refactor: Eliminate VmResources::track_dirty_pages getter

All other fields of `VmResources` and the contained `VmConfig` struct
are accessed directly, with `track_dirty_pages` being the odd one out.
Let's make it uniform.

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

Author: roypat

src/vmm/src/builder.rs

@@ -252,8 +252,6 @@ pub fn build_microvm_for_boot(
         .boot_source_builder()
         .ok_or(MissingKernelConfig)?;
 
-    let track_dirty_pages = vm_resources.track_dirty_pages();
-
     let vhost_user_device_used = vm_resources
         .block
         .devices
@@ -272,15 +270,15 @@ pub fn build_microvm_for_boot(
     let guest_memory = if vhost_user_device_used {
         GuestMemoryMmap::memfd_backed(
             vm_resources.vm_config.mem_size_mib,
-            track_dirty_pages,
+            vm_resources.vm_config.track_dirty_pages,
             vm_resources.vm_config.huge_pages,
         )
         .map_err(StartMicrovmError::GuestMemory)?
     } else {
         let regions = crate::arch::arch_memory_regions(vm_resources.vm_config.mem_size_mib << 20);
         GuestMemoryMmap::from_raw_regions(
             &regions,
-            track_dirty_pages,
+            vm_resources.vm_config.track_dirty_pages,
             vm_resources.vm_config.huge_pages,
         )
         .map_err(StartMicrovmError::GuestMemory)?
@@ -299,7 +297,7 @@ pub fn build_microvm_for_boot(
         event_manager,
         guest_memory,
         None,
-        track_dirty_pages,
+        vm_resources.vm_config.track_dirty_pages,
         vm_resources.vm_config.vcpu_count,
         cpu_template.kvm_capabilities.clone(),
     )?;

src/vmm/src/resources.rs

@@ -234,11 +234,6 @@ impl VmResources {
         Ok(())
     }
 
-    /// Returns whether dirty page tracking is enabled or not.
-    pub fn track_dirty_pages(&self) -> bool {
-        self.vm_config.track_dirty_pages
-    }
-
     /// Add a custom CPU template to the VM resources
     /// to configure vCPUs.
     pub fn set_custom_cpu_template(&mut self, cpu_template: CustomCpuTemplate) {

src/vmm/src/rpc_interface.rs

@@ -755,7 +755,7 @@ impl RuntimeApiController {
         log_dev_preview_warning("Virtual machine snapshots", None);
 
         if create_params.snapshot_type == SnapshotType::Diff
-            && !self.vm_resources.track_dirty_pages()
+            && !self.vm_resources.vm_config.track_dirty_pages
         {
             return Err(VmmActionError::NotSupported(
                 "Diff snapshots are not allowed on uVMs with dirty page tracking disabled."