misc: clippy: add needless_pass_by_value

This is a follow-up of [0].

# Advantages

- This saves dozens of unneeded clone()s across the whole code base
- Makes it much easier to reason about how parameters are used
  (often we passed owned Arc/Rc versions without actually needing
  ownership)

# Exceptions

For certain code paths, the alternatives would require awkward or overly
complex code, and in some cases the functions are the logical owners of
the values they take. In those cases, I've added
#[allow(clippy::needless_pass_by_value)].

This does not mean that one should not improve this in the future.

[0] 6a86c157af

Signed-off-by: Philipp Schuster <philipp.schuster@cyberus-technology.de>
On-behalf-of: SAP philipp.schuster@sap.com

arch/src/aarch64/fdt.rs

@@ -88,6 +88,7 @@ pub enum Error {
 }
 type Result<T> = result::Result<T, Error>;
 
+#[derive(Copy, Clone)]
 pub enum CacheLevel {
     /// L1 data cache
     L1D = 0,
@@ -207,7 +208,7 @@ pub fn get_cache_shared(cache_level: CacheLevel) -> bool {
 pub fn create_fdt<T: DeviceInfoForFdt + Clone + Debug, S: ::std::hash::BuildHasher>(
     guest_mem: &GuestMemoryMmap,
     cmdline: &str,
-    vcpu_mpidr: Vec<u64>,
+    vcpu_mpidr: &[u64],
     vcpu_topology: Option<(u16, u16, u16, u16)>,
     device_info: &HashMap<(DeviceType, String), T, S>,
     gic_device: &Arc<Mutex<dyn Vgic>>,
@@ -234,7 +235,7 @@ pub fn create_fdt<T: DeviceInfoForFdt + Clone + Debug, S: ::std::hash::BuildHash
     // This is not mandatory but we use it to point the root node to the node
     // containing description of the interrupt controller for this VM.
     fdt.property_u32("interrupt-parent", GIC_PHANDLE)?;
-    create_cpu_nodes(&mut fdt, &vcpu_mpidr, vcpu_topology, numa_nodes)?;
+    create_cpu_nodes(&mut fdt, vcpu_mpidr, vcpu_topology, numa_nodes)?;
     create_memory_node(&mut fdt, guest_mem, numa_nodes)?;
     create_chosen_node(&mut fdt, cmdline, initrd)?;
     create_gic_node(&mut fdt, gic_device)?;
@@ -258,10 +259,10 @@ pub fn create_fdt<T: DeviceInfoForFdt + Clone + Debug, S: ::std::hash::BuildHash
     Ok(fdt_final)
 }
 
-pub fn write_fdt_to_memory(fdt_final: Vec<u8>, guest_mem: &GuestMemoryMmap) -> Result<()> {
+pub fn write_fdt_to_memory(fdt_final: &[u8], guest_mem: &GuestMemoryMmap) -> Result<()> {
     // Write FDT to memory.
     guest_mem
-        .write_slice(fdt_final.as_slice(), super::layout::FDT_START)
+        .write_slice(fdt_final, super::layout::FDT_START)
         .map_err(Error::WriteFdtToMemory)?;
     Ok(())
 }

arch/src/aarch64/mod.rs

@@ -125,7 +125,7 @@ pub fn arch_memory_regions() -> Vec<(GuestAddress, usize, RegionType)> {
 pub fn configure_system<T: DeviceInfoForFdt + Clone + Debug, S: ::std::hash::BuildHasher>(
     guest_mem: &GuestMemoryMmap,
     cmdline: &str,
-    vcpu_mpidr: Vec<u64>,
+    vcpu_mpidr: &[u64],
     vcpu_topology: Option<(u16, u16, u16, u16)>,
     device_info: &HashMap<(DeviceType, String), T, S>,
     initrd: &Option<super::InitramfsConfig>,
@@ -154,7 +154,7 @@ pub fn configure_system<T: DeviceInfoForFdt + Clone + Debug, S: ::std::hash::Bui
         fdt::print_fdt(&fdt_final);
     }
 
-    fdt::write_fdt_to_memory(fdt_final, guest_mem).map_err(Error::WriteFdtToMemory)?;
+    fdt::write_fdt_to_memory(&fdt_final, guest_mem).map_err(Error::WriteFdtToMemory)?;
 
     Ok(())
 }

arch/src/riscv64/fdt.rs

@@ -101,10 +101,10 @@ pub fn create_fdt<T: DeviceInfoForFdt + Clone + Debug, S: ::std::hash::BuildHash
     Ok(fdt_final)
 }
 
-pub fn write_fdt_to_memory(fdt_final: Vec<u8>, guest_mem: &GuestMemoryMmap) -> Result<()> {
+pub fn write_fdt_to_memory(fdt_final: &[u8], guest_mem: &GuestMemoryMmap) -> Result<()> {
     // Write FDT to memory.
     guest_mem
-        .write_slice(fdt_final.as_slice(), super::layout::FDT_START)
+        .write_slice(fdt_final, super::layout::FDT_START)
         .map_err(Error::WriteFdtToMemory)?;
     Ok(())
 }

arch/src/riscv64/mod.rs

@@ -187,7 +187,7 @@ pub fn configure_system<T: DeviceInfoForFdt + Clone + Debug, S: ::std::hash::Bui
         fdt::print_fdt(&fdt_final);
     }
 
-    fdt::write_fdt_to_memory(fdt_final, guest_mem).map_err(Error::WriteFdtToMemory)?;
+    fdt::write_fdt_to_memory(&fdt_final, guest_mem).map_err(Error::WriteFdtToMemory)?;
 
     Ok(())
 }