cloud-hypervisor/vm-virtio/src/rng.rs

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// 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 file.
use epoll;
use libc::EFD_NONBLOCK;
use std;
use std::fs::File;
use std::io;
use std::os::unix::io::AsRawFd;
use std::result;
use std::sync::Arc;
use std::thread;
use super::Error as DeviceError;
use super::{
ActivateError, ActivateResult, DeviceEventT, Queue, VirtioDevice, VirtioDeviceType,
VIRTIO_F_VERSION_1,
};
use crate::{VirtioInterrupt, VirtioInterruptType};
use vm_memory::{Bytes, GuestMemoryMmap};
use vmm_sys_util::eventfd::EventFd;
const QUEUE_SIZE: u16 = 256;
const NUM_QUEUES: usize = 1;
const QUEUE_SIZES: &[u16] = &[QUEUE_SIZE];
// New descriptors are pending on the virtio queue.
const QUEUE_AVAIL_EVENT: DeviceEventT = 0;
// The device has been dropped.
const KILL_EVENT: DeviceEventT = 1;
struct RngEpollHandler {
queues: Vec<Queue>,
mem: GuestMemoryMmap,
random_file: File,
interrupt_cb: Arc<VirtioInterrupt>,
queue_evt: EventFd,
kill_evt: EventFd,
}
impl RngEpollHandler {
fn process_queue(&mut self) -> bool {
let queue = &mut self.queues[0];
let mut used_desc_heads = [(0, 0); QUEUE_SIZE as usize];
let mut used_count = 0;
for avail_desc in queue.iter(&self.mem) {
let mut len = 0;
// Drivers can only read from the random device.
if avail_desc.is_write_only() {
// Fill the read with data from the random device on the host.
if self
.mem
.read_from(
avail_desc.addr,
&mut self.random_file,
avail_desc.len as usize,
)
.is_ok()
{
len = avail_desc.len;
}
}
used_desc_heads[used_count] = (avail_desc.index, len);
used_count += 1;
}
for &(desc_index, len) in &used_desc_heads[..used_count] {
queue.add_used(&self.mem, desc_index, len);
}
used_count > 0
}
fn signal_used_queue(&self) -> result::Result<(), DeviceError> {
(self.interrupt_cb)(&VirtioInterruptType::Queue, Some(&self.queues[0])).map_err(|e| {
error!("Failed to signal used queue: {:?}", e);
DeviceError::FailedSignalingUsedQueue(e)
})
}
fn run(&mut self) -> result::Result<(), DeviceError> {
// Create the epoll file descriptor
let epoll_fd = epoll::create(true).map_err(DeviceError::EpollCreateFd)?;
// Add events
epoll::ctl(
epoll_fd,
epoll::ControlOptions::EPOLL_CTL_ADD,
self.queue_evt.as_raw_fd(),
epoll::Event::new(epoll::Events::EPOLLIN, u64::from(QUEUE_AVAIL_EVENT)),
)
.map_err(DeviceError::EpollCtl)?;
epoll::ctl(
epoll_fd,
epoll::ControlOptions::EPOLL_CTL_ADD,
self.kill_evt.as_raw_fd(),
epoll::Event::new(epoll::Events::EPOLLIN, u64::from(KILL_EVENT)),
)
.map_err(DeviceError::EpollCtl)?;
const EPOLL_EVENTS_LEN: usize = 100;
let mut events = vec![epoll::Event::new(epoll::Events::empty(), 0); EPOLL_EVENTS_LEN];
'epoll: loop {
let num_events = match epoll::wait(epoll_fd, -1, &mut events[..]) {
Ok(res) => res,
Err(e) => {
if e.kind() == io::ErrorKind::Interrupted {
// It's well defined from the epoll_wait() syscall
// documentation that the epoll loop can be interrupted
// before any of the requested events occurred or the
// timeout expired. In both those cases, epoll_wait()
// returns an error of type EINTR, but this should not
// be considered as a regular error. Instead it is more
// appropriate to retry, by calling into epoll_wait().
continue;
}
return Err(DeviceError::EpollWait(e));
}
};
for event in events.iter().take(num_events) {
let ev_type = event.data as u16;
match ev_type {
QUEUE_AVAIL_EVENT => {
if let Err(e) = self.queue_evt.read() {
error!("Failed to get queue event: {:?}", e);
break 'epoll;
} else if self.process_queue() {
if let Err(e) = self.signal_used_queue() {
error!("Failed to signal used queue: {:?}", e);
break 'epoll;
}
}
}
KILL_EVENT => {
debug!("KILL_EVENT received, stopping epoll loop");
break 'epoll;
}
_ => {
error!("Unknown event for virtio-block");
}
}
}
}
Ok(())
}
}
/// Virtio device for exposing entropy to the guest OS through virtio.
pub struct Rng {
kill_evt: Option<EventFd>,
random_file: Option<File>,
avail_features: u64,
acked_features: u64,
}
impl Rng {
/// Create a new virtio rng device that gets random data from /dev/urandom.
pub fn new(path: &str) -> io::Result<Rng> {
let random_file = File::open(path)?;
let avail_features = 1u64 << VIRTIO_F_VERSION_1;
Ok(Rng {
kill_evt: None,
random_file: Some(random_file),
avail_features,
acked_features: 0u64,
})
}
}
impl Drop for Rng {
fn drop(&mut self) {
if let Some(kill_evt) = self.kill_evt.take() {
// Ignore the result because there is nothing we can do about it.
let _ = kill_evt.write(1);
}
}
}
impl VirtioDevice for Rng {
fn device_type(&self) -> u32 {
VirtioDeviceType::TYPE_RNG as u32
}
fn queue_max_sizes(&self) -> &[u16] {
QUEUE_SIZES
}
fn features(&self, page: u32) -> u32 {
match page {
// Get the lower 32-bits of the features bitfield.
0 => self.avail_features as u32,
// Get the upper 32-bits of the features bitfield.
1 => (self.avail_features >> 32) as u32,
_ => {
warn!("Received request for unknown features page.");
0u32
}
}
}
fn ack_features(&mut self, page: u32, value: u32) {
let mut v = match page {
0 => u64::from(value),
1 => u64::from(value) << 32,
_ => {
warn!("Cannot acknowledge unknown features page.");
0u64
}
};
// Check if the guest is ACK'ing a feature that we didn't claim to have.
let unrequested_features = v & !self.avail_features;
if unrequested_features != 0 {
warn!("Received acknowledge request for unknown feature.");
// Don't count these features as acked.
v &= !unrequested_features;
}
self.acked_features |= v;
}
fn read_config(&self, _offset: u64, _data: &mut [u8]) {
warn!("No currently device specific configration defined");
}
fn write_config(&mut self, _offset: u64, _data: &[u8]) {
warn!("No currently device specific configration defined");
}
fn activate(
&mut self,
mem: GuestMemoryMmap,
interrupt_cb: Arc<VirtioInterrupt>,
queues: Vec<Queue>,
mut queue_evts: Vec<EventFd>,
) -> ActivateResult {
if queues.len() != NUM_QUEUES || queue_evts.len() != NUM_QUEUES {
error!(
"Cannot perform activate. Expected {} queue(s), got {}",
NUM_QUEUES,
queues.len()
);
return Err(ActivateError::BadActivate);
}
let (self_kill_evt, kill_evt) =
match EventFd::new(EFD_NONBLOCK).and_then(|e| Ok((e.try_clone()?, e))) {
Ok(v) => v,
Err(e) => {
error!("failed creating kill EventFd pair: {}", e);
return Err(ActivateError::BadActivate);
}
};
self.kill_evt = Some(self_kill_evt);
if let Some(random_file) = self.random_file.take() {
let mut handler = RngEpollHandler {
queues,
mem,
random_file,
interrupt_cb,
queue_evt: queue_evts.remove(0),
kill_evt,
};
let worker_result = thread::Builder::new()
.name("virtio_rng".to_string())
.spawn(move || handler.run());
if let Err(e) = worker_result {
error!("failed to spawn virtio_rng worker: {}", e);
return Err(ActivateError::BadActivate);;
}
return Ok(());
}
Err(ActivateError::BadActivate)
}
}