misc: Adapt consistent import style formatting

Historically the Cloud Hypervisor coding style has been to ensure that
all imports are ordered and placed in a single group. Unfortunately
cargo fmt has no support for ensuring that all imports are in a single
group so if whitespace lines were added as part of the import statements
then they would only be odered correctly in the group.

By adopting "group_imports="StdExternalCrate" we can enforce a style
where imports are placed in at most three groups for std, external
crates and the crate itself. Choosing a style enforceable by the tooling
reduces the reviewer burden.

Signed-off-by: Rob Bradford <rbradford@rivosinc.com>

arch/src/aarch64/fdt.rs

@@ -6,17 +6,22 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the THIRD-PARTY file.
 
-use crate::{NumaNodes, PciSpaceInfo};
-use byteorder::{BigEndian, ByteOrder};
-use hypervisor::arch::aarch64::gic::Vgic;
 use std::cmp;
 use std::collections::HashMap;
 use std::ffi::CStr;
 use std::fmt::Debug;
+use std::fs;
+use std::path::Path;
 use std::result;
 use std::str;
 use std::sync::{Arc, Mutex};
 
+use byteorder::{BigEndian, ByteOrder};
+use hypervisor::arch::aarch64::gic::Vgic;
+use thiserror::Error;
+use vm_fdt::{FdtWriter, FdtWriterResult};
+use vm_memory::{Address, Bytes, GuestMemory, GuestMemoryError, GuestMemoryRegion};
+
 use super::super::DeviceType;
 use super::super::GuestMemoryMmap;
 use super::super::InitramfsConfig;
@@ -24,11 +29,7 @@ use super::layout::{
     IRQ_BASE, MEM_32BIT_DEVICES_SIZE, MEM_32BIT_DEVICES_START, MEM_PCI_IO_SIZE, MEM_PCI_IO_START,
     PCI_HIGH_BASE, PCI_MMIO_CONFIG_SIZE_PER_SEGMENT,
 };
-use std::fs;
-use std::path::Path;
-use thiserror::Error;
-use vm_fdt::{FdtWriter, FdtWriterResult};
-use vm_memory::{Address, Bytes, GuestMemory, GuestMemoryError, GuestMemoryRegion};
+use crate::{NumaNodes, PciSpaceInfo};
 
 // This is a value for uniquely identifying the FDT node declaring the interrupt controller.
 const GIC_PHANDLE: u32 = 1;

arch/src/aarch64/mod.rs

@@ -11,16 +11,18 @@ pub mod regs;
 /// Module for loading UEFI binary.
 pub mod uefi;
 
-pub use self::fdt::DeviceInfoForFdt;
-use crate::{DeviceType, GuestMemoryMmap, NumaNodes, PciSpaceInfo, RegionType};
-use hypervisor::arch::aarch64::gic::Vgic;
-use log::{log_enabled, Level};
 use std::collections::HashMap;
 use std::fmt::Debug;
 use std::sync::{Arc, Mutex};
+
+use hypervisor::arch::aarch64::gic::Vgic;
+use log::{log_enabled, Level};
 use thiserror::Error;
 use vm_memory::{Address, GuestAddress, GuestMemory, GuestMemoryAtomic};
 
+pub use self::fdt::DeviceInfoForFdt;
+use crate::{DeviceType, GuestMemoryMmap, NumaNodes, PciSpaceInfo, RegionType};
+
 pub const _NSIG: i32 = 65;
 
 /// Errors thrown while configuring aarch64 system.

arch/src/aarch64/uefi.rs

@@ -5,6 +5,7 @@
 use std::io::{Read, Seek, SeekFrom};
 use std::os::fd::AsFd;
 use std::result;
+
 use thiserror::Error;
 use vm_memory::{GuestAddress, GuestMemory};
 

arch/src/lib.rs

@@ -10,15 +10,17 @@
 #[macro_use]
 extern crate log;
 
-#[cfg(target_arch = "x86_64")]
-use crate::x86_64::SgxEpcSection;
-use serde::{Deserialize, Serialize};
 use std::collections::BTreeMap;
 use std::fmt;
 use std::result;
 use std::sync::Arc;
+
+use serde::{Deserialize, Serialize};
 use thiserror::Error;
 
+#[cfg(target_arch = "x86_64")]
+use crate::x86_64::SgxEpcSection;
+
 type GuestMemoryMmap = vm_memory::GuestMemoryMmap<vm_memory::bitmap::AtomicBitmap>;
 type GuestRegionMmap = vm_memory::GuestRegionMmap<vm_memory::bitmap::AtomicBitmap>;
 

arch/src/x86_64/mod.rs

@@ -12,22 +12,24 @@ pub mod layout;
 mod mpspec;
 mod mptable;
 pub mod regs;
-use crate::GuestMemoryMmap;
-use crate::InitramfsConfig;
-use crate::RegionType;
+use std::collections::BTreeMap;
+use std::mem;
+
 use hypervisor::arch::x86::{CpuIdEntry, CPUID_FLAG_VALID_INDEX};
 use hypervisor::{CpuVendor, HypervisorCpuError, HypervisorError};
 use linux_loader::loader::bootparam::{boot_params, setup_header};
 use linux_loader::loader::elf::start_info::{
     hvm_memmap_table_entry, hvm_modlist_entry, hvm_start_info,
 };
-use std::collections::BTreeMap;
-use std::mem;
 use thiserror::Error;
 use vm_memory::{
     Address, Bytes, GuestAddress, GuestAddressSpace, GuestMemory, GuestMemoryAtomic,
     GuestMemoryRegion, GuestUsize,
 };
+
+use crate::GuestMemoryMmap;
+use crate::InitramfsConfig;
+use crate::RegionType;
 mod smbios;
 use std::arch::x86_64;
 #[cfg(feature = "tdx")]
@@ -1551,9 +1553,10 @@ fn update_cpuid_sgx(
 
 #[cfg(test)]
 mod tests {
-    use super::*;
     use linux_loader::loader::bootparam::boot_e820_entry;
 
+    use super::*;
+
     #[test]
     fn regions_base_addr() {
         let regions = arch_memory_regions();

arch/src/x86_64/mptable.rs

@@ -5,16 +5,18 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE-BSD-3-Clause file.
 
-use crate::layout::{APIC_START, HIGH_RAM_START, IOAPIC_START};
-use crate::x86_64::{get_x2apic_id, mpspec};
-use crate::GuestMemoryMmap;
-use libc::c_uchar;
 use std::mem;
 use std::result;
 use std::slice;
+
+use libc::c_uchar;
 use thiserror::Error;
 use vm_memory::{Address, ByteValued, Bytes, GuestAddress, GuestMemory, GuestMemoryError};
 
+use crate::layout::{APIC_START, HIGH_RAM_START, IOAPIC_START};
+use crate::x86_64::{get_x2apic_id, mpspec};
+use crate::GuestMemoryMmap;
+
 // This is a workaround to the Rust enforcement specifying that any implementation of a foreign
 // trait (in this case `ByteValued`) where:
 // *    the type that is implementing the trait is foreign or
@@ -304,12 +306,13 @@ pub fn setup_mptable(
 
 #[cfg(test)]
 mod tests {
-    use super::*;
-    use crate::layout::MPTABLE_START;
     use vm_memory::{
         bitmap::BitmapSlice, GuestUsize, VolatileMemoryError, VolatileSlice, WriteVolatile,
     };
 
+    use super::*;
+    use crate::layout::MPTABLE_START;
+
     fn table_entry_size(type_: u8) -> usize {
         match type_ as u32 {
             mpspec::MP_PROCESSOR => mem::size_of::<MpcCpuWrapper>(),

arch/src/x86_64/regs.rs

@@ -6,17 +6,19 @@
 // Portions Copyright 2017 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE-BSD-3-Clause file.
+use std::sync::Arc;
+use std::{mem, result};
+
+use hypervisor::arch::x86::gdt::{gdt_entry, segment_from_gdt};
+use hypervisor::arch::x86::regs::CR0_PE;
+use hypervisor::arch::x86::{FpuState, SpecialRegisters};
+use thiserror::Error;
+use vm_memory::{Address, Bytes, GuestMemory, GuestMemoryError};
+
 use crate::layout::{
     BOOT_GDT_START, BOOT_IDT_START, BOOT_STACK_POINTER, PVH_INFO_START, ZERO_PAGE_START,
 };
 use crate::{EntryPoint, GuestMemoryMmap};
-use hypervisor::arch::x86::gdt::{gdt_entry, segment_from_gdt};
-use hypervisor::arch::x86::regs::CR0_PE;
-use hypervisor::arch::x86::{FpuState, SpecialRegisters};
-use std::sync::Arc;
-use std::{mem, result};
-use thiserror::Error;
-use vm_memory::{Address, Bytes, GuestMemory, GuestMemoryError};
 
 #[derive(Debug, Error)]
 pub enum Error {
@@ -186,9 +188,10 @@ pub fn configure_segments_and_sregs(
 
 #[cfg(test)]
 mod tests {
-    use super::*;
     use vm_memory::GuestAddress;
 
+    use super::*;
+
     fn create_guest_mem() -> GuestMemoryMmap {
         GuestMemoryMmap::from_ranges(&[(GuestAddress(0), 0x10000)]).unwrap()
     }

arch/src/x86_64/smbios.rs

@@ -6,16 +6,18 @@
 //
 // SPDX-License-Identifier: Apache-2.0 AND BSD-3-Clause
 
-use crate::layout::SMBIOS_START;
-use crate::GuestMemoryMmap;
 use std::mem;
 use std::result;
 use std::slice;
+
 use thiserror::Error;
 use uuid::Uuid;
 use vm_memory::ByteValued;
 use vm_memory::{Address, Bytes, GuestAddress};
 
+use crate::layout::SMBIOS_START;
+use crate::GuestMemoryMmap;
+
 #[derive(Debug, Error)]
 pub enum Error {
     /// There was too little guest memory to store the entire SMBIOS table.

arch/src/x86_64/tdx/mod.rs

@@ -1,14 +1,16 @@
 // Copyright © 2021 Intel Corporation
 //
 // SPDX-License-Identifier: Apache-2.0
-use crate::GuestMemoryMmap;
 use std::fs::File;
 use std::io::{Read, Seek, SeekFrom};
 use std::str::FromStr;
+
 use thiserror::Error;
 use uuid::Uuid;
 use vm_memory::{ByteValued, Bytes, GuestAddress, GuestMemoryError};
 
+use crate::GuestMemoryMmap;
+
 #[derive(Error, Debug)]
 pub enum TdvfError {
     #[error("Failed read TDVF descriptor: {0}")]