cloud-hypervisor/virtio-devices/src/block.rs

// Copyright 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
//
// Portions 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-BSD-3-Clause file.
//
// Copyright © 2020 Intel Corporation
//
// SPDX-License-Identifier: Apache-2.0 AND BSD-3-Clause

use super::Error as DeviceError;
use super::{
    ActivateError, ActivateResult, EpollHelper, EpollHelperError, EpollHelperHandler, Queue,
    RateLimiterConfig, VirtioCommon, VirtioDevice, VirtioDeviceType, VirtioInterruptType,
    EPOLL_HELPER_EVENT_LAST,
};
use crate::seccomp_filters::{get_seccomp_filter, Thread};
use crate::VirtioInterrupt;
use block_util::{
    async_io::AsyncIo, async_io::AsyncIoError, async_io::DiskFile, build_disk_image_id, Request,
    RequestType, VirtioBlockConfig,
};
use rate_limiter::{RateLimiter, TokenType};
use seccomp::{SeccompAction, SeccompFilter};
use std::io;
use std::num::Wrapping;
use std::os::unix::io::AsRawFd;
use std::path::PathBuf;
use std::result;
use std::sync::atomic::{AtomicBool, AtomicU64, Ordering};
use std::sync::{Arc, Barrier};
use std::thread;
use std::{collections::HashMap, convert::TryInto};
use virtio_bindings::bindings::virtio_blk::*;
use vm_memory::{ByteValued, Bytes, GuestAddressSpace, GuestMemoryAtomic, GuestMemoryMmap};
use vm_migration::{Migratable, MigratableError, Pausable, Snapshot, Snapshottable, Transportable};
use vmm_sys_util::eventfd::EventFd;

const SECTOR_SHIFT: u8 = 9;
pub const SECTOR_SIZE: u64 = 0x01 << SECTOR_SHIFT;

// New descriptors are pending on the virtio queue.
const QUEUE_AVAIL_EVENT: u16 = EPOLL_HELPER_EVENT_LAST + 1;
// New completed tasks are pending on the completion ring.
const COMPLETION_EVENT: u16 = EPOLL_HELPER_EVENT_LAST + 2;
// New 'wake up' event from the rate limiter
const RATE_LIMITER_EVENT: u16 = EPOLL_HELPER_EVENT_LAST + 3;

#[derive(Debug)]
pub enum Error {
    /// Failed to parse the request.
    RequestParsing(block_util::Error),
    /// Failed to execute the request.
    RequestExecuting(block_util::ExecuteError),
    /// Missing the expected entry in the list of requests.
    MissingEntryRequestList,
    /// The asynchronous request returned with failure.
    AsyncRequestFailure,
    /// Failed synchronizing the file
    Fsync(AsyncIoError),
}

pub type Result<T> = result::Result<T, Error>;

#[derive(Default, Clone)]
pub struct BlockCounters {
    read_bytes: Arc<AtomicU64>,
    read_ops: Arc<AtomicU64>,
    write_bytes: Arc<AtomicU64>,
    write_ops: Arc<AtomicU64>,
}

struct BlockEpollHandler {
    queue: Queue,
    mem: GuestMemoryAtomic<GuestMemoryMmap>,
    disk_image: Box<dyn AsyncIo>,
    disk_nsectors: u64,
    interrupt_cb: Arc<dyn VirtioInterrupt>,
    disk_image_id: Vec<u8>,
    kill_evt: EventFd,
    pause_evt: EventFd,
    writeback: Arc<AtomicBool>,
    counters: BlockCounters,
    queue_evt: EventFd,
    request_list: HashMap<u16, Request>,
    rate_limiter: Option<RateLimiter>,
}

impl BlockEpollHandler {
    fn process_queue_submit(&mut self) -> Result<bool> {
        let queue = &mut self.queue;
        let mem = self.mem.memory();

        let mut used_desc_heads = Vec::new();
        let mut used_count = 0;

        for avail_desc in queue.iter(&mem) {
            let mut request = Request::parse(&avail_desc, &mem).map_err(Error::RequestParsing)?;

            if let Some(rate_limiter) = &mut self.rate_limiter {
                // If limiter.consume() fails it means there is no more TokenType::Ops
                // budget and rate limiting is in effect.
                if !rate_limiter.consume(1, TokenType::Ops) {
                    // Stop processing the queue and return this descriptor chain to the
                    // avail ring, for later processing.
                    queue.go_to_previous_position();
                    break;
                }
                // Exercise the rate limiter only if this request is of data transfer type.
                if request.request_type == RequestType::In
                    || request.request_type == RequestType::Out
                {
                    let mut bytes = Wrapping(0);
                    for (_, data_len) in &request.data_descriptors {
                        bytes += Wrapping(*data_len as u64);
                    }

                    // If limiter.consume() fails it means there is no more TokenType::Bytes
                    // budget and rate limiting is in effect.
                    if !rate_limiter.consume(bytes.0, TokenType::Bytes) {
                        // Revert the OPS consume().
                        rate_limiter.manual_replenish(1, TokenType::Ops);
                        // Stop processing the queue and return this descriptor chain to the
                        // avail ring, for later processing.
                        queue.go_to_previous_position();
                        break;
                    }
                };
            }

            request.set_writeback(self.writeback.load(Ordering::Acquire));

            if request
                .execute_async(
                    &mem,
                    self.disk_nsectors,
                    self.disk_image.as_mut(),
                    &self.disk_image_id,
                    avail_desc.index as u64,
                )
                .map_err(Error::RequestExecuting)?
            {
                self.request_list.insert(avail_desc.index, request);
            } else {
                // We use unwrap because the request parsing process already
                // checked that the status_addr was valid.
                mem.write_obj(VIRTIO_BLK_S_OK, request.status_addr).unwrap();

                // If no asynchronous operation has been submitted, we can
                // simply return the used descriptor.
                used_desc_heads.push((avail_desc.index, 0));
                used_count += 1;
            }
        }

        for &(desc_index, len) in used_desc_heads.iter() {
            queue.add_used(&mem, desc_index, len);
        }

        Ok(used_count > 0)
    }

    fn process_queue_complete(&mut self) -> Result<bool> {
        let queue = &mut self.queue;

        let mut used_desc_heads = Vec::new();
        let mut used_count = 0;
        let mem = self.mem.memory();
        let mut read_bytes = Wrapping(0);
        let mut write_bytes = Wrapping(0);
        let mut read_ops = Wrapping(0);
        let mut write_ops = Wrapping(0);

        let completion_list = self.disk_image.complete();
        for (user_data, result) in completion_list {
            let desc_index = user_data as u16;
            let request = self
                .request_list
                .remove(&desc_index)
                .ok_or(Error::MissingEntryRequestList)?;

            let (status, len) = if result >= 0 {
                match request.request_type {
                    RequestType::In => {
                        for (_, data_len) in &request.data_descriptors {
                            read_bytes += Wrapping(*data_len as u64);
                        }
                        read_ops += Wrapping(1);
                    }
                    RequestType::Out => {
                        if !request.writeback {
                            self.disk_image.fsync(None).map_err(Error::Fsync)?;
                        }
                        for (_, data_len) in &request.data_descriptors {
                            write_bytes += Wrapping(*data_len as u64);
                        }
                        write_ops += Wrapping(1);
                    }
                    _ => {}
                }

                (VIRTIO_BLK_S_OK, result as u32)
            } else {
                error!(
                    "Request failed: {:?}",
                    io::Error::from_raw_os_error(-result)
                );
                return Err(Error::AsyncRequestFailure);
            };

            // We use unwrap because the request parsing process already
            // checked that the status_addr was valid.
            mem.write_obj(status, request.status_addr).unwrap();

            used_desc_heads.push((desc_index as u16, len));
            used_count += 1;
        }

        for &(desc_index, len) in used_desc_heads.iter() {
            queue.add_used(&mem, desc_index, len);
        }

        self.counters
            .write_bytes
            .fetch_add(write_bytes.0, Ordering::AcqRel);
        self.counters
            .write_ops
            .fetch_add(write_ops.0, Ordering::AcqRel);

        self.counters
            .read_bytes
            .fetch_add(read_bytes.0, Ordering::AcqRel);
        self.counters
            .read_ops
            .fetch_add(read_ops.0, Ordering::AcqRel);

        Ok(used_count > 0)
    }

    fn signal_used_queue(&self) -> result::Result<(), DeviceError> {
        self.interrupt_cb
            .trigger(&VirtioInterruptType::Queue, Some(&self.queue))
            .map_err(|e| {
                error!("Failed to signal used queue: {:?}", e);
                DeviceError::FailedSignalingUsedQueue(e)
            })
    }

    fn run(
        &mut self,
        paused: Arc<AtomicBool>,
        paused_sync: Arc<Barrier>,
    ) -> result::Result<(), EpollHelperError> {
        let mut helper = EpollHelper::new(&self.kill_evt, &self.pause_evt)?;
        helper.add_event(self.queue_evt.as_raw_fd(), QUEUE_AVAIL_EVENT)?;
        helper.add_event(self.disk_image.notifier().as_raw_fd(), COMPLETION_EVENT)?;
        if let Some(rate_limiter) = &self.rate_limiter {
            helper.add_event(rate_limiter.as_raw_fd(), RATE_LIMITER_EVENT)?;
        }
        helper.run(paused, paused_sync, self)?;

        Ok(())
    }
}

impl EpollHelperHandler for BlockEpollHandler {
    fn handle_event(&mut self, _helper: &mut EpollHelper, event: &epoll::Event) -> bool {
        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);
                    return true;
                }

                let rate_limit_reached =
                    self.rate_limiter.as_ref().map_or(false, |r| r.is_blocked());

                // Process the queue only when the rate limit is not reached
                if !rate_limit_reached {
                    match self.process_queue_submit() {
                        Ok(needs_notification) => {
                            if needs_notification {
                                if let Err(e) = self.signal_used_queue() {
                                    error!("Failed to signal used queue: {:?}", e);
                                    return true;
                                }
                            }
                        }
                        Err(e) => {
                            error!("Failed to process queue (submit): {:?}", e);
                            return true;
                        }
                    }
                }
            }
            COMPLETION_EVENT => {
                if let Err(e) = self.disk_image.notifier().read() {
                    error!("Failed to get queue event: {:?}", e);
                    return true;
                }

                match self.process_queue_complete() {
                    Ok(needs_notification) => {
                        if needs_notification {
                            if let Err(e) = self.signal_used_queue() {
                                error!("Failed to signal used queue: {:?}", e);
                                return true;
                            }
                        }
                    }
                    Err(e) => {
                        error!("Failed to process queue (complete): {:?}", e);
                        return true;
                    }
                }
            }
            RATE_LIMITER_EVENT => {
                if let Some(rate_limiter) = &mut self.rate_limiter {
                    // Upon rate limiter event, call the rate limiter handler
                    // and restart processing the queue.
                    if rate_limiter.event_handler().is_ok() {
                        match self.process_queue_submit() {
                            Ok(needs_notification) => {
                                if needs_notification {
                                    if let Err(e) = self.signal_used_queue() {
                                        error!("Failed to signal used queue: {:?}", e);
                                        return true;
                                    }
                                }
                            }
                            Err(e) => {
                                error!("Failed to process queue (submit): {:?}", e);
                                return true;
                            }
                        }
                    }
                } else {
                    error!("Unexpected 'RATE_LIMITER_EVENT' when rate_limiter is not enabled.");
                    return true;
                }
            }
            _ => {
                error!("Unexpected event: {}", ev_type);
                return true;
            }
        }
        false
    }
}

/// Virtio device for exposing block level read/write operations on a host file.
pub struct Block {
    common: VirtioCommon,
    id: String,
    disk_image: Box<dyn DiskFile>,
    disk_path: PathBuf,
    disk_nsectors: u64,
    config: VirtioBlockConfig,
    writeback: Arc<AtomicBool>,
    counters: BlockCounters,
    seccomp_action: SeccompAction,
    rate_limiter_config: Option<RateLimiterConfig>,
}

#[derive(Serialize, Deserialize)]
pub struct BlockState {
    pub disk_path: String,
    pub disk_nsectors: u64,
    pub avail_features: u64,
    pub acked_features: u64,
    pub config: VirtioBlockConfig,
}

impl Block {
    /// Create a new virtio block device that operates on the given file.
    #[allow(clippy::too_many_arguments)]
    pub fn new(
        id: String,
        mut disk_image: Box<dyn DiskFile>,
        disk_path: PathBuf,
        is_disk_read_only: bool,
        iommu: bool,
        num_queues: usize,
        queue_size: u16,
        seccomp_action: SeccompAction,
        rate_limiter_config: Option<RateLimiterConfig>,
    ) -> io::Result<Self> {
        let disk_size = disk_image.size().map_err(|e| {
            io::Error::new(
                io::ErrorKind::Other,
                format!("Failed getting disk size: {}", e),
            )
        })?;
        if disk_size % SECTOR_SIZE != 0 {
            warn!(
                "Disk size {} is not a multiple of sector size {}; \
                 the remainder will not be visible to the guest.",
                disk_size, SECTOR_SIZE
            );
        }

        let mut avail_features = (1u64 << VIRTIO_F_VERSION_1)
            | (1u64 << VIRTIO_BLK_F_FLUSH)
            | (1u64 << VIRTIO_BLK_F_CONFIG_WCE);

        if iommu {
            avail_features |= 1u64 << VIRTIO_F_IOMMU_PLATFORM;
        }

        if is_disk_read_only {
            avail_features |= 1u64 << VIRTIO_BLK_F_RO;
        }

        let disk_nsectors = disk_size / SECTOR_SIZE;
        let mut config = VirtioBlockConfig {
            capacity: disk_nsectors,
            writeback: 1,
            ..Default::default()
        };

        if num_queues > 1 {
            avail_features |= 1u64 << VIRTIO_BLK_F_MQ;
            config.num_queues = num_queues as u16;
        }

        Ok(Block {
            common: VirtioCommon {
                device_type: VirtioDeviceType::Block as u32,
                avail_features,
                paused_sync: Some(Arc::new(Barrier::new(num_queues + 1))),
                queue_sizes: vec![queue_size; num_queues],
                min_queues: 1,
                ..Default::default()
            },
            id,
            disk_image,
            disk_path,
            disk_nsectors,
            config,
            writeback: Arc::new(AtomicBool::new(true)),
            counters: BlockCounters::default(),
            seccomp_action,
            rate_limiter_config,
        })
    }

    fn state(&self) -> BlockState {
        BlockState {
            disk_path: self.disk_path.to_str().unwrap().to_owned(),
            disk_nsectors: self.disk_nsectors,
            avail_features: self.common.avail_features,
            acked_features: self.common.acked_features,
            config: self.config,
        }
    }

    fn set_state(&mut self, state: &BlockState) {
        self.disk_path = state.disk_path.clone().into();
        self.disk_nsectors = state.disk_nsectors;
        self.common.avail_features = state.avail_features;
        self.common.acked_features = state.acked_features;
        self.config = state.config;
    }

    fn update_writeback(&mut self) {
        // Use writeback from config if VIRTIO_BLK_F_CONFIG_WCE
        let writeback = if self.common.feature_acked(VIRTIO_BLK_F_CONFIG_WCE.into()) {
            self.config.writeback == 1
        } else {
            // Else check if VIRTIO_BLK_F_FLUSH negotiated
            self.common.feature_acked(VIRTIO_BLK_F_FLUSH.into())
        };

        info!(
            "Changing cache mode to {}",
            if writeback {
                "writeback"
            } else {
                "writethrough"
            }
        );
        self.writeback.store(writeback, Ordering::Release);
    }
}

impl Drop for Block {
    fn drop(&mut self) {
        if let Some(kill_evt) = self.common.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 device_type(&self) -> u32 {
        self.common.device_type
    }

    fn queue_max_sizes(&self) -> &[u16] {
        &self.common.queue_sizes
    }

    fn features(&self) -> u64 {
        self.common.avail_features
    }

    fn ack_features(&mut self, value: u64) {
        self.common.ack_features(value)
    }

    fn read_config(&self, offset: u64, data: &mut [u8]) {
        self.read_config_from_slice(self.config.as_slice(), offset, data);
    }

    fn write_config(&mut self, offset: u64, data: &[u8]) {
        // The "writeback" field is the only mutable field
        let writeback_offset =
            (&self.config.writeback as *const _ as u64) - (&self.config as *const _ as u64);
        if offset != writeback_offset || data.len() != std::mem::size_of_val(&self.config.writeback)
        {
            error!(
                "Attempt to write to read-only field: offset {:x} length {}",
                offset,
                data.len()
            );
            return;
        }

        self.config.writeback = data[0];
        self.update_writeback();
    }

    fn activate(
        &mut self,
        mem: GuestMemoryAtomic<GuestMemoryMmap>,
        interrupt_cb: Arc<dyn VirtioInterrupt>,
        mut queues: Vec<Queue>,
        mut queue_evts: Vec<EventFd>,
    ) -> ActivateResult {
        self.common.activate(&queues, &queue_evts, &interrupt_cb)?;

        let disk_image_id = build_disk_image_id(&self.disk_path);
        self.update_writeback();

        let mut epoll_threads = Vec::new();
        for i in 0..queues.len() {
            let queue_evt = queue_evts.remove(0);
            let queue = queues.remove(0);
            let queue_size = queue.size;
            let kill_evt = self
                .common
                .kill_evt
                .as_ref()
                .unwrap()
                .try_clone()
                .map_err(|e| {
                    error!("failed to clone kill_evt eventfd: {}", e);
                    ActivateError::BadActivate
                })?;
            let pause_evt = self
                .common
                .pause_evt
                .as_ref()
                .unwrap()
                .try_clone()
                .map_err(|e| {
                    error!("failed to clone pause_evt eventfd: {}", e);
                    ActivateError::BadActivate
                })?;

            let rate_limiter: Option<RateLimiter> = self
                .rate_limiter_config
                .map(RateLimiterConfig::try_into)
                .transpose()
                .map_err(ActivateError::CreateRateLimiter)?;

            let mut handler = BlockEpollHandler {
                queue,
                mem: mem.clone(),
                disk_image: self
                    .disk_image
                    .new_async_io(queue_size as u32)
                    .map_err(|e| {
                        error!("failed to create new AsyncIo: {}", e);
                        ActivateError::BadActivate
                    })?,
                disk_nsectors: self.disk_nsectors,
                interrupt_cb: interrupt_cb.clone(),
                disk_image_id: disk_image_id.clone(),
                kill_evt,
                pause_evt,
                writeback: self.writeback.clone(),
                counters: self.counters.clone(),
                queue_evt,
                request_list: HashMap::with_capacity(queue_size.into()),
                rate_limiter,
            };

            let paused = self.common.paused.clone();
            let paused_sync = self.common.paused_sync.clone();

            // Retrieve seccomp filter for virtio_block thread
            let virtio_block_seccomp_filter =
                get_seccomp_filter(&self.seccomp_action, Thread::VirtioBlock)
                    .map_err(ActivateError::CreateSeccompFilter)?;

            thread::Builder::new()
                .name(format!("{}_q{}", self.id.clone(), i))
                .spawn(move || {
                    if let Err(e) = SeccompFilter::apply(virtio_block_seccomp_filter) {
                        error!("Error applying seccomp filter: {:?}", e);
                    } else if let Err(e) = handler.run(paused, paused_sync.unwrap()) {
                        error!("Error running worker: {:?}", e);
                    }
                })
                .map(|thread| epoll_threads.push(thread))
                .map_err(|e| {
                    error!("failed to clone the virtio-block epoll thread: {}", e);
                    ActivateError::BadActivate
                })?;
        }

        self.common.epoll_threads = Some(epoll_threads);
        event!("virtio-device", "activated", "id", &self.id);

        Ok(())
    }

    fn reset(&mut self) -> Option<Arc<dyn VirtioInterrupt>> {
        let result = self.common.reset();
        event!("virtio-device", "reset", "id", &self.id);
        result
    }

    fn counters(&self) -> Option<HashMap<&'static str, Wrapping<u64>>> {
        let mut counters = HashMap::new();

        counters.insert(
            "read_bytes",
            Wrapping(self.counters.read_bytes.load(Ordering::Acquire)),
        );
        counters.insert(
            "write_bytes",
            Wrapping(self.counters.write_bytes.load(Ordering::Acquire)),
        );
        counters.insert(
            "read_ops",
            Wrapping(self.counters.read_ops.load(Ordering::Acquire)),
        );
        counters.insert(
            "write_ops",
            Wrapping(self.counters.write_ops.load(Ordering::Acquire)),
        );

        Some(counters)
    }
}

impl Pausable for Block {
    fn pause(&mut self) -> result::Result<(), MigratableError> {
        self.common.pause()
    }

    fn resume(&mut self) -> result::Result<(), MigratableError> {
        self.common.resume()
    }
}

impl Snapshottable for Block {
    fn id(&self) -> String {
        self.id.clone()
    }

    fn snapshot(&mut self) -> std::result::Result<Snapshot, MigratableError> {
        Snapshot::new_from_state(&self.id(), &self.state())
    }

    fn restore(&mut self, snapshot: Snapshot) -> std::result::Result<(), MigratableError> {
        self.set_state(&snapshot.to_state(&self.id)?);
        Ok(())
    }
}
impl Transportable for Block {}
impl Migratable for Block {}