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>

hypervisor/src/kvm/aarch64/gic/dist_regs.rs

@@ -1,12 +1,13 @@
 // Copyright 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 // SPDX-License-Identifier: Apache-2.0
 
+use kvm_ioctls::DeviceFd;
+
 use crate::arch::aarch64::gic::{Error, Result};
 use crate::device::HypervisorDeviceError;
 use crate::kvm::kvm_bindings::{
     kvm_device_attr, KVM_DEV_ARM_VGIC_GRP_DIST_REGS, KVM_DEV_ARM_VGIC_GRP_NR_IRQS,
 };
-use kvm_ioctls::DeviceFd;
 
 /*
  Distributor registers as detailed at page 456 from

hypervisor/src/kvm/aarch64/gic/icc_regs.rs

@@ -2,6 +2,8 @@
 // Copyright 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 // SPDX-License-Identifier: Apache-2.0
 
+use kvm_ioctls::DeviceFd;
+
 use crate::arch::aarch64::gic::{Error, Result};
 use crate::device::HypervisorDeviceError;
 use crate::kvm::kvm_bindings::{
@@ -10,7 +12,6 @@ use crate::kvm::kvm_bindings::{
     KVM_REG_ARM64_SYSREG_OP0_MASK, KVM_REG_ARM64_SYSREG_OP0_SHIFT, KVM_REG_ARM64_SYSREG_OP1_MASK,
     KVM_REG_ARM64_SYSREG_OP1_SHIFT, KVM_REG_ARM64_SYSREG_OP2_MASK, KVM_REG_ARM64_SYSREG_OP2_SHIFT,
 };
-use kvm_ioctls::DeviceFd;
 
 const KVM_DEV_ARM_VGIC_V3_MPIDR_SHIFT: u32 = 32;
 const KVM_DEV_ARM_VGIC_V3_MPIDR_MASK: u64 = 0xffffffff << KVM_DEV_ARM_VGIC_V3_MPIDR_SHIFT as u64;

hypervisor/src/kvm/aarch64/gic/mod.rs

@@ -6,16 +6,18 @@ mod dist_regs;
 mod icc_regs;
 mod redist_regs;
 
-use crate::arch::aarch64::gic::{Error, Result, Vgic, VgicConfig};
-use crate::device::HypervisorDeviceError;
-use crate::kvm::KvmVm;
-use crate::{CpuState, Vm};
+use std::any::Any;
+
 use dist_regs::{get_dist_regs, read_ctlr, set_dist_regs, write_ctlr};
 use icc_regs::{get_icc_regs, set_icc_regs};
 use kvm_ioctls::DeviceFd;
 use redist_regs::{construct_gicr_typers, get_redist_regs, set_redist_regs};
 use serde::{Deserialize, Serialize};
-use std::any::Any;
+
+use crate::arch::aarch64::gic::{Error, Result, Vgic, VgicConfig};
+use crate::device::HypervisorDeviceError;
+use crate::kvm::KvmVm;
+use crate::{CpuState, Vm};
 
 const GITS_CTLR: u32 = 0x0000;
 const GITS_IIDR: u32 = 0x0004;

hypervisor/src/kvm/aarch64/gic/redist_regs.rs

@@ -2,6 +2,8 @@
 // Copyright 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 // SPDX-License-Identifier: Apache-2.0
 
+use kvm_ioctls::DeviceFd;
+
 use crate::arch::aarch64::gic::{Error, Result};
 use crate::device::HypervisorDeviceError;
 use crate::kvm::kvm_bindings::{
@@ -12,7 +14,6 @@ use crate::kvm::kvm_bindings::{
 use crate::kvm::Register;
 use crate::kvm::VcpuKvmState;
 use crate::CpuState;
-use kvm_ioctls::DeviceFd;
 
 // Relevant redistributor registers that we want to save/restore.
 const GICR_CTLR: u32 = 0x0000;

hypervisor/src/kvm/aarch64/mod.rs

@@ -10,7 +10,6 @@
 
 pub mod gic;
 
-use crate::kvm::{KvmError, KvmResult};
 use kvm_bindings::{
     kvm_mp_state, kvm_one_reg, kvm_regs, KVM_REG_ARM_COPROC_MASK, KVM_REG_ARM_CORE,
     KVM_REG_SIZE_MASK, KVM_REG_SIZE_U32, KVM_REG_SIZE_U64,
@@ -19,6 +18,8 @@ pub use kvm_bindings::{kvm_one_reg as Register, kvm_vcpu_init as VcpuInit, RegLi
 use serde::{Deserialize, Serialize};
 pub use {kvm_ioctls::Cap, kvm_ioctls::Kvm};
 
+use crate::kvm::{KvmError, KvmResult};
+
 // This macro gets the offset of a structure (i.e `str`) member (i.e `field`) without having
 // an instance of that structure.
 #[macro_export]

hypervisor/src/kvm/mod.rs

@@ -8,6 +8,23 @@
 //
 //
 
+use std::any::Any;
+use std::collections::HashMap;
+#[cfg(target_arch = "x86_64")]
+use std::fs::File;
+#[cfg(target_arch = "x86_64")]
+use std::os::unix::io::AsRawFd;
+#[cfg(feature = "tdx")]
+use std::os::unix::io::RawFd;
+use std::result;
+#[cfg(target_arch = "x86_64")]
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::Mutex;
+use std::sync::{Arc, RwLock};
+
+use kvm_ioctls::{NoDatamatch, VcpuFd, VmFd};
+use vmm_sys_util::eventfd::EventFd;
+
 #[cfg(target_arch = "aarch64")]
 use crate::aarch64::gic::KvmGicV3Its;
 #[cfg(target_arch = "aarch64")]
@@ -24,35 +41,9 @@ use crate::vm::{self, InterruptSourceConfig, VmOps};
 use crate::HypervisorType;
 #[cfg(target_arch = "aarch64")]
 use crate::{arm64_core_reg_id, offset_of};
-use kvm_ioctls::{NoDatamatch, VcpuFd, VmFd};
-use std::any::Any;
-use std::collections::HashMap;
-#[cfg(target_arch = "x86_64")]
-use std::fs::File;
-#[cfg(target_arch = "x86_64")]
-use std::os::unix::io::AsRawFd;
-#[cfg(feature = "tdx")]
-use std::os::unix::io::RawFd;
-use std::result;
-#[cfg(target_arch = "x86_64")]
-use std::sync::atomic::{AtomicBool, Ordering};
-use std::sync::Mutex;
-use std::sync::{Arc, RwLock};
-use vmm_sys_util::eventfd::EventFd;
 // x86_64 dependencies
 #[cfg(target_arch = "x86_64")]
 pub mod x86_64;
-#[cfg(target_arch = "x86_64")]
-use crate::arch::x86::{
-    CpuIdEntry, FpuState, LapicState, MsrEntry, SpecialRegisters, XsaveState, NUM_IOAPIC_PINS,
-};
-#[cfg(target_arch = "x86_64")]
-use crate::ClockData;
-use crate::StandardRegisters;
-use crate::{
-    CpuState, IoEventAddress, IrqRoutingEntry, MpState, UserMemoryRegion,
-    USER_MEMORY_REGION_LOG_DIRTY, USER_MEMORY_REGION_READ, USER_MEMORY_REGION_WRITE,
-};
 #[cfg(target_arch = "aarch64")]
 use aarch64::{RegList, Register};
 #[cfg(target_arch = "x86_64")]
@@ -64,9 +55,24 @@ use kvm_bindings::{
 use x86_64::check_required_kvm_extensions;
 #[cfg(target_arch = "x86_64")]
 pub use x86_64::{CpuId, ExtendedControlRegisters, MsrEntries, VcpuKvmState};
+
+#[cfg(target_arch = "x86_64")]
+use crate::arch::x86::{
+    CpuIdEntry, FpuState, LapicState, MsrEntry, SpecialRegisters, XsaveState, NUM_IOAPIC_PINS,
+};
+#[cfg(target_arch = "x86_64")]
+use crate::ClockData;
+use crate::StandardRegisters;
+use crate::{
+    CpuState, IoEventAddress, IrqRoutingEntry, MpState, UserMemoryRegion,
+    USER_MEMORY_REGION_LOG_DIRTY, USER_MEMORY_REGION_READ, USER_MEMORY_REGION_WRITE,
+};
 // aarch64 dependencies
 #[cfg(target_arch = "aarch64")]
 pub mod aarch64;
+#[cfg(target_arch = "aarch64")]
+use std::mem;
+
 pub use kvm_bindings;
 pub use kvm_bindings::{
     kvm_clock_data, kvm_create_device, kvm_device_type_KVM_DEV_TYPE_VFIO, kvm_guest_debug,
@@ -85,8 +91,6 @@ use kvm_bindings::{
 use kvm_bindings::{kvm_run__bindgen_ty_1, KVMIO};
 pub use kvm_ioctls;
 pub use kvm_ioctls::{Cap, Kvm};
-#[cfg(target_arch = "aarch64")]
-use std::mem;
 use thiserror::Error;
 use vfio_ioctls::VfioDeviceFd;
 #[cfg(feature = "tdx")]
@@ -104,7 +108,6 @@ const KVM_CAP_SGX_ATTRIBUTE: u32 = 196;
 
 #[cfg(target_arch = "x86_64")]
 use vmm_sys_util::ioctl_io_nr;
-
 #[cfg(all(not(feature = "tdx"), target_arch = "x86_64"))]
 use vmm_sys_util::ioctl_ioc_nr;
 

hypervisor/src/kvm/x86_64/mod.rs

@@ -8,13 +8,7 @@
 //
 //
 
-use crate::arch::x86::{
-    CpuIdEntry, DescriptorTable, FpuState, LapicState, MsrEntry, SegmentRegister, SpecialRegisters,
-    XsaveState, CPUID_FLAG_VALID_INDEX,
-};
-use crate::kvm::{Cap, Kvm, KvmError, KvmResult};
 use serde::{Deserialize, Serialize};
-
 ///
 /// Export generically-named wrappers of kvm-bindings for Unix-based platforms
 ///
@@ -28,6 +22,12 @@ pub use {
     kvm_bindings::KVM_CPUID_FLAG_SIGNIFCANT_INDEX,
 };
 
+use crate::arch::x86::{
+    CpuIdEntry, DescriptorTable, FpuState, LapicState, MsrEntry, SegmentRegister, SpecialRegisters,
+    XsaveState, CPUID_FLAG_VALID_INDEX,
+};
+use crate::kvm::{Cap, Kvm, KvmError, KvmResult};
+
 ///
 /// Check KVM extension for Linux
 ///