Devices

This chapter describes emulated devices in crosvm. These devices work like hardware for the guest.

List of devices

Here is a (non-comprehensive) list of emulated devices provided by crosvm.

Emulated Devices

• CMOS/RTC - Used to get the current calendar time.
• i8042 - Used by the guest kernel to exit crosvm.
• usb - xhci emulation to provide USB device passthrough.
• serial - x86 I/O port driven serial devices that print to stdout and take input from stdin.

VirtIO Devices

• balloon - Allows the host to reclaim the guest's memories.
• block - Basic read/write block device.
• console - Input and outputs on console.
• fs - Shares file systems over the FUSE protocol.
• gpu - Graphics adapter.
• input - Creates virtual human interface devices such as keyboards.
• iommu - Emulates an IOMMU device to manage DMA from endpoints in the guest.
• net - Device to interface the host and guest networks.
• p9 - Shares file systems over the 9P protocol.
• pmem - Persistent memory.
• rng - Entropy source used to seed guest OS's entropy pool.
• scsi - SCSI device.
• snd - Encodes and decodes audio streams.
• tpm - Creates a TPM (Trusted Platform Module) device backed by vTPM daemon.
• video - Allows the guest to leverage the host's video capabilities.
• wayland - Allows the guest to use the host's Wayland socket.
• vsock - Enables use of virtual sockets for the guest.
• vhost-user - VirtIO devices which offloads the device implementation to another process through the vhost-user protocol:
  • frontend side: Shares its virtqueues.
  • backend side: Consumes virtqueues.

Device hotplug (experimental)

A hotplug-capable device can be added as a PCI device to the guest. To enable hotplug, compile crosvm with feature flag pci-hotplug:

cargo build --features=pci-hotplug #additional parameters

When starting the VM, specify the number of slots with --pci-hotplug-slots option. Additionally, specify a control socket specified with -s option for sending hotplug commands.

For example, to run a VM with 3 PCI hotplug slots and control socket:

VM_SOCKET=/run/crosvm.socket
crosvm run \
    -s ${VM_SOCKET} \
    --pci-hotplug-slots 3
    # usual crosvm args

Currently, only network devices are supported.