// 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 crate::transport::{VirtioTransport, NOTIFY_REG_OFFSET};
use crate::{
    Queue, VirtioDevice, VirtioInterrupt, VirtioInterruptType, DEVICE_ACKNOWLEDGE, DEVICE_DRIVER,
    DEVICE_DRIVER_OK, DEVICE_FAILED, DEVICE_FEATURES_OK, DEVICE_INIT,
    INTERRUPT_STATUS_CONFIG_CHANGED, INTERRUPT_STATUS_USED_RING,
};
use arc_swap::ArcSwap;
use byteorder::{ByteOrder, LittleEndian};
use devices::BusDevice;
use libc::EFD_NONBLOCK;
use std::result;
use std::sync::atomic::{AtomicUsize, Ordering};
use std::sync::{Arc, Mutex};
use vm_device::interrupt::InterruptSourceGroup;
use vm_device::{Migratable, MigratableError, Pausable, Snapshotable};
use vm_memory::{GuestAddress, GuestMemoryMmap};
use vmm_sys_util::{errno::Result, eventfd::EventFd};

const VENDOR_ID: u32 = 0;

const MMIO_MAGIC_VALUE: u32 = 0x7472_6976;
const MMIO_VERSION: u32 = 2;

pub struct VirtioInterruptIntx {
    interrupt_status: Arc<AtomicUsize>,
    interrupt: Arc<Box<dyn InterruptSourceGroup>>,
}

impl VirtioInterruptIntx {
    pub fn new(
        interrupt_status: Arc<AtomicUsize>,
        interrupt: Arc<Box<dyn InterruptSourceGroup>>,
    ) -> Self {
        VirtioInterruptIntx {
            interrupt_status,
            interrupt,
        }
    }
}

impl VirtioInterrupt for VirtioInterruptIntx {
    fn trigger(
        &self,
        int_type: &VirtioInterruptType,
        _queue: Option<&Queue>,
    ) -> std::result::Result<(), std::io::Error> {
        let status = match int_type {
            VirtioInterruptType::Config => INTERRUPT_STATUS_CONFIG_CHANGED,
            VirtioInterruptType::Queue => INTERRUPT_STATUS_USED_RING,
        };
        self.interrupt_status
            .fetch_or(status as usize, Ordering::SeqCst);

        self.interrupt.trigger(0)
    }
}

/// Implements the
/// [MMIO](http://docs.oasis-open.org/virtio/virtio/v1.0/cs04/virtio-v1.0-cs04.html#x1-1090002)
/// transport for virtio devices.
///
/// This requires 3 points of installation to work with a VM:
///
/// 1. Mmio reads and writes must be sent to this device at what is referred to here as MMIO base.
/// 1. `Mmio::queue_evts` must be installed at `virtio::NOTIFY_REG_OFFSET` offset from the MMIO
/// base. Each event in the array must be signaled if the index is written at that offset.
/// 1. `Mmio::interrupt_evt` must signal an interrupt that the guest driver is listening to when it
/// is written to.
///
/// Typically one page (4096 bytes) of MMIO address space is sufficient to handle this transport
/// and inner virtio device.
pub struct MmioDevice {
    device: Arc<Mutex<dyn VirtioDevice>>,
    device_activated: bool,

    features_select: u32,
    acked_features_select: u32,
    queue_select: u32,
    interrupt_status: Arc<AtomicUsize>,
    interrupt_cb: Option<Arc<dyn VirtioInterrupt>>,
    driver_status: u32,
    config_generation: u32,
    queues: Vec<Queue>,
    queue_evts: Vec<EventFd>,
    mem: Option<Arc<ArcSwap<GuestMemoryMmap>>>,
}

impl MmioDevice {
    /// Constructs a new MMIO transport for the given virtio device.
    pub fn new(
        mem: Arc<ArcSwap<GuestMemoryMmap>>,
        device: Arc<Mutex<dyn VirtioDevice>>,
    ) -> Result<MmioDevice> {
        let device_clone = device.clone();
        let locked_device = device_clone.lock().unwrap();
        let mut queue_evts = Vec::new();
        for _ in locked_device.queue_max_sizes().iter() {
            queue_evts.push(EventFd::new(EFD_NONBLOCK)?)
        }
        let queues = locked_device
            .queue_max_sizes()
            .iter()
            .map(|&s| Queue::new(s))
            .collect();
        Ok(MmioDevice {
            device,
            device_activated: false,
            features_select: 0,
            acked_features_select: 0,
            queue_select: 0,
            interrupt_status: Arc::new(AtomicUsize::new(0)),
            interrupt_cb: None,
            driver_status: DEVICE_INIT,
            config_generation: 0,
            queues,
            queue_evts,
            mem: Some(mem),
        })
    }

    /// Gets the list of queue events that must be triggered whenever the VM writes to
    /// `virtio::NOTIFY_REG_OFFSET` past the MMIO base. Each event must be triggered when the
    /// value being written equals the index of the event in this list.
    fn queue_evts(&self) -> &[EventFd] {
        self.queue_evts.as_slice()
    }

    fn is_driver_ready(&self) -> bool {
        let ready_bits = DEVICE_ACKNOWLEDGE | DEVICE_DRIVER | DEVICE_DRIVER_OK | DEVICE_FEATURES_OK;
        self.driver_status == ready_bits && self.driver_status & DEVICE_FAILED == 0
    }

    fn are_queues_valid(&self) -> bool {
        if let Some(mem) = self.mem.as_ref() {
            self.queues.iter().all(|q| q.is_valid(mem.load().as_ref()))
        } else {
            false
        }
    }

    fn with_queue<U, F>(&self, d: U, f: F) -> U
    where
        F: FnOnce(&Queue) -> U,
    {
        match self.queues.get(self.queue_select as usize) {
            Some(queue) => f(queue),
            None => d,
        }
    }

    fn with_queue_mut<F: FnOnce(&mut Queue)>(&mut self, f: F) -> bool {
        if let Some(queue) = self.queues.get_mut(self.queue_select as usize) {
            f(queue);
            true
        } else {
            false
        }
    }

    pub fn assign_interrupt(&mut self, interrupt: Arc<Box<dyn InterruptSourceGroup>>) {
        self.interrupt_cb = Some(Arc::new(VirtioInterruptIntx::new(
            self.interrupt_status.clone(),
            interrupt,
        )));
    }
}

impl VirtioTransport for MmioDevice {
    fn ioeventfds(&self, base_addr: u64) -> Vec<(&EventFd, u64)> {
        let notify_base = base_addr + u64::from(NOTIFY_REG_OFFSET);
        self.queue_evts()
            .iter()
            .map(|event| (event, notify_base))
            .collect()
    }
}

impl BusDevice for MmioDevice {
    fn read(&mut self, _base: u64, offset: u64, data: &mut [u8]) {
        match offset {
            0x00..=0xff if data.len() == 4 => {
                let v = match offset {
                    0x0 => MMIO_MAGIC_VALUE,
                    0x04 => MMIO_VERSION,
                    0x08 => self.device.lock().unwrap().device_type(),
                    0x0c => VENDOR_ID, // vendor id
                    0x10 => {
                        self.device.lock().unwrap().features(self.features_select)
                            | if self.features_select == 1 { 0x1 } else { 0x0 }
                    }
                    0x34 => self.with_queue(0, |q| u32::from(q.get_max_size())),
                    0x44 => self.with_queue(0, |q| q.ready as u32),
                    0x60 => self.interrupt_status.load(Ordering::SeqCst) as u32,
                    0x70 => self.driver_status,
                    0xfc => self.config_generation,
                    _ => {
                        warn!("unknown virtio mmio register read: 0x{:x}", offset);
                        return;
                    }
                };
                LittleEndian::write_u32(data, v);
            }
            0x100..=0xfff => self
                .device
                .lock()
                .unwrap()
                .read_config(offset - 0x100, data),
            _ => {
                warn!(
                    "invalid virtio mmio read: 0x{:x}:0x{:x}",
                    offset,
                    data.len()
                );
            }
        };
    }

    fn write(&mut self, _base: u64, offset: u64, data: &[u8]) {
        fn hi(v: &mut GuestAddress, x: u32) {
            *v = (*v & 0xffff_ffff) | (u64::from(x) << 32)
        }

        fn lo(v: &mut GuestAddress, x: u32) {
            *v = (*v & !0xffff_ffff) | u64::from(x)
        }

        let mut mut_q = false;
        match offset {
            0x00..=0xff if data.len() == 4 => {
                let v = LittleEndian::read_u32(data);
                match offset {
                    0x14 => self.features_select = v,
                    0x20 => self
                        .device
                        .lock()
                        .unwrap()
                        .ack_features(self.acked_features_select, v),
                    0x24 => self.acked_features_select = v,
                    0x30 => self.queue_select = v,
                    0x38 => mut_q = self.with_queue_mut(|q| q.size = v as u16),
                    0x44 => mut_q = self.with_queue_mut(|q| q.ready = v == 1),
                    0x64 => {
                        self.interrupt_status
                            .fetch_and(!(v as usize), Ordering::SeqCst);
                    }
                    0x70 => self.driver_status = v,
                    0x80 => mut_q = self.with_queue_mut(|q| lo(&mut q.desc_table, v)),
                    0x84 => mut_q = self.with_queue_mut(|q| hi(&mut q.desc_table, v)),
                    0x90 => mut_q = self.with_queue_mut(|q| lo(&mut q.avail_ring, v)),
                    0x94 => mut_q = self.with_queue_mut(|q| hi(&mut q.avail_ring, v)),
                    0xa0 => mut_q = self.with_queue_mut(|q| lo(&mut q.used_ring, v)),
                    0xa4 => mut_q = self.with_queue_mut(|q| hi(&mut q.used_ring, v)),
                    _ => {
                        warn!("unknown virtio mmio register write: 0x{:x}", offset);
                        return;
                    }
                }
            }
            0x100..=0xfff => {
                return self
                    .device
                    .lock()
                    .unwrap()
                    .write_config(offset - 0x100, data)
            }
            _ => {
                warn!(
                    "invalid virtio mmio write: 0x{:x}:0x{:x}",
                    offset,
                    data.len()
                );
                return;
            }
        }

        if self.device_activated && mut_q {
            warn!("virtio queue was changed after device was activated");
        }

        if !self.device_activated && self.is_driver_ready() && self.are_queues_valid() {
            if let Some(interrupt_cb) = self.interrupt_cb.take() {
                if self.mem.is_some() {
                    let mem = self.mem.as_ref().unwrap().clone();
                    self.device
                        .lock()
                        .unwrap()
                        .activate(
                            mem,
                            interrupt_cb,
                            self.queues.clone(),
                            self.queue_evts.split_off(0),
                        )
                        .expect("Failed to activate device");
                    self.device_activated = true;
                }
            }
        }
    }
}

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

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

impl Snapshotable for MmioDevice {}
impl Migratable for MmioDevice {}