// 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 std::fs::File;
use std::io::{Seek, SeekFrom, Read, Write};
use std::os::unix::io::{AsRawFd, RawFd};
use std::result;
use std::sync::Arc;
use std::sync::atomic::{AtomicUsize, Ordering};
use std::thread::spawn;
use byteorder::{ByteOrder, LittleEndian};
use sys_util::Result as SysResult;
use sys_util::{EventFd, GuestAddress, GuestMemory, GuestMemoryError, Poller};
use super::{VirtioDevice, Queue, DescriptorChain, INTERRUPT_STATUS_USED_RING, TYPE_BLOCK};
const QUEUE_SIZE: u16 = 256;
const QUEUE_SIZES: &'static [u16] = &[QUEUE_SIZE];
const SECTOR_SHIFT: u8 = 9;
const VIRTIO_BLK_T_IN: u32 = 0;
const VIRTIO_BLK_T_OUT: u32 = 1;
const VIRTIO_BLK_T_FLUSH: u32 = 4;
const VIRTIO_BLK_S_OK: u8 = 0;
const VIRTIO_BLK_S_IOERR: u8 = 1;
const VIRTIO_BLK_S_UNSUPP: u8 = 2;
#[derive(PartialEq)]
enum RequestType {
In,
Out,
Flush,
Unsupported(u32),
}
#[derive(Debug)]
enum ParseError {
/// Guest gave us bad memory addresses
GuestMemory(GuestMemoryError),
/// Guest gave us offsets that would have overflowed a usize.
CheckedOffset(GuestAddress, usize),
/// Guest gave us a write only descriptor that protocol says to read from.
UnexpectedWriteOnlyDescriptor,
/// Guest gave us a read only descriptor that protocol says to write to.
UnexpectedReadOnlyDescriptor,
/// Guest gave us too few descriptors in a descriptor chain.
DescriptorChainTooShort,
/// Guest gave us a descriptor that was too short to use.
DescriptorLengthTooSmall,
}
fn request_type(mem: &GuestMemory,
desc_addr: GuestAddress)
-> result::Result<RequestType, ParseError> {
let type_ = mem.read_obj_from_addr(desc_addr)
.map_err(ParseError::GuestMemory)?;
match type_ {
VIRTIO_BLK_T_IN => Ok(RequestType::In),
VIRTIO_BLK_T_OUT => Ok(RequestType::Out),
VIRTIO_BLK_T_FLUSH => Ok(RequestType::Flush),
t => Ok(RequestType::Unsupported(t)),
}
}
fn sector(mem: &GuestMemory, desc_addr: GuestAddress) -> result::Result<u64, ParseError> {
const SECTOR_OFFSET: usize = 8;
let addr = match mem.checked_offset(desc_addr, SECTOR_OFFSET) {
Some(v) => v,
None => return Err(ParseError::CheckedOffset(desc_addr, SECTOR_OFFSET)),
};
mem.read_obj_from_addr(addr)
.map_err(ParseError::GuestMemory)
}
#[derive(Debug)]
enum ExecuteError {
Io,
Unsupported(u32),
}
impl ExecuteError {
fn status(&self) -> u8 {
match self {
&ExecuteError::Io => VIRTIO_BLK_S_IOERR,
&ExecuteError::Unsupported(_) => VIRTIO_BLK_S_UNSUPP,
}
}
}
struct Request {
request_type: RequestType,
sector: u64,
data_addr: GuestAddress,
data_len: u32,
status_addr: GuestAddress,
}
impl Request {
fn parse(avail_desc: &DescriptorChain,
mem: &GuestMemory)
-> result::Result<Request, ParseError> {
// The head contains the request type which MUST be readable.
if avail_desc.is_write_only() {
return Err(ParseError::UnexpectedWriteOnlyDescriptor);
}
let req_type = request_type(&mem, avail_desc.addr)?;
let sector = sector(&mem, avail_desc.addr)?;
let data_desc = avail_desc
.next_descriptor()
.ok_or(ParseError::DescriptorChainTooShort)?;
let status_desc = data_desc
.next_descriptor()
.ok_or(ParseError::DescriptorChainTooShort)?;
if data_desc.is_write_only() && req_type == RequestType::Out {
return Err(ParseError::UnexpectedWriteOnlyDescriptor);
}
if !data_desc.is_write_only() && req_type == RequestType::In {
return Err(ParseError::UnexpectedReadOnlyDescriptor);
}
// The status MUST always be writable
if !status_desc.is_write_only() {
return Err(ParseError::UnexpectedReadOnlyDescriptor);
}
if status_desc.len < 1 {
return Err(ParseError::DescriptorLengthTooSmall);
}
Ok(Request {
request_type: req_type,
sector: sector,
data_addr: data_desc.addr,
data_len: data_desc.len,
status_addr: status_desc.addr,
})
}
fn execute<T: Seek + Read + Write>(&self,
disk: &mut T,
mem: &GuestMemory)
-> result::Result<u32, ExecuteError> {
// TODO(zachr): When VolatileMemory merges, make ExecuteError::Io more descriptive.
disk.seek(SeekFrom::Start(self.sector << SECTOR_SHIFT))
.map_err(|_| ExecuteError::Io)?;
match self.request_type {
RequestType::In => {
mem.read_to_memory(self.data_addr, disk, self.data_len as usize)
.map_err(|_| ExecuteError::Io)?;
return Ok(self.data_len);
}
RequestType::Out => {
mem.write_from_memory(self.data_addr, disk, self.data_len as usize)
.map_err(|_| ExecuteError::Io)?
}
RequestType::Flush => disk.flush().map_err(|_| ExecuteError::Io)?,
RequestType::Unsupported(t) => return Err(ExecuteError::Unsupported(t)),
};
Ok(0)
}
}
struct Worker {
queues: Vec<Queue>,
mem: GuestMemory,
disk_image: File,
interrupt_status: Arc<AtomicUsize>,
interrupt_evt: EventFd,
}
impl Worker {
fn process_queue(&mut self, queue_index: usize) -> bool {
let queue = &mut self.queues[queue_index];
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 len;
match Request::parse(&avail_desc, &self.mem) {
Ok(request) => {
let status = match request.execute(&mut self.disk_image, &self.mem) {
Ok(l) => {
len = l;
VIRTIO_BLK_S_OK
}
Err(e) => {
println!("block: error executing disk request: {:?}", e);
len = 1; // 1 byte for the status
e.status()
}
};
// We use unwrap because the request parsing process already checked that the
// status_addr was valid.
self.mem
.write_obj_at_addr(status, request.status_addr)
.unwrap();
}
Err(e) => {
println!("block: error processing available descriptor chain: {:?}",
e);
len = 0;
}
}
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) {
self.interrupt_status
.fetch_or(INTERRUPT_STATUS_USED_RING as usize, Ordering::SeqCst);
self.interrupt_evt.write(1).unwrap();
}
fn run(&mut self, queue_evt: EventFd, kill_evt: EventFd) {
const Q_AVAIL: u32 = 0;
const KILL: u32 = 1;
let mut poller = Poller::new(2);
'poll: loop {
let tokens = match poller.poll(&[(Q_AVAIL, &queue_evt), (KILL, &kill_evt)]) {
Ok(v) => v,
Err(e) => {
println!("block: error polling for events: {:?}", e);
break;
}
};
let mut needs_interrupt = false;
for &token in tokens {
match token {
Q_AVAIL => {
if let Err(e) = queue_evt.read() {
println!("block: error reading queue EventFd: {:?}", e);
break 'poll;
}
needs_interrupt |= self.process_queue(0);
}
KILL => break 'poll,
_ => unreachable!(),
}
}
if needs_interrupt {
self.signal_used_queue();
}
}
}
}
/// Virtio device for exposing block level read/write operations on a host file.
pub struct Block {
kill_evt: Option<EventFd>,
disk_size: u64,
disk_image: Option<File>,
}
impl Block {
/// Create a new virtio block device that operates on the given file.
///
/// The given file must be seekable and sizable.
pub fn new(mut disk_image: File) -> SysResult<Block> {
let disk_size = disk_image.seek(SeekFrom::End(0))? as u64;
Ok(Block {
kill_evt: None,
disk_size: disk_size,
disk_image: Some(disk_image),
})
}
}
impl Drop for Block {
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 Block {
fn keep_fds(&self) -> Vec<RawFd> {
let mut keep_fds = Vec::new();
if let Some(ref disk_image) = self.disk_image {
keep_fds.push(disk_image.as_raw_fd());
}
keep_fds
}
fn device_type(&self) -> u32 {
TYPE_BLOCK
}
fn queue_max_sizes(&self) -> &[u16] {
QUEUE_SIZES
}
fn read_config(&self, offset: u64, data: &mut [u8]) {
// We only support the first word of configuration space.
let v = match offset {
0 => ((self.disk_size + 0x511) >> SECTOR_SHIFT) as u32,
_ => return,
};
LittleEndian::write_u32(data, v);
}
fn activate(&mut self,
mem: GuestMemory,
interrupt_evt: EventFd,
status: Arc<AtomicUsize>,
queues: Vec<Queue>,
mut queue_evts: Vec<EventFd>) {
if queues.len() != 1 || queue_evts.len() != 1 {
return;
}
let (self_kill_evt, kill_evt) =
match EventFd::new().and_then(|e| Ok((e.try_clone()?, e))) {
Ok(v) => v,
Err(e) => {
println!("block: error creating kill EventFd pair: {:?}", e);
return;
}
};
self.kill_evt = Some(self_kill_evt);
if let Some(disk_image) = self.disk_image.take() {
spawn(move || {
let mut worker = Worker {
queues: queues,
mem: mem,
disk_image: disk_image,
interrupt_status: status,
interrupt_evt: interrupt_evt,
};
worker.run(queue_evts.remove(0), kill_evt);
});
}
}
}