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>

virtio-devices/src/vsock/csm/connection.rs

@@ -672,13 +672,15 @@ where
 
 #[cfg(test)]
 mod tests {
+    use std::io::{Error as IoError, Result as IoResult};
+
+    use libc::EFD_NONBLOCK;
+    use virtio_queue::QueueOwnedT;
+    use vmm_sys_util::eventfd::EventFd;
+
     use super::super::super::tests::TestContext;
     use super::super::defs as csm_defs;
     use super::*;
-    use libc::EFD_NONBLOCK;
-    use std::io::{Error as IoError, Result as IoResult};
-    use virtio_queue::QueueOwnedT;
-    use vmm_sys_util::eventfd::EventFd;
 
     const LOCAL_CID: u64 = 2;
     const PEER_CID: u64 = 3;

virtio-devices/src/vsock/csm/txbuf.rs

@@ -144,11 +144,12 @@ impl TxBuf {
 
 #[cfg(test)]
 mod tests {
-    use super::*;
     use std::io::Error as IoError;
     use std::io::ErrorKind;
     use std::io::Result as IoResult;
 
+    use super::*;
+
     struct TestSink {
         data: Vec<u8>,
         err: Option<IoError>,

virtio-devices/src/vsock/device.rs

@@ -8,6 +8,26 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the THIRD-PARTY file.
 
+use std::io;
+use std::os::unix::io::AsRawFd;
+use std::path::PathBuf;
+use std::result;
+use std::sync::atomic::AtomicBool;
+use std::sync::{Arc, Barrier, RwLock};
+
+use anyhow::anyhow;
+use byteorder::{ByteOrder, LittleEndian};
+use seccompiler::SeccompAction;
+use serde::{Deserialize, Serialize};
+use virtio_queue::Queue;
+use virtio_queue::QueueOwnedT;
+use virtio_queue::QueueT;
+use vm_memory::GuestAddressSpace;
+use vm_memory::GuestMemoryAtomic;
+use vm_migration::{Migratable, MigratableError, Pausable, Snapshot, Snapshottable, Transportable};
+use vm_virtio::AccessPlatform;
+use vmm_sys_util::eventfd::EventFd;
+
 /// This is the `VirtioDevice` implementation for our vsock device. It handles the virtio-level
 /// device logic: feature negotiation, device configuration, and device activation.
 /// The run-time device logic (i.e. event-driven data handling) is implemented by
@@ -37,24 +57,6 @@ use crate::{
     EpollHelperHandler, VirtioCommon, VirtioDevice, VirtioDeviceType, VirtioInterruptType,
     EPOLL_HELPER_EVENT_LAST, VIRTIO_F_IN_ORDER, VIRTIO_F_IOMMU_PLATFORM, VIRTIO_F_VERSION_1,
 };
-use anyhow::anyhow;
-use byteorder::{ByteOrder, LittleEndian};
-use seccompiler::SeccompAction;
-use serde::{Deserialize, Serialize};
-use std::io;
-use std::os::unix::io::AsRawFd;
-use std::path::PathBuf;
-use std::result;
-use std::sync::atomic::AtomicBool;
-use std::sync::{Arc, Barrier, RwLock};
-use virtio_queue::Queue;
-use virtio_queue::QueueOwnedT;
-use virtio_queue::QueueT;
-use vm_memory::GuestAddressSpace;
-use vm_memory::GuestMemoryAtomic;
-use vm_migration::{Migratable, MigratableError, Pausable, Snapshot, Snapshottable, Transportable};
-use vm_virtio::AccessPlatform;
-use vmm_sys_util::eventfd::EventFd;
 
 const QUEUE_SIZE: u16 = 256;
 const NUM_QUEUES: usize = 3;
@@ -522,11 +524,12 @@ impl<B> Migratable for Vsock<B> where B: VsockBackend + Sync + 'static {}
 
 #[cfg(test)]
 mod tests {
+    use libc::EFD_NONBLOCK;
+
     use super::super::tests::{NoopVirtioInterrupt, TestContext};
     use super::super::*;
     use super::*;
     use crate::ActivateError;
-    use libc::EFD_NONBLOCK;
 
     #[test]
     fn test_virtio_device() {

virtio-devices/src/vsock/mod.rs

@@ -13,13 +13,14 @@ mod device;
 mod packet;
 mod unix;
 
+use std::os::unix::io::RawFd;
+
+use packet::VsockPacket;
+
 pub use self::device::Vsock;
 pub use self::unix::VsockUnixBackend;
 pub use self::unix::VsockUnixError;
 
-use packet::VsockPacket;
-use std::os::unix::io::RawFd;
-
 mod defs {
 
     /// Max vsock packet data/buffer size.
@@ -162,6 +163,16 @@ pub trait VsockBackend: VsockChannel + VsockEpollListener + Send {}
 
 #[cfg(test)]
 mod tests {
+    use std::os::unix::io::AsRawFd;
+    use std::path::PathBuf;
+    use std::sync::{Arc, RwLock};
+
+    use libc::EFD_NONBLOCK;
+    use virtio_bindings::virtio_ring::{VRING_DESC_F_NEXT, VRING_DESC_F_WRITE};
+    use vm_memory::{GuestAddress, GuestMemoryAtomic};
+    use vm_virtio::queue::testing::VirtQueue as GuestQ;
+    use vmm_sys_util::eventfd::EventFd;
+
     use super::device::{VsockEpollHandler, RX_QUEUE_EVENT, TX_QUEUE_EVENT};
     use super::packet::VSOCK_PKT_HDR_SIZE;
     use super::*;
@@ -169,14 +180,6 @@ mod tests {
     use crate::epoll_helper::EpollHelperHandler;
     use crate::EpollHelper;
     use crate::GuestMemoryMmap;
-    use libc::EFD_NONBLOCK;
-    use std::os::unix::io::AsRawFd;
-    use std::path::PathBuf;
-    use std::sync::{Arc, RwLock};
-    use virtio_bindings::virtio_ring::{VRING_DESC_F_NEXT, VRING_DESC_F_WRITE};
-    use vm_memory::{GuestAddress, GuestMemoryAtomic};
-    use vm_virtio::queue::testing::VirtQueue as GuestQ;
-    use vmm_sys_util::eventfd::EventFd;
 
     pub struct NoopVirtioInterrupt {}
 

virtio-devices/src/vsock/packet.rs

@@ -16,16 +16,17 @@
 //! in guest memory. This is done to avoid unnecessarily copying data from guest memory
 //! to temporary buffers, before passing it on to the vsock backend.
 
-use byteorder::{ByteOrder, LittleEndian};
 use std::ops::Deref;
 use std::sync::Arc;
 
+use byteorder::{ByteOrder, LittleEndian};
+use virtio_queue::DescriptorChain;
+use vm_memory::{Address, GuestMemory};
+use vm_virtio::{AccessPlatform, Translatable};
+
 use super::defs;
 use super::{Result, VsockError};
 use crate::get_host_address_range;
-use virtio_queue::DescriptorChain;
-use vm_memory::{Address, GuestMemory};
-use vm_virtio::{AccessPlatform, Translatable};
 
 // The vsock packet header is defined by the C struct:
 //
@@ -420,15 +421,16 @@ impl VsockPacket {
 #[cfg(test)]
 #[allow(clippy::undocumented_unsafe_blocks)]
 mod tests {
-    use super::super::tests::TestContext;
-    use super::*;
-    use crate::vsock::defs::MAX_PKT_BUF_SIZE;
-    use crate::GuestMemoryMmap;
     use virtio_bindings::virtio_ring::VRING_DESC_F_WRITE;
     use virtio_queue::QueueOwnedT;
     use vm_memory::GuestAddress;
     use vm_virtio::queue::testing::VirtqDesc as GuestQDesc;
 
+    use super::super::tests::TestContext;
+    use super::*;
+    use crate::vsock::defs::MAX_PKT_BUF_SIZE;
+    use crate::GuestMemoryMmap;
+
     macro_rules! create_context {
         ($test_ctx:ident, $handler_ctx:ident) => {
             let $test_ctx = TestContext::new();

virtio-devices/src/vsock/unix/muxer.rs

@@ -849,12 +849,14 @@ impl VsockMuxer {
 
 #[cfg(test)]
 mod tests {
+    use std::io::Write;
+    use std::path::{Path, PathBuf};
+
+    use virtio_queue::QueueOwnedT;
+
     use super::super::super::csm::defs as csm_defs;
     use super::super::super::tests::TestContext as VsockTestContext;
     use super::*;
-    use std::io::Write;
-    use std::path::{Path, PathBuf};
-    use virtio_queue::QueueOwnedT;
 
     const PEER_CID: u32 = 3;
     const PEER_BUF_ALLOC: u32 = 64 * 1024;