Result<ArchVm, VmError> {
+        let fd = kvm.fd.create_vm().map_err(VmError::VmFd)?;
+        Ok(ArchVm {
+            fd,
+            irqchip_handle: None,
+        })
+    }
+
     /// Creates the GIC (Global Interrupt Controller).
     pub fn setup_irqchip(&mut self, vcpu_count: u8) -> Result<(), ArchVmError> {
         self.irqchip_handle = Some(

src/vmm/src/vstate/vm/mod.rs

@@ -8,11 +8,8 @@
 use kvm_bindings::{kvm_userspace_memory_region, KVM_MEM_LOG_DIRTY_PAGES};
 use kvm_ioctls::VmFd;
 
-#[cfg(target_arch = "aarch64")]
-use crate::arch::aarch64::gic::GICDevice;
 #[cfg(target_arch = "x86_64")]
 use crate::utils::u64_to_usize;
-use crate::vstate::kvm::Kvm;
 use crate::vstate::memory::{Address, GuestMemory, GuestMemoryMmap, GuestMemoryRegion};
 
 #[cfg(target_arch = "x86_64")]
@@ -22,7 +19,7 @@ mod arch;
 #[path = "aarch64.rs"]
 mod arch;
 
-pub use arch::{ArchVmError, VmState};
+pub use arch::{ArchVm as Vm, ArchVmError, VmState};
 
 /// Errors associated with the wrappers over KVM ioctls.
 /// Needs `rustfmt::skip` to make multiline comments work
@@ -39,38 +36,8 @@ pub enum VmError {
     Arch(#[from] ArchVmError),
 }
 
-/// A wrapper around creating and using a VM.
-#[derive(Debug)]
-pub struct Vm {
-    fd: VmFd,
-
-    // Arm specific fields.
-    // On aarch64 we need to keep around the fd obtained by creating the VGIC device.
-    #[cfg(target_arch = "aarch64")]
-    irqchip_handle: Option<GICDevice>,
-}
-
 /// Contains Vm functions that are usable across CPU architectures
 impl Vm {
-    /// Create a new `Vm` struct.
-    pub fn new(kvm: &Kvm) -> Result<Self, VmError> {
-        // Create fd for interacting with kvm-vm specific functions.
-        let vm_fd = kvm.fd.create_vm().map_err(VmError::VmFd)?;
-
-        #[cfg(target_arch = "aarch64")]
-        {
-            Ok(Vm {
-                fd: vm_fd,
-                irqchip_handle: None,
-            })
-        }
-
-        #[cfg(target_arch = "x86_64")]
-        {
-            Ok(Vm { fd: vm_fd })
-        }
-    }
-
     /// Initializes the guest memory.
     pub fn memory_init(&self, guest_mem: &GuestMemoryMmap) -> Result<(), VmError> {
         self.set_kvm_memory_regions(guest_mem)?;
@@ -122,6 +89,7 @@ impl Vm {
 pub(crate) mod tests {
     use super::*;
     use crate::test_utils::single_region_mem;
+    use crate::vstate::kvm::Kvm;
     use crate::vstate::memory::GuestMemoryMmap;
 
     // Auxiliary function being used throughout the tests.

src/vmm/src/vstate/vm/x86_64.rs

@@ -7,9 +7,10 @@ use kvm_bindings::{
     kvm_clock_data, kvm_irqchip, kvm_pit_config, kvm_pit_state2, KVM_CLOCK_TSC_STABLE,
     KVM_IRQCHIP_IOAPIC, KVM_IRQCHIP_PIC_MASTER, KVM_IRQCHIP_PIC_SLAVE, KVM_PIT_SPEAKER_DUMMY,
 };
+use kvm_ioctls::VmFd;
 use serde::{Deserialize, Serialize};
 
-use crate::Vm;
+use crate::vstate::vm::VmError;
 
 /// Error type for [`Vm::restore_state`]
 #[allow(missing_docs)]
@@ -40,7 +41,19 @@ pub enum ArchVmError {
     VmSetIrqChip(kvm_ioctls::Error),
 }
 
-impl Vm {
+/// Structure representing the current architecture's understand of what a "virtual machine" is.
+#[derive(Debug)]
+pub struct ArchVm {
+    pub(super) fd: VmFd,
+}
+
+impl ArchVm {
+    /// Create a new `Vm` struct.
+    pub fn new(kvm: &crate::vstate::kvm::Kvm) -> Result<ArchVm, VmError> {
+        let fd = kvm.fd.create_vm().map_err(VmError::VmFd)?;
+        Ok(ArchVm { fd })
+    }
+
     /// Restores the KVM VM state.
     ///
     /// # Errors