devices/src/virtio/wl.rs

// 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.

//! This module implements the virtio wayland used by the guest to access the host's wayland server.
//!
//! The virtio wayland protocol is done over two queues: `in` and `out`. The `in` queue is used for
//! sending commands to the guest that are generated by the host, usually messages from the wayland
//! server. The `out` queue is for commands from the guest, usually requests to allocate shared
//! memory, open a wayland server connection, or send data over an existing connection.
//!
//! Each `WlVfd` represents one virtual file descriptor created by either the guest or the host.
//! Virtual file descriptors contain actual file descriptors, either a shared memory file descriptor
//! or a unix domain socket to the wayland server. In the shared memory case, there is also an
//! associated slot that indicates which KVM memory slot the memory is installed into, as well as a
//! page frame number that the guest can access the memory from.
//!
//! The types starting with `Ctrl` are structures representing the virtio wayland protocol "on the
//! wire." They are decoded and executed in the `execute` function and encoded as some variant of
//! `WlResp` for responses.
//!
//! There is one `WlState` instance that contains every known vfd and the current state of `in`
//! queue. The `in` queue requires extra state to buffer messages to the guest in case the `in`
//! queue is already full. The `WlState` also has a control socket necessary to fulfill certain
//! requests, such as those registering guest memory.
//!
//! The `Worker` is responsible for the poll loop over all possible events, encoding/decoding from
//! the virtio queue, and routing messages in and out of `WlState`. Possible events include the kill
//! event, available descriptors on the `in` or `out` queue, and incoming data on any vfd's socket.

use std::cell::RefCell;
use std::collections::btree_map::Entry;
use std::collections::{BTreeMap as Map, BTreeSet as Set, VecDeque};
use std::convert::From;
use std::error::Error as StdError;
use std::fmt::{self, Display};
use std::fs::File;
use std::io::{self, Read, Seek, SeekFrom, Write};
use std::mem::size_of;
#[cfg(feature = "wl-dmabuf")]
use std::os::raw::{c_uint, c_ulonglong};
use std::os::unix::io::{AsRawFd, FromRawFd, RawFd};
use std::os::unix::net::UnixStream;
use std::path::{Path, PathBuf};
use std::rc::Rc;
use std::result;
use std::sync::atomic::AtomicUsize;
use std::sync::Arc;
use std::thread;
use std::time::Duration;
use sync::Mutex;

#[cfg(feature = "wl-dmabuf")]
use libc::{dup, EBADF, EINVAL};

use data_model::VolatileMemoryError;
use data_model::*;

use msg_socket::{MsgError, MsgReceiver, MsgSender};
#[cfg(feature = "wl-dmabuf")]
use resources::GpuMemoryDesc;
#[cfg(feature = "wl-dmabuf")]
use sys_util::ioctl_iow_nr;
use sys_util::{
    error, pipe, round_up_to_page_size, warn, Error, EventFd, FileFlags, GuestMemory,
    GuestMemoryError, PollContext, PollToken, Result, ScmSocket, SharedMemory,
};

#[cfg(feature = "wl-dmabuf")]
use sys_util::ioctl_with_ref;

use super::resource_bridge::*;
use super::{
    DescriptorChain, Interrupt, Queue, Reader, VirtioDevice, Writer, TYPE_WL, VIRTIO_F_VERSION_1,
};
use crate::pci::MsixConfig;
use vm_control::{MaybeOwnedFd, VmMemoryControlRequestSocket, VmMemoryRequest, VmMemoryResponse};

const VIRTWL_SEND_MAX_ALLOCS: usize = 28;
const VIRTIO_WL_CMD_VFD_NEW: u32 = 256;
const VIRTIO_WL_CMD_VFD_CLOSE: u32 = 257;
const VIRTIO_WL_CMD_VFD_SEND: u32 = 258;
const VIRTIO_WL_CMD_VFD_RECV: u32 = 259;
const VIRTIO_WL_CMD_VFD_NEW_CTX: u32 = 260;
const VIRTIO_WL_CMD_VFD_NEW_PIPE: u32 = 261;
const VIRTIO_WL_CMD_VFD_HUP: u32 = 262;
#[cfg(feature = "wl-dmabuf")]
const VIRTIO_WL_CMD_VFD_NEW_DMABUF: u32 = 263;
#[cfg(feature = "wl-dmabuf")]
const VIRTIO_WL_CMD_VFD_DMABUF_SYNC: u32 = 264;
#[cfg(feature = "gpu")]
const VIRTIO_WL_CMD_VFD_SEND_FOREIGN_ID: u32 = 265;
const VIRTIO_WL_RESP_OK: u32 = 4096;
const VIRTIO_WL_RESP_VFD_NEW: u32 = 4097;
#[cfg(feature = "wl-dmabuf")]
const VIRTIO_WL_RESP_VFD_NEW_DMABUF: u32 = 4098;
const VIRTIO_WL_RESP_ERR: u32 = 4352;
const VIRTIO_WL_RESP_OUT_OF_MEMORY: u32 = 4353;
const VIRTIO_WL_RESP_INVALID_ID: u32 = 4354;
const VIRTIO_WL_RESP_INVALID_TYPE: u32 = 4355;
const VIRTIO_WL_RESP_INVALID_FLAGS: u32 = 4356;
const VIRTIO_WL_RESP_INVALID_CMD: u32 = 4357;
const VIRTIO_WL_VFD_WRITE: u32 = 0x1;
const VIRTIO_WL_VFD_READ: u32 = 0x2;
const VIRTIO_WL_VFD_MAP: u32 = 0x2;
const VIRTIO_WL_VFD_CONTROL: u32 = 0x4;
const VIRTIO_WL_F_TRANS_FLAGS: u32 = 0x01;

const QUEUE_SIZE: u16 = 16;
const QUEUE_SIZES: &[u16] = &[QUEUE_SIZE, QUEUE_SIZE];

const NEXT_VFD_ID_BASE: u32 = 0x40000000;
const VFD_ID_HOST_MASK: u32 = NEXT_VFD_ID_BASE;
// Each in-vq buffer is one page, so we need to leave space for the control header and the maximum
// number of allocs.
const IN_BUFFER_LEN: usize =
    0x1000 - size_of::<CtrlVfdRecv>() - VIRTWL_SEND_MAX_ALLOCS * size_of::<Le32>();

#[cfg(feature = "wl-dmabuf")]
const VIRTIO_WL_VFD_DMABUF_SYNC_VALID_FLAG_MASK: u32 = 0x7;

#[cfg(feature = "wl-dmabuf")]
const DMA_BUF_IOCTL_BASE: c_uint = 0x62;

#[cfg(feature = "wl-dmabuf")]
#[repr(C)]
#[derive(Copy, Clone)]
struct dma_buf_sync {
    flags: c_ulonglong,
}

#[cfg(feature = "wl-dmabuf")]
ioctl_iow_nr!(DMA_BUF_IOCTL_SYNC, DMA_BUF_IOCTL_BASE, 0, dma_buf_sync);

const VIRTIO_WL_CTRL_VFD_SEND_KIND_LOCAL: u32 = 0;
const VIRTIO_WL_CTRL_VFD_SEND_KIND_VIRTGPU: u32 = 1;

fn encode_vfd_new(
    writer: &mut Writer,
    resp: bool,
    vfd_id: u32,
    flags: u32,
    pfn: u64,
    size: u32,
) -> WlResult<()> {
    let ctrl_vfd_new = CtrlVfdNew {
        hdr: CtrlHeader {
            type_: Le32::from(if resp {
                VIRTIO_WL_RESP_VFD_NEW
            } else {
                VIRTIO_WL_CMD_VFD_NEW
            }),
            flags: Le32::from(0),
        },
        id: Le32::from(vfd_id),
        flags: Le32::from(flags),
        pfn: Le64::from(pfn),
        size: Le32::from(size),
    };

    writer
        .write_obj(ctrl_vfd_new)
        .map_err(WlError::WriteResponse)
}

#[cfg(feature = "wl-dmabuf")]
fn encode_vfd_new_dmabuf(
    writer: &mut Writer,
    vfd_id: u32,
    flags: u32,
    pfn: u64,
    size: u32,
    desc: GpuMemoryDesc,
) -> WlResult<()> {
    let ctrl_vfd_new_dmabuf = CtrlVfdNewDmabuf {
        hdr: CtrlHeader {
            type_: Le32::from(VIRTIO_WL_RESP_VFD_NEW_DMABUF),
            flags: Le32::from(0),
        },
        id: Le32::from(vfd_id),
        flags: Le32::from(flags),
        pfn: Le64::from(pfn),
        size: Le32::from(size),
        width: Le32::from(0),
        height: Le32::from(0),
        format: Le32::from(0),
        stride0: Le32::from(desc.planes[0].stride),
        stride1: Le32::from(desc.planes[1].stride),
        stride2: Le32::from(desc.planes[2].stride),
        offset0: Le32::from(desc.planes[0].offset),
        offset1: Le32::from(desc.planes[1].offset),
        offset2: Le32::from(desc.planes[2].offset),
    };

    writer
        .write_obj(ctrl_vfd_new_dmabuf)
        .map_err(WlError::WriteResponse)
}

fn encode_vfd_recv(writer: &mut Writer, vfd_id: u32, data: &[u8], vfd_ids: &[u32]) -> WlResult<()> {
    let ctrl_vfd_recv = CtrlVfdRecv {
        hdr: CtrlHeader {
            type_: Le32::from(VIRTIO_WL_CMD_VFD_RECV),
            flags: Le32::from(0),
        },
        id: Le32::from(vfd_id),
        vfd_count: Le32::from(vfd_ids.len() as u32),
    };
    writer
        .write_obj(ctrl_vfd_recv)
        .map_err(WlError::WriteResponse)?;

    for &recv_vfd_id in vfd_ids.iter() {
        writer
            .write_obj(Le32::from(recv_vfd_id))
            .map_err(WlError::WriteResponse)?;
    }

    writer.write_all(data).map_err(WlError::WriteResponse)
}

fn encode_vfd_hup(writer: &mut Writer, vfd_id: u32) -> WlResult<()> {
    let ctrl_vfd_new = CtrlVfd {
        hdr: CtrlHeader {
            type_: Le32::from(VIRTIO_WL_CMD_VFD_HUP),
            flags: Le32::from(0),
        },
        id: Le32::from(vfd_id),
    };

    writer
        .write_obj(ctrl_vfd_new)
        .map_err(WlError::WriteResponse)
}

fn encode_resp(writer: &mut Writer, resp: WlResp) -> WlResult<()> {
    match resp {
        WlResp::VfdNew {
            id,
            flags,
            pfn,
            size,
            resp,
        } => encode_vfd_new(writer, resp, id, flags, pfn, size),
        #[cfg(feature = "wl-dmabuf")]
        WlResp::VfdNewDmabuf {
            id,
            flags,
            pfn,
            size,
            desc,
        } => encode_vfd_new_dmabuf(writer, id, flags, pfn, size, desc),
        WlResp::VfdRecv { id, data, vfds } => encode_vfd_recv(writer, id, data, vfds),
        WlResp::VfdHup { id } => encode_vfd_hup(writer, id),
        r => writer
            .write_obj(Le32::from(r.get_code()))
            .map_err(WlError::WriteResponse),
    }
}

#[allow(dead_code)]
#[derive(Debug)]
enum WlError {
    NewAlloc(Error),
    NewPipe(Error),
    AllocSetSize(Error),
    SocketConnect(io::Error),
    SocketNonBlock(io::Error),
    VmControl(MsgError),
    VmBadResponse,
    CheckedOffset,
    ParseDesc(io::Error),
    GuestMemory(GuestMemoryError),
    VolatileMemory(VolatileMemoryError),
    SendVfd(Error),
    WritePipe(io::Error),
    RecvVfd(Error),
    ReadPipe(io::Error),
    PollContextAdd(Error),
    DmabufSync(io::Error),
    WriteResponse(io::Error),
}

impl Display for WlError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        use self::WlError::*;

        match self {
            NewAlloc(e) => write!(f, "failed to create shared memory allocation: {}", e),
            NewPipe(e) => write!(f, "failed to create pipe: {}", e),
            AllocSetSize(e) => write!(f, "failed to set size of shared memory: {}", e),
            SocketConnect(e) => write!(f, "failed to connect socket: {}", e),
            SocketNonBlock(e) => write!(f, "failed to set socket as non-blocking: {}", e),
            VmControl(e) => write!(f, "failed to control parent VM: {}", e),
            VmBadResponse => write!(f, "invalid response from parent VM"),
            CheckedOffset => write!(f, "overflow in calculation"),
            ParseDesc(e) => write!(f, "error parsing descriptor: {}", e),
            GuestMemory(e) => write!(f, "access violation in guest memory: {}", e),
            VolatileMemory(e) => write!(f, "access violating in guest volatile memory: {}", e),
            SendVfd(e) => write!(f, "failed to send on a socket: {}", e),
            WritePipe(e) => write!(f, "failed to write to a pipe: {}", e),
            RecvVfd(e) => write!(f, "failed to recv on a socket: {}", e),
            ReadPipe(e) => write!(f, "failed to read a pipe: {}", e),
            PollContextAdd(e) => write!(f, "failed to listen to FD on poll context: {}", e),
            DmabufSync(e) => write!(f, "failed to synchronize DMABuf access: {}", e),
            WriteResponse(e) => write!(f, "failed to write response: {}", e),
        }
    }
}

impl std::error::Error for WlError {}

type WlResult<T> = result::Result<T, WlError>;

impl From<GuestMemoryError> for WlError {
    fn from(e: GuestMemoryError) -> WlError {
        WlError::GuestMemory(e)
    }
}

impl From<VolatileMemoryError> for WlError {
    fn from(e: VolatileMemoryError) -> WlError {
        WlError::VolatileMemory(e)
    }
}

#[derive(Clone)]
struct VmRequester {
    inner: Rc<RefCell<VmMemoryControlRequestSocket>>,
}

impl VmRequester {
    fn new(vm_socket: VmMemoryControlRequestSocket) -> VmRequester {
        VmRequester {
            inner: Rc::new(RefCell::new(vm_socket)),
        }
    }

    fn request(&self, request: VmMemoryRequest) -> WlResult<VmMemoryResponse> {
        let mut inner = self.inner.borrow_mut();
        let vm_socket = &mut *inner;
        vm_socket.send(&request).map_err(WlError::VmControl)?;
        vm_socket.recv().map_err(WlError::VmControl)
    }
}

#[repr(C)]
#[derive(Copy, Clone, Default)]
struct CtrlHeader {
    type_: Le32,
    flags: Le32,
}

#[repr(C)]
#[derive(Copy, Clone, Default)]
struct CtrlVfdNew {
    hdr: CtrlHeader,
    id: Le32,
    flags: Le32,
    pfn: Le64,
    size: Le32,
}

unsafe impl DataInit for CtrlVfdNew {}

#[repr(C)]
#[derive(Copy, Clone, Default)]
#[cfg(feature = "wl-dmabuf")]
struct CtrlVfdNewDmabuf {
    hdr: CtrlHeader,
    id: Le32,
    flags: Le32,
    pfn: Le64,
    size: Le32,
    width: Le32,
    height: Le32,
    format: Le32,
    stride0: Le32,
    stride1: Le32,
    stride2: Le32,
    offset0: Le32,
    offset1: Le32,
    offset2: Le32,
}

#[cfg(feature = "wl-dmabuf")]
unsafe impl DataInit for CtrlVfdNewDmabuf {}

#[repr(C)]
#[derive(Copy, Clone, Default)]
#[cfg(feature = "wl-dmabuf")]
struct CtrlVfdDmabufSync {
    hdr: CtrlHeader,
    id: Le32,
    flags: Le32,
}

#[cfg(feature = "wl-dmabuf")]
unsafe impl DataInit for CtrlVfdDmabufSync {}

#[repr(C)]
#[derive(Copy, Clone)]
struct CtrlVfdRecv {
    hdr: CtrlHeader,
    id: Le32,
    vfd_count: Le32,
}

unsafe impl DataInit for CtrlVfdRecv {}

#[repr(C)]
#[derive(Copy, Clone, Default)]
struct CtrlVfd {
    hdr: CtrlHeader,
    id: Le32,
}

unsafe impl DataInit for CtrlVfd {}

#[repr(C)]
#[derive(Copy, Clone, Default)]
struct CtrlVfdSend {
    hdr: CtrlHeader,
    id: Le32,
    vfd_count: Le32,
    // Remainder is an array of vfd_count IDs followed by data.
}

unsafe impl DataInit for CtrlVfdSend {}

#[repr(C)]
#[derive(Copy, Clone, Default)]
struct CtrlVfdSendVfd {
    kind: Le32,
    id: Le32,
}

unsafe impl DataInit for CtrlVfdSendVfd {}

#[derive(Debug)]
#[allow(dead_code)]
enum WlResp<'a> {
    Ok,
    VfdNew {
        id: u32,
        flags: u32,
        pfn: u64,
        size: u32,
        // The VfdNew variant can be either a response or a command depending on this `resp`. This
        // is important for the `get_code` method.
        resp: bool,
    },
    #[cfg(feature = "wl-dmabuf")]
    VfdNewDmabuf {
        id: u32,
        flags: u32,
        pfn: u64,
        size: u32,
        desc: GpuMemoryDesc,
    },
    VfdRecv {
        id: u32,
        data: &'a [u8],
        vfds: &'a [u32],
    },
    VfdHup {
        id: u32,
    },
    Err(Box<dyn StdError>),
    OutOfMemory,
    InvalidId,
    InvalidType,
    InvalidFlags,
    InvalidCommand,
}

impl<'a> WlResp<'a> {
    fn get_code(&self) -> u32 {
        match *self {
            WlResp::Ok => VIRTIO_WL_RESP_OK,
            WlResp::VfdNew { resp, .. } => {
                if resp {
                    VIRTIO_WL_RESP_VFD_NEW
                } else {
                    VIRTIO_WL_CMD_VFD_NEW
                }
            }
            #[cfg(feature = "wl-dmabuf")]
            WlResp::VfdNewDmabuf { .. } => VIRTIO_WL_RESP_VFD_NEW_DMABUF,
            WlResp::VfdRecv { .. } => VIRTIO_WL_CMD_VFD_RECV,
            WlResp::VfdHup { .. } => VIRTIO_WL_CMD_VFD_HUP,
            WlResp::Err(_) => VIRTIO_WL_RESP_ERR,
            WlResp::OutOfMemory => VIRTIO_WL_RESP_OUT_OF_MEMORY,
            WlResp::InvalidId => VIRTIO_WL_RESP_INVALID_ID,
            WlResp::InvalidType => VIRTIO_WL_RESP_INVALID_TYPE,
            WlResp::InvalidFlags => VIRTIO_WL_RESP_INVALID_FLAGS,
            WlResp::InvalidCommand => VIRTIO_WL_RESP_INVALID_CMD,
        }
    }
}

#[derive(Default)]
struct WlVfd {
    socket: Option<UnixStream>,
    guest_shared_memory: Option<(u64 /* size */, File)>,
    remote_pipe: Option<File>,
    local_pipe: Option<(u32 /* flags */, File)>,
    slot: Option<(u32 /* slot */, u64 /* pfn */, VmRequester)>,
    #[cfg(feature = "wl-dmabuf")]
    is_dmabuf: bool,
}

impl fmt::Debug for WlVfd {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "WlVfd {{")?;
        if let Some(s) = &self.socket {
            write!(f, " socket: {}", s.as_raw_fd())?;
        }
        if let Some((slot, pfn, _)) = &self.slot {
            write!(f, " slot: {} pfn: {}", slot, pfn)?;
        }
        if let Some(s) = &self.remote_pipe {
            write!(f, " remote: {}", s.as_raw_fd())?;
        }
        if let Some((_, s)) = &self.local_pipe {
            write!(f, " local: {}", s.as_raw_fd())?;
        }
        write!(f, " }}")
    }
}

impl WlVfd {
    fn connect<P: AsRef<Path>>(path: P) -> WlResult<WlVfd> {
        let socket = UnixStream::connect(path).map_err(WlError::SocketConnect)?;
        socket
            .set_nonblocking(true)
            .map_err(WlError::SocketNonBlock)?;
        let mut vfd = WlVfd::default();
        vfd.socket = Some(socket);
        Ok(vfd)
    }

    fn allocate(vm: VmRequester, size: u64) -> WlResult<WlVfd> {
        let size_page_aligned = round_up_to_page_size(size as usize) as u64;
        let mut vfd_shm = SharedMemory::named("virtwl_alloc").map_err(WlError::NewAlloc)?;
        vfd_shm
            .set_size(size_page_aligned)
            .map_err(WlError::AllocSetSize)?;
        let register_response = vm.request(VmMemoryRequest::RegisterMemory(
            MaybeOwnedFd::Borrowed(vfd_shm.as_raw_fd()),
            vfd_shm.size() as usize,
        ))?;
        match register_response {
            VmMemoryResponse::RegisterMemory { pfn, slot } => {
                let mut vfd = WlVfd::default();
                vfd.guest_shared_memory = Some((vfd_shm.size(), vfd_shm.into()));
                vfd.slot = Some((slot, pfn, vm));
                Ok(vfd)
            }
            _ => Err(WlError::VmBadResponse),
        }
    }

    #[cfg(feature = "wl-dmabuf")]
    fn dmabuf(
        vm: VmRequester,
        width: u32,
        height: u32,
        format: u32,
    ) -> WlResult<(WlVfd, GpuMemoryDesc)> {
        let allocate_and_register_gpu_memory_response =
            vm.request(VmMemoryRequest::AllocateAndRegisterGpuMemory {
                width,
                height,
                format,
            })?;
        match allocate_and_register_gpu_memory_response {
            VmMemoryResponse::AllocateAndRegisterGpuMemory {
                fd,
                pfn,
                slot,
                desc,
            } => {
                let mut vfd = WlVfd::default();
                // Duplicate FD for shared memory instance.
                let raw_fd = unsafe { File::from_raw_fd(dup(fd.as_raw_fd())) };
                let vfd_shm = SharedMemory::from_raw_fd(raw_fd).map_err(WlError::NewAlloc)?;
                vfd.guest_shared_memory = Some((vfd_shm.size(), vfd_shm.into()));
                vfd.slot = Some((slot, pfn, vm));
                vfd.is_dmabuf = true;
                Ok((vfd, desc))
            }
            _ => Err(WlError::VmBadResponse),
        }
    }

    #[cfg(feature = "wl-dmabuf")]
    fn dmabuf_sync(&self, flags: u32) -> WlResult<()> {
        if !self.is_dmabuf {
            return Err(WlError::DmabufSync(io::Error::from_raw_os_error(EINVAL)));
        }

        match &self.guest_shared_memory {
            Some((_, fd)) => {
                let sync = dma_buf_sync {
                    flags: flags as u64,
                };
                // Safe as fd is a valid dmabuf and incorrect flags will return an error.
                if unsafe { ioctl_with_ref(fd, DMA_BUF_IOCTL_SYNC(), &sync) } < 0 {
                    Err(WlError::DmabufSync(io::Error::last_os_error()))
                } else {
                    Ok(())
                }
            }
            None => Err(WlError::DmabufSync(io::Error::from_raw_os_error(EBADF))),
        }
    }

    fn pipe_remote_read_local_write() -> WlResult<WlVfd> {
        let (read_pipe, write_pipe) = pipe(true).map_err(WlError::NewPipe)?;
        let mut vfd = WlVfd::default();
        vfd.remote_pipe = Some(read_pipe);
        vfd.local_pipe = Some((VIRTIO_WL_VFD_WRITE, write_pipe));
        Ok(vfd)
    }

    fn pipe_remote_write_local_read() -> WlResult<WlVfd> {
        let (read_pipe, write_pipe) = pipe(true).map_err(WlError::NewPipe)?;
        let mut vfd = WlVfd::default();
        vfd.remote_pipe = Some(write_pipe);
        vfd.local_pipe = Some((VIRTIO_WL_VFD_READ, read_pipe));
        Ok(vfd)
    }

    fn from_file(vm: VmRequester, mut fd: File) -> WlResult<WlVfd> {
        // We need to determine if the given file is more like shared memory or a pipe/socket. A
        // quick and easy check is to seek to the end of the file. If it works we assume it's not a
        // pipe/socket because those have no end. We can even use that seek location as an indicator
        // for how big the shared memory chunk to map into guest memory is. If seeking to the end
        // fails, we assume it's a socket or pipe with read/write semantics.
        match fd.seek(SeekFrom::End(0)) {
            Ok(fd_size) => {
                let size = round_up_to_page_size(fd_size as usize) as u64;
                let register_response = vm.request(VmMemoryRequest::RegisterMemory(
                    MaybeOwnedFd::Borrowed(fd.as_raw_fd()),
                    size as usize,
                ))?;

                match register_response {
                    VmMemoryResponse::RegisterMemory { pfn, slot } => {
                        let mut vfd = WlVfd::default();
                        vfd.guest_shared_memory = Some((size, fd));
                        vfd.slot = Some((slot, pfn, vm));
                        Ok(vfd)
                    }
                    _ => Err(WlError::VmBadResponse),
                }
            }
            _ => {
                let flags = match FileFlags::from_file(&fd) {
                    Ok(FileFlags::Read) => VIRTIO_WL_VFD_READ,
                    Ok(FileFlags::Write) => VIRTIO_WL_VFD_WRITE,
                    Ok(FileFlags::ReadWrite) => VIRTIO_WL_VFD_READ | VIRTIO_WL_VFD_WRITE,
                    _ => 0,
                };
                let mut vfd = WlVfd::default();
                vfd.local_pipe = Some((flags, fd));
                Ok(vfd)
            }
        }
    }

    fn flags(&self, use_transition_flags: bool) -> u32 {
        let mut flags = 0;
        if use_transition_flags {
            if self.socket.is_some() {
                flags |= VIRTIO_WL_VFD_WRITE | VIRTIO_WL_VFD_READ;
            }
            if let Some((f, _)) = self.local_pipe {
                flags |= f;
            }
        } else {
            if self.socket.is_some() {
                flags |= VIRTIO_WL_VFD_CONTROL;
            }
            if self.slot.is_some() {
                flags |= VIRTIO_WL_VFD_WRITE | VIRTIO_WL_VFD_MAP
            }
        }
        flags
    }

    // Page frame number in the guest this VFD was mapped at.
    fn pfn(&self) -> Option<u64> {
        self.slot.as_ref().map(|s| s.1)
    }

    // Size in bytes of the shared memory VFD.
    fn size(&self) -> Option<u64> {
        self.guest_shared_memory.as_ref().map(|&(size, _)| size)
    }

    // The FD that gets sent if this VFD is sent over a socket.
    fn send_fd(&self) -> Option<RawFd> {
        self.guest_shared_memory
            .as_ref()
            .map(|(_, fd)| fd.as_raw_fd())
            .or(self.socket.as_ref().map(|s| s.as_raw_fd()))
            .or(self.remote_pipe.as_ref().map(|p| p.as_raw_fd()))
    }

    // The FD that is used for polling for events on this VFD.
    fn poll_fd(&self) -> Option<&dyn AsRawFd> {
        self.socket
            .as_ref()
            .map(|s| s as &dyn AsRawFd)
            .or(self.local_pipe.as_ref().map(|(_, p)| p as &dyn AsRawFd))
    }

    // Sends data/files from the guest to the host over this VFD.
    fn send(&mut self, fds: &[RawFd], data: &mut Reader) -> WlResult<WlResp> {
        if let Some(socket) = &self.socket {
            socket
                .send_with_fds(
                    data.get_iovec(usize::max_value())
                        .map_err(WlError::ParseDesc)?,
                    fds,
                )
                .map_err(WlError::SendVfd)?;
            Ok(WlResp::Ok)
        } else if let Some((_, local_pipe)) = &mut self.local_pipe {
            // Impossible to send fds over a simple pipe.
            if !fds.is_empty() {
                return Ok(WlResp::InvalidType);
            }
            data.read_to(local_pipe, usize::max_value())
                .map_err(WlError::WritePipe)?;
            Ok(WlResp::Ok)
        } else {
            Ok(WlResp::InvalidType)
        }
    }

    // Receives data/files from the host for this VFD and queues it for the guest.
    fn recv(&mut self, in_file_queue: &mut Vec<File>) -> WlResult<Vec<u8>> {
        if let Some(socket) = self.socket.take() {
            let mut buf = vec![0; IN_BUFFER_LEN];
            let mut fd_buf = [0; VIRTWL_SEND_MAX_ALLOCS];
            // If any errors happen, the socket will get dropped, preventing more reading.
            let (len, file_count) = socket
                .recv_with_fds(&mut buf[..], &mut fd_buf)
                .map_err(WlError::RecvVfd)?;
            // If any data gets read, the put the socket back for future recv operations.
            if len != 0 || file_count != 0 {
                buf.truncate(len);
                buf.shrink_to_fit();
                self.socket = Some(socket);
                // Safe because the first file_counts fds from recv_with_fds are owned by us and
                // valid.
                in_file_queue.extend(
                    fd_buf[..file_count]
                        .iter()
                        .map(|&fd| unsafe { File::from_raw_fd(fd) }),
                );
                return Ok(buf);
            }
            Ok(Vec::new())
        } else if let Some((flags, mut local_pipe)) = self.local_pipe.take() {
            let mut buf = Vec::new();
            buf.resize(IN_BUFFER_LEN, 0);
            let len = local_pipe.read(&mut buf[..]).map_err(WlError::ReadPipe)?;
            if len != 0 {
                buf.truncate(len);
                buf.shrink_to_fit();
                self.local_pipe = Some((flags, local_pipe));
                return Ok(buf);
            }
            Ok(Vec::new())
        } else {
            Ok(Vec::new())
        }
    }

    // Called after this VFD is sent over a socket to ensure the local end of the VFD receives hang
    // up events.
    fn close_remote(&mut self) {
        self.remote_pipe = None;
    }

    fn close(&mut self) -> WlResult<()> {
        if let Some((slot, _, vm)) = self.slot.take() {
            vm.request(VmMemoryRequest::UnregisterMemory(slot))?;
        }
        self.socket = None;
        self.remote_pipe = None;
        self.local_pipe = None;
        Ok(())
    }
}

impl Drop for WlVfd {
    fn drop(&mut self) {
        let _ = self.close();
    }
}

#[derive(Debug)]
enum WlRecv {
    Vfd { id: u32 },
    Data { buf: Vec<u8> },
    Hup,
}

struct WlState {
    wayland_path: PathBuf,
    vm: VmRequester,
    resource_bridge: Option<ResourceRequestSocket>,
    use_transition_flags: bool,
    poll_ctx: PollContext<u32>,
    vfds: Map<u32, WlVfd>,
    next_vfd_id: u32,
    in_file_queue: Vec<File>,
    in_queue: VecDeque<(u32 /* vfd_id */, WlRecv)>,
    current_recv_vfd: Option<u32>,
    recv_vfds: Vec<u32>,
}

impl WlState {
    fn new(
        wayland_path: PathBuf,
        vm_socket: VmMemoryControlRequestSocket,
        use_transition_flags: bool,
        resource_bridge: Option<ResourceRequestSocket>,
    ) -> WlState {
        WlState {
            wayland_path,
            vm: VmRequester::new(vm_socket),
            resource_bridge,
            poll_ctx: PollContext::new().expect("failed to create PollContext"),
            use_transition_flags,
            vfds: Map::new(),
            next_vfd_id: NEXT_VFD_ID_BASE,
            in_file_queue: Vec::new(),
            in_queue: VecDeque::new(),
            current_recv_vfd: None,
            recv_vfds: Vec::new(),
        }
    }

    fn new_pipe(&mut self, id: u32, flags: u32) -> WlResult<WlResp> {
        if id & VFD_ID_HOST_MASK != 0 {
            return Ok(WlResp::InvalidId);
        }

        if flags & !(VIRTIO_WL_VFD_WRITE | VIRTIO_WL_VFD_READ) != 0 {
            return Ok(WlResp::InvalidFlags);
        }

        if flags & VIRTIO_WL_VFD_WRITE != 0 && flags & VIRTIO_WL_VFD_READ != 0 {
            return Ok(WlResp::InvalidFlags);
        }

        match self.vfds.entry(id) {
            Entry::Vacant(entry) => {
                let vfd = if flags & VIRTIO_WL_VFD_WRITE != 0 {
                    WlVfd::pipe_remote_read_local_write()?
                } else if flags & VIRTIO_WL_VFD_READ != 0 {
                    WlVfd::pipe_remote_write_local_read()?
                } else {
                    return Ok(WlResp::InvalidFlags);
                };
                self.poll_ctx
                    .add(vfd.poll_fd().unwrap(), id)
                    .map_err(WlError::PollContextAdd)?;
                let resp = WlResp::VfdNew {
                    id,
                    flags: 0,
                    pfn: 0,
                    size: 0,
                    resp: true,
                };
                entry.insert(vfd);
                Ok(resp)
            }
            Entry::Occupied(_) => Ok(WlResp::InvalidId),
        }
    }

    fn new_alloc(&mut self, id: u32, flags: u32, size: u32) -> WlResult<WlResp> {
        if id & VFD_ID_HOST_MASK != 0 {
            return Ok(WlResp::InvalidId);
        }

        if self.use_transition_flags {
            if flags != 0 {
                return Ok(WlResp::InvalidFlags);
            }
        } else if flags & !(VIRTIO_WL_VFD_WRITE | VIRTIO_WL_VFD_MAP) != 0 {
            return Ok(WlResp::Err(Box::from("invalid flags")));
        }

        match self.vfds.entry(id) {
            Entry::Vacant(entry) => {
                let vfd = WlVfd::allocate(self.vm.clone(), size as u64)?;
                let resp = WlResp::VfdNew {
                    id,
                    flags,
                    pfn: vfd.pfn().unwrap_or_default(),
                    size: vfd.size().unwrap_or_default() as u32,
                    resp: true,
                };
                entry.insert(vfd);
                Ok(resp)
            }
            Entry::Occupied(_) => Ok(WlResp::InvalidId),
        }
    }

    #[cfg(feature = "wl-dmabuf")]
    fn new_dmabuf(&mut self, id: u32, width: u32, height: u32, format: u32) -> WlResult<WlResp> {
        if id & VFD_ID_HOST_MASK != 0 {
            return Ok(WlResp::InvalidId);
        }

        match self.vfds.entry(id) {
            Entry::Vacant(entry) => {
                let (vfd, desc) = WlVfd::dmabuf(self.vm.clone(), width, height, format)?;
                let resp = WlResp::VfdNewDmabuf {
                    id,
                    flags: 0,
                    pfn: vfd.pfn().unwrap_or_default(),
                    size: vfd.size().unwrap_or_default() as u32,
                    desc,
                };
                entry.insert(vfd);
                Ok(resp)
            }
            Entry::Occupied(_) => Ok(WlResp::InvalidId),
        }
    }

    #[cfg(feature = "wl-dmabuf")]
    fn dmabuf_sync(&mut self, vfd_id: u32, flags: u32) -> WlResult<WlResp> {
        if flags & !(VIRTIO_WL_VFD_DMABUF_SYNC_VALID_FLAG_MASK) != 0 {
            return Ok(WlResp::InvalidFlags);
        }

        match self.vfds.get_mut(&vfd_id) {
            Some(vfd) => {
                vfd.dmabuf_sync(flags)?;
                Ok(WlResp::Ok)
            }
            None => Ok(WlResp::InvalidId),
        }
    }

    fn new_context(&mut self, id: u32) -> WlResult<WlResp> {
        if id & VFD_ID_HOST_MASK != 0 {
            return Ok(WlResp::InvalidId);
        }

        let flags = if self.use_transition_flags {
            VIRTIO_WL_VFD_WRITE | VIRTIO_WL_VFD_READ
        } else {
            VIRTIO_WL_VFD_CONTROL
        };

        match self.vfds.entry(id) {
            Entry::Vacant(entry) => {
                let vfd = entry.insert(WlVfd::connect(&self.wayland_path)?);
                self.poll_ctx
                    .add(vfd.poll_fd().unwrap(), id)
                    .map_err(WlError::PollContextAdd)?;
                Ok(WlResp::VfdNew {
                    id,
                    flags,
                    pfn: 0,
                    size: 0,
                    resp: true,
                })
            }
            Entry::Occupied(_) => Ok(WlResp::InvalidId),
        }
    }

    fn process_poll_context(&mut self) {
        let events = match self.poll_ctx.wait_timeout(Duration::from_secs(0)) {
            Ok(v) => v.to_owned(),
            Err(e) => {
                error!("failed polling for vfd evens: {}", e);
                return;
            }
        };

        for event in events.as_ref().iter_readable() {
            if let Err(e) = self.recv(event.token()) {
                error!("failed to recv from vfd: {}", e)
            }
        }

        for event in events.as_ref().iter_hungup() {
            if !event.readable() {
                let vfd_id = event.token();
                if let Some(fd) = self.vfds.get(&vfd_id).and_then(|vfd| vfd.poll_fd()) {
                    if let Err(e) = self.poll_ctx.delete(fd) {
                        warn!("failed to remove hungup vfd from poll context: {}", e);
                    }
                }
                self.in_queue.push_back((vfd_id, WlRecv::Hup));
            }
        }
    }

    fn close(&mut self, vfd_id: u32) -> WlResult<WlResp> {
        let mut to_delete = Set::new();
        for (dest_vfd_id, q) in &self.in_queue {
            if *dest_vfd_id == vfd_id {
                if let WlRecv::Vfd { id } = q {
                    to_delete.insert(*id);
                }
            }
        }
        for vfd_id in to_delete {
            // Sorry sub-error, we can't have cascading errors leaving us in an inconsistent state.
            let _ = self.close(vfd_id);
        }
        match self.vfds.remove(&vfd_id) {
            Some(mut vfd) => {
                self.in_queue.retain(|&(id, _)| id != vfd_id);
                vfd.close()?;
                Ok(WlResp::Ok)
            }
            None => Ok(WlResp::InvalidId),
        }
    }

    fn send(
        &mut self,
        vfd_id: u32,
        vfd_count: usize,
        foreign_id: bool,
        reader: &mut Reader,
    ) -> WlResult<WlResp> {
        // First stage gathers and normalizes all id information from guest memory.
        let mut send_vfd_ids = [CtrlVfdSendVfd::default(); VIRTWL_SEND_MAX_ALLOCS];
        for vfd_id in send_vfd_ids.iter_mut().take(vfd_count) {
            *vfd_id = if foreign_id {
                reader.read_obj().map_err(WlError::ParseDesc)?
            } else {
                CtrlVfdSendVfd {
                    kind: Le32::from(VIRTIO_WL_CTRL_VFD_SEND_KIND_LOCAL),
                    id: reader.read_obj().map_err(WlError::ParseDesc)?,
                }
            }
        }

        // Next stage collects corresponding file descriptors for each id.
        let mut fds = [0; VIRTWL_SEND_MAX_ALLOCS];
        #[cfg(feature = "gpu")]
        let mut bridged_files = Vec::new();
        for (&send_vfd_id, fd) in send_vfd_ids[..vfd_count].iter().zip(fds.iter_mut()) {
            let id = send_vfd_id.id.to_native();
            match send_vfd_id.kind.to_native() {
                VIRTIO_WL_CTRL_VFD_SEND_KIND_LOCAL => match self.vfds.get(&id) {
                    Some(vfd) => match vfd.send_fd() {
                        Some(vfd_fd) => *fd = vfd_fd,
                        None => return Ok(WlResp::InvalidType),
                    },
                    None => {
                        warn!("attempt to send non-existant vfd 0x{:08x}", id);
                        return Ok(WlResp::InvalidId);
                    }
                },
                #[cfg(feature = "gpu")]
                VIRTIO_WL_CTRL_VFD_SEND_KIND_VIRTGPU if self.resource_bridge.is_some() => {
                    if let Err(e) = self
                        .resource_bridge
                        .as_ref()
                        .unwrap()
                        .send(&ResourceRequest::GetResource { id })
                    {
                        error!("error sending resource bridge request: {}", e);
                        return Ok(WlResp::InvalidId);
                    }
                    match self.resource_bridge.as_ref().unwrap().recv() {
                        Ok(ResourceResponse::Resource(bridged_file)) => {
                            *fd = bridged_file.as_raw_fd();
                            bridged_files.push(bridged_file);
                        }
                        Ok(ResourceResponse::Invalid) => {
                            warn!("attempt to send non-existant gpu resource {}", id);
                            return Ok(WlResp::InvalidId);
                        }
                        Err(e) => {
                            error!("error receiving resource bridge response: {}", e);
                            // If there was an error with the resource bridge, it can no longer be
                            // trusted to continue to function.
                            self.resource_bridge = None;
                            return Ok(WlResp::InvalidId);
                        }
                    }
                }
                VIRTIO_WL_CTRL_VFD_SEND_KIND_VIRTGPU => {
                    let _ = self.resource_bridge.as_ref();
                    warn!("attempt to send foreign resource kind but feature is disabled");
                }
                kind => {
                    warn!(
                        "attempt to send unknown foreign resource kind: {} id: {:08x}",
                        kind, id
                    );
                    return Ok(WlResp::InvalidId);
                }
            }
        }

        // Final stage sends file descriptors and data to the target vfd's socket.
        match self.vfds.get_mut(&vfd_id) {
            Some(vfd) => match vfd.send(&fds[..vfd_count], reader)? {
                WlResp::Ok => {}
                _ => return Ok(WlResp::InvalidType),
            },
            None => return Ok(WlResp::InvalidId),
        }
        // The vfds with remote FDs need to be closed so that the local side can receive
        // hangup events.
        for &send_vfd_id in &send_vfd_ids[..vfd_count] {
            if send_vfd_id.kind == VIRTIO_WL_CTRL_VFD_SEND_KIND_LOCAL {
                if let Some(vfd) = self.vfds.get_mut(&send_vfd_id.id.into()) {
                    vfd.close_remote();
                }
            }
        }
        Ok(WlResp::Ok)
    }

    fn recv(&mut self, vfd_id: u32) -> WlResult<()> {
        let buf = match self.vfds.get_mut(&vfd_id) {
            Some(vfd) => vfd.recv(&mut self.in_file_queue)?,
            None => return Ok(()),
        };
        if self.in_file_queue.is_empty() && buf.is_empty() {
            self.in_queue.push_back((vfd_id, WlRecv::Hup));
            return Ok(());
        }
        for file in self.in_file_queue.drain(..) {
            let vfd = WlVfd::from_file(self.vm.clone(), file)?;
            if let Some(poll_fd) = vfd.poll_fd() {
                self.poll_ctx
                    .add(poll_fd, self.next_vfd_id)
                    .map_err(WlError::PollContextAdd)?;
            }
            self.vfds.insert(self.next_vfd_id, vfd);
            self.in_queue.push_back((
                vfd_id,
                WlRecv::Vfd {
                    id: self.next_vfd_id,
                },
            ));
            self.next_vfd_id += 1;
        }
        self.in_queue.push_back((vfd_id, WlRecv::Data { buf }));

        Ok(())
    }

    fn execute(&mut self, reader: &mut Reader) -> WlResult<WlResp> {
        let type_ = {
            let mut type_reader = reader.clone();
            type_reader.read_obj::<Le32>().map_err(WlError::ParseDesc)?
        };
        match type_.into() {
            VIRTIO_WL_CMD_VFD_NEW => {
                let ctrl = reader
                    .read_obj::<CtrlVfdNew>()
                    .map_err(WlError::ParseDesc)?;
                self.new_alloc(ctrl.id.into(), ctrl.flags.into(), ctrl.size.into())
            }
            VIRTIO_WL_CMD_VFD_CLOSE => {
                let ctrl = reader.read_obj::<CtrlVfd>().map_err(WlError::ParseDesc)?;
                self.close(ctrl.id.into())
            }
            VIRTIO_WL_CMD_VFD_SEND => {
                let ctrl = reader
                    .read_obj::<CtrlVfdSend>()
                    .map_err(WlError::ParseDesc)?;
                let foreign_id = false;
                self.send(
                    ctrl.id.into(),
                    ctrl.vfd_count.to_native() as usize,
                    foreign_id,
                    reader,
                )
            }
            #[cfg(feature = "gpu")]
            VIRTIO_WL_CMD_VFD_SEND_FOREIGN_ID => {
                let ctrl = reader
                    .read_obj::<CtrlVfdSend>()
                    .map_err(WlError::ParseDesc)?;
                let foreign_id = true;
                self.send(
                    ctrl.id.into(),
                    ctrl.vfd_count.to_native() as usize,
                    foreign_id,
                    reader,
                )
            }
            VIRTIO_WL_CMD_VFD_NEW_CTX => {
                let ctrl = reader.read_obj::<CtrlVfd>().map_err(WlError::ParseDesc)?;
                self.new_context(ctrl.id.into())
            }
            VIRTIO_WL_CMD_VFD_NEW_PIPE => {
                let ctrl = reader
                    .read_obj::<CtrlVfdNew>()
                    .map_err(WlError::ParseDesc)?;
                self.new_pipe(ctrl.id.into(), ctrl.flags.into())
            }
            #[cfg(feature = "wl-dmabuf")]
            VIRTIO_WL_CMD_VFD_NEW_DMABUF => {
                let ctrl = reader
                    .read_obj::<CtrlVfdNewDmabuf>()
                    .map_err(WlError::ParseDesc)?;
                self.new_dmabuf(
                    ctrl.id.into(),
                    ctrl.width.into(),
                    ctrl.height.into(),
                    ctrl.format.into(),
                )
            }
            #[cfg(feature = "wl-dmabuf")]
            VIRTIO_WL_CMD_VFD_DMABUF_SYNC => {
                let ctrl = reader
                    .read_obj::<CtrlVfdDmabufSync>()
                    .map_err(WlError::ParseDesc)?;
                self.dmabuf_sync(ctrl.id.into(), ctrl.flags.into())
            }
            op_type => {
                warn!("unexpected command {}", op_type);
                Ok(WlResp::InvalidCommand)
            }
        }
    }

    fn next_recv(&self) -> Option<WlResp> {
        if let Some(q) = self.in_queue.front() {
            match *q {
                (vfd_id, WlRecv::Vfd { id }) => {
                    if self.current_recv_vfd.is_none() || self.current_recv_vfd == Some(vfd_id) {
                        match self.vfds.get(&id) {
                            Some(vfd) => Some(WlResp::VfdNew {
                                id,
                                flags: vfd.flags(self.use_transition_flags),
                                pfn: vfd.pfn().unwrap_or_default(),
                                size: vfd.size().unwrap_or_default() as u32,
                                resp: false,
                            }),
                            _ => Some(WlResp::VfdNew {
                                id,
                                flags: 0,
                                pfn: 0,
                                size: 0,
                                resp: false,
                            }),
                        }
                    } else {
                        Some(WlResp::VfdRecv {
                            id: self.current_recv_vfd.unwrap(),
                            data: &[],
                            vfds: &self.recv_vfds[..],
                        })
                    }
                }
                (vfd_id, WlRecv::Data { ref buf }) => {
                    if self.current_recv_vfd.is_none() || self.current_recv_vfd == Some(vfd_id) {
                        Some(WlResp::VfdRecv {
                            id: vfd_id,
                            data: &buf[..],
                            vfds: &self.recv_vfds[..],
                        })
                    } else {
                        Some(WlResp::VfdRecv {
                            id: self.current_recv_vfd.unwrap(),
                            data: &[],
                            vfds: &self.recv_vfds[..],
                        })
                    }
                }
                (vfd_id, WlRecv::Hup) => Some(WlResp::VfdHup { id: vfd_id }),
            }
        } else {
            None
        }
    }

    fn pop_recv(&mut self) {
        if let Some(q) = self.in_queue.front() {
            match *q {
                (vfd_id, WlRecv::Vfd { id }) => {
                    if self.current_recv_vfd.is_none() || self.current_recv_vfd == Some(vfd_id) {
                        self.recv_vfds.push(id);
                        self.current_recv_vfd = Some(vfd_id);
                    } else {
                        self.recv_vfds.clear();
                        self.current_recv_vfd = None;
                        return;
                    }
                }
                (vfd_id, WlRecv::Data { .. }) => {
                    self.recv_vfds.clear();
                    self.current_recv_vfd = None;
                    if !(self.current_recv_vfd.is_none() || self.current_recv_vfd == Some(vfd_id)) {
                        return;
                    }
                }
                (_, WlRecv::Hup) => {
                    self.recv_vfds.clear();
                    self.current_recv_vfd = None;
                }
            }
        }
        self.in_queue.pop_front();
    }
}

struct Worker {
    interrupt: Interrupt,
    mem: GuestMemory,
    in_queue: Queue,
    out_queue: Queue,
    state: WlState,
}

impl Worker {
    fn new(
        mem: GuestMemory,
        interrupt_evt: EventFd,
        interrupt_resample_evt: EventFd,
        interrupt_status: Arc<AtomicUsize>,
        msix_config: Option<Arc<Mutex<MsixConfig>>>,
        in_queue: Queue,
        out_queue: Queue,
        wayland_path: PathBuf,
        vm_socket: VmMemoryControlRequestSocket,
        use_transition_flags: bool,
        resource_bridge: Option<ResourceRequestSocket>,
    ) -> Worker {
        Worker {
            interrupt: Interrupt::new(
                interrupt_status,
                interrupt_evt,
                interrupt_resample_evt,
                msix_config,
            ),
            mem,
            in_queue,
            out_queue,
            state: WlState::new(
                wayland_path,
                vm_socket,
                use_transition_flags,
                resource_bridge,
            ),
        }
    }

    fn run(&mut self, mut queue_evts: Vec<EventFd>, kill_evt: EventFd) {
        let mut in_desc_chains: VecDeque<DescriptorChain> =
            VecDeque::with_capacity(QUEUE_SIZE as usize);
        let in_queue_evt = queue_evts.remove(0);
        let out_queue_evt = queue_evts.remove(0);
        #[derive(PollToken)]
        enum Token {
            InQueue,
            OutQueue,
            Kill,
            State,
            InterruptResample,
        }

        let poll_ctx: PollContext<Token> = match PollContext::build_with(&[
            (&in_queue_evt, Token::InQueue),
            (&out_queue_evt, Token::OutQueue),
            (&kill_evt, Token::Kill),
            (&self.state.poll_ctx, Token::State),
            (self.interrupt.get_resample_evt(), Token::InterruptResample),
        ]) {
            Ok(pc) => pc,
            Err(e) => {
                error!("failed creating PollContext: {}", e);
                return;
            }
        };

        'poll: loop {
            let mut signal_used_in = false;
            let mut signal_used_out = false;
            let events = match poll_ctx.wait() {
                Ok(v) => v,
                Err(e) => {
                    error!("failed polling for events: {}", e);
                    break;
                }
            };

            for event in &events {
                match event.token() {
                    Token::InQueue => {
                        let _ = in_queue_evt.read();
                        // Used to buffer descriptor indexes that are invalid for our uses.
                        let mut rejects = [0u16; QUEUE_SIZE as usize];
                        let mut rejects_len = 0;
                        let min_in_desc_len = (size_of::<CtrlVfdRecv>()
                            + size_of::<Le32>() * VIRTWL_SEND_MAX_ALLOCS)
                            as u32;
                        in_desc_chains.extend(self.in_queue.iter(&self.mem).filter_map(|d| {
                            if d.len >= min_in_desc_len && d.is_write_only() {
                                Some(d)
                            } else {
                                // Can not use queue.add_used directly because it's being borrowed
                                // for the iterator chain, so we buffer the descriptor index in
                                // rejects.
                                rejects[rejects_len] = d.index;
                                rejects_len += 1;
                                None
                            }
                        }));
                        for &reject in &rejects[..rejects_len] {
                            signal_used_in = true;
                            self.in_queue.add_used(&self.mem, reject, 0);
                        }
                    }
                    Token::OutQueue => {
                        let _ = out_queue_evt.read();
                        while let Some(desc) = self.out_queue.pop(&self.mem) {
                            let desc_index = desc.index;
                            match (
                                Reader::new(&self.mem, desc.clone()),
                                Writer::new(&self.mem, desc),
                            ) {
                                (Ok(mut reader), Ok(mut writer)) => {
                                    let resp = match self.state.execute(&mut reader) {
                                        Ok(r) => r,
                                        Err(e) => WlResp::Err(Box::new(e)),
                                    };

                                    match encode_resp(&mut writer, resp) {
                                        Ok(()) => {}
                                        Err(e) => {
                                            error!(
                                                "failed to encode response to descriptor chain: {}",
                                                e
                                            );
                                        }
                                    }

                                    self.out_queue.add_used(
                                        &self.mem,
                                        desc_index,
                                        writer.bytes_written() as u32,
                                    );
                                    signal_used_out = true;
                                }
                                (_, Err(e)) | (Err(e), _) => {
                                    error!("invalid descriptor: {}", e);
                                    self.out_queue.add_used(&self.mem, desc_index, 0);
                                    signal_used_out = true;
                                }
                            }
                        }
                    }
                    Token::Kill => break 'poll,
                    Token::State => self.state.process_poll_context(),
                    Token::InterruptResample => {
                        self.interrupt.interrupt_resample();
                    }
                }
            }

            // Because this loop should be retried after the in queue is usable or after one of the
            // VFDs was read, we do it after the poll event responses.
            while !in_desc_chains.is_empty() {
                let mut should_pop = false;
                if let Some(in_resp) = self.state.next_recv() {
                    // in_desc_chains is not empty (checked by loop condition) so unwrap is safe.
                    let desc = in_desc_chains.pop_front().unwrap();
                    let index = desc.index;
                    match Writer::new(&self.mem, desc) {
                        Ok(mut writer) => {
                            match encode_resp(&mut writer, in_resp) {
                                Ok(()) => {
                                    should_pop = true;
                                }
                                Err(e) => {
                                    error!("failed to encode response to descriptor chain: {}", e);
                                }
                            };
                            signal_used_in = true;
                            self.in_queue
                                .add_used(&self.mem, index, writer.bytes_written() as u32);
                        }
                        Err(e) => {
                            error!("invalid descriptor: {}", e);
                            self.in_queue.add_used(&self.mem, index, 0);
                            signal_used_in = true;
                        }
                    }
                } else {
                    break;
                }
                if should_pop {
                    self.state.pop_recv();
                }
            }

            if signal_used_in {
                self.interrupt.signal_used_queue(self.in_queue.vector);
            }

            if signal_used_out {
                self.interrupt.signal_used_queue(self.out_queue.vector);
            }
        }
    }
}

pub struct Wl {
    kill_evt: Option<EventFd>,
    worker_thread: Option<thread::JoinHandle<()>>,
    wayland_path: PathBuf,
    vm_socket: Option<VmMemoryControlRequestSocket>,
    resource_bridge: Option<ResourceRequestSocket>,
    use_transition_flags: bool,
}

impl Wl {
    pub fn new<P: AsRef<Path>>(
        wayland_path: P,
        vm_socket: VmMemoryControlRequestSocket,
        resource_bridge: Option<ResourceRequestSocket>,
    ) -> Result<Wl> {
        Ok(Wl {
            kill_evt: None,
            worker_thread: None,
            wayland_path: wayland_path.as_ref().to_owned(),
            vm_socket: Some(vm_socket),
            resource_bridge,
            use_transition_flags: false,
        })
    }
}

impl Drop for Wl {
    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);
        }

        if let Some(worker_thread) = self.worker_thread.take() {
            let _ = worker_thread.join();
        }
    }
}

impl VirtioDevice for Wl {
    fn keep_fds(&self) -> Vec<RawFd> {
        let mut keep_fds = Vec::new();

        if let Some(vm_socket) = &self.vm_socket {
            keep_fds.push(vm_socket.as_raw_fd());
        }
        if let Some(resource_bridge) = &self.resource_bridge {
            keep_fds.push(resource_bridge.as_raw_fd());
        }

        keep_fds
    }

    fn device_type(&self) -> u32 {
        TYPE_WL
    }

    fn queue_max_sizes(&self) -> &[u16] {
        QUEUE_SIZES
    }

    fn features(&self) -> u64 {
        1 << VIRTIO_WL_F_TRANS_FLAGS | 1 << VIRTIO_F_VERSION_1
    }

    fn ack_features(&mut self, value: u64) {
        if value & (1 << VIRTIO_WL_F_TRANS_FLAGS) != 0 {
            self.use_transition_flags = true;
        }
    }

    fn activate(
        &mut self,
        mem: GuestMemory,
        interrupt_evt: EventFd,
        interrupt_resample_evt: EventFd,
        msix_config: Option<Arc<Mutex<MsixConfig>>>,
        status: Arc<AtomicUsize>,
        mut queues: Vec<Queue>,
        queue_evts: Vec<EventFd>,
    ) {
        if queues.len() != QUEUE_SIZES.len() || queue_evts.len() != QUEUE_SIZES.len() {
            return;
        }

        let (self_kill_evt, kill_evt) = match EventFd::new().and_then(|e| Ok((e.try_clone()?, e))) {
            Ok(v) => v,
            Err(e) => {
                error!("failed creating kill EventFd pair: {}", e);
                return;
            }
        };
        self.kill_evt = Some(self_kill_evt);

        if let Some(vm_socket) = self.vm_socket.take() {
            let wayland_path = self.wayland_path.clone();
            let use_transition_flags = self.use_transition_flags;
            let resource_bridge = self.resource_bridge.take();
            let worker_result =
                thread::Builder::new()
                    .name("virtio_wl".to_string())
                    .spawn(move || {
                        Worker::new(
                            mem,
                            interrupt_evt,
                            interrupt_resample_evt,
                            status,
                            msix_config,
                            queues.remove(0),
                            queues.remove(0),
                            wayland_path,
                            vm_socket,
                            use_transition_flags,
                            resource_bridge,
                        )
                        .run(queue_evts, kill_evt);
                    });

            match worker_result {
                Err(e) => {
                    error!("failed to spawn virtio_wl worker: {}", e);
                    return;
                }
                Ok(join_handle) => {
                    self.worker_thread = Some(join_handle);
                }
            }
        }
    }
}