misc: use prelude size_of

size_of is part of std::prelude as of Rust 1.80 (with size_of_val,
align_of, align_of_val), and the workspace MSRV is 1.89, so qualifying
it (mem::size_of, std::mem::size_of, core::mem::size_of) is unnecessary.

Convert every qualified size_of call-site to the bare prelude form and
drop the now-redundant `use std::mem::size_of;` imports, keeping
`use std::mem;` where it still serves non-prelude items (transmute,
swap, replace, take, zeroed, MaybeUninit, offset_of). size_of is the
only one of the four currently used in the tree.

Pure refactor, no behavioural change. Follow-up to the
clippy::absolute_paths cleanup (#7670), as discussed in #8444.

Signed-off-by: Henry Hrvoje Tonkovac <htonkovac@gmail.com>
Assisted-by: Claude:Opus-4.8

vmm/src/cpu.rs

@@ -3498,7 +3498,7 @@ mod unit_tests {
 #[cfg(test)]
 mod unit_tests {
     #[cfg(feature = "kvm")]
-    use std::{mem, mem::offset_of};
+    use std::mem::offset_of;
 
     use arch::layout;
     use hypervisor::arch::aarch64::regs::MPIDR_EL1;

vmm/src/igvm/igvm_loader.rs

@@ -8,7 +8,6 @@ use std::collections::HashMap;
 use std::ffi::CString;
 #[cfg(feature = "kvm")]
 use std::iter;
-use std::mem::size_of;
 use std::sync::{Arc, Mutex};
 use std::{ffi, io};
 

vmm/src/sev.rs

@@ -3,7 +3,6 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 
-use core::mem::size_of;
 use std::ffi::CString;
 use std::fs::File;
 use std::io::{self, Cursor, Read, Seek, SeekFrom};

vmm/src/uffd.rs

@@ -13,11 +13,11 @@
 //! original memory mapping, so it remains compatible with VFIO device
 //! passthrough and shared-memory-backed guest RAM.
 
+use std::fmt;
 use std::fs::{File, OpenOptions};
 use std::io::{self, Error, Read};
 use std::os::fd::{AsFd, AsRawFd, BorrowedFd, FromRawFd, OwnedFd, RawFd};
 use std::os::unix::fs::FileExt;
-use std::{fmt, mem};
 
 use vm_migration::protocol::{MemoryRange, Request, Response, Status};
 
@@ -65,7 +65,7 @@ pub(crate) struct UffdMsg {
     _pad: [u8; 8],
 }
 
-const _: () = assert!(mem::size_of::<UffdMsg>() == 32);
+const _: () = assert!(size_of::<UffdMsg>() == 32);
 
 /// Try to obtain a userfaultfd via /dev/userfaultfd (Linux 6.1+).
 ///

vmm/src/vm.rs

@@ -16,8 +16,6 @@ use std::collections::{BTreeMap, BTreeSet, HashMap};
 use std::ffi;
 use std::fs::{File, OpenOptions};
 use std::io::{self, Seek, SeekFrom, Write};
-#[cfg(all(target_arch = "x86_64", feature = "guest_debug"))]
-use std::mem::size_of;
 use std::num::Wrapping;
 use std::ops::Deref;
 use std::os::unix::net::UnixStream;