vmm: reevaluate #[allow] attributes

Remove stale #[allow]s whose lints no longer fire, convert the
unconditionally-firing ones to #[expect], and keep the
arch/feature-conditional ones as #[allow]. Verified across kvm/mshv,
x86_64/aarch64, and --all-features.

Part of #8326.

Signed-off-by: Tushar Khatri <hello@tusharkhatri.in>

vmm/src/api/http/mod.rs

@@ -98,7 +98,7 @@ const HTTP_ROOT: &str = "/api/v1";
 /// The error message contained in the response is supposed to be user-facing,
 /// thus insightful and helpful while balancing technical accuracy and
 /// simplicity.
-#[allow(clippy::needless_pass_by_value)]
+#[expect(clippy::needless_pass_by_value)]
 pub fn error_response(error: HttpError) -> Response {
     let mut response = Response::new(Version::Http11, error.status_code());
 

vmm/src/api/mod.rs

@@ -603,7 +603,7 @@ pub trait RequestHandler {
 pub type ApiRequest =
     Box<dyn FnOnce(&mut dyn RequestHandler) -> Result<bool, VmmError> + Send + 'static>;
 
-#[allow(clippy::needless_pass_by_value)]
+#[expect(clippy::needless_pass_by_value)]
 fn get_response<Action: ApiAction>(
     action: &Action,
     api_evt: EventFd,

vmm/src/clone3.rs

@@ -7,7 +7,6 @@ pub const CLONE_CLEAR_SIGHAND: u64 = 0x100000000;
 
 #[repr(C)]
 #[derive(Default)]
-#[allow(non_camel_case_types)]
 pub struct clone_args {
     pub flags: u64,
     pub pidfd: u64,

vmm/src/config.rs

@@ -1046,7 +1046,7 @@ impl PlatformConfig {
 }
 
 impl MemoryConfig {
-    #[allow(clippy::needless_pass_by_value)]
+    #[expect(clippy::needless_pass_by_value)]
     pub fn parse(memory: &str, memory_zones: Option<Vec<&str>>) -> Result<Self> {
         let mut parser = OptionParser::new();
         parser
@@ -4517,7 +4517,6 @@ mod unit_tests {
     }
 
     #[track_caller]
-    #[allow(clippy::too_many_arguments)]
     fn make_vhost_user_config(
         socket: &str,
         virtio_id: u64,

vmm/src/cpu.rs

@@ -842,8 +842,8 @@ impl VcpuState {
 }
 
 impl CpuManager {
-    #[allow(unused_variables)]
-    #[allow(clippy::too_many_arguments)]
+    #[expect(unused_variables)]
+    #[expect(clippy::too_many_arguments)]
     pub fn new(
         config: &CpusConfig,
         vm: Arc<dyn hypervisor::Vm>,

vmm/src/device_manager.rs

@@ -1197,7 +1197,7 @@ fn use_64bit_bar_for_virtio_device(
 }
 
 impl DeviceManager {
-    #[allow(clippy::too_many_arguments)]
+    #[expect(clippy::too_many_arguments)]
     pub fn new(
         io_bus: Arc<Bus>,
         mmio_bus: Arc<Bus>,
@@ -1465,7 +1465,7 @@ impl DeviceManager {
         self.add_interrupt_controller(snapshot)
     }
 
-    #[allow(clippy::needless_pass_by_value)]
+    #[expect(clippy::needless_pass_by_value)]
     pub fn create_devices(
         &mut self,
         console_info: Option<ConsoleInfo>,
@@ -4305,7 +4305,7 @@ impl DeviceManager {
         Ok(vec![])
     }
 
-    #[allow(clippy::too_many_arguments)]
+    #[expect(clippy::too_many_arguments)]
     fn add_virtio_pci_device(
         &mut self,
         virtio_device: Arc<Mutex<dyn virtio_devices::VirtioDevice>>,
@@ -4842,7 +4842,6 @@ impl DeviceManager {
             .pci_device_handle
             .as_ref()
             .ok_or(DeviceManagerError::MissingPciDevice)?;
-        #[allow(irrefutable_let_patterns)]
         if let PciDeviceHandle::Virtio(virtio_pci_device) = pci_device_handle {
             let device_type = VirtioDeviceType::from(
                 virtio_pci_device

vmm/src/igvm/igvm_loader.rs

@@ -273,7 +273,7 @@ pub fn extract_sev_features(igvm_file: &IgvmFile) -> u64 {
 /// NOTE: KVM and MSHV have different page type values and CPUID/VMSA handling.
 /// Hypervisor-specific code paths are gated by runtime type checks. A future
 /// refactor could split these into separate KVM/MSHV loader implementations.
-#[allow(clippy::needless_pass_by_value)]
+#[expect(clippy::needless_pass_by_value)]
 pub fn load_igvm(
     igvm_file: IgvmFile,
     memory_manager: Arc<Mutex<MemoryManager>>,

vmm/src/lib.rs

@@ -447,8 +447,7 @@ pub fn start_event_monitor_thread(
         .map_err(Error::EventMonitorThreadSpawn)
 }
 
-#[allow(unused_variables)]
-#[allow(clippy::too_many_arguments)]
+#[expect(clippy::too_many_arguments)]
 pub fn start_vmm_thread(
     vmm_version: VmmVersionInfo,
     http_path: &Option<String>,
@@ -717,7 +716,7 @@ impl Vmm {
 
         for signal in signals.forever() {
             match signal {
-                #[allow(clippy::collapsible_match)]
+                #[expect(clippy::collapsible_match)]
                 SIGTERM | SIGINT => {
                     if exit_evt.write(1).is_err() {
                         // Resetting the terminal is usually done as the VMM exits

vmm/src/memory_manager.rs

@@ -1140,7 +1140,7 @@ impl MemoryManager {
     /// snapshot file followed by a `UFFDIO_COPY` to resolve the fault and
     /// wake the faulting thread. When no fault is pending, one prefault
     /// page is copied per loop iteration.
-    #[allow(clippy::needless_pass_by_value)]
+    #[expect(clippy::needless_pass_by_value)]
     fn uffd_handler_loop(
         uffd_fd: OwnedFd,
         stop_event: EventFd,
@@ -1643,7 +1643,6 @@ impl MemoryManager {
         Ok(())
     }
 
-    #[allow(clippy::too_many_arguments)]
     pub fn new(
         vm: Arc<dyn hypervisor::Vm>,
         config: &MemoryConfig,
@@ -1899,7 +1898,7 @@ impl MemoryManager {
         Ok(Arc::new(Mutex::new(memory_manager)))
     }
 
-    #[allow(clippy::too_many_arguments)]
+    #[expect(clippy::too_many_arguments)]
     pub fn new_from_snapshot(
         snapshot: &Snapshot,
         vm: Arc<dyn hypervisor::Vm>,
@@ -2042,7 +2041,7 @@ impl MemoryManager {
         }
     }
 
-    #[allow(clippy::too_many_arguments)]
+    #[expect(clippy::too_many_arguments)]
     pub fn create_ram_region_raw(
         backing_file: &Option<PathBuf>,
         file_offset: u64,
@@ -2179,7 +2178,7 @@ impl MemoryManager {
         Ok(region)
     }
 
-    #[allow(clippy::too_many_arguments)]
+    #[expect(clippy::too_many_arguments)]
     pub fn create_ram_region(
         backing_file: &Option<PathBuf>,
         file_offset: u64,

vmm/src/vm.rs

@@ -560,8 +560,8 @@ impl Vm {
             .with_migrate_ma(0)
     }
 
-    #[allow(clippy::needless_pass_by_value)]
-    #[allow(clippy::too_many_arguments)]
+    #[expect(clippy::needless_pass_by_value)]
+    #[expect(clippy::too_many_arguments)]
     pub fn new_from_memory_manager(
         config: Arc<Mutex<VmConfig>>,
         memory_manager: Arc<Mutex<MemoryManager>>,
@@ -751,7 +751,7 @@ impl Vm {
     }
 
     /// Create and configure the CPU manager.
-    #[allow(clippy::too_many_arguments)]
+    #[expect(clippy::too_many_arguments)]
     fn create_cpu_manager(
         config: &Arc<Mutex<VmConfig>>,
         vm: Arc<dyn hypervisor::Vm>,
@@ -828,7 +828,7 @@ impl Vm {
     }
 
     /// Create and configure the device manager.
-    #[allow(clippy::too_many_arguments)]
+    #[expect(clippy::too_many_arguments)]
     fn create_device_manager(
         io_bus: Arc<Bus>,
         mmio_bus: Arc<Bus>,
@@ -881,7 +881,7 @@ impl Vm {
     /// - KVM (x86_64, aarch64, riscv64)
     /// - MSHV (x86_64, aarch64)
     /// - SEV-SNP (MSHV with confidential computing)
-    #[allow(clippy::too_many_arguments)]
+    #[expect(clippy::too_many_arguments)]
     fn hypervisor_specific_init(
         vm: &Arc<dyn hypervisor::Vm>,
         memory_manager: &Arc<Mutex<MemoryManager>>,
@@ -995,7 +995,7 @@ impl Vm {
 
     /// Initialize SEV-SNP specific components.
     #[cfg(feature = "sev_snp")]
-    #[allow(clippy::too_many_arguments)]
+    #[expect(clippy::too_many_arguments)]
     fn init_sev_snp(
         vm: &Arc<dyn hypervisor::Vm>,
         memory_manager: &Arc<Mutex<MemoryManager>>,
@@ -1325,7 +1325,7 @@ impl Vm {
         Ok(numa_nodes)
     }
 
-    #[allow(clippy::too_many_arguments)]
+    #[expect(clippy::too_many_arguments)]
     pub fn new(
         vm_config: Arc<Mutex<VmConfig>>,
         exit_evt: EventFd,
@@ -1496,7 +1496,7 @@ impl Vm {
         Ok(cmdline)
     }
 
-    #[allow(clippy::needless_pass_by_value)]
+    #[expect(clippy::needless_pass_by_value)]
     #[cfg(any(target_arch = "aarch64", target_arch = "riscv64"))]
     fn load_firmware(
         mut firmware: &File,
@@ -1561,7 +1561,7 @@ impl Vm {
     }
 
     #[cfg(feature = "igvm")]
-    #[allow(clippy::needless_pass_by_value)]
+    #[expect(clippy::needless_pass_by_value)]
     fn load_igvm(
         igvm_file: IgvmFile,
         memory_manager: Arc<Mutex<MemoryManager>>,
@@ -1619,7 +1619,7 @@ impl Vm {
     ///
     /// For x86_64, the boot path is the same.
     #[cfg(target_arch = "x86_64")]
-    #[allow(clippy::needless_pass_by_value)]
+    #[expect(clippy::needless_pass_by_value)]
     fn load_kernel(
         mut kernel: File,
         cmdline: Option<Cmdline>,