commit | 933938798fe6a3aef70dfec003e00b5efe45dc54 | [log] [tgz] |
---|---|---|
author | Daniel Verkamp <dverkamp@chromium.org> | Thu May 14 21:49:10 2020 |
committer | Commit Bot <commit-bot@chromium.org> | Mon Jun 01 19:56:24 2020 |
tree | c9707db8ce4378dd918cd9cbfe35fdcc161842a9 | |
parent | 744e7b99b56fc4aac031b06a70445176d38d911d [diff] |
devices: usb: ignore busy flag in interrupter This works around an issue where the xhci controller hangs from the guest's point of view, with the guest kernel eventually timing out and disabling the controller. The xHCI spec says that the EHB (Event Handler Busy) bit should be cleared before signalling another interrupt. This bit is set by the controller before triggering an interrupt, and it is meant to be cleared by the guest (via write-1-to-clear) when it is done handling the interrupt. However, it seems that there is a race going on between the clearing and setting of this bit. Removing the check seems to avoid the issue, since we never get into the state where we think EHB is set but the guest thinks it is clear (where no further interrupts would be triggered). This will potentially trigger more interrupts than strictly necessary, but the Linux kernel xhci driver handles interrupts with no events available gracefully. BUG=chromium:1082930 TEST=`while adb shell echo hi; do : ; done` for 8+ hours without hangs Change-Id: I3c08f0c5675be10d8e46f73714d684f7ba3a3903 Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2202745 Reviewed-by: Dylan Reid <dgreid@chromium.org> Tested-by: kokoro <noreply+kokoro@google.com> Commit-Queue: Daniel Verkamp <dverkamp@chromium.org> (cherry picked from commit 9a0ffde0537136c97c82fb76a004c7e1322e069b) Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2225556 Reviewed-by: Daniel Verkamp <dverkamp@chromium.org> Tested-by: Daniel Verkamp <dverkamp@chromium.org>
This component, known as crosvm, runs untrusted operating systems along with virtualized devices. This only runs VMs through the Linux's KVM interface. What makes crosvm unique is a focus on safety within the programming language and a sandbox around the virtual devices to protect the kernel from attack in case of an exploit in the devices.
The channel #crosvm on freenode is used for technical discussion related to crosvm development and integration.
crosvm on Chromium OS is built with Portage, so it follows the same general workflow as any cros_workon
package. The full package name is chromeos-base/crosvm
.
See the Chromium OS developer guide for more on how to build and deploy with Portage.
See the README from the docker
subdirectory to learn how to build crosvm in enviroments outside of the Chrome OS chroot.
NOTE: Building for Linux natively is new and not fully supported.
First, set up depot_tools and use repo
to sync down the crosvm source tree. This is a subset of the entire Chromium OS manifest with just enough repos to build crosvm.
mkdir crosvm cd crosvm repo init -g crosvm -u https://chromium.googlesource.com/chromiumos/manifest.git --repo-url=https://chromium.googlesource.com/external/repo.git repo sync
A basic crosvm build links against libcap
and libfdt
. On a Debian-based system, you can install libcap-dev
and libfdt-dev
.
Handy Debian one-liner for all build and runtime deps, particularly if you're running Crostini:
sudo apt install build-essential libcap-dev libfdt-dev pkg-config python
Known issues:
sudo mkdir /usr/share/policy && sudo ln -s /path/to/crosvm/seccomp/x86_64 /usr/share/policy/crosvm
. We'll eventually build the precompiled policies into the crosvm binary./var/empty
doesn’t exist. sudo mkdir -p /var/empty
to work around this for now.And that's it! You should be able to cargo build/run/test
.
To see the usage information for your version of crosvm, run crosvm
or crosvm run --help
.
To run a very basic VM with just a kernel and default devices:
$ crosvm run "${KERNEL_PATH}"
The uncompressed kernel image, also known as vmlinux, can be found in your kernel build directory in the case of x86 at arch/x86/boot/compressed/vmlinux
.
In most cases, you will want to give the VM a virtual block device to use as a root file system:
$ crosvm run -r "${ROOT_IMAGE}" "${KERNEL_PATH}"
The root image must be a path to a disk image formatted in a way that the kernel can read. Typically this is a squashfs image made with mksquashfs
or an ext4 image made with mkfs.ext4
. By using the -r
argument, the kernel is automatically told to use that image as the root, and therefore can only be given once. More disks can be given with -d
or --rwdisk
if a writable disk is desired.
To run crosvm with a writable rootfs:
WARNING: Writable disks are at risk of corruption by a malicious or malfunctioning guest OS.
crosvm run --rwdisk "${ROOT_IMAGE}" -p "root=/dev/vda" vmlinux
NOTE: If more disks arguments are added prior to the desired rootfs image, the
root=/dev/vda
must be adjusted to the appropriate letter.
If the control socket was enabled with -s
, the main process can be controlled while crosvm is running. To tell crosvm to stop and exit, for example:
NOTE: If the socket path given is for a directory, a socket name underneath that path will be generated based on crosvm's PID.
$ crosvm run -s /run/crosvm.sock ${USUAL_CROSVM_ARGS} <in another shell> $ crosvm stop /run/crosvm.sock
WARNING: The guest OS will not be notified or gracefully shutdown.
This will cause the original crosvm process to exit in an orderly fashion, allowing it to clean up any OS resources that might have stuck around if crosvm were terminated early.
By default crosvm runs in multiprocess mode. Each device that supports running inside of a sandbox will run in a jailed child process of crosvm. The appropriate minijail seccomp policy files must be present either in /usr/share/policy/crosvm
or in the path specified by the --seccomp-policy-dir
argument. The sandbox can be disabled for testing with the --disable-sandbox
option.
Virtio Wayland support requires special support on the part of the guest and as such is unlikely to work out of the box unless you are using a Chrome OS kernel along with a termina
rootfs.
To use it, ensure that the XDG_RUNTIME_DIR
enviroment variable is set and that the path $XDG_RUNTIME_DIR/wayland-0
points to the socket of the Wayland compositor you would like the guest to use.
The following are crosvm's default arguments and how to override them.
-m
)-c
)-r
, -d
, or --rwdisk
)--host_ip
, --netmask
, and --mac
)XDG_RUNTIME_DIR
enviroment variable is set (disable with --no-wl
)-p
)--disable-sandbox
)-s
)A Linux kernel with KVM support (check for /dev/kvm
) is required to run crosvm. In order to run certain devices, there are additional system requirements:
virtio-wayland
- The memfd_create
syscall, introduced in Linux 3.17, and a Wayland compositor.vsock
- Host Linux kernel with vhost-vsock support, introduced in Linux 4.8.multiprocess
- Host Linux kernel with seccomp-bpf and Linux namespacing support.virtio-net
- Host Linux kernel with TUN/TAP support (check for /dev/net/tun
) and running with CAP_NET_ADMIN
privileges.Device | Description |
---|---|
CMOS/RTC | Used to get the current calendar time. |
i8042 | Used by the guest kernel to exit crosvm. |
serial | x86 I/O port driven serial devices that print to stdout and take input from stdin. |
virtio-block | Basic read/write block device. |
virtio-net | Device to interface the host and guest networks. |
virtio-rng | Entropy source used to seed guest OS's entropy pool. |
virtio-vsock | Enabled VSOCKs for the guests. |
virtio-wayland | Allowed guest to use host Wayland socket. |
build_test
There are no automated tests run before code is committed to crosvm. In order to maintain sanity, please execute build_test
before submitting code for review. All tests should be passing or ignored and there should be no compiler warnings or errors. All supported architectures are built, but only tests for x86_64 are run. In order to build everything without failures, sysroots must be supplied for each architecture. See build_test -h
for more information.
rustfmt
All code should be formatted with rustfmt
. We have a script that applies rustfmt to all Rust code in the crosvm repo: please run bin/fmt
before checking in a change. This is different from cargo fmt --all
which formats multiple crates but a single workspace only; crosvm consists of multiple workspaces.
With a few exceptions, external dependencies inside of the Cargo.toml
files are not allowed. The reason being that community made crates tend to explode the binary size by including dozens of transitive dependencies. All these dependencies also must be reviewed to ensure their suitability to the crosvm project. Currently allowed crates are:
cc
- Build time dependency needed to build C source code used in crosvm.libc
- Required to use the standard library, this crate is a simple wrapper around libc
's symbols.The crosvm source code is written in Rust and C. To build, crosvm generally requires the most recent stable version of rustc.
Source code is organized into crates, each with their own unit tests. These crates are:
crosvm
- The top-level binary front-end for using crosvm.devices
- Virtual devices exposed to the guest OS.io_jail
- Creates jailed process using libminijail
.kernel_loader
- Loads elf64 kernel files to a slice of memory.kvm_sys
- Low-level (mostly) auto-generated structures and constants for using KVM.kvm
- Unsafe, low-level wrapper code for using kvm_sys
.net_sys
- Low-level (mostly) auto-generated structures and constants for creating TUN/TAP devices.net_util
- Wrapper for creating TUN/TAP devices.sys_util
- Mostly safe wrappers for small system facilities such as eventfd
or syslog
.syscall_defines
- Lists of syscall numbers in each architecture used to make syscalls not supported in libc
.vhost
- Wrappers for creating vhost based devices.virtio_sys
- Low-level (mostly) auto-generated structures and constants for interfacing with kernel vhost support.vm_control
- IPC for the VM.x86_64
- Support code specific to 64 bit intel machines.The seccomp
folder contains minijail seccomp policy files for each sandboxed device. Because some syscalls vary by architecture, the seccomp policies are split by architecture.